Combination of dispersive solid-phase extraction with dispersive liquid-liquid microextraction followed by high-performance liquid chromatography for trace determination of chlorpyrifos in urine samples

The aim of this study was to develop an effective sample preparation method for the extraction and trace determination of chlorpyrifos pesticide. The method was a combination of dispersive solid-phase extraction (DSPE) and dispersive liquid-liquid microextraction (DLLME) coupled with high-performance liquid chromatography (HPLC). Different factors affecting the performance of the extraction steps in both methods were thoroughly investigated and optimised. They included type and volume of the extractor and disperser solvents in DLLME extraction, as well as type and volume of the elution solvent, type and amount of sorbent in DSPE extraction. The salt addition, pH of solution, and also centrifuging time and speed were taken into account. Under optimal conditions, the enrichment factors were between 177 and 293, and the extraction recoveries were 91-98%. The linear range was 5-400 mu g L-1, and limits of detection (LOD) were between 0.9 and 1.8 mu g L-1. The relative standard deviations (RSDs) for 100 mu g L-1 of chlorpyrifos in urine were in the range of 1.9-3.7% (n = 6). The relative recoveries of the pesticide from urine samples spiked with levels of 10, 100 and 300 mu g L-1 were obtained 95.1-101.3%. Compared to other extraction techniques, DSPE-DLLME-HPLC method enjoys some advantages such as the shorter extraction time, high extraction efficiency, and good enrichment factor for the extraction of chlorpyrifos from human urine samples. In addition, it is simple, inexpensive, and highly sensitive, and it can be successfully applied to separation, pre-concentration, and determination of the pesticides in different aqueous samples.