Analysis of acidic herbicides in water using a toroidal coil CCC

Abstract

A newly developed compact toroidal coil centrifuge chromatograph (TCCC) has been proven to be able to achieve high-resolution counter-current chromatography (CCC) separations. The potential of this devise is studied for analytical applications. The TCCC was used for the analysis of acidic herbicides in order to reduce the interference due to humic substances. Aqueous samples were pretreated with solid-phase extraction (SPE) and eluted with the lower phase of an n-hexane-ethyl acetate-water (15: 7: 20, v/v/v) solvent system. Because the humic substances were more hydrophilic than the herbicides, they were eluted first and separated from the herbicides. Although four herbicides were well resolved,. quantification of compound 2,4-dichloro-phenoxyacetic acid was, to some extent affected by the tailing signal of humic substances. Samples of analytes of 20 mug/L spiked in deionized water containing 6 and 12 mg/L humic acid, and in lake water, were analyzed. Mean recoveries ranged between 66 and 96%, with RSDs between 2 and 11%. While CCC has been known as a preparative chromatographic technique, the potential of using a TCCC device for quantitative analysis under complex matrices is demonstrated.