Capillary Gas Chromatographic Determination of Prometryn and Its Degradation Products in Parsley

Residue analysis of the herbicide prometryn (2,4-bis(isopropylamino)- 6-methylthio-l,3,5-triazine) is widely known, but an analytical method for determining its metabolities or degradation products in addition to the parent chemical has not yet been reported in the literature. The procedure reported here is for the extraction and determination of prometryn and 2 metabolites, 2-amino-4-isopropylamino-6-methylthio- l,3,5-triazine and 2,4-diamino-6-methylthio-l,3,5-triazine, in parsley. Crops were extracted with 2-propanol followed by concentration of the extract and partitioning with a minimum amount of hexane in the presence of a large excess of water to remove most of the green pigment. The aqueous phase was divided into 2 equal halves: (A) Onehalf portion was partitioned with dichloromethane in the presence of saturated sodium chloride solution, the dichloromethane phase was separated, and the aqueous phase was discarded. The organic solvent was evaporated, and the contents were reconstituted in petroleum ether before prometryn analysis. (B) The other half was made slightly alkaline with ammonium hydroxide solution and was partitioned with ethyl acetate in the presence of saturated sodium chloride solution. The ethyl acetate phase was concentrated, centrifuged to remove any turbidity, and analyzed for the 2 metabolities above. Fused silica capillary gas chromatography (GC) with nitrogen-phosphorus (N-P) detection was used for quantitation. The limit of detection was 0.05 mg/kg for all the compounds examined. Recoveries from fortified parsley samples ranged from 59 to 73% at fortification levels of 0.05 to 1.0 mg/kg.