Innovative techniques for the analysis of chlorophenols and acid herbicides in soils and water

Abstract

A new method of analyzing soils and water utilizes the solid-phase microextraction (SPME) technique which allows the derivatization of the analytes on the polyacrylate fibre coating eliminating the traditional cleanup process when analyzing acid herbicides and chlorophenols. Confirmation of the chlorophenols was performed by derivatization with diazomethane and comparison with commercially available chloroanisoles or by GC with ion trap detection. LOD ranged from 0.01 $\mu$g/L to 0.05 $\mu$g/L whereas LOQ ranged from 0.03 $\mu$g/L to 0.07 $\mu$g/L for 2,4,5-T and dicamba respectively. Reproducibility expressed as % RSDs for the derivatization method ranged from 2.7-31.4%. The use of the SPME technique has been optimized to allow for the analysis of chlorophenols and acid herbicides in soils and water through decreased pH, addition of NaCl, sample agitation and derivatization of the analyte. Sample agitation was achieved through the development of the 'Woodpecker' apparatus in conjunction with the conventional static autosampler with equilibrium being reached in approximately 20 min. However, this was not as effective as the more vigorous stirring with the insertion of magnetic stir bars into each sample vial used in manual SPME. The SPME technique enables the calculation of partition coefficients (K$\sb{\rm SPME})$ which closely parallel log K$\sb{\rm OW}$ values. Conventional extraction techniques allow for the quantification of the total residue contained within the sample. However, due to the inherent nature of the fibre coating and the gentler extraction conditions, this new method allows the analyst to measure only the portion of the analyte which is able to partition into the fibre coating, viz., the freely dissolved analyte. (Abstract shortened by UMI.)