This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Rapid Multiresidue Pesticides Analysis Using Fast-GC/MS and Chromatogram
Deconvolution Software
Richard Whitney1, Charles R. Lyle1, Haruhiko Miyagawa2, Keisuke Matsuda2, Katsuhiro Nakagawa2
1Shimadzu Scientific Instruments, Columbia, MD; 2Shimadzu Corporation, Kyoto, Japan
IntroductionGC/MS methods for pesticide residue analysis in food are commonly used for regulatory monitoring because fast pesticide determination is frequently required. Although fast-GC/MS is one of the methods of choice for increasing efficiency, the chromatographic separation using this technique is not as complete compared with conventional GC/MS.
Confirmation of target compounds in samples with complex matrices such as food is often very difficult because target compound peaks are often masked by co-eluting matrix background peaks of much higher intensity. In order to identify the target compound peaks in such complex matrices, deconvolution software was applied to data obtained using fast-GC/MS.
More than 100 pesticides were added to real samples and analyzed using fast-GC/MS. The data were processed by chromatogram deconvolution software to obtain mass chromatograms free from co-eluting compounds; the deconvolved mass chromatograms were then used for quantitative analysis. Fast-GC/MS coupled with chromatogram deconvolution software significantly shortened the analysis time and indicated accurate results for food samples with complex matrices.
Experimental
Shimadzu GCMS-QP2010 with GCMSsolution
Auto-injector: AOC-20i and AOC-20s, (Shimadzu) Column: DB-5MS 30m, 0.25mm ID, 0.25um, (J&W) Guard column: Deactivated tubing 2m, 0.25mm ID (J&W)Connector: Press-tight connector (Restek) Standards: Pesticides standard mixture #21,#22 (Kanto Chemical)Deconvolution Software: ‘IST for GC/MS’, Ion Signature Technology, Inc.
Analytical ConditionsGas Chromatograph GC-2010Injection Mode: SplitlessGlass Liner: Deactivated glass liner with glass wool (Restek)Inlet Temperature: 250ºCFlow Control Mode: Constant Linear Velocity (47.2 cm/sec)Temperature Program: 50ºC(1min)-(40ºC/min)-200ºC-(20ºC/min) - 300ºC
The target compounds are all regulated pesticides in Japan. These compounds are commonly analyzed by the GC/MS multiresidue method.
Chromatogram
Fast-GC/MS Total Ion Chromatogram (0.1µg/mL)
Using conventional conditions, the pesticides eluted in 4.48min (Methamidophos) to 13.60min (Imibenconazole). Total analysis time was 30min., including column bake time. All pesticides of 0.1 µg/mL concentration were readily detected in the full-scan mode.
Six pesticides eluted between 7.4 and7.5 min, and the TIC shows overlapping chromatograms. By selecting the appropriate target ion and reference ions, these pesticide peaks were readily resolved. The mass chromatograms were used for quantitative analysis and accurate identifications were made possible using ion ratios.
Abundance of pesticide in real sample Abundance of pesticide in STD
x 100
To evaluate the quantitative results for the fast-GC/MS’s multiresidue simultaneous analysis, the peak abundance obtained by the analysis of pesticides, which were added in the real sample, was compared with the peak abundance obtained by the analysis of the same concentration standard sample. The data were processed using GCMSsolution software with ‘IST for GC/MS’ deconvolution software.
Quantitative Evaluation 1
0 50 100 150 200 250 300
M ethamidophos
DDVP(Dichlorvos)
EPTC
Butylate
Acephate
M IPC(Isoprocarb)
BPM C(Fenobucarb)
Ethoprophos
IPC(Chlorpropham)
Bendiocarb
Cadusafos
alpha-BHC
Thiometon
beta-BHC
Dimethipin
gamma-BHC
Terbufos
Diazinon
Tefluthrin
Etrimfos
delta-BHC
Pirimicarb
Ethio fencarb
Benfuresate
Parathion-methyl
To lclophos-methyl
NAC(Carbaryl)
P irimiphos-methyl
M EP(Fenitro thion)
M ethiocarb
Dichlofluanid
Esprocarb
M alathion
M eto lachlor
Chlorpyrifos
Thiobencarb
Dimethylvinphos
Diethofenccarb
M PP(Fenthion)
GCMSsolutionIST for GC/ MS
0 50 100 150 200 250 300
Parathion
Isofenphos P=O
dicofo l deg.
Fosthiazate-1
Fosthiazate-2
PendimethalinCVP(Chlorfenvinp
hos)-EPyrifenox-Z
IsofenphosCVP(Chlorfenvinp
hos)-ZPAP(Phenthoate)
Quinalphos
Captan
Triadimenol-1
Triadimeno l-2
Chinomethionat
Pyrifenox-E
Pacrobutrazo l
Fluto lanil
Prothiophos
Tricyclazole
Pretilachlor
p,p'-DDE
M yclobutanil
Flusilazole
Cyproconazo le
Chlorobenzilate
Fensulfothion
p,p'-DDD
M epronil
Propiconazole-1
EDDP(Edifenphos)
Propiconazo le-2
Lenacil
Thenylchlor
Tebuconazo le
Acetamiprid
EPN
GCMSsolutionIST for GC/ MS
0 50 100 150 200 250 300 350
Tebufenpyrad
PhosalonCyhalo thrin-1
Pyriproxyfen
M efenacet
Cyhalothrin-2Acrinathrin
Fenapanil
Pyraclofos
Bitertano l-1Permethrin-1
Bitertanol-2
Permethrin-2
PyridabenCyfluthrin-1
Cyfluthrin-2
Cyfluthrin-3,4
Cypermethrin-1
Halfenprox
Cypermethrin-2
Cypermethrin-3,4
Flucythrinate-1
Flucythrinate-2
Silafluofen
Pyrimidifen
Fenvalerate-1
Fluvalinate-1
Fluvalinate-2
Fenvalerate-2
Difenoconazole-1
Difenoconazole-2
Deltamethrin
Imibenconazo le
GCMSsolutionIST for GC/ MS
The ratio of 100% is the theoretical value, but most ratios were greater than 100% . This was attributed to a matrix effect. The pesticides indicated by red arrows showed a ratio of over 200% using only GCMSsolution (without deconvolution) processing; this anomaly was due to co-eluting compounds overlapping. Using deconvolutionprocessing, the overlapping was eliminated and the pesticides were selectively detected accurately.
Mass Chromatogram Integration
7.65 7.70 7.750.00
0.25
0.50
0.75
1.00
1.25
1.50 (x10,000)
283.00199.00195.00
10.7 10.8 10.90.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0(x1,000)
226.00165.00206.00
6.85 6.90 6.95 7.00
2.5
5.0
7.5
10.0
(x10,000)
168.00108.00107.00
10.75 10.80 10.85 10.90 10.950.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
(x1,000)
226.00165.00206.00
7.60 7.65 7.70 7.750.00
0.25
0.50
0.75
1.00
1.25
(x10,000)
283.00199.00195.00
6.85 6.90 6.95 7.000.00
0.25
0.50
0.75
1.00
1.25
1.50
(x100,000)
168.00108.00107.00
Ethiofencarb Fosthiazate-1 Cyfuluthrin-3,4
Ethiofencarb Fosthiazate-1 Cyfuluthrin-3,4
Ethiofencarb Fosthiazate-1 Cyfuluthrin-3,4
Standard Chromatogram
Target Compound Chromatograms in Carrot Matrix
Deconvolved Mass Chromatograms in Carrot Matrix Using IST for GC/MS Software
Interference by the Matrix
Orange Peel (ENVI-Carb/LC-NH2 SPE cleanup)
5.0 7.5 10.0 12.5 15.0 17.5
1.0
2.0
3.0
4.0
(x1,000,000)
5.0 7.5 10.0 12.5 15.0 17.5
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0(x10,000,000)
TIC
Total ion chromatogram of orange peel extract sample
Overlaid total ion chromatogram with analytical standard (0.1µg/mL)
Abundance of pesticide in real sample Abundance of pesticide in STD x 100
0 100 200 300 400
ParathionIsofenphos P=O
dicofo l deg.Fosthiazate-1
Fosthiazate-2Pendimethalin
CVP(Chlorfenvinphos)-EPyrifenox-Z
IsofenphosCVP(Chlorfenvinp
hos)-ZPAP(Phenthoate)
Quinalphos
Captan
Triadimenol-1
Triadimenol-2
Chinomethionat
Pyrifenox-E
Pacrobutrazol
Fluto lanilPro thiophos
Tricyclazo lePretilachlor
p,p'-DDEM yclobutanil
Flusilazo leCyproconazo le
ChlorobenzilateFensulfothion
p,p'-DDD
M epronil
Propiconazole-1
EDDP(Edifenphos)
Propiconazo le-2
Lenacil
Thenylchlor
Tebuconazo le
AcetamipridEPN
GCMSsolutionIST for GC/ MS
0 50 100 150 200 250 300
M ethamidophos
DDVP(Dichlorvos)
EPTCButylate
Acephate
M IPC(Isoprocarb)BPM C(Fenobucarb)
Ethoprophos
IPC(Chlorpropham)Bendiocarb
Cadusafos
alpha-BHCThiometon
beta-BHC
Dimethipingamma-BHC
Terbufos
DiazinonTefluthrin
Etrimfos
delta-BHCPirimicarb
Ethio fencarb
BenfuresateParathion-methyl
Tolclophos-methyl
NAC(Carbaryl)P irimiphos-methyl
M EP(Fenitro thion)
M ethiocarbDichlo fluanid
Esprocarb
M alathionM eto lachlor
Chlorpyrifos
ThiobencarbDimethylvinphos
Diethofenccarb
M PP(Fenthion)
GCMSsolutionIST for GC/ MS
0 100 200 300 400
TebufenpyradPhosalon
Cyhalothrin-1Pyriproxyfen
MefenacetCyhalothrin-2
AcrinathrinFenapanil
PyraclofosBitertanol-1
Permethrin-1Bitertanol-2
Permethrin-2Pyridaben
Cyfluthrin-1Cyfluthrin-2
Cyfluthrin-3,4Cypermethrin-1
HalfenproxCypermethrin-2Cypermethrin-
3,4Flucythrinate-1Flucythrinate-2
Silaf luofenPyrimidifen
Fenvalerate-1Fluvalinate-1Fluvalinate-2
Fenvalerate-2Difenoconazol
e-1Difenoconazole-2
DeltamethrinImibenconazole
GCMSsolutionIST for GC/ MS
Quantitative Evaluation 3
7.60 7.65 7.70 7.750.0
0.5
1.0
1.5
2.0
2.5
3.0
(x10,000)
283.00199.00195.00
10.45 10.50 10.55 10.600.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
(x10,000)
309.00148.00147.00
11.0 11.1 11.20.0
2.5
5.0
7.5
10.0(x1,000)
181.00165.00163.00
7.5 7.6 7.7 7.80.00
0.25
0.50
0.75
1.00
(x10,000)
283.00199.00195.00
10.45 10.50 10.55 10.60 10.650.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0(x10,000)
309.00148.00147.00
10.9 11.0 11.10.0
1.0
2.0
3.0
4.0
5.0
6.0
(x1,000)
181.00165.00163.00
Mass Chromatogram Integration
Standard Chromatogram
Target Compound Mass Chromatograms in Cabbage Matrix
Deconvolved Mass Chromatograms in Cabbage Matrixusing IST for GC//MS Software
Interference by the Matrix
Fosthiazate-1 Pyridaben Cypermethrin-3,4
Fosthiazate-1 Pyridaben Cypermethrin-3,4
Fosthiazate-1 Pyridaben Cypermethrin-3,4
Screening of PesticidesUsing IST software for GC/MS, chromatograms were reconstructed for the target pesticides’identification. The reconstructed ion chromatograms showed clear positive detection in samples with very complex matrices. The six pesticides whose retention times were very close were easily and clearly identified.
Cabbage Sample
reconstructed chromatogram
Conclusions• Analytical productivity is significantly increased by fast-GC/MS. More
than 100 pesticides are detected with a 15-minute GC/MS run.• By selecting appropriate ions, overlapping pesticide peaks can be easily
resolved. Each pesticide was identified clearly and accurately using ion ratios.
• The GCMS-QP2010 could detect low-level pesticides in the full-scan mode. Accurate qualitative analysis was possible using the GCMSsolution workstation for samples employing the SPE cleanup sample (carrot, orange peel) and the untreated sample extracts (cabbage).
• For some pesticides, the chromatographic peaks were overlapped by the co-eluting peaks from the sample matrix, which affected the quantitative results. IST deconvolution software was effective in decreasing the interferences and producing accurate results.