Development of sequential injection-lab-at-valve (SI-LAV) micro-extraction instrumentation for the spectrophotometric determination of an anionic surfactant.

The development of instrumentation for sequential injection analysis with a "lab-at-valve" (SIA-LAV) micro-extraction system is presented. The extractive determination of an anionic surfactant using methylene blue was selected as a model. Sample, reagents and organic solvent were sequentially aspirated into an extraction coil connected to the center of a selection valve, where extraction took place by flow reversal. The aqueous and organic phases were separated in a LAV unit attached to one port of the valve. The LAV unit situated a fiber-optic spectrophotometer to monitor the absorbance change of the extract product in the organic phase. The developed SIA-LAV system offers an alternative micro-total analysis system for automated micro-extraction.