A fiber optic spectrophotometric determination of urinary indoxyl sulfate (indican) after cloud point extraction

Abstract

This work describes a new, simple, and sensitive colorimetric determination method for indoxyl sulfate (indican) by fiber optic UV-Vis spectrophotometry coupled to cloud point extraction as the separation-preconcentration method. This method is based on the diazotization of sulphanilic acid in acidic medium followed by its coupling with indoxyl sulfate (indican), which gives an azo product and extraction of the colored product using the cloud point extraction (CPE) technique. The optimal extraction and reaction conditions (e.g., acid and reagent concentrations, effect of time) were studied, and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration factor) were obtained. Linear response was achieved within 0.9-44 mu g/mL and the detection limit was estimated as 0.6 mu g/mL. The inter-day and intraday relative standard deviations were in the ranges 1.2-1.3% and 1.6-1.8% for indican. The method was applied to the determination of indican in human spiked urine samples; Recoveries within 96-99% were obtained.