Reversed phase liquid chromatography trace analysis of pesticides in soil by on-column sample pumping large volume...

The idea of utilization of one hydraulic line of a common commercial HPLC pump for direct on-column sample pumping injection of large sample volumes, 20 mL, was further investigated with the aim to develop multicomponent pesticides trace residues HPLC method in gram soil samples. Target pesticides group involve asulam, atrazine, 2,4-D, PCA, propazine, simazine, 4-chloro-2-methylphenoxyacetic acid, 2-(4-chloro-2-tolyloxy) propionic acid, chlortoluron, metoxuron, epoxiconazole. The results proved the applicability of this approach in experiments with mixtures of analytes at low ng/mL levels. Analysis of 20 mL of soil leachates and extracts of fortified soil samples containing these pesticides at the 10-50 ng/g level (in dry soil) revealed good figures of merit, also in the presence of large excess of humics. LODs achieved by detection at 220 nm evaluated from calibration runs of spiked soil extracts by Hubaux et al. method ranged from 5-12 ng per injected volume. For 20 mL large volume injection it represents 0.25-0.6 ng/mL of diluted soil extract, or 2.5-6 ng/mL of crude extract, or 6-5 ng/g dry soil. Recoveries of pesticides at concentration levels approaching half of maximum allowable concentration of pesticides in soil (100 ng/g) ranged from 85 to 98% with acceptable reproducibility, except asulam and metoxuron.