A conically fixed position single drop microextraction method for isolation of aryloxyphenoxypropionate herbicides from aquatic media

Abstract

A new and convenient format of single drop microextraction (SDME) was developed and applied for isolation of some selected aryloxyphenoxypropionate herbicides from aquatic media. In contrast to the conventional SDME procedure, in this set-up the extraction microdrop was positioned at the bottom of a conical vial in order to provide much higher stability for the organic extraction phase while a magnetic bar was used for stirring the aqueous solution. A simple magnet was used for positioning the bar on the top of the microdrop prior to stirring. The whole set-up led to the use of any volume of extraction solvent with unlimited stirring rates. Some important extraction parameters such as the type of solvent, stirring rate, temperature and extraction time were investigated and optimized. Selection of a microdrop volume of 3 μL with a sampling time of 35 min along with the use of carbon tetrachloride as the most appropriate solvent led to the highest enrichment factors. The linearity was studied by preconcentration of 1 mL of water samples spiked with a standard solution of aryloxyphenoxypropionates in the concentration range of 0.1–300 μg L⁻¹. The coefficient of determination was satisfactory (r² > 0.99) for all the studied analytes and the relative standard deviation (RSD%) values under the optimized conditions were found to be in the range of 5.1 to 10.1% at the concentrations of 0.6 and 50 μg L⁻¹. Detection limits were obtained to be in the range of 0.02–0.05 μg L⁻¹ using time-scheduled selected ion monitoring (SIM). The developed method was successfully applied for the extraction and determination of aryloxyphenoxypropionates in river water samples.