Determination of Organochlorine Pesticides by Gas Chromatography Mass Spectrometry Utilizing Negative Ion Chemical Ionization

Abstract

A rapid and highly selective method for the simultaneous determination of 13 organochlorine pesticides and related compounds (Table 1) in soil, bottom deposit and river water was developed by gas chromatography mass spectrometry (GC/MS) utilizing negative ion chemical ionization. The procedure is as follows. [Pretreatment] the modifications were done along the proposed method. Main points are as follows; 1) Elimination of a reflux treatment for removal of free sulfur by copper powder in the case of soil and bottom deposit was done, 2)Developing solvents in Florisil column chromatography were changed to 200 ml portions of diethyl ether/hexane (15/85) and acetone/hexane (5/95) and 2.5 g of Florisil was used, 3) Elimination of silica-gel column chromatography for removal of PCB's was done. [Measurement]the concentrated solution of the effluent from Florisil column is introduced into a GC/MS instrument equipped with a SE-54 fused silica capillary column. Methane is used as a reagent gas. Benzil is used as an internal standard. The mass fragmentograms are recorded by monitoring specific peaks of each compound (Table 2, Fig.2). Because of high selectivity of the proposed method, 13 organochlorine pesticides could be determined simultaneously without preseparation of PCB's and phthalic acid esters (Table 4). The determination values of individual constituents were in the range 0.1-2300 ppb in the case of soil and bottom deposit and 1.9-45 ppt in the case of river water (Table 5, Fig.3). Minimum detectable amounts of pesticides for this method were 0.2-50 pg and time required for GC/MS measurements was within 15 minutes.