Journal of Chromatography A, 1255 (2012) 38–55 · Tadeusz Górecki, Ahmed Mostafa, Matthew...

Tadeusz Górecki, Ahmed Mostafa, Matthew EdwardsDepartment of Chemistry, University of Waterloo (ON)

Journal of Chromatography A, 1255 (2012) 38Journal of Chromatography A, 1255 (2012) 38––5555

• Analysis of volatile and semi-volatile compounds• Max. theoretical peak capacity: ~22 peaks/min

◦ (15m x 0.1mm x 0.1µm column, 50cm/s, n = 150000, 15 min analysis)

Carrier GasColumn

OvenSample

ElectrometerData Recorder

InjectorDetector

3

Segment of a chromatogram of a sediment sample subjected to pyrolysis with TOF-MS detection (AIC)27 peaks visible

4

Overlay of selected masses (magnified 20 - 40 x)95 peaks found through spectral deconvolution.

nc ~ f x N 0.5 f < 2

tfirst tlast

Courtesy of Prof. Pat Sandra 5

6

Column n Peak capacity

25 m x 0.25 mm 100.000 316 – 632

50 m x 0.25 mm 200.000 447 - 894

100 m x 0.25 mm 400.000 632 - 1264

80 m x 0.1 mm 800.000 895 - 1790

Slide courtesy of Prof. Pat Sandra

T.A. Berger, Chromatographia 42 (1996) 63.

450 m x 0.25 mm x 0.25 µm PONA1,300,000 plates

Peak capacity over 1,000

100 min segments

T.A. Berger, Chromatographia 42 (1996) 63.

450 m x 0.25 mm PONA30 m x 0.25 mm PONA

9

… using the statistical theory of peak overlap …

… peak resolution is severely compromised when the number of components present in a sample overrates 1/3 of the peak capacity.J.M. Davis, J.C. Giddings, Anal. Chem. 55 (1983) 418

…in order to resolve 98% of the components, the peak capacity must exceed the number of components by a factor of 100.J.C. Giddings, J. Chromatogr. A 703 (1995) 3

100 analytes peak capacity should be 100 x 100 = 10.000, or N ca. 100.000.000 plates !!!

Slide courtesy of Prof. Pat Sandra

Solvent 1 front

Firs

t dim

ensi

on e

lutio

n

Solvent 1 front

10

Firs

t dim

ensi

on e

lutio

n

Solvent 1 front

First dimension elution11

Sol

vent

1 fr

ont

Sec

ond

dim

ensi

on e

lutio

n

Solvent 2 front

Separated!

Solvent 2 front

First dimension elution12

13

1st dimension retention time

2nd dimension chromatogram

14


2nd dimension chromatogram 2nd

dimension chromatogram

15


2nd dimension chromatograms

1D-GCHeartcut GCGCxGC16

• Interface traps effluent from 1st column and injects into 2nd

column• Times of injections are recorded• Second dimension is fast (0.5 - 10s)

InjectorCarrier Gas

PrimaryColumn

OvenSample

ElectrometerData Recorder

SecondaryColumn

Interface

Detector

1717

1D: 30 m x 0.25 – 0.32 mm x 0.25 – 1 µm, non-polar 2D: 0.5 – 2 m x 0.1 mm x 0.1 µm, polar Modulation period resulting in 2.5 to 3 cuts per peak

All parameters treated somewhat independently

Can it really be that simple?

Directly controllable

Green arrows: parameters whose values increase as the input parameter value increases

Red arrows: parameters whose values decrease as the input parameter value increases

1df 2df

2dc 1dc

1wh

Mass perModulation

Chance of overloading 1D


1l 2l

Capacity of 2D

Capacity of 1D

2Δp 1Δp

1u 2u

2D retention

2Rs 1Rs

2wh

Allowed / Required 2D Space

Oven Programming Rate

Te

AnalysisTime

PM

1uopt

Inlet Pressure

1Δp

ΔpT

Thermal modulators◦ heater-based ◦ cooling-based

cryogeniccryogen-free

Flow modulators

Thermal modulators◦ Modulation period◦ Modulation temperature ◦ Stationary phase thicknessFlow modulators◦ Modulation period◦ Carrier gas flow rates

Model 1D separation1st dimension peak width 24s

PM = 6 s (4-5 cuts)

PM = 12 s (2-3 cuts)

0 0.5 1 1.5

5

10

15

20

Retention Time (min)

Sig

nal I

nten

sity

0 0.5 1 1.5

500

1000

1500

2000

Retention Time (min)

Sig

nal I

nten

sity

0 0.5 1 1.5

500

1000

1500

2000

Retention Time (min)S

igna

l Int

ensi

ty

L. Ramos, J. Sanz, in: D. Barcelo (Ed). Comprehensive Analytical Chemistry, Elsevier, Amsterdam, Netherlands, 2009, p. 283.

5 s 6 s 7 s

(1) indeno[1,2,3-cd]pyrene, (2) dibenzo[a,h]anthracene, (3) benzo[ghi]perylene

Liquid-cooled thermal modulatorLibardoni et al., Anal. Chem. 2005, 77, 2786-2794

24

Constant heating voltage

Programmed heating voltage

C40C16 C20

N-PAHs

120 min

5 s

1D and 2D columns connected through a specially modified segment of a coated stainless steel capillaryCapillary is compressed between two passive coolersCapacitive discharge resistively heats the trapping capillary

2828

12.80 12.81 12.82 12.83 12.84 12.85 12.86 12.87 12.88 12.89 12.90

150000

200000

250000

300000

350000

400000

450000

500000

e

Signal: 12112204.D\FID1B.CH

25.20 25.21 25.22 25.23 25.24 25.25 25.26 25.27 25.28 25.29 25.30 25.31

120000

130000

140000

150000

160000

170000

180000

190000

200000

210000

220000

230000

240000

250000

260000

270000

280000

290000

300000

310000

e

Signal: 12112204.D\FID1B.CH

LMCSQuad-jet modulatorDelay-loop modulator

T

R

Longitudinally Modulated Cryogenic System (LMCS)

Kinghorn and Marriott (1998-2000)

3535

Temperature difference between the oven and the trap crucialOptimum peak width in both dimensions when ΔT =~70 °C ◦ Smaller ΔT trapping inefficient◦ Larger ΔT release inefficient (peak broadening in

both dimensions)

37

Built by LECO under license from Zoex Corporation

10 °C 20 °C

40 °C 80 °C

39

Carrier gas

40

Carrier gas

41

3.551300

3.5751300

3.61300

3.6251300

3.651300

3.6751300

3.71300

25000

75000

125000

175000

1st Time (s)2nd Time (s)

S2

2.65244

2.7244

2.75244

2.8244

2.85244

2.9244

10000

20000

30000

40000

50000


S2

100 Hz

60 ms

40 ms

42

1184

3.5184

2188

0.5192

3192

1.5196

0200

2.5200

1204

3.5204

10000

20000

30000

40000

50000


S2

44

1: 2,3-butanediol; 2: n-decane; 3: 1-octanol; 4: 2-ethylhexanoic acid; 5: nonanal; 6: n-undecane; 7: 2,6-dimethylphenol; 8: 2,6-dimethylaniline; 9: methyl decanoate; 10: dicyclohexylamine; 11:

methylundecanoate; 12: methyl decanoate

Constant flow Programmed flow

46

Adjustments to the modulation period usually require changes to the loop length or the carrier gas flow◦ When the loop is too short, the analyte band is not

refocused at the second cold spot (breakthrough) ◦ When the loop is too long, multiple injections from

the first cold spot could be present within the loop simultaneously (possible breakthrough, changes in 1D retention times)

47

Journal of Chromatography A, 1218 (2011) 4952– 4959

◦ Analysis of 45 FAME

http://www.chem.agilent.com/cag/prod/GC/2DGC_amj2_05_02_07D1a.pdf

48

Modulation period range limited by the fixed volume of the collecting loop◦ Too long modulation periods lead to loop

overfilling (breakthrough)Typical modulation periods ~2 s

◦ Larger loop volumes result in broader 2D peaksPossible artifacts when high concentration peaks elute

49

(A) Reverse fill/flush (RFF) modulator: flow path of fill cycle. (B) Reverse fill/flush (RFF) modulator: flow path of flush cycle.

Griffith et al., J. Chromatogr. A 1226 (2012) 116– 123

50

Griffith et al., J. Chromatogr. A 1226 (2012) 116– 12351

1D (length m × i.d. µm) 2D (length m ×

i.d. µm) Analyte/sample Reference

Poly(ethylene glycol) (21 m × 250 µm) 100% Polydimethylsilocxane (PDMS) (1 m ×

100 µm)A hydrocarbon mixture and a coal liquids sample [7]

(SolGel + poly(ethylene glycol)) composite phase (SolGel-WAX (30 m ×

250 µm)

5% Phenyl polysilphenylene siloxane (1 m × 100 µm) Roasted coffee bean volatiles [72]

Poly(ethylene glycol) (30 m × 250 µm) 5% Phenyl polysilphenylene siloxane (1 m ×

100 µm)Lipids and roasted coffee bean volatiles [73, 74]

Polyethylene glycol (TPA-treated) (30 m × 250 µm)

35% Phenyl-polysilphenylenesiloxane (1 m × 100 µm) Food analysis [75]

(5%-Phenyl)(1%-Vinyl)- methylpolysiloxane (2 m ×

100 µm)

14% Cyanopropylphenyl) methylpolysiloxane (0.5 m × 100 µm) Test mixtures [35]

100% PDMS (30 m × 250 µm) (SolGel + Poly(ethylene glycol)) composite

phase (SolGel-WAX (1.5 m × 250 µm)Volatile components of Pinotage wines [65]

100% PDMS (50 m × 530 µm) 50% Phenyl-polysilphenylene siloxane (2.2

m × 150 µm)Volatile organic compounds in urban air [76]

100% Cyclodextrin directly bonded to PDMS (10 m ×

100 µm)

(50% Liquid crystal / 50% dimethyl) siloxane column (1 m × 100 µm) PCBs in environmental samples [77]

100% PDMS (1 m × 100 µm) 14% Cyanopropylphenyl)

methylpolysiloxane (2 m × 100 µm) Essential oils [78]

Polyethylene glycol (60 m × 250 µm) (14%-Cyanopropyl-phenyl)-

methylpolysiloxane (3 m × 100 µm) Cigarette smoke condensates [79]

Poly(5%-phenyl–95%-methyl)siloxane phase (40 m ×

100 µm)

1,12-Di (tripropylphosphonium) dodecane bis (trifluoromethanesulfonyl) imide (3 m × 100 µm)

PCBs [80]

Poly(methyltrifluoropropyl siloxane) (30 m ×

250 µm)

Poly(dimethyldiphenylsiloxane) (5 m × 250 µm)

Trace biodiesel in petroleum- based fuel [81]

1D Length of BPX5 column*

Length of BP20 column*

A 20 0B 15 5C 10 10D 5 15E 0 20

D. Ryan, P. Morrison, P. Marriott, J. Chromatogr. A 1071 (2005) 47.

Typical 1D columns: 0.25 – 0.32 mm IDTypical 2D columns: 0.1 mm ID

This is not always optimal!

0.1 mm ID

0.25 mm ID

Mixture of pure compounds 1,000 x dilution

(15 m × 0.25 mm i.d) × (1.5 m × 0.1 mm i.d)

(30 m × 0.32 mm i.d) × (1.5 m × 0.18 mm i.d)

J. Beens, H. Janssen, M. Adahchour, U.A.T. Brinkman, J. Chromatogr. A 1086 (2005) 141.

Pin (KPa) 1N 2N 1ū (cm/s) 2ū (cm/s) PRopt

30 m × 0.32 mm + 1.5 m × 0.18 mm

56 86000 9000 16 64 4

88 100000 8000 24 106 5

132 98000 6500 35 140 6

15 m × 0.25 mm + 1.5 m × 0.10 mm

112 44000 15000 10 80 4

224 65000 10000 18 160 7

400 40000 4000 30 280 12

J. Beens in cooperation with www.chromedia.org, Comprehensive Two-Dimensional Gas Chromatography the State-of-Separation-Arts Theory. Part 2, 2010.

No split

35:65 split

P.Q. Tranchida, A. Casilli, P. Dugo, G. Dugo, L. Mondello, Anal. Chem. 79 (2007) 2266.

Primary – IsothermalSecondary - Isothermal

Primary – IsothermalSecondary – Temperature incremented

Primary – Temperature programmedSecondary - Isothermal

Primary – Temperature ProgrammedSecondary – Temperature Incremented

2D peaks very narrow – fast detectors requiredAt least 10 data points across a peak needed for quantitative determinations◦ Data acquisition rate of at least 50 Hz required Detectors must have low internal volume and short time constantsMost popular detectors: FID, TOF-MS

Detector Analyte/sample References

µECD

Pesticides in sediments [116-118]PCBs/OCs/CBz in soils, sediments and sludges [119, 120]Dioxins and dioxin-like PCBs in food and feed [121]Chiral toxaphenes typically found in real-life samples [122]Polybrominated diphenyl ethers [123]Polychlorinated dibenzo-p-dioxins, dibenzofurans and PCBs in food [124, 125]Chiral PCBs in food [125]PCBs in Baltic grey seals [126]Toxaphene [127]Polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and PCAs in a cod liver extract and a standard mixture [99]

NPD

Nitrogen-containing compounds in Brazilian heavy gas oil [128]

Volatile fraction of creosote-treated railway wood sleepers [129]Nanoparticles in roadside atmosphere [130]methoxypyrazines in coffee headspace [131]Fungicide residues in vegetable samples [132]Methoxypyrazines in wine [133]

SCD

Sulfur-containing compounds in straight run diesel oil [134]

Sulfur-containing compounds in heavy petroleum cuts [135]

Sulfur-containing compounds in middle distillates [136]Sulfur-containing compounds in crude oils [137]Sulfur compounds in diesel oils [138]Sulfur-containing compounds in diesel [139]

AED Sulfur-containing compounds in crude oil [140]MPDD Pyrolysis of gasoline (cracked naphtha) and pyrolysis of a polyethylene copolymer [141]

TOF-MS most popular owing to very high data acquisition rates (up to 500 Hz)Quadrupole MS slower, but can be used for qualitative work (quantitative determinations often possible with narrower mass range)HRTOF-MS very promising

Hopanes

Phenanthrenes

TIC

Sample and assistance provided by Jack Cochran and Michelle Misselwitz of Restek Corporation.Data provided by LECO Corporation using a prototype GCxGC-HRT system.

64

Hopanes

Phenanthrenes


65

Hopanes

Phenanthrenes


66

Hopanes

Phenanthrenes


67

HopanesFWHH 0.090 sec

191.179852.2 ppm error

191.179450.12 ppm error

191.17940-0.14 ppm error

191.179530.54 ppm error 191.18078

7.1 ppm error

68

FWHH 0.060 sec

191.085881.8 ppm error

191.085841.6 ppm error

191.085700.91 ppm error

191.08526-1.4 ppm error

Phenanthrenes

69

GCxGC approaches a mature status, but there is still room for improvementCareful optimization is required to reach the full potential of the techniqueGC×GC separation optimization is not as simple as in conventional 1D-GC because of the column coupling◦ any changes to the 1D column, flow rate, modulation,

oven temperature programming rate, etc., affect the separation in the 2D as well

70

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O. Panic, C. McNeish, T.N. Oldridge, A. Mostafa

◦ NSERC◦ RESTEK◦ LECO◦ SGE◦ DoE◦ Polymicro Technologies

1df 2df

2dc 1dc

1wh

Mass perModulation



1l 2l

Capacity of 2D

Capacity of 1D

2Δp 1Δp

1u 2u

2D retention

2Rs 1Rs

2wh

Allowed / Required 2D Space

Oven Programming Rate

Te

AnalysisTime

PM

1uopt

Inlet Pressure

1Δp

ΔpT

72

Journal of Chromatography A, 1255 (2012) 38–55 · Tadeusz Górecki, Ahmed Mostafa, Matthew...

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