Determination of atrazine and simazine in estuarine samples by high-resolution gas chromatography and nitrogen selective detection

Abstract

A method for the determination of ultra trace concentrations of triazine herbicides in natural water using silica C 18 solid-phase extraction (SPE) and high-resolution gas chromatography with nitrogen-selective detection (GC-NDP) has been developed and optimized for estuarine conditions. Recoveries of spiked dissolved simazine and atrazine at a concentration of 100 ng l −1 were 82–85% and 87–97%, respectively and were onl slightly affected by the range of salinities and pH encountered for estuarine samples. The sediment-bound (particulate) triazines were ultrasonically extracted with high recoveries (86–91%) using dichloromethane. The water sample extracts were analysed without selective detection provided interference-free detection of simazine and atrazine in the extracts. The detection limits for simazine and atrazine in water and sediment were 1 ng l −1 for 1 l of water and 5 ng g −1 200 mg of suspended sediments. The reproducibility of the determination of atrazine and simazine in real water samples at low ng l −1 concentrations as shown by %R.S.D., was better than 10%. A comparison of the GC-NPD determination with an alternative method using ion selective detection (GC-ITD) showed very good agreement and indicated superior (ca. 5 fold) sensitivity of the NPD. The method was applied to a study of triazine herbicides in estuarine waters of the Rivers, Tamar, Thames and Mersey.