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Intensity x 10,000

Results and discussion

The matrix effect study revealed that the percentages of pesticides withirrelevant matrix effect (suppression lower than 20 %) was 99 % in tomato,87 % in orange and 62 % in leek, whereas significant suppression (higherthan 50 %) was not found in tomato and only 1 % of the compounds inorange and 3 % in leek (Figure 4). These results compare favorably withthat typically obtained in LC–MS/MS.

Figure 4: Matrix-effect (164 pesticides).

The absence of water in the mobile phase also provided some importantadvantages regarding LC–MS/MS as (i) higher retention of polarcompounds in the column, which elute with high sensitivity and good peakshape and (ii) a general increase of the sensitivity of the analysis,consequence of the high ionization and ion extraction efficiency (Figure 3).Pesticides evaluated were identified following the SANTE/11813/2017. Atthe spiking concentration of 5 μg/kg, 98 % of the pesticides were identified intomato, 98 % in orange and 94 % in leek, whereas for the concentration of10 μg/kg all the compounds were identified in tomato and only spiromesifenwas not identified in orange and leek. At the concentration of 20 μg/kg,spiromesifen was also identified in these two matrices. The linearity andreproducibility of the method were evaluated with results which guaranteehigh quality in the analytical measurements. Even though only 2 μL of finalextract were injected, the sensitivity of the SFC method was enough toachieve stringent LOQs. Real samples, including 6 different fruits andvegetables, were analyzed by the SFC-MS/MS proposed method, theresults being similar to those obtained by LC–MS/MS.

Figure 5: 164 pesticides spiked at the default MRL of 0.01 mg/kg (orange matrix).Quantifier ion is shown.

Conclusion

Carbon dioxide as mobile phase with methanol as modifier can represent agood alternative to LC-MS/MS with reduction of matrix effects and shorterrun times.

Reference

V. Cutillas, M. M. Galera, Ł. Rajski, A. R. Fernández-Alba, J. Chrom. A, 2018,1545, 67-74

Last eluting compound at 7.19 min

Polar compounds

Introduction

Supercritical fluid chromatography coupled to triple quadrupole massspectrometry (SFC-MS/MS, Nexera UC with LCMS-8060, ShimadzuCorporation, Kyoto, Japan) has been evaluated for pesticide residues infood. In order to check its advantages and limitations it was developed amethod to identify and quantify 164 pesticides in three different matrices(tomato, orange and leek).

Materials and Methods

A carbon dioxide gradient with methanol (containing 1 mM ammoniumformate) was used allowing a flow rate of 1.5 mL/min that made the total runtime of 12 min without any problem of overpressure. Addition of a postcolumn flow 150 μL/min of methanol with ammonium formate / formic acidwas necessary to improve the ionization (Figure 2).

Figure 1: Top: Shimadzu Nexera UC with triplequadrupole massspectrometer Shimadzu LCMS-8050. Bottom: LC/SFC-MS/MS switchingsystem for automatic change between LC- and SFC-MS/MS.

Figure 2: SFC-MS/MS conditions and system configuration

Figure 3: Examples of some compounds that increase their sensitivity usingSFC-MS/MS. 100 µg/kg tomato.

Evaluation of supercritical fluid chromatography coupled to tandem mass spectrometry for pesticide residues in foodV. Cutillas1, M. M. Galera1, Ł. Rajski1, A. R. Fernández-Alba1

European Union Reference Laboratory for Pesticide Residues in Fruit & Vegetables (EURL-FV), University of Almeria, Agrifood Campus of International Excellence (ceiA3) Department of Hydrogeology and Analytical Chemistry, Almería/ES

HPLC system

LC/SFC switching system

SFC system

Injection volume: 2 µL

40 ºC

BPR pressure: 150 barBPR Temperature: 50 ºC

MeOH 1 mM HCOONH4

MeOH 5 mM HCOONH4 0.1 % HCOOH

ESIpolarity:

positive and negative

FLOW 1.5 mL/min

CO2

pump

Modifierpump

LCMS-8060

Modifier solventCO2

cylinder

Column ovenAutosampler

Backpressure regulator

2,4-DFluazifop MCPA

RT: 5.568 min

SFC LCSFC LC SFC LC

RT: 3.741 min RT: 5.036 minRT: 7.343 minRT: 7.494min RT: 7.481 min

8,2x104 8,2x1041,7x105 1,7x105 5,9x104 5,9x104

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

0 50 100 150 200 250 300 350 400 450 500

Tomato Orange Leek

Carbaryl

Proquinazid

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Nu

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er

of

pe

sti

cid

es

wit

h io

n s

up

pre

ss

ion

Ion suppression

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2000000

4000000

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10000000

12000000

0 50 100 150 200 250 300 350 400 450 500

Tomato Orange Leek0-20 % 20-50 % >50 %

Tomato

Orange

Leek