Comparative evaluation of solid-phase extraction and in-tube liquid-liquid extraction for the determination of Organophosphorus pesticides in the surface water from Medjerda River, Tunisia

Abstract

In the present work, we develop, validate, and compare two extraction procedures (in-tube liquid-liquid extraction (ITLLE) and solid-phase extraction (SPE)). The parameters that influence extraction efficiency, the nature and volume of the extraction solvent, as well as the pH nature, were improved and a standard solution of Organophosphorus pesticides (OPPs) was used. Results indicated that SPE is clearly more successful than ITLLE extraction under optimum conditions. The validated method showed that this approach had good linearity, with correlation coefficients ranging from 0.991 to 0.998 and low detection and quantification limits of 0.01–0.03 ng L−1 and 0.03–0.9 ng L−1, respectively. Relative standard deviations were in the range of 0.2 and 1.2%, while extraction recoveries varied from 79 to 97%. The SPE was selected and, optimum recoveries for OPPs were obtained at pH 7, with 10 mL of ethyl acetate. The suggested approach was effectively applied to the analysis of water samples collected from the Medjerda River in two seasons. The average OPPs concentrations ranged from not detected (ND) to 17.5 ng L−1 during the dry season and from not detected ND to 13.1 ng L−1 during the wet season. The results demonstrate that none of the OPPs concentrations measured exceeded the regulatory limits.