Pang et al.: J ournal of AOAC I nternational V ol. 98, N o. 5, 2015  1431

Figure 1. Number of blank, fortified, incurred, and aged samples for the collaborative study. (Fortified samples are designed per principle of blinds duplication).

( i ) R 2 for each of the 20 pesticides based on at least a five point matrix-matched calibration standard curve shall be greater than 0.995 for GC/MS, GC/MS/MS, or LC/MS/MS ( ii ) Recoveries shall fall within 70–120% with RSD <15% ( n = 5) ( iii ) Ion abundance of the targeted pesticides should be in accordance with recommended maximum permitted tolerances of AOAC guidelines or the EU regulation (EU Document No. SANCO/10684/2009 Method validation and QC procedures for pesticide residues analysis in food and feed and ISO 34) [ Note : If ≥30% of the data generated in a laboratory for recovery, RSD, ion abundance, or R 2 values fail the acceptance criteria, then the laboratory is considered nonproficient in the use of the method, and data generated from the laboratory are excluded from the final analysis and interpretation of the data generated for the collaborative study.] (b)  System suitability check.— Before making determinations of each consignment sample, use QC standard working solutions supplied by the Study Director to check the sensitivity and stability of the instrument. ( 1 )  Instrumental sensitivity (calculated per internal standard reference S/N) .—GC/MS >500, GC/MS/MS >1000, and LC/MS/MS >500. ( 2 )  Instrumental stability (calculated per internal standard peaks) .—Retention time deviation <3% (two successive injections); peak area deviation <10% (two successive injections). ( 3 ) GC/MS, GC/MS/MS, and LC/MS/MS instruments must all be equipped with a data processing software system. (c)  Reagent blank and pesticide residue-free (blank sample) test .—Confirm that there are no interference peaks from reagents by running a reagent blank test of the whole process. Run the reagent blank sample the same as described in the Collaborative Study Method without adding the sample. (d)  Calibration check.— Prepare a five-point matrix-matched standard calibration curve with internal standard. The R 2 for the calibration curve must be ≥0.995.

AOAC Official Method 2014.09 Determination and Confirmation of Residues of 653 Multiclass Pesticides

and Chemical Pollutants in Tea GC/MS, GC/MS/MS, and LC/MS/MS First Action 2014

Forty representative pesticides were selected based on guidance from the AOAC Method-Centric Committee on Pesticide Residues to conduct a multilaboratory validation study of the single-laboratory validated (SLV) method using two representative brands of tea. The representative pesticides selected for the multilaboratory validation study of the SLV method are as follows: 2,4′-DDE, 4,4′-DDE, benalaxyl, bifenthrin, bromophos-ethyl, bromopropylate, chlorfenapyr, diflufenican, dimethenamid, fenchlorphos, picoxystrobin, pirimicarb, pirimiphos-methyl, procymidone, propyzamide, pyrimethanil, quinoxyfen, tefluthrin, tolclofos-methyl, and trifluralin by GC/MS and GC/MS/MS; and acetochlor, benalaxyl, bensulide, butralin, chlorpyrifos, clomazone, diazinon, ethoprophos, flutolanil, imidacloprid, indoxacarb, kresoxim-methyl, monolinuron, picoxystrobin, pirimiphos- methyl, propoxur, quinoxyfen, tebufenpyrad, triadimefon, and trifloxystrobin by LC/MS/MS. LOQs for the 653 pesticides included in the SLV ranged from 0.03 to 1210 μg/kg. LODs of the GC/MS method ranged from 1.0 to 500 μg/kg, and the corresponding LOQs ranged from 2.0 to 1000 μg/kg. LODs of the GC/MS/MS method ranged from 1.0 to 900 μg/kg, and the corresponding LOQs ranged from 2.0 to 1800 μg/kg. LODs of the LC/MS/MS method ranged from 0.03 to 4820 μg/kg, and the corresponding LOQs ranged from 0.06 to 9640 μg/kg. A total of 482 of the 653 pesticides can be analyzed by GC/MS and GC/MS/MS, while 417 of the 653 pesticides can be analyzed by LC/MS/MS with LODs ≤100 μg/kg. There are 264 out of the 653 pesticides that can be analyzed by GC/MS, and 325 out of 653 by LC/MS/MS with LODs ≤10 μg/kg. There are 270 pesticides that can be analyzed by both GC/MS and LC/ MS/MS. Of these, there are 264 pesticides that can be analyzed by GC/MS and 247 by LC/MS/MS, with LODs ≤100 μg/kg for the GC/MS method. There are, however, 133 pesticides that can be analyzed by GC/MS and 200 by LC/MS/MS, with LODs ≤10 μg/kg.

Made with FlippingBook flipbook maker