Validation Report 21

Transcription

1 EURL for Cereals and Feeding stuff National Food Institute Technical University of Denmark Validation Report 21 Determination of pesticide residues in maize for livestock feed by GC-MS/MS and LC-MS/MS (QuEChERS method) Susan Strange Herrmann Mette Erecius Poulsen December 2016

2 Page 2 of 17 CONTENT: 1. Introduction Principle of analysis Validation design Chromatograms and calibration curves Validation parameters Criteria for the acceptance of validation results Results and discussion Conclusions References... 9 Appendix 1a. MRM transitions GC-MS/MS Appendix 1b. MRM transitions for LC-MS/MS Appendix 2. Recoveries, repeatability (RSD r ), Combined Uncertainty (Comb. U.) and Limit of Quantification (LOQ) for pesticides validated on maize for livestock feed Appendix 3: Principles of the QuEChERS method for feed extraction... 17

3 Page 3 of Introduction This report describes the validation of the QuEChERS method combined with GC-MS/MS and LC- MS/MS. The method was sought validated for 80 pesticides in maize for livestock feed (in-house standard mixture B). The QuEChERS method is an extraction method which has been developed to be Quick, Easy, Cheap, Efficient, Rugged and Safe. The method is most commonly used on fruit, vegetables and cereals Principle of analysis Sample preparation: The samples were milled with a sieve size of 1 mm. Extraction: The sample was shaken and a salt and buffer mixture was added and the sample shaken again. Clean-up: After centrifugation the supernatant was transferred to a clean tube and put in -80 degree freezer. When the extract was almost thawed it was centrifuged and the supernatant was transferred to a tube containing PSA and MgSO 4. After shaking and an additional centrifugation step the final extract was diluted 1:1 with acetonitrile to obtain the same matrix concentration as in the matrix matched calibration standards. The principle of the extraction and clean-up procedure is outlined in Appendix 3. Quantification and qualification: The final extract was analysed by GC/MS/MS and LC-MS/MS. GC-MS/MS: The pesticide residues were separated on a DB5-MS column and analysed by triple quadrupole operating in the multiple reaction monitoring mode (MRM) with electron energy at 70 ev, source temperature at 180 C and transfer line at 250 C. The injection volume was 4 µl. For each pesticide two sets of precursor and product ions were determined. One for quantification and one for qualification. The MRM transitions for the pesticides and degradation products are given in Appendix 1a. LC-MS/MS: The pesticide residues were separated on a reversed-phase column and detected by tandem mass spectrometry (MS/MS) by electrospray (ESI). The validation includes pesticides determined with both positive and negative ESI. 13 C 6 -carbaryl was used as internal standard. All pesticides were detected in the MRM mode. For each pesticide precursor ion and 2 product ions were determined. One product ion for quantification and one for qualification. The MRM transitions for the pesticides and degradation products sought validated are given in Appendix 1b.

4 Page 4 of Validation design The method was south validated for 80 pesticides or degradation products in maize (see Table 1). The validation was performed on 5-6 replicates at each of four spiking levels; 0.005, 0.01, 0.02 and 0.1 mg/kg. A blank sample of maize was included in each analytical batch. Table 1. Pesticides included in the recovery experiments. Pesticides included in recovery experiments Acetamiprid EPN Iprovalicarb Phoxim Acrinathrin Ethoprophos Isofenphos methyl Profenofos Aldicarb Etofenprox Lufenuron Propargit Aldicarb sulfon Fenamiphos Mepanipyrim Propyzamide Bitertanol Fenamiphos sulfoxide Methamidophos Prothiofos Bromopropylate Fenamiphos sulfone Methidathion Pyridaben Bromuconazole Fenarimol Methiocarb Pyriproxyfen Bupirimate Fenazaquin Methiocarb sulfone Spinosyn A Buprofezin Fenoxycarb Methiocarb sulfoxide Spinosyn D Cadusafos Fenpropathrin Monocrotophos Spirodiclofen Carbendazim Fenthion Myclobutanil Tau Fluvalinate Chlorfenapyr Fenthion oxon Oxadixyl Tebufenpyrad Chlorobenzilate Fenthion oxon sulfon Oxamyl Tefluthrin Clofentezine Fenthion oxon sulfoxid Paraoxon methyl Tetraconazole Dicloran Fenthion sulfone Parathion methyl Tetradifon Dimethomorph Fenthion sulfoxide Pencycuron Thiabendazole Diphenylamine Flufenoxuron Phenthoate Tolclofos methyl DMF Fosthiazate Phosalone Tolylfluanid DMPF Hexythiazox Phosmet Triflumuron DMST Indoxacarb Phosmet oxon Zoxamide 4. Chromatograms and calibration curves The calibration curves were based on at least 4 calibration levels, i.e , 0.01, and 0.1 µg/ml. The calibration curves were in general best fitted to a linear curve. The quantification was performed from the mean of two bracketing calibration curves. The majority of the correlation coefficients (R) were higher or equal to Examples of chromatograms and calibration curves obtained when analysing extracts by GC-MS/MS and LC-MS/MS are presented in Figure 1-2 and Figure 3-4, respectively.

5 Page 5 of st10 Smooth(Mn,2x2) 6. EUPT-CF 9 Spk ppm C Diphenylamine;9.73; ;35006 F1:MRM of 6 channels,ei+ 169> e+004 % st10 Smooth(Mn,2x2) 6. EUPT-CF 9 Spk ppm C 100 Diphenylamine;9.73; ;29917 min F1:MRM of 6 channels,ei+ 168> e+004 % Figure 1: Examples of GC-MS/MS chromatograms for diphenylamine in maize for livestock feed obtained when analysing extract of sample spiked with mg/kg (Quantifier and qualifier MRM transitions are shown). min _13 Smooth(SG,1x2) 6. EUPT-CF 9 spk ppm C 99 % Lufenuron F8:MRM of 8 channels,es+ 511 > e min _13 Smooth(SG,1x2) 6. EUPT-CF 9 spk ppm C 99 % Lufenuron F8:MRM of 8 channels,es+ 511> e min Figure 2: Examples of LC-MS/MS chromatograms lufenuron in maize for livestock feed obtained in positive mode when analysing extract of sample spiked with mg/kg (Quantifier and qualifier MRM transitions are shown).

6 Page 6 of 17 Compound name: Diphenylamine Correlation coefficient: r = , r^2 = Calibration curve: e+006 * x Response type: External Std, Area Curve type: Linear, Origin: Exclude, Weighting: 1/x, Axis trans: None Response ug/ml Figure 3. Examples of GC-MS/MS calibration curves for diphenylamine matrix matched with maize for livestock feed (concentrations from µg/ml) Compound name: Lufenuron Correlation coefficient: r = , r^2 = Calibration curve: * x Response type: Internal Std ( Ref 1 ), Area * ( IS Conc. / IS Area ) Curve type: Linear, Origin: Exclude, Weighting: 1/x, Axis trans: None Response Conc Figure 4. Examples of LC-MS/MS calibration curves for lufenuron matrix matched with maize for livestock feed (concentrations from µg/ml).

7 Page 7 of Validation parameters Precision repeatability Repeatability was calculated for all pesticides and degradation products on four spiking levels (0.005, 0.01, 0.02 and 0.1 mg/kg). Repeatability is the relative standard deviation on the results from two or more analysis of replicate samples, prepared by the same technician, on the same instrument and within a short period of time. Repeatability (RSD r ) in this validation was calculated from the 5-6 replicate determinations as given in ISO Accuracy Recovery The accuracy was determined from recovery studies in which samples were spiked at three levels (0.005, 0.01 mg/kg, 0.02 and 0.1 mg/kg) with the relevant pesticides, isomers and degradation products. Robustness The QuEChERS method has, in connection with the development of the method, been shown to be robust by Anastassiades et al Limit of quantification, LOQ The quantification limits (LOQ) was determined as the lowest spike level for which the acceptance criteria (se Section 6) were meet. The obtained results including recovery, RSD r, quantification (LOQ), are presented in Appendix 2. combined uncertainty (U c ) and limit of 6. Criteria for the acceptance of validation results For the pesticides to be accepted as validated the following criteria for precision and trueness must to be fulfilled: 1. The relative standard deviation of the repeatability should be 20% The average relative recovery must be between 70 and 120% 3. If the above mentioned criteria have been meet, the quantification limits, LOQs is stated. The combined uncertainty given by: U c =

8 Page 8 of 17 Where Bias is the measurement uncertainty of the method (100 - Recovery (%)) and RSD is the standard deviation on the bias or recovery. 7. Results and discussion Overall validation All 80 compounds included in the study were possible to validate using QuEChERS combined with GCMSMS or LCMSMS. 35 compounds were possible to validate using GCMSMS and 52 using LCMSMS and thus seven of the compounds where possible to validate using both LCMSMS and GCMSMS. Of the 35 compounds amenable to GCMSMS a LOQ of mg/kg was obtained for 31 compounds and a LOQ of 0.01 mg/kg for 4 compounds. For 6 of the GCMSMS amenable compounds the results needs to be corrected for recovery in order to obtain acceptable precision. Of the 52 compounds amendable to LCMSMS a LOQ of mg/kg were obtained for 39 compound, and a LOQ of 0.01 mg/kg for 8 compounds, LOQ of 0.02 mg/kg for two compounds and an LOQ of 0.1 mg/kg for the last three compounds. For 13 of the LCMSMS amenable compounds the results needs to be corrected for recovery in order to obtain acceptable precision (see Appendix 2). Low recoveries were found for fenamiphos sulfoxide and oxadixyl (51-56%). The validation data was accepted despite these low recoveries, because the recovery was at the same low level for all spike levels and the standard deviation on the results were acceptable. 8. Conclusions In conclusion 80 pesticides were successfully validated on maize for livestock feeding using the QuEChERS method and GC-MS/MS or/and LC-MS/MS. LOQs at mg/kg were obtained for 64 of the 80 compounds.

9 Page 9 of References 1 EN 15662:2008. Foods of plant origin - Determination of pesticide residues using GC-MS and/or LC-MS/MS following acetonitrile extraction/partitioning and clean-up by dispersive SPE - QuEChERS-method 2 ISO :1994. Accuracy (trueness and precision) of measurement methods and results Part2. Basic method for the determination of repeatability and reproducibility of standard measurement method. First edition. December Guidance document on analytical quality control and method validation procedures for pesticides residues analysis in food and feed. Document No SANTE/11945/2015, 01/01/2016. Published by European Commission Directorate-General for health and food safety.

10 Page 10 of 17 Appendix 1a. MRM transitions GC-MS/MS. GC-MS/MS Retention time Precursor ion-1 Product ion-1 CE Precursor ion-2 Product ion-2 CE Acrinathrin Acrinathrin Bitertanol Bromopropylate Bromuconazole Bromuconazole Cadusafos Chlorfenapyr Chlorobenzilate Clofentezine Dicloran Diphenylamine EPN Fenamiphos Fenarimol Fenpropathrin Fenthion Flufenoxuron Fosthiazate Indoxacarb Isofenphos-methyl Mepanipyrim Methidathion Monocrotophos Myclobutanil Oxadixyl Parathion-methyl Pencycuron

11 Page 11 of 17 GC-MS/MS Retention time Precursor ion-1 Product ion-1 CE Precursor ion-2 Product ion-2 CE Phenthoate Phosalone Profenofos Propyzamide Prothiofos Tau-Fluvalinate Tau-Fluvalinate Tefluthrin Tetraconazole Tetradifon Tolclofos-methyl Tolylfluanid

12 Page 12 of 17 Appendix 1b. MRM transitions for LC-MS/MS. LC-MS/MS Retention time Precurso r ion-1 Product ion-1 CV CE Precurso r ion-2 Product ion-2 Acetamiprid Acrinathrin Aldicarb Aldicarb sulfon Bitertanol Bupirimat Buprofezin Cadusafos Carbendazim Clofentezine Dimethomorph 16.73/ Diphenylamine DMF (N-2,4-dimethylphenylformamide) DMPF (2.4 dimethylphenyl-n-methylformamidine) DMST (dimethylaminosulfutoluidide) Ethoprophos Etofenprox Fenamiphos Fenamiphos sulfone Fenamiphos sulfoxide Fenazaquin Fenoxycarb Fenthion Fenthion oxon Fenthion oxon-sulfon Fenthion oxon-sulfoxid Fenthion sulfone Fenthion sulfoxide CV CE

13 LC-MS/MS Retention time Page 13 of 17 Precurso r ion-1 Product ion-1 CV CE Precurso r ion-2 Product ion-2 Flufenoxuron Hexythiazox Iprovalicarb Lufenuron Lufenuron Mepanipyrim Methamidophos Methiocarb Methiocarb sulfone Methiocarb sulfoxide Monocrotophos Oxadixyl Oxamyl Paraoxon-methyl Phosmet Phosmet oxon Phoxim Propargit Pyridaben Pyriproxyfen Spinosyn A Spinosyn D Spirodiclofen Tebufenpyrad Thiabendazole Tolylfluanid Triflumuron Zoxamide CV CE

14 Page 14 of 17 Appendix 2. Recoveries, repeatability (RSD r ), Combined Uncertainty (Comb. U.) and Limit of Quantification (LOQ) for pesticides validated on maize for livestock feed. Numbers in italic is outside % recovery or above 20% RSD Spike level mg/kg Spike level mg/kg Spike level mg/kg Spike level mg/kg Recovery % RSDr, % U c Recovery % RSDr, % U c Recovery % RSDr, % U c Recovery % RSDr, % U c LOQ Reco -very corr. LC Acetamiprid No GC Acrinathrin No LC Aldicarb Yes LC Aldicarb sulfon No GC Bitertanol No LC Bitertanol Yes GC Bromopropylate No GC Bromuconazole No LC Bupirimate No LC Buprofezin No GC Cadusafos No LC Cadusafos No LC Carbendazim Yes GC Chlorfenapyr No GC Chlorobenzilate No GC Clofentezine No GC Dicloran No LC Dimethomorph No GC Diphenylamine No LC DMF No LC DMPF No LC DMST No GC EPN No LC Ethoprophos No LC Etofenprox Yes GC Fenamiphos No LC Fenamiphos No

15 Page 15 of 17 LC Fenamiphos sulf one No LC Fenamiphos sulfoxide Yes GC Fenarimol No LC Fenazaquin No LC Fenoxycarb No GC Fenpropathrin No GC Fenthion No LC Fenthion No LC Fenthion oxon No Fenthion oxonsulfon LC response not detectable No Fenthion oxonsulfoxid LC No LC Fenthion sulfone No LC Fenthion sulfoxide No GC Flufenoxuron No LC Flufenoxuron Yes GC Fosthiazate Yes LC Hexythiazox No GC Indoxacarb Yes LC Iprovalicarb No GC Isofenphos-methyl Yes LC Lufenuron No GC Mepanipyrim No LC Mepanipyrim No LC Methamidophos Yes GC Methidathion Yes LC Methiocarb No LC Methiocarb sulfone Yes Methiocarb LC sulfoxide No LC Monocrotophos No GC Myclobutanil No GC Oxadixyl No LC Oxadixyl Yes LC Oxamyl No

16 Page 16 of 17 LC Paraoxon-methyl response smaller than lowest calibration Yes GC Parathion-methyl No GC Pencycuron No GC Phenthoate No GC Phosalone No LC Phosmet Yes LC Phosmet oxon No LC Phoxim No GC Profenofos Yes LC Propargite No GC Propyzamide Yes GC Prothiofos No LC Pyridaben Yes LC Pyriproxyfen No LC Spinosyn A No LC Spinosyn D No LC Spirodiclofen No GC Tau-Fluvalinate No LC Tebufenpyrad No GC Tefluthrin No GC Tetraconazole No GC Tetradifon No LC Thiabendazole Yes GC Tolclofos-methyl No LC Tolylfluanid response not detectable No LC Triflumuron No LC Zoxamide No

17 Page 17 of 17 Appendix 3: Principles of the QuEChERS method for feed extraction QuEChERS for cereals (FP417) Weigh 5 g (±0.05 g) of flour into a 50 ml single use centrifuge tube (red cap). Add internal standard and/or spike standard (maximum 25 µl) Add a ceramic homogenizer and 10 g of cold water and shake briefly Add 10 ml acetonitrile and shake vigorously by hand for 1 min. (1. extraction) Add the prepared mixture of 4 g MgSO 4, 1 g NaCl, 1 g Na 3 citrate dihydrate and 0.5 g Na 2 H cirate sesquihydrate. Shake for a few seconds after each addition to prevent lumps. Shake vigorously for 1 min. (2. Extraction with phase separation) Centrifuge for 10 min at 4500 rpm Transfer at least 8 ml of the extract to a 15 ml single use centrifuge tube and store in the freezer (-80 C for 1 hour or over night). When the extract are almost thawed (i.e. About -40 C) centrifugate (should be cold 5 C) for 5 min. at 4500 rpm. Transfer 6 ml of the cold extract to a 15 ml single use centrifuge tube containing 150 mg PSA and 900 mg MgSO 4. Close the tube and shake vigorously for 30 seconds. Centrifuge for 5 min. at 4500 rpm Transfer 4 ml of the extract to a 15 ml single use centrifuge tube. Add 40 l of 5% formic acid solution in acetonitrile (10 l/ml extract). Dilute the extract 1:1 with acetonitrile Transfer the final extract into auto sampler vials and analyse by GC and LC.