GERSTEL Solutions No. 3.pdf - Research Institute for Chromatography

21

GERSTEL solutions worldwide 3 / Trade Fair Special / October 2002GERSTEL solutions worldwide 3 / Trade Fair Special / October 2002

20

News from GERSTEL GmbH & Co. KG · Aktienstraße 232 – 234 · D-45473 Mülheim an der Ruhr · Germany · Phone +49 (0) 208 - 76503-0 · Fax +49 (0) 208 - 7650333

ISS

N 1

619

-007

6

Informationen der GERSTEL GmbH & Co.KG · Aktienstraße 232 – 234 · D-45473 Mülheim an der Ruhr · Telefon (02 08) 7 65 03-0 · Telefax (02 08) 7 65 03 33

ISS

N 1

618

-590

0

News from GERSTEL GmbH & Co. KG · Aktienstraße 232 – 234 · D-45473 Mülheim an der Ruhr · Germany · Phone +49 (0) 208 - 76503-0 · Fax +49 (0) 208 - 7650333

GERSTEL GmbH & Co. KGAktienstraße 232 - 234D-45473 Mülheim an der RuhrGermany

+49 (0) 208 - 7 65 03-0+49 (0) 208 - 7 65 03 [email protected]

GERSTEL Inc.Caton Research Center1510 Caton Center Drive, Suite HBaltimore, MD 21227USA

+1 (410) 247 5885+1 (410) 247 [email protected]

ISS

N 1

619

-007

6

G L O B A L A N A L Y T I C A L S O L U T I O N S

G L O B A L A N A L Y T I C A L S O L U T I O N SG L O B A L A N A L Y T I C A L S O L U T I O N S

Subject to change.

GERSTEL, GRAPHPACK and TWISTER are registeredtrademarks of GERSTEL GmbH & Co.KG.

Printed in the Fed. Rep. of Germany • 0302b

© Copyright by GERSTEL GmbH & Co.KG

GERSTEL AGEnterpriseSurentalstrasse 10CH-6210 SurseeSwitzerland

+41 (41) 9 21 97 23+41 (41) 9 21 97 [email protected]

Imprint

Published byGERSTEL GmbH & Co. KG,Aktienstraße 232 – 234,45473 Mülheim an der Ruhr,Germany

EditorGuido Deußing,ScienceCommunication,Neuss, Germany

ISSN 1619-0076

Discoveryourbenefits

Interview

Automatedsamplepreparation

Application

Effluentanalysismade easy

ChemSensor System

Food and aromaclassification

Trade fair highlights 2002

Trade Fair SpecialGERSTEL among the mostinnovative medium-sized companiesin Germany

TOP 100 of 2002 chosen

Berlin/Mülheim an der Ruhr,Germany – The one hundred mostinnovative medium-sized companiesin Germany for 2002 have beenselected – GERSTEL GmbH & Co.KG from Mülheim an der Ruhr isamong this „TOP 100“. The expertpanel of the „Best of TOP 100Germany Innovation Competition“,under the patronage of Dr. Hans-Jürgen Warnecke, president of therespected German Frauenhofer-Gesellschaft in Munich, came to thisconclusion.

This is the eighth time the competition has beenheld. It promotes the performance of the companieschosen and the image of medium-sized companies, the„backbone of German business“ according to War-necke. „In Germany there are around 30,000 medium-sized companies that undertake research anddevelopment“, said Warnecke at the prize ceremony inBerlin. A significant number, considering many medium-sized companies are contractors. Because thesecompanies aren’t in the news like large companies are,

GERSTEL solutions worldwide / Trade Fair Special News

it is easy to overlook the fact that they are the real motorof the economy.

Innovative medium-sized companies are distin-guished, said Prof. Dr. Hans Hörschgen, Professor ofEconomics at the University of Hohenheim, Germany,and a marketing expert, „by being more flexible, quickerand smarter than larger companies“. In order to remaincompetitive, medium-sized companies have had toconstantly improve the quality of their work and theirproducts.

The choice of the TOP-100 companies was madeusing a procedure developed by Hörschgen, in whichdetails of each company, such as its economicdevelopment, its innovation in the areas of product,organisation, personnel and company culture, wereevaluated.

„Companies were selected if they demonstratedsuccess in these areas as measured by increasedcompetitiveness – and GERSTEL fulfilled the quali-fication”, said Holger Gerstel, managing director and co-owner of the Mülheim company.

Scientific adviserDr. Arnd Heiden,[email protected]

Eike Kleine-Benne,[email protected]

DesignPaura Design, Hagen, Germany

Printed byBasseDruck, Hagen, Germany

You can find further

information on times,

services and products on

our internet home page

at www.gerstel.com

www.gerstel.com

October 2002

ManagementFrom left: Eberhard G.Gerstel, Ralf Bremer,Holger Gerstel

Nr. 3

3


2

GERSTEL isthere for youNovember 02Het InstrumentUtrecht, Netherlands04. – 08.11.2002PollutecLyon, France26. – 29.11.2002expoquimiaBarcelona, Spain26. – 30.11.2002

March 03Pittcon 2003Orlando, Florida, USA09. – 14.03.2003

Further informationon dates, exhibitions and productson the internet at www.gerstel.de.

„Despite careful attention to customer needs duringproduct development, we are never really sure inadvance how clients will react to a new productintroduction. Once a new product is launched at a tradefair, we get a clearer picture of the impact of newproducts.“

After numerous technical developments and tradefair visits, Ralf Bremer, Technical Director of GERSTELGmbH & Co. KG, knows what he is talking about. Thisyear, the company has already presented its newproducts several times to a wide professional public atimportant scientific expositions, including the PittConConference in New Orleans, USA; Analytica in Munich,Germany; and the 25th International Symposium onCapillary Chromatography in Riva del Garda, Italy.

Bremer believes that the results so far confirm this:„We have achieved successful launch and precisionlanding with our new products and customer-orientedsolutions.“

Applications-oriented work was the focus of PittConin March of this year: „Our company presented ten tech-nical posters with applications“, says the manager,„more than ever before.“ Among these posters wereapplications of the new GERSTEL Headspace Chem-Sensor.

At Analytica, the main focus was automated thermaldesorption using GERSTEL Twisters by means of the

new Twister Desor-ption Unit TDU

and Multi Pur-pose SamplerMPS Twister

Trade fair review 2002

Precision landing fornew GERSTEL products

Option. Designed specifically for Twisterdesorption, the TDU unit can be used withthe MPS Twister Option to automaticallyprocess 196 Twisters. „The great interest inthe TDU suggests that Twister Stir BarSorptive Extraction (SBSE) will increasinglybecome the sample preparation andextraction technique of choice“, saysBremer.

Many visitors to the exhibit at Analytica,with 30% higher attendance than 2000,were interested in new developments withthe GERSTEL Multi Purpose Sampler MPS 2,including the new PrepStation withSamplePrep software. The PrepStation isthe latest MPS 2 system, providing full auto-mation of both sample preparation and sample intro-duction steps for higher analytical productivity.

The PrepStation is a unique dual-rail, dual-robot con-figuration of the MPS 2. Bremer asserts that the mostdistinctive feature of the PrepStation is its controlsoftware, which enables very complex processes to beperformed extremely simply - „without any need formacro programming“, Bremer emphasized. ThePrepStation was also a big hit at PittCon.

GERSTEL presented eight scientific publications atRiva. Among these were papers describing use of thenew Headspace ChemSensor in applications such asclassification and quality measurement of constituentsin food and beverages. Lectures presented by GERSTELscientists attracted a great deal of attention, said Bremer,with audiences of at least 150 people.

„It is striking“, says the manager, summarizing hisimpressions, „that more and more users are seekingeffective, economical solutions that can be tailored totheir individual needs. These needs are satisfied with theflexi-bility of the GERSTEL Modular Analytical Systemsconcept, which provides for customer-specific modi-fication.“

New product: TDUWhen combined with an MPS 2, allows

automatic processing of up to 196 Twisterswith the GERSTEL Thermo Desorption Unit TDU. 3

Impressions of Analytica 2002

GERSTEL solutions worldwide / Trade Fair Special News

OverwhelmingCustomer Response

hen you visit any of the major science tradeshows, it is clear that all companies focus consider-able effort on obtaining complete customer satis-faction. Achieving this requires continuous improve-ment in all services provided to the customer andnot taking even the smallest detail for granted.

GERSTEL sees itself as your partner. We havemade it our mission to provide you with the toolsneeded to solve your most difficult analyticalquestions, and we want to continue to develop andcustomise these tools to suit your individual needs.In order to do this, we collaborate closely with ourcustomers, because we can’t provide useful solutionsunless we fully understand your needs.

The overwhelming response that we received thisyear at the trade shows we participated in, showthat our customers agree with our approach. Neverin the history of our company have we experiencedsuch response to our products and completeanalytical solutions.

Holger GerstelManaging Director,GERSTELGmbH & Co. KG

GERSTEL solutions worldwide / Trade Fair Special Editorial

It was alsovery hearten-ing that manyof the peoplethat came toour booth wereexcited aboutusing our newproducts tosolve theirexisting analytical problems. This is further proofthat we are reaching you and that we are on theright track.

Many thanks for the great trust that you haveplaced in us. I hope that we will continue to benefitfrom our successful partnership and that you willenjoy the articles in this special trade show editionof GERSTEL Solutions worldwide.

Yours sincerely

W

In this issue

News Page

Trade Fair 2002: Precision landing for newGERSTEL products 3

Further international expansion 12

On lecture tour in Japan and Korea 15

GERSTEL chosen among the TOP 100innovative medium-sizedcompanies in Germany 20

Application

Effluent analysis made easy 4 – 7

Monitoring pesticides indifferent matrices 8 / 9

Distributors

Ireland: Presentation Carl Stuart Limited 9

Italy: Distributor with new name 12

Begium: RIC new official distributor 14

Spain and Portugal: PresentationAndaluza De Instrumentation S.L. 19

Innovation

ODP-Software: Visualisation of olfactoryintensities 12

MASter Software now integrated inGC-ChemStation 13

Twister

Semi-automated determination of PAH 14

Twister beats SPME fibre by far 15

ChemSensor System

Aroma analysis of the finest 16

ChemSensor confirms the authenticitiyof whiskey 17

Efficient determination of thespoiling of food 17

Classification of coffee varietieswith the ChemSensor 17

Interview

Innovative automated samplepreparation 18 / 19

Overview

Exhibitions: GERSTEL is there for you 3

Contact: GERSTEL worldwide 10 / 11

Imprint 20

5


4

Membrane-supported solvent extractionFor membrane extraction, 8 to 10 membrane bags

were conditioned by extracting three times with 50 mLhexane at room temperature. The vial was filled with15 mL aqueous sample, the membrane bag was fixed tothe metal funnel using a Viton ring, and the funnelsuspended in the opening of the vial. Finally, themembrane bag was filled with 500 µL hexane to which1 µL of the simetryne internal standard was added, andthe vial was sealed with a metallic crimp cap.

For extraction, the vial was placed in the intervalshaker of the MPS and shaken for a defined time at a settemperature. Finally, it was automatically removed fromthe MPS and transferred to the sample tray. The organicextract was removed manually from the membrane bagusing a microlitre syringe and transferred into a 2 mLsampler vial.

Editor’s remark: In the time since this studywas performed a new PrepStation software for theMulti Purpose Samplers MPS has been released.This software allows automation of all steps of theMembrane Extraction method.

LLE of river waterIn order to compare the quantitative results of

membrane-supported LLE with in-vial LLE without amembrane, 15 mL river water was filled in a 20-mLheadspace vial with 1 and 5 µg/L of each analyte and1.3 µg/L pentachlorobenzene as internal standard. Afterintroduction of 1 mL hexane, the vial was sealed with ametal crimp cap and shaken for 30 minutes at 35 °C ata rate of 750 rpm in the MPS 2 interval shaker. Theorganic layer was removed using a microlitre syringeand transferred to a auto sampler vial. Large-VolumeInjection was used for GC/MS analysis with an injectionvolume of 100 µL. Direct calibration of the LVI/GC-MSwas achieved with mixed standards in hexane and aninjection volume of 100 µL (1µL/s) for determination ofthe analytes spiked in river water.

Results and discussionMembrane-supported solvent extraction

With Membrane Extraction, hydrophobic organiccompounds are extracted through a membrane into asmall volume of organic solvent. Relatively non-polarsolvents are used, since they have low solubility in water,and solvent loss through the membrane is avoided. Onthe other hand, very polar solvents can be used withminimal loss through the membrane. Water-misciblepolar solvents cannot be used for normal LLE. This isdifferent for Membrane Extraction, because they do notget in contact with water phase. In a pilot HPLC study,polyaromatic hydrocarbons were successfully extractedfrom aqueous samples using acetonitrile inside themembrane bag.

The solvent should also not be too volatile, sinceit may diffuse through the membrane and into theheadspace of the sample and condense there. It needsto be volatile enough, however, to be removed effectivelyby the split vent during the LVI.

Editor’s remark: GERSTEL supplies ready-preparedmembrane bags with a wall thickness of 0.03 mm,suitable for the application described here, and testedwith cyclohexane as the solvent.

Optimisation ofthe extractionparametersEffect of matrixconstituents

Table 1 (page 6) shows theoptimised parameters affec-ting membrane-supportedsolvent extraction: salt,methanol content and pH.If the solution is saturatedwith NaCl, extraction oftriazines is improved; theseare relatively polar analytes.By contrast, the recoveryrate of the nonpolar consti-tuents -HCH andphenanthrene slightly fell.

If the methanol contentwas increased to 6.66Vol%, it had no significanteffect on the extraction ofmost constituents, withexception of S-triazines,whose recovery rate fell to10 to 20 %.

The pK values oftriazines range from 1.6(simazine) to 4.3 (prometone).

The pH value of theaqueous sample shouldtherefore by somewhathigher than 6; an even higher pH value does notimprove the extraction results. For all extractions, theaqueous samples were saturated with 333 g/L NaCl(5 g NaCl in 15 mL water).

Optimisation of shaking rateThe sample must be mixed thoroughly and the

boundary layers in the membrane bag minimised, inorder to improve the transport of the analytes throughthe membrane into the organic solvent. The shaking rateof the MPS 2 was varied between 250 and 750 rpm. Theextraction yields increased for all analytes by 30 – 50 %when agitation speed was increased to 500 rpm; furtherincreases in speed gave only minimal increased yield.Mixing was more important for triazines than for non-polar constituents ( -HCH and phenanthrene); for allfurther studies, the shaking rate of the MPS 2 wastherefore set at 750 rpm.

GERSTEL solutions worldwide / Trade Fair Special Application

Figure 2 Optimisation of extraction time(6,7 µg/L each component, 333 g/L NaCl, 55 °C,750 rpm, injection volume 10 µL)

Instruments and analytical conditions used• Gas chromatograph 6890 (Agilent Technologies)Column: HP5MS, length 30 m, ID 0.25 mm,Film thickness: 0.25 µmCarrier gas: HeliumFlow: 1 mL/min (constant flow)Column pressure: 53 kPa (initial)Oven temperature profile:

50 °C – 2 min – 10 °C/min –160 °C – 1 min – 3 °C/min –200 °C – 1 min – 10 °C/min –250 °C – 2 min

• Mass spectrometer 5973 (Agilent Technologies)Acquisition mode: Scan 30 – 350 amuTemperatures: Transfer liner 280 °C

MS-Quadrupol 150 °CMS-Ion source 230 °C

• Cooled Injection System CIS 4 (GERSTEL; LN2 cooling)

Empty and buffled glas liner were used and hadbeen manually deactivated.Injector temperature: 20 °C (initial)Column pre-pressure: 5 kPa reducedMode: Solvent VentingFlow: 100 mL/min at split vent, up to

0.08 min, then splitless.Temperature programm:20 °C - 0,12 min - 12 °C/s - 250 °C -1 min - 12 °C/s - 330 °C - 3 min.

• Multi Purpose Sampler MPS 2 (GERSTEL)

Shakingat increasedtemperature

Metalliccrimp cap

Stainless steel funnelwith tube (6 mm OD)

Heat-sealedmembrane bag madeof polypropylene,6 mm ID, 4 cm long

Extraction vialLarge Volume

Injection /GC-MS

Viton ring

500 µLHexane

15 mLaqueoussample

Authors

Barbara Hauser and Peter Popp,UFZ Umweltforschungszentrum Leipzig-Halle, Sektion Analytik,Permoserstraße 15, D-04318 Leipzig, Germany

Eike Kleine-Benne, GERSTEL GmbH & Co.KG,Aktienstraße 232 – 234, 45473 Mülheim an der Ruhr, Germany

IntroductionWe can do without oil but not without water. The need

to investigate water for possible contamination isobvious; not only drinking water, but more particularlyeffluent and brackish water, in order to identify thecauses of the contamination. If the sample has a highcontent of suspended foreign particles, analysis may becomplicated. Membrane Extraction can simplify analysisof difficult samples: a new automatable method forsample preparation developed by the EnvironmentalResearch Institute (UFZ) Leipzig-Halle with furtherdevelopment and marketing under licence by GERSTEL.

Numerous sample preparation methods have beendeveloped for chromatography using recognisedlaboratory procedures for Liquid-Liquid Extraction (LLE),although this technique has several known dis-advantages: it is difficult to automate many of thesteps, and it results in relatively large volumes of possiblytoxic organic solvents. The extract may need severalpurification steps with volume reduction in orderto achieve acceptable detection limits. There arecurrently no viable alternatives to LLE for the manyapplications, leaving many users without options.However, Membrane Extraction changes all that:

Membrane-supported solvent extraction leads tosmall volume LLE using a flat Low-Density Polyethylenemembrane (LDPE), which separates the aqueoussample from the organic solvent. Like Liquid PhaseMicro extraction (LPME), Membrane Extraction is carriedout offline in a vial, from which the organic extract istransferred into a sampler vial: it is followed by a LargeVolume Injection (LVI). This technique was recentlyintroduced by Hauser et al. [1]

In this study, the extraction method was adapted formembrane-supported LLE, to allow use of a conven-tional 20-mL headspace vial. A flat, 0.05 mm thick non-porous polypropylene membrane was heat-sealed intoa tube of 6 mm outer diameter to form a membranebag, which was fastened to a stainless steel funneland placed in a 20-mL glass vial filled with 15 mL ofthe aqueous sample. Annotation: GERSTEL now offersmembrane bags with a wall thickness of 0.03 mm.

The sampler is a Multi Purpose Sampler MPS 2 fromGERSTEL, which is able to fill the membrane bag with500 µL of an organic solvent, shake it at a definedtemperature and injects the extract directly into GC,where LVI is possible.

MethodsPreparation of standards

Pure standard substances were dissolved to makesolutions of 1 µg/µL, mixed working standards wereprepared containing 0.05, 0.5, 5 and 50 ng/µL. Theinternal standard consisted of methanolic solutionsof simetryne (50 ng/µL) and pentachlorobenzene(20 ng/µL); simetryne was used as the internal standardfor optimisation of the extraction parameters and addeddirectly to the hexane extraction medium.

Pentachlorobenzene was used for calibration ofthe membrane-supported LLE and was added to theaqueous sample before extraction. The LVI/GC-MS wascalibrated directly with mixed standards: 1 – 500 pg/µLin hexane for 10-µL injection; 0.01 – 100 pg/µL for100-µL injection.

For membrane-supported LLE, aqueous standardswere prepared: suitable aliquots of methanolic mixedstandards were diluted with 15 mL water, the methanolcontent not exceeding 0.2 percent by volume. To eachaqueous sample, 5 g sodium chloride was added, inorder to promote extraction of triazines.

GERSTEL solutions worldwide / Trad Fair Special Application

Effluent analysis made easyMembrane Extraction versus Liquid-Liquid Extraction

Figure 1 Schematic diagram of Membrane Extraction

7


6

In order to improve the detection limits, 100 µL wasinjected. This led to detection limits of 1 – 10 ng/L and alinear dynamic range of 0.005 – 10 µg/L; the regressioncoefficient was 0.9970 or better.

The results of validation showed semi-automatedmembrane-supported LLE is a reliable sample pre-paration technique for aqueous samples. Editor’sremark: In the time since this study was performed a newPrepStation software for the Multi Purpose Samplers hasbeen released that allows a wider choice of syringe sizeoptions for full automation of the Membrane Extraction.For example, using a 250 µL syringe allows transport ofup to 1 mL extraction solvent (4x250 µL), while stillallowing injection volumes as small as 25 µL. If aninjection volume of 100 µL is chosen, the solvent additionin the membrane bag can be integrated in the automatedprocedure. For the purpose, the sampler can be pro-vided with a 1000-µL syringe; this allows both preciseaddition of 500 µL hexane and also use of 100 µL aliquotfor the LVI after extraction.

Membrane Extraction versusIn-Vial-Extraction

The results of membrane-supported solventextraction were compared with in-vial extraction ofspiked river water (Table 3). The river water samples weretaken from the White Elster in Leipzig, and were spikedwith 1 and 5 µg/L methanolic mixed standards. Theanalyte levels in spiked river water extracted usingmembrane-supported LE were determined by calibra-tion using aqueous standards (0.001 – 10 µg/L) extractedunder identical conditions. The in-vial LLE was carriedout as described above.

The recovery rate of in-vial LLE was 100 %. It was,however, difficult to remove the organic extract since theorganic layer was very shallow and the phase boundarywas distorted by particles. Automation of in-vial LLErequired use of at least 4 mL hexane in order to ensurea clear phase separation and to enable removal of theextract through the sampler vial – without risking removaland injection of water. Since the Membrane Extractionapproach can easily use 500 µL extraction volume, the4 mL extraction volume needed for LLE results in 8-foldmore diluted sample for injection and therefore poorerdetection limits.


Figure 3LVI/GC-MS-Chromatogramof Single-Ion Monitoringafter Membrane Extractionof 15 mL water, spikedwith 0.05 µg/L of eachcomponent (extractiontime: 1 h, 333 g/L NaCl,45 °C, 750 rpm, injectionvolume 100 µL)

Literature

[1] B. Hauser andP. Popp, J. Sep.Sci., 24 (2001),551.

[2] TVO-BRD,appendix 2/I,01.04.1998.

[3] WHO: Guidelinesfor drinkingwater quality,2nd edition,volume 1,Geneva 1993.

The analytical accuracy of in-vial extraction wasbetter than that of membrane-supported solvent extrac-tion (Table 3). The mean variation of analytical resultsfrom the spiked concentration values was: 12.4 % for in-vial LLE with 5 µg/L spiked river water and 22.9 % forMembrane Extraction, which is, however, easier toperform: If an injection volume of 100 µL was used, thewhole procedure, that is extraction and injection, can befully automated.

SummaryThe Multi Purpose Sampler MPS 2 allows complete

automation of membrane-supported solvent extraction,which is a promising enrichment technique for variousorganic substances, including polar analytes such astriazines: under optimised conditions with an extractiontime of 30 minutes, recoveries of 60 to 100 % wereobtained. The detection limits were in the low ng/L range.Since the non-porous polypropylene membrane holdsback water, salts, particles and macromolecular consti-tuents from the organic extract, Membrane Extraction isespecially suitable for complex samples with a highorganic content.

Membrane Extraction is especially suitable forapplications in food analysis and bioanalysis: bychoosing solvents that are miscible with water, such asacetonitrile, the method can be used with reversedphase HPLC. Polar solvents do not dissolve in themembrane material and therefore cannot pass into theaqueous sample.

In combination with GERSTEL MASter software, insample preparation mode, the MPS 2 allows automationof a sequence of membrane-supported solvent extrac-tions, giving high sample throughput.

ConclusionGERSTEL Membrane Extraction, shown here with

the example of triazines and other semi-volatile con-taminants, with direct coupling to Large Volume Injectionand GC-MS detection is an advantageous procedure interms of cost and time for investigation of effluent andbrackish water with high content of suspended material.It fulfils the requirements of the German Drinking WaterOrdinance (0.1 µg/L for individual pesticides) [2] andDrinking Water Recommendations of the World HealthOrganisation WHO (2 µg/L atrazine and simazine) [3].

Optimisation of temperatureThe interval shaker of the MPS 2 can be set to a

defined temperature. Increasing the temperature duringthe shaking phase from 35 to 55 °C (hexane boils at69 °C) improved the recovery of all constituents by 10to 30 %; the effect was particularly marked for water-soluble triazines, and less for 2,4-dichloroaniline, -HCHand phenanthrene. For determining the validationvalues, extraction was carried out at 55 °C for sub-sequent 10-µL injection.

Optimisation of extraction timeAn extraction time of 30 minutes led to optimal

enrichment of all components (Figure 2); increasing thetime did not lead to any improvement. After 30 minutes,the recovery was 60 to 100 %, sufficient for validation ofthe method.

Validation of methodThe performance of membrane-supported solvent

extraction was tested under optimised extractionconditions; table 2 shows the validation results. Thelinear dynamic range was determined by extraction ofspiked aqueous samples, and for 10 µL ranged from 0.05to 100 µg/L; the regression coefficient was 0.9965 orbetter. After 30 minutes extraction, the detection limit of10 to 100 ng/L was achieved (see summary).

The detection limits were determined by blank valuesfrom co-extracting matrix components; components inthe blanks originate from the heat-sealed bag made ofpolypropylene. The co-extracting components were alsorecorded in single-ion mode. Figure 3 shows thechromatogram of an extract obtained after membrane-supported solvent extraction of water again spiked with50 ng/L; this should illustrate the high background, seenespecially with the 100-µL injections, reducing theaccuracy of peak integration at low concentrations.

The reproducibility of the whole extraction procedureproved to be good. The coefficient of variation of fivesuccessive extractions ranged between 2.1 and 14.3 %.


Table 1Effect of matrix components onextraction recovery for MembraneExtraction (spiking level 6.7 µg/L,extraction time 1 h at 35 °C and750 rpm; injection volume 10 µL)

Table 2Validation results for MembraneExtraction: 10-µL injection(a): extraction time 30 min,333 g/L NaCl, 750 rpm; 6.7 µg/Leach component. 100-µL injection(b): extraction duration 1 h,333 g/L NaCl, 45 °C, 750 rpm.

Table 3Analytical results (µg/L) of spikedriver water; comparison of MembraneExtraction (a) with in-Vial LLE (b)[a: extraction time 1h, 333 g/L NaCl,45 °C, 750 rpm, 1.3 µg/Lpentachlorobenzene as internalstandard in water. b: extraction time30 min, 333 g/L NaCl, 45 °C,750 rpm, 1.3 µg/L pentachlorobenzeneas internal standard, 1 mL hexaneas extraction solvent:injection volume 100 µL]

98


The author

Pat Sandra is part-timeprofessor in SeparationSciences at the Ghent University,Belgium, and at the University ofStellenbosch, South Africa. He is director ofthe Research Institute for Chromatography(RIC) in Kortrijk, Belgium, a center ofexcellence for research and education inchromatography and mass spectrometry.RIC is also the GERSTEL representative inFrance and Belgium.

FurtherinformationCarl Stuart Ltd.Tallaght Business ParkWhitestownDublin 24Ireland 00 35 3 (1) 4523 - 432 00 35 3 (1) 4523 - 967 [email protected] www.carlstuart.com

Figure 3 Ion extracted chromatogram of the pesticides positivelyidentified by the RTL screener and quantified in the grapes.

Figure 2 RTL screenerfor permethrin II

GERSTEL solutions worldwide / Trade Fair Special Distributor

µm HP-5MS column. The oven temperature was pro-grammed from 70 °C - 2 min - 25 °C/min - 150 °C - 3 °C/min - 200 °C - 8 °C/min - 300 °C. This is the RTL programand locking was performed on p,p’-DDT (26.999 min).The MS was operated in the scan mode (m/z 40-500).

Figure 1 shows the total ion chromatogram and onthis chromatogram the RTL screener was applied.

Figure 2 shows a typical screening result. Perme-thrin II is identified through its retention time and fourspecific ions. The total screening then gives all pesticidespositively identified in the grapes (Figure 3) and bystandard addition the quantities could be measured.

Note that chlorpyrifos is present at the 0.1 ppb levelwhich means that whatever the matrix is e.g. drinkingwater, beverages, fruits, vegetables, etc., limits of determi-nation can easily be reached in the MS scan mode.

Operation of the MS in the ion monitoring modeallows ppt level measurements which can be of use tocheck on the pesticide zero-tolerance in baby food.

Acknowledgement

My coworkers and co-authors of the article in LC.GCEurope, F. David (RIC) and B. Tienpont (Ghent University)are thanked for their contribution.

References

1. Ph. Wylie and B. Quimby, Agilent Technologies Appli-cation note 5967-5860 E (2000) www.chem.agilent.com

2. C. Kai Meng, Agilent Technologies applicationnote 5988-4392EN (2001) www.chem.agilent.com

3. P. Sandra, B. Tienpont and F. David, submittedLC.GC Europe.

Pesticide residue analysis is usually costly and time-consuming. Analysis of individual pesticides or classesof pesticides e.g. organochloro pesticides (OCPs),organophosphorus pesticides (OPPs), triazines, etc., ismore and more replaced by multiresidue methods. Thefirst aim of a multiresidue method (MRM) is to detect asmany pesticides as possible with one analyticaltechnique including sample preparation and chroma-tographic analysis. Only after elucidation of thepesticides in a specific matrix, accurate and precisequantification can be performed.

In recent years important improvements have beenmade in multiresidue analysis by capillary gaschromatography – mass spectroscopy. Through the fea-tures of Electronic Pneumatic Control (EPC), Retentiontime Locked Libraries (RTL) for GC amenable pesticidesand endocrine disrupters could be constructed and bylinking the locked retention times to the mass spectraldata hardly any pesticide that is in the library can escapedetection and elucidation [1,2]. The Agilent TechnologiesRTL-MS library presently comprises 567 substances.

An MRM also requires sample preparation andnumerous methods have been developed for thispurpose. We recently evaluated the GERSTEL Twister assample preparation technique for the enrichment ofpesticides from different matrices and came to the

conclusion that 440 pesticides out of the RTL-MS librarycan be enriched from water, beverages, fruits andvegetables with recoveries complying with the requiredLimits Of Quantification (LOQ) set by regulatoryorganizations. The complete list of pesticides amenableto Twister enrichment and RTL-Capillary-GC-MSanalysis will be published in one of the next issues ofLC.GC Europe [3]. The recent introduction by GERSTELof the new Twister Desorption Unit TDU that can beinstalled on the MPS 2 enables fully automated analysisof 98 or 196 Twister stir bars. This makes the applicationof this new MRM very cost-effective.

The principle and potential of Twister-RTL-Capillary-GC-MS is illustrated with the determination of pesticidesin grapes. The sample preparation, valid for all fruits andvegetables, is as follows:

15 gram grapes purchased from a local supermarketwere mixed with 30 mL methanol and 1 mL of the extractwas diluted with 10 mL water. A Twister was added andstirred for 60 min. The Twister was then desorbed at280 °C (5 min) in the splitless mode at 50 mL/min and thesolutes were cryofocused at –100°C. The GERSTEL CISoperated in the splitless mode was then programmed at600 °C/min to 280 °C (2 min). Analysis was done on anAgilent Technologies 6890 GC with 5973 MSDcombination equipped with a 30 m x 0.25 mm I.D., 0.25

Figure 1 Total ion chromatogram ofTwister-RTL-Capillary GC-MS of grapes

A versatile method to monitor 440Pesticides in different matrices likeWater, Beverages, Fruits or Vegetables

Twister-RTL-Capillary GC-MS.


The company was formed in 1984 by Stuart and GillianSmith. It has grown steadily over the years and nowemploys over thirty people. Our core competence is in thesales and support of high technology products. Currentlythe company is divided into six main areas of activity:• Analytical laboratory products• Environmental products, both laboratory and field based• Materials characterisation• Calibration and preventative maintenance• Process filtration• Food serviceThe company operates out of its own custombuilt modern facility in Tallaght and has beenISO 9002 accredited since 1994.

Service Level CapabilityExtensive inventory is maintained in our Dublinwarehouse. Standard delivery is via overnightservice using approved logistics providers.Courier delivery service available upon request.Our own personnel provide instrumentcalibration, repair, and preventativemaintenance. Full IQ, OQ and PQ facilitiesavailable on all instrumentation supplied byus and on certain items purchased fromother vendors.

Technical SupportFor each of the above divisions there is aminimum of two technical support personnelcapable of travelling to the customer’s site aswell as in-house support personnel. All technicalsupport personnel undergo factory-basedtraining on a continuous basis. For newapplications or special requirements we have theresources of our suppliers to call upon if needed.

Product QualityOur principle method of assuring product quality is to dealwith established suppliers of highest calibre and reputationand to ensure that quality is continuously monitored bycompliance with internationally recognised standards suchas ISO. It is our intention to apply for and comply with thenew ISO 17025 standard as it applies to laboratoryaccreditation.

Initiatives to ensure pricecompetitivenessWe operate in an open market and continually monitorwhat our competitors are offering. It is important howeverto realise however that one is comparing articles of asimilar quality. It is very easy to supply an article, whichcost less, however it is the total cost of ownership that hasto be considered. A simple yet typical example would beautosampler vials. It would be very easy to supply lowercost vials, however if you run the risk of a single vialjamming or breaking in an autosampler or a sampledegrading then the consequences of this are that the costof ownership will easily exceed any saving made on lowercost vials. What are needed are vials of a consistently goodquality, which are reasonably priced. It is our opinion thatyou cannot divorce technical support from price.

Our Distributor in Ireland

Carl Stuart Limited

� ArmeniaInterLab Inc.Moscow OfficeTihvinsky per., 11 str. 2127055 MoscowRussia

007 (095) 97320-3, -4, -5007 (095) 775 77 [email protected]

� PolandCHROMTECChromatographia Apparature AkcesoriaUl. Rakowiecka02532 WarszawaPoland

0048 (22) 6 06 38 830048 (22) 8 49 10 [email protected]

� South AfricaChemetrix (Pty Ltd.)Block J, Central Park400 16th Road, MidrandP.O. Box 5226Halfway House 1685Republic South Africa

0027 (11) 5 41 98 010027 (11) 5 41 98 02

� IsraelEldan Electronic Instrument Co. Ltd.Idan twin building, New industr. park Afek21 Ha’Melacha st.48091 Rosh Ha‘AyinIsrael

00972 (3) 9 02 13 3000972 (3) 9 02 13 [email protected]

� ItalyA.I.Tech s.r.l.C. so IV Novembre 5815100 AlessandriaItaly

0039 131 - 32 55 280039 131 - 25 78 [email protected]

� GreeceHELLAMCO S.A.Scientific Laboratory Equipment7 Marathonos str. &Macedonias15233 Chalandri AthensGreece

0030 (1) 6 89 52 600030 (1) 6 80 16 [email protected]

Distributorsworldwide

� AustraliaLasersan Pty.Ltd.P.O.Box 3279Robina Town Centre, 4230QueenslandAustralia

0061 (417) 62 76 670061 (7) 55 25 28 [email protected]

If your countryis not shown in ourlist of distributors,

please contact:

Bernd WiesendSales Manager International

0049 (0)208 – 7 65 03-310049 (0)208 – 7 65 03-33,[email protected]

Jan Pieter StoutjesdijkSales Representative International

0049 (0)208 – 7 65 02-720049 (0)208 – 7 65 [email protected]

GERSTEL Inc.Caton Research Center1510 Caton Center DriveSuite HBaltimore, MD 21227United States of America

001 (410) 2 47 58 85001 (410) 2 47 58 [email protected]

GERSTEL AGEnterpriseSurentalstrasse 106210 SurseeSwitzerland

0041 (41) 9 21 97 230041 (41) 9 21 97 [email protected]

GERSTELworldwide

� BerlinHarriet Diedering

0049 (0)30 – 21 90 98 280049 (0)30 – 21 90 98 [email protected]

� BremenMichael Gröger

0049 (0)421 – 3 47 56 240049 (0)421 – 3 47 56 [email protected]

� KarlsruheKlaus Klöckner

0049 (0)721 – 9 63 92 100049 (0)721 – 9 63 92 [email protected]

� Mülheim an der RuhrDetlef Bergemann

0049 (0)208 – 7 65 03-250049 (0)208 – 7 65 [email protected]

� MunichHelmut Boljahn

0049 (0)89 – 93 08 65 140049 (0)89 – 93 08 61 [email protected]

Technical officesGermany

Support ManagerAsia/Pacific

GERSTEL GmbH & Co. KGAktienstraße 232-23445473 Mülheim an der RuhrGermany

0049 (0)208 – 7 65 03-00049 (0)208 – 7 65 [email protected]

Head office Subsidiaries

GERSTEL Twister Desorption Unit TDUThe GERSTEL Thermal Desorption Unit (TDU) is a designedinstrument for use with GERSTEL Twister stir bars. TheTDU is used with the GERSTEL Cooled InjectionSystem CIS on a GC or GC/MS system to enable ultra-trace analysis of aqueous and other liquid samples.

� Czech RepublicHPST, s.r.o.K zatácce 518/814300 Prag 4Czech Republic

00420 4440-24 2400420 4440-25 [email protected]

� IndiaTritech10, Ellora, Shradhanand RoadNear Telephone Exchange, Vile Parle(E)Mumbai – 400 057India

0091 (22) 401 72 440091 (22) 401 72 [email protected]

� KoreaYoung In Scientific Co., Ltd.Young-Wha Bldg. 547Shin Sa-Dong, Kang Nam-KuSeoul, 135-120Korea

0082 (2) 5 19 73 000082 (2) 5 19 74 [email protected]

� SpainAndaluza De Intrumentación S.L.Manufactura 8 EdificioBoudere I 2a Planta – Poligono PISA41927 Mairena de Aljarafe – SevillaSpain

0034 (95) 5 60 01 170034 (95) 4 18 20 [email protected]

� SloveniaChemass d.o.o.Baznikova 401000 LjubljanaSlovenia

00386 (1) 4 27 75 6000386 (1) 4 27 75 [email protected]

� JapanYokogawa Analytical Systems Inc.Sales Department / Gas Phase ProductsMitaka Takagi Bldg.1-15-5 Nakacho, Musashino.shi180 TokyoJapan

0081 (422) 56 93 930081 (422) 56 94 [email protected]

� HungaryKromat Kft.Fehérvári út 1441116 BudapestHungary

0036 (1) 4 63 07 770036 (1) 2 06 29 [email protected]

� ChinaTegent Technology Ltd.Room 2103-05, Westin Centre26 Hung To RoadHong Kong

00852 - 27 59 21 8200852 - 27 58 38 [email protected]

� TaiwanGreat EngineeringTechnology Corp.11F-1, No. 372 Chung Cheng 1st Rd.Kaohsiung Taiwan R.O.C.Taiwan

00886 – 7 711 – 22 05 10100886 – 7 711 – 46 [email protected]

� UkraineALSI Advanced LaboratoryShovkunenko str. 8/20, Ap. 51Kiev, 03049Ukraine

0038 (044) 245 32 240038 (044) 245 32 [email protected]

� BelgiumResearch Institute forChromatographyKennedypark 20B-8500 KortrijkBelgium

0032 56 - 20 40 310032 56 - 20 48 59

� Belorussia, Georgia, Mongolia, RussiaInterLab Inc.Moscow OfficeTihvinsky per., 11 str. 2127055 MoscowRussia

007 (095) 973203 - 3, - 4, - 5007 (095) 775 77 [email protected]

� CyprusHELLAMCO S. A.Scienific Laboratory Equipment7 Marathonos str.15233 Chalandri - AthensGreece

0030 1 68952600030 1 [email protected]

� Luxembourg & The NetherlandsAnalytical Applications Brielle B.V.Amer 9,3232 HA BrielleNetherlands

0031 181 - 4165550031 181 - [email protected]@anaplications.nl

� United Arabian Emirates (UAE)Labins Laboratory SuppliesGarden Tower, Near Capital GardenOff Hamdan Street, Flat# C-14Abu DhabiUnited Arabian Emirates (UAE)

009 712 2671 888009 712 2670 [email protected]

� United KingdomAnalytical Applications Reading Ltd.Unit 3, Farnborough Business CentreFarnboroughHampshire GU14 7XAUnited Kingdom

0044 870 - 2 41 20 710044 870 - 2 41 16 [email protected]

October 2002

Dr. Manfred Schwarzer0081 3 57 31 22 810081 3 57 31 22 [email protected]://jp.gerstel.com

� NorwayMatriks ASForskningsparkenGaustadallèen 210349 OsloNorway

0047 (22) 95 85 640047 (22) 95 85 [email protected]

� Denmark, Sweden, FinnlandImpressed ABHumanistgatan 8 B21456 MalmöSweden

0046 (40) 30 92 130046 (40) 6 72 69 02

� FranceRIC France SAS8, Rue Maréchal d.l.d. Tassigny59800 LilleFrance

0033 – (6) 20 – 73 45 580033 – (4) 78 01 71 [email protected]

� IrelandCarl Stuart LimitedTallaght Business ParkDublin 24Ireland

00353 (1) 4523 - 43200353 (1) 4523 - [email protected]

1312


A mouse click selects the desired dialogue box toenter method parameters for all GERSTEL modules aswell as choosing sample injection techniques such asTDS, SPME, headspace and liquid injection. The methodparameters are stored together with the parameters forthe GC-ChemStation. An extended sequence tableallows choice of tray and injector.

„At last, thingsthat belong togetherare together”, saysDr. Stefan Bobinger.He predicts: „In thenear future, a similarsoftware packagewill be available forMS-ChemStationusers.“

In the past, if you wanted to use theGERSTEL Thermal Desorption System TDS orthe GERSTEL Cooled Injection System CIS withan Agilent Technologies gas chromatographysystem (GC) you had to use two methods andtwo sequences when analysing a set of samples.Users asked: Is there an easier way?

The software experts from GERSTEL cameup with a great solution. „When you open ChemStation,you now find Gerstel in the menu bar“, says Dr. StefanBobinger, chemist and software developer at GERSTEL.The menu item opens the GERSTEL MASter Software,which has recently been incorporated into the GC-ChemStation. In other words: „People no longer have toswitch from one program to another to carry out theiranalyses“, says Dr. Bobinger. „The GERSTEL modulesand GC can now be programmed using a single softwarepackage.“

GERSTEL ODPwith new speechrecognition software

When analysing aromatic substances, conventionalmethods rapidly become inadequate. Only whensensitive analytical tools and the human senses, in thiscase the nose, are used in parallel, can meaningful andreliable information be obtained.

The GERSTEL Olfactory Detection Port ODP 2 addsan „aromagram“ of the sample to the chromatogram, fordetection of either a single substance or a complexpattern of aromas. The ODP 2 allows (by combination ofa commercial gas chromatography with mass-selectivedetection) clear-cut characterisation of aromaticcompounds.

The development of the new GERSTEL OlfactoryRecording Software package makes a significantcontribution to olfactory analysis. Now the aromagramcan provide 4 levels of aroma intensity and be annotatedwith text that is produced during the olfactory analysis.

This is how it works. When an aroma is detected, oneof four keys is pressed on a USB based OlfactoryIntensity Pad. The four keys provide four intensity levels

GERSTEL solutions worldwide / Trade Fair Special InnovationGERSTEL solutions worldwide / Trade Fair Special News / Innovation

MASter Software now intergrated inGC-ChemStation from Agilent Technologies

Simple, rapid and comfortable

TDSmethod

parameter

MPS 2headspacemethod parameter

CISmethod

parameter

Sequence tableadditional selection oftray and injector

MPS 2liquid injection method parameter

MPS 2SPME method parameter

Italy: distributor witha new name

A.I.Tech s.r.l.represents GERSTEL

at the most importantanalytical exhibition

in Italy (Milan) inOctober 2001

The Italian GERSTEL distributor has changed itsname as part of a process of extensive internal corporaterestructuring: Abreg s.r.l. has become A. I. Tech s.r.l. Thecompany continues to be run by Roberto Gaita.

FurtherinformationA.I.Tech s.r.l.C. so IV Novembre 5815100 AlessandriaItaly +39 131 - 32 55 28 +39 131 - 25 78 47 [email protected]

GERSTEL is continuing to expand steadily and is nowrepresented in 40 different countries.

Most of the company’s approximately 100 em-ployees around the world are located in Germany - at theheadquarters in Mülheim an der Ruhr and at theproduction facility in Duisburg. The company does,however, also have a US subsidiary GERSTEL Inc., whichis respon-sible for North America (the biggest market inthe world for instrumental analysis), Mexico and Canada,and GERSTEL AG in Switzerland. In 33 countries GERSTELis represented by distributors (see page 10 and 11).

In the past three years, GERSTEL succeeded inestablishing itself and performing effectively on thegrowing Asian market in particular. The company is nowfocussing its operations primarily on Eastern Europe aswell; contracts have been concluded with distributorsfound in Russia, Belarus, Ukraine, Mongolia and Hungary.Eastern Europe is considered to be a very promisingoverall market with tremendous growth potential.

Further internationalexpansion

Visualisation of olfactory intensities

GERSTEL Olfactory Recorder SoftwareClassification of characterised aroma data in an „aromagram“

that are represented as different peak heights in thearomagram. The aromagram is then stored with datafrom any other detectors connected in parallel with theODP 2. Pressing a key also activates the voice recordingfunction and the aroma description spoken during thattime is also stored along with the aromagram.

Once the olfactory analysis is completed, the spokencommentary can be reviewed, and corrected ifnecessary. A complete report can be generated thatcontains aroma detection times, descriptions and GCrun information.

1514


From food and beverages to environmental waterand effluent analysis, and in numerous analytical labora-tories, the GERSTEL Twister is increasingly being usedfor extraction of volatile and semi-volatile analytes fromaqueous matrices. With good reason:

When compared to SPME fibres, the Twisterprovides a much larger capacity. In addition, the PDMSfunctions as an immobilised liquid phase, in which thesample is concentrated by sorption not by adsorption.The combination of high capacity and sorptive extractionminimises or even eliminates competitive and dis-placement effects caused by highly concentrated matrixcomponents, as is often observed with extractiontechniques based on adsorption.

Experiments were performed to confirm this:The limits of sorption capacity of the Twister were

determined gravimetrically by extracting hexadecanefrom aqueous isopropanol solutions. Under normal

Twister beats SPME fibres by far

Stir Bar Sorptive Extraction –Capacity Comparison

conditions, the PDMS phase of the Twister can absorbmilligram amounts of hexadecane. From a practicalpoint of view, the highest analyte concentration thatgives a linear calibration curve, is the working range ofthe stirring bar.

For evaluation of thecompetitive and drag effects,model components, such aspesticides and methylesters,were extracted from waterwith the Twister and withSPME (also using a PDMSphase) in the presence of upto 5 ppm limonene.

Results: The PDMS phaseof the Twister showed up to25-fold higher capacity com-pared with the SPME phase.

VermouthInvestigated withthe Twister

It is now possible to automate the SBSE desorptionstep and to transfer the liquid extract by means of aGERSTEL Multi Purpose Sampler MPS 3 to an HPLCsystem using a procedure developed at the UFZ Leipzig-Halle and marketed by GERSTEL. Called Twister BackExtraction, it requires an MPS 3 equipped with a tem-perature programmable agitator and special software.

There is only one manual step. The Twister must beremoved by hand from the sample vial and transferredto a 250-µL glass insert located in a 2-mL sample vial.The MPS 3 adds the acetonitrile-water mixture, andtransports the vial to the agitator. After it is agitatedat a pre-set time and temperature, the vial is thenremoved and an aliquot of the solvent is injected into theHPLC system.

Combination of SBSE with solvent Back Extractionfollowed by LC fluorescence detection allows sensitiveand reproducible determination of PAHs, pesticides, her-bicides and phenols as well as many other non-volatileand thermally labile compounds in aqueous matrices.

The Twister Back Extraction technique greatlyreduces the manual labour involved when performingextractions. The procedure is also robust, easy toimplement, and allows high sample throughput byextraction of many samples in parallel.

The GERSTEL TwisterStir Bar Sorptive Extraction (SBSE) is a sample

preparation technique developed at the ResearchInstitute for Chromatography (RIC) in Belgium andis sold commercially as the GERSTEL Twister.The technique is comparable to Solid Phase MicroExtraction (SPME). The crucial difference betweenSPME and SBSE is that analyte extraction isaccomplished using a much thicker phase (0.5 to

Semi-automated determination of PAHs

The GERSTEL Twister forsample preparation in HPLC

1-mm vs. 100-µm). For the Twister, this phase consistsof pure polydimethylsiloxane (PDMS). The phase ratio -the ratio of the aqueous phase to the PDMS phasevolume – is much lower for SBSE, and the recovery rateis thus higher. Extremely low detection limits can beachieved when compounds sorbed onto the Twister aretransferred to the gas chromatograph by thermaldesorption.

For the first time, we briefly describe how SBSEcan be combined with liquid chromatography

(HPLC). Analytes are extracted from the Twisterusing a small volume of acetonitrile (ACN) or an

acetonitrile-water mixture. Aliquots of the resultingsolution are then transferred manually to the

HPLC system and analysed.

GERSTEL solutions worldwide / Trade Fair Special Twister GERSTEL solutions worldwide / Trade Fair Special Twister / News

„Always 180 to 250 seminar atten-dees-informative discussions-contractswithin a few days. The journey to Asia was

a success.“ The plan of Andreas Hoffmann, Applicationsspecialist at GERSTEL, and Prof. Dr. Pat Sandra from theResearch Institute for Chromatography (RIC), Belgium,was to give talks in Japan and Korea with the aim toinform users about GERSTEL’s expanding productportfolio and recent scientific developments. Emphasiswas placed on work performed at the RIC and atGERSTEL’s main laboratories in Germany using theGERSTEL Twister (SBSE).

Eberhard G. Gerstel and Ralf Bremer, both ManagingDirectors, used the journey to visit key custumers in Japan.„Our first impression was confirmed“, says Eberhard G.Gerstel. „GERSTEL is in greater demand than ever.“

GERSTEL on lecture tour in Japan and Korea

»In greater demand than ever«Four years ago, the company intensified

its activities in Asia, especially in Japan.„The recession was at its worst then, andthe economic situation has not improvedmuch“, says the managing director and co-owner. „However, we have been able toprovide analytical solutions that are in greatdemand. The name GERSTEL is becominga key for users to solve their most difficultanalytical problems.“

GERSTEL has received excellentsupport from its Japanese business partnerYokogawa Analytical Systems Inc. and its localrepresentative, Dr. Manfred Schwarzer. „In summary, ourtrip achieved successes comparable to our recent tradeshows“, says Eberhard G. Gerstel.

Eberhard G. GerstelProduct presentation forcustomers in Japan.

RIC officialdistributor forBelgiumThe Research Institute for Chromatography (RIC) hasbeen the official new GERSTEL distributor in Belgiumsince September 2002. The company has commissionedits previous representative, Analytical Application BrielleB.V., to concentrate its operations on the Netherlands andEngland in particular.

Further informationResearch Institute for Chromatography RICKennedypark 20B-8500 KortrijkBelgium + 32 56 - 20 40 31 + 32 56 - 20 48 59

TwisterBackExtraction

1 Ethyl Acetate2 Isoamyl Alcohol3 Isoamyl Acetate4 Ethyl Caproate5 p-Cymene6 Limonene7 1,8-Cineole8 γ-Terpinene9 Artemisia Ketone10 Linalool11 Thujone12 Phenylethyl Alcohol13 Diethyl Succinate14 Ethyl Caprylate15 Thymol16 Vanillin

Abundance

1e+06

4e+06

Time--> 10.00 15.00

1

5.00

3

4

2

5

67

89

102e+06

3e+06

5e+06

1112

13

14

15

16

6e+06

Vermouth

1716


Consistent quality is a basic requirement forlong-term client relationships – in the case ofluxury foods, aroma can be a significant part ofthe product’s appeal, and this is particularly truefor coffee. The distinctive aroma of variousvarieties of coffee and mixtures must bemaintained. How can we classify coffeevarieties rapidly and reliably in order to be ableto produce a variety of products with consistentquality and aroma?

To answer this, simultaneous, semi-quantitativesteam-distillation extraction gaschromatography with mass-selective detection(SDE-GC-MS), a technique commonly used inthe coffee industry, was compared with theresults obtained using the GERSTEL HeadspaceChemSensor System. The latter is an electronicnose, using quadrupole mass spectrometry andheadspace sampling.

Using SDE-GC-MS, taste analysis was carriedout with freshly roasted and ground greencoffee beans, using Arabica and Robustavarieties. Principle Component Analysis (PCA)showed a clear difference between the twovarieties. Furthermore, the Arabica variety gavea cluster corresponding to its sensorydescriptors – confirming the goodcorrespondence between sensory and chemicalanalysis data.

Interim results: while classical SDE-GC-MSpermitted good classification, it was very timeconsuming (total analysis time per coffeesample: 6 h of which 4 h for SDE).

Measurement using the Headspace ChemSensorSystem, in which the results were analysedusing special pattern recognition softwareshowed the coffee varieties successfullyclassified, but in a much shorter time.

Conclusion: use of the Headspace ChemSensorSystems from GERSTEL is an effective alternativeto classical SDE-CG-MS in classification of coffeevarieties.

Classification of coffeevarieties with theChemSensor

It‘s quicker …

Spoiled food contains sub-stances that can be used as indi-cators of the degree of contami-nation, such as dimethyl sulphide in

poultry and eggs, diacetyl in orange juice, or tri-methylamine in fish and milk. Since the spectrum ofvolatile components alters with the degree of spoilage,it can be followed by determination of the amounts ofthese indicators. The GERSTEL ChemSensor has beenshown to be the rapid and reliable method of choice forthis type of analysis.

Many statistical methods can be used to develop amodel for detection of indicators of spoiling. Explorativeanalysis methods, such as Principle ComponentAnalysis (PCA) or Hierarchical Cluster Analysis (HCA)indicate the suitability of data for the classificationmodes. Soft Independent Modeling of Class Analogy(SIMCA) and the procedure known as K NearestNeighbours (KNN) were used to develop twoclassification models. Regression models were foundusing partial least squares regression (PLS).

Results: Both SIMCA and KNN allowed rapid andsecure identification of the foods noted above with and

Sometimes food QC departments havereal trouble confirming the authenticity of aproduct. For example, alcoholic bever-ages such as bourbon can be adulteratedby addition of caramel colouring and wateror by adding a lower quality whiskey. Witha little skill you can create what theinexperienced consumer will perceive asdrinkable bourbon. Experts can tell thedifference in taste. However, a taste test isnot on the same level as a statement suchas „the probability limits are …“. Authenticor fake? A new procedure sheds light.

Several bourbons were analysed withGERSTEL Headspace ChemSensor withmass-selective detection. Sampling wascarried out using the headspace injectiontechnique. For validation of the resultsand clarification of which individualcomponents are relevant, the sampleswere also analysed using the GERSTELTwister (Stir Bar Sorptive Extraction)technique.

Efficient determination of the spoiling of food

Traces of theculprits

Headspace technique and GERSTEL Twister combined

ChemSensor confirms theauthenticity of whiskey

without spoilage indi-cators. The concentrationof spoilage indicators wasdetermined using PLSmodels to be in the lowerand middle ppm ranges.

The ChemSensor allowsrapid and reliable deter-mination of spoilageindicators and thus signsabout the degree ofspoilage. Further studiesare needed to confirm theextent to which the Chem-Sensor can be used for detection of other spoilageindicators. It is conceivable that the ChemSensor, inSingle-Ion Monitoring (SIM) mode, may improve thedetection limit to less than 10 ppm.

Since some odours are frequently present even atlow concentrations, other sampling techniques shouldbe tested, such as Stir Bar Sorptive Extraction (SBSE)and Solid Phase Micro Extraction (SPME).

GERSTEL solutions worldwide / Trade Fair Special ChemSensor System

Results: with the aid of multivariateanalysis techniques such as SoftIndependent Modeling of Class Analogy(SIMCA) and Principle ComponentRegression (PCR), the blendedbourbons were successfully identified.

Blending with cheap bourbons orother adulterants adds traces of newcomponents and allows the resulting„bourbon“ to be classified as a blend andnot authentic; classification models forboth sample preparation techniquesconfirmed the results. In particular,SBSE allowed identification of compo-nents that were not found using theheadspace sampling technique (HS).

Identification of blended bourbonsby a combination of HS and SBSE canbe seen as confirmation of the versatilityand applicability of the GERSTEL Chem-Sensor for rapid, precise and accuratedifferentiation of samples with similarchemical compositions.

The GERSTEL Headspace ChemSensor is a specialversion of the GERSTEL ChemSensor that has beenused successfully for classification of various fruitaromas. These aromas present a challenge forclassification because they contain large amounts ofpropandiol and ethanol that can interfere with theanalysis.

The Headspace ChemSensor consists of a head-space sampler directly coupled to a quadrupole massspectrometer. The advantage of this configuration is thatthe analysis time is only three to four minutes per sample.Using multivariate data analysis, the data are classifiedby Pirouette pattern recognition software fromInfometrix. Integration of the Headspace ChemSensorinto routine analysis allows qualitative (classification) andquantitative (regression) analysis of various aromas.

For qualitative analysis, a multivariate analysismethod, the algorithm of Soft Independent Modeling of

GERSTEL solutions worldwide / Trade Fair Special ChemSensor System

Aroma analysis of the finest

ChemSensor inresearch and routine

People follow their noses, andnot only physically. Of all thesenses, the sense of smell is

the subtilest and controls us likeno other. Bad smells startle us,

and make us recoil. By contrast,we are drawn to pleasant smells

and they can control ourdesires. For good reasons,

aroma manufacturers devotethemselves to keeping their

formulations secret and try tofind out others’ recipes through

chemical analysis.

Class Analogy (SIMCA) is used. SIMCA projection of thecomposite mass spectrum of an aroma sample can berepresented as a point in a 3-dimensional space.The data (points) of similar aromas cluster together in thediagram; aromas with different volatile compositions aredistributed over the entire diagram.

Quantitative determination is carried out using PartialLeast Squares Regression (PLS). In predictive mode, thealgorithm compares the mass spectrum finger-prints of unknown and known aroma samples. TheChemSensor was able to recognise differences incomposition using the mass spectra fingerprints ofaromas with true/false and yes/no classifications.

Conclusion: the results of aroma studies using theHeadspace ChemSensor from GERSTEL can be used asobjective guidelines in food processing, for qualitycontrol of starting materials as well as intermediateand finished products.

GERSTELHeadspaceChemSensor

19


18

About the scientist

One of the software experts in the company: Dr.Stefan Bobinger. After studying chemistry, he obtainedhis Ph.D. in analytical chemistry and foccused his workon software programming. In the R&D department at GERSTEL Dr. Bobingercombines both skills and develops software solutions for customers.

Dr. Stefan Bobinger

we have improved its functionality with the help ofMASter Software.

Can you describe it in more detail?With the help of the control software, we have broken

the whole process of sample preparation into itsindividual steps that can be combined in any way theanalyst chooses. With this software, even a singleMPS 2 can be used as a flexible PrepStation. Thesoftware allows automation of numerous steps requiredin sample preparation.

So you don’t need two samplers as well?That depends on the complexity of the task. For

blood alcohol analysis, the GERSTEL PrepStation ismost suitable, to allow automated headspace samplingwith addition of the internal standard. For that you needa combination of liquid and headspace samplers.

What distinguishes the „Sample Preparation“function of GERSTEL MASter Software from controlsoftware from other manufacturers?

Programming time and cost. While conventionalsystems usually require a lot of time to program macrocommands, our PrepStation requires only a fewsequence lines entered using the mouse. This makesthe number of possible mistakes very small. Using onlyhalf a dozen commands, all the steps that the MPS iscapable of can be carried out. All steps are configurable.Operation could not be simpler.

So, there is no alternative to the PrepStation?I think that on the software side, the PrepStation has

no competitors. This is true not only in the simple sense,but – as I have already said – MASter Software allows

parallel sample preparation of several vials.Maximum sample throughput is possible, theonly limit being the capacity of the analyser.

Does it make sense to add a third orfourth MPS?

We have developed the PrepStation withaim of making sample preparation and samplingsimple and easy by automating the routine steps.This includes addition of liquids, transport of samples,mixing and heating. Adding a third or fourth samplerwould produce a much more complicated system withvery little real benefits. We have other ideas forenhancing the PrepStation’s capabilities.

Such as?A filtration function or chromatographic column clean

up. If you want a comprehensive answer, just ask thelaboratory user. The PrepStation, in its current form, canmeet most common laboratory sample preparationneeds, but we are constantly coming up with ways toimprove its capabilities.

GERSTEL MPSMASter softwarewith the SamplePreparation option.

GERSTEL solutions worldwide / Trade Fair Special Interview / Distributor

Dr. Bobinger, can you tell ushow the idea of two MPS one ontop of the other, came about?

As with many of products andproduct enhancements, GERSTELwas asked by a customer to helpthem with their special samplepreparation needs. Our solution ofusing two MPS 2 samplers andcustomised software, the GERSTELPrepStation, fulfilled this need. Wesee an enormous need for moresophisticated sample preparationthat the PrepStation will be able toaddress.

What is the advantage of twoMulti Purpose Samplers placedone on the other?

The functionality of one sampler is very limited sinceit only has one available syringe.

Can you explain that in more detail?A conventional sampler usually has only one means

of moving the syringe, which ideally can be moved inthree dimensions. Simply put, if you add a secondsampler, this doubles the number of usable syringes.Since the syringes can be of different types, and usedfor different injection techniques, this provides multiplesample preparation possibilities.

Can you give a simple example?Take blood alcohol analysis, which is mostly carried

out using an internal standard. If you mount a syringefor liquid injection on one MPS and one for headspaceinjection on the other, you can add the internal standardduring the process and sample using headspace

injection. SPME injection is also possible. You can alsouse two liquid syringes of different sizes for preparationand injection.

What are the main characteristics of the MultiPurpose Sampler?

The MPS is a laboratory robot, which can move inthree dimensions. This functionality is a prerequisite forautomated sample preparation. When two are combinedto make a PrepStation, the intelligence and innovativefeatures of the control software are what really allows thesystem to be such a powerful tool, not the samplerhardware.

Are you talking about MASter Software?Exactly, with the Sample Preparation option.

Basically, we have not added functions to the MPS, but

Automated sample preparation

GERSTEL MPS PrepStationCleverly designed control software makesthe MPS 2 an extremely versatileautomatic sample preparation system.

The lab, endless work.Here we are in 2002 - and usersstill have to cope with the factsample preparation is still the mosttime consuming and critical part toproviding high quality quantitativeor qualitative sample analysis. Thisis not going to change. However,time and expense can be reduced,and manual steps can beautomated. GERSTEL is in a greatposition to provide new levels ofsample preparation with the MPSPrepStation. Why configure aninstrument with more than onesampler? GERSTEL Solutionsworldwide in conversation withchemist and co-developerDr. Stefan Bobinger.

GERSTEL solutions worldwide / Trade Fair Special Interview

Selection of modules usingthe mouse

Andaluza deInstrumentación S.L.

was founded in April 1994.The head office is in Seville, but

Andaluza belongs to the BiomasterGroup that started as Productos Quimicos de Murciaover 20 years ago. The group’s main business areas are:

- Sales of Analytical Instrumentation.- Contract Chemical Analysis- Environmental Consulting.

Andaluza de Instrumentación is responsible for salesof Agilent Technologies instrumentation as well as allinternational business activities in the Biomaster Group,including GERSTEL. Our offices in Madrid, Murcia,Seville, Valencia, Vigo, and our newest office inBarcelona support these sales activities. We have threelaboratories, the largest is in Murcia, the others are inSeville and Lisbon.

We have had a growth rate of 25-30% each year forthe last 10 years. Our staff includes 45 people: 13 de-dicated to sales of analytical instrumentation. GERSTELproducts have provided the Biomaster Group withexcellent business opportunities because Spain andPortugal have big markets for food, flavours andenvironmental analytical solutions where GERSTEL is anindustry leader. With the GERSTEL Twister technique wecan offer our customers an ideal solution to their needs.

Our Distributor for Spain and PortugalAndaluza deInstrumentación S.L.

GERSTEL’s business approach is the same as ours:selling and offering solutions, not just instrumentation.This philosophy combined with our many years ofexperience in solving analytical problems allows us tooffer our Spanish and Portuguese customers effectivesolutions to a wide variety of problems.

We have two key customers that we work with aspartners for Twister applications in Spain:

LABAQUA: Specialists in water analysis, they are acontract lab that uses the Twister to determine 85compounds in water (PAHs, PCBs, Pesticides, VOC, etc.)using only a single Twister per sample. They are our mainreference in Spain, and they also collaborate with us todemonstrate GERSTEL systems mainly for water analysis.

OSBORNE: A wine producer, they use Twister todetermine pesticides, and trichloroanisole in wine as wellas general analysis of flavours, etc.

Further informationAndaluza de Instrumentación S.L.Francísco Montalbán, Sales ManagerC/ Manufactura 8 Edificio Boudere I 2ª PlantaPolígono PISA41927 MAIRENA DEL ALJARAFE – Sevilla + 34 95-5600117 + 34 95-4182034 [email protected] www.andaluza.com

GERSTEL Solutions No. 3.pdf - Research Institute for Chromatography

Documents

Transcript of GERSTEL Solutions No. 3.pdf - Research Institute for Chromatography