Electrical field assisted liquid phase microextraction for determination of chromate ion

Abstract

An electrical field assisted liquid phase microextraction (LPME) was studied and developed for extraction of metal oxoanion in aqueous samples. Chromium (VI) was chosen as a model analyte. Electrical field can enhance the transportation of ionic analyte across the organic liquid hollow fiber membrane. The transportation of ionic analyte was mainly based on electrokinetic migration and ion-exchange mechanism. After extraction, Chromium (VI) was determined by complexing with 1,5-diphenylcarbazide and detected by a fiber optic UV-Vis spectrophotometer with z-floe cell at 544 nm. 1-heptanol mixed with ionic carrier (methyltrialkyl-ammonium chloride, Aliqua336) was chosen as extracting solvent. Aliqua336 concentration, composition of acceptor solution, extraction rime, applied voltage, stirring rate and matrix effect were investigated and optimized. The working range of 3 to 15 µg L ⁻¹ chromium(VI) was obtained with 5 min extraction with good linearity (R² > 0.99). Limits of detection were 1.0 and 3.5 µg L ⁻¹ for milli Q water and drinking water, respectively. The recovery of spiked Cr(VI) in drinking water was in the range of 86.7% to104.3%. The relative standard deviation was in the range of 4.11-1187%. The method provided high enrichment factor in the range of 185-220. The method is faster, provides higher preconcentration and cheaper than the traditional hollow fiber membrane liquid phase microextraction.