Immersed solvent microextraction of aryloxyphenoxypropionate herbicides from aquatic media

Abstract

An immersed solvent microextraction (SME) method was successfully developed for the trace enrichment of aryloxyphenoxypropionate herbicides from aquatic media. A microdrop of toluene was used as the extraction solvent. Some important extraction parameters such as type of solvent, solvent dropsize, stirring rate, ionic strength and extraction time were investigated and optimized. The microdrop volume of 1.5 µL, a sampling time of 25 min, and use of toluene were major parameters for achieving high enrichment factors. The linearity was studied by preconcentration of 4 mL of the water samples spiked with a standard solution of aryloxyphenoxypropionates at the concentration range of 0.15 to 30 ng mL⁻¹. The coefficient of determination was satisfactory (r ²> 0.99) for all the studied analyte and the relative standard deviations (RSD%) values under the optimized condition were found to be 1.7 to 14.2% at the concentrations of 1 and 10 ng mL⁻¹. The enrichment factors were from 217 to 403 for the samples spiked at 1 ng mL⁻¹. Detection limits were obtained to be in the range of 0.05 to 0.15 ng mL⁻¹ using time-scheduled selected ion monitoring (SIM). The EI mass spectra of these herbicides revealed that fenoxaprop-P-ethyl and quizalofop-P-ethyl exhibited [M-COOC₂H₅]⁺ as the base peak while, clodinafop-propargyl, haloxyfop-etotyl and haloxyfop-P-methyl showed [M-C₂H₄COOC₃H₃]⁺, [M-CH₂COOC₄H₈O]⁺ and [M-COOCH₃]⁺ as the base peaks, respectively. The developed method was successfully applied to the extraction and determination of aryloxyphenoxypropionates in river water samples.

Keywords:

• immersed solvent microextraction (SME)
• aryloxyphenoxypropionate herbicides
• water analysis
• gas chromatography-mass spectrometry

Acknowledgements

The Research Council and Graduates School of Sharif University of Technology (SUT) are thanked for supporting the project.