chapter  4
104 Pages

Pesticides

Due to the worldwide application of various pesticides and pesticide mixtures they are abundant in soil and ground and surface waters. The exact determination of the quantity of unmodified pesticides and their metabolites is of paramount importance for the agrochemical practice, environmental protection and health risk assessment. The semivolatile character of the majority of pesticides make possible the application of both gas and liquid chromatographic methods for their determination. Similarly to other environ­ mental pollutants pesticides occur in very low concentration and various enrichment procedures have to use prior chromatographic analysis. The sorbents used for SPE of polar organic micropollutants from water were previously reviewed (Masque et a l , 1998a).

As the volatility of the majority of pesticides is generally not enough for the spontaneous evaporation into the atmosphere the number of studies dealing with their occurrence in air is fairly low (Baker et al., 1996). The separation and quantitative determination of chlordane-related enantiomers in air was performed by GC/ECD and GC/MS (Ulrich and Hites, 1998). Pollutants were collected on an Amberlite XAD-2 resin then extracted in a Soxhlet apparatus with acetone-n-hexane 1:1 v/v for 24h. After extraction the solvent was changed to hexane and applied on a silica column for preffactionation. Enantiomer separations were performed a-and T-cyclodextrin capillary columns (20 m x 0.25 mm I.D., film thickness 0.25 pm). Initial temperature of a-cyclodextrin column was 50°C for 1 min, to 130°C at 5°C/min, to 155°C at 0.2°C/min, to 230°C at 20°C/min, final hold 1 min. The temperature program was different for T-cyclodextrin column: initial temperature 50°C for 1 min, to 150°C at 20°C/min, to 185°C at 0.5°C/min, to 230°C at 20°C/min, final hold 1 min. The concentration of chlordane components are compiled in Table 4.1. It was stated that the method is selective and sensitive enough to be employed for the determination of chlordane-related enantiomers in air samples.