Pesticide Residue Methods

Category Others
Class Name Pesticide Specific Enforcement Method, Abamectin and Avermectins
Method Title HPLC-Fluorescence Determination for Avermectin B1 and 8,9-Z-Avermectin B1 in Pears and Apples
Method Date 1992/12/14
Method Type Quantitative
Scope and Application Analysis for Avermectin B1 and 8,9-Z-Avermectin B1 Analysis of apple and pear Can be used with minor modifications for most crop matrices HPLC - Fluorescence Analysis and Detection.
Method Summary Ten gram pear or apple samples are treated with pectinase. The pectinase hydrolyzes the pectin (polygalacturonic, acid, MW. 30 - 300K) making the sample soluble in the extraction solvent. Residues of avermectin B1 and 8,9-Z-avermectin B1 are extracted from the hydrolyzed apple or pear homogenate by blending with 50:50 acetonitrile/water. The extract is filtered and made more aqueous by the addition of water. The aqueous solution is passed through a C-8 column, loading the avermectins onto the column. The eluant is discarded and the avermectins are eluted with a small volume of acetonitrile. The acetonitrile is concentrated and water is added to the acetonitrile. The aqueous acetonitrile is extracted with hexane three times, removing the avermectins from the aqueous acetonitrile. The hexane extracts are combined and loaded onto an aminopropyl column, which retains the avermectins. The hexane eluant is discarded. The column is washed with hexane, toluene, and methylene chloride and the avermectins are eluted with 50:50 acetone:methylene chloride. This eluant is evaporated to dryness and the residue is dissolved and diluted to 10 mL using methylene chloride. The sample is split, evaporated to dryness and a fluorescent derivative is formed by reaction with a mixture of N,N-dimethylformamide, trifluoroacetic anhydride and 1-methylimidazole (Reagent A-1) for 1 hour at 30 C, followed by reaction with methanolic ammonium hydroxide (Reagent A-2) for 1/2 hour at 30 C. The reaction mixture is dissolved in chloroform and passed through a silica gel column for separation of the derivatized residue from the derivatization reagents. The eluant is taken to dryness and dissolved in methanol. The derivatized residue is determined by reversed-phase liquid chromatography with fluorescence detection. As derivatization of 8,9-Z avermectin B1 produces the same derivative as avermectin B1, the derivatized residue quantitated represents the sum of avermectin B1 and 8,9-Z-avermectin B1.
Applicable Concentration Range Estimated LOQ: 2 ng/g
QC Requirements See Attached Method
Method Performance/Validation See Attached Method
Method Source US EPA and Merck
Method SOP PDF icon SOP 
Citation Merck Research Laboratories Method No. 8000. Rev. 4