Non-Extractive Quenchophotometric Method for Determination of Trace Arsenic in Alloys, Environmental Waters, Biological and Soil Samples

摘要

A simple, non-extractive, highly sensitive and selective quenchophotometric method for the rapid determination of arsenic at trace levels in aqueous medium has been developed. The method is based on the oxidation of arsenic (III) by potassium bromate in the presence of potassium bromide and methyl orange. The decrease in native absorbance of the reagent blank ( λ_(max) = 393 nm) was inversely proportional to the amount of arsenic in aqueous solution. The absorbance quenching due to arsenic (III) is achieved by subtracting the relative absorbance of arsenic-reagent system from that of the corresponding reagent blank system. The reaction is instantaneous and the absorbance remains stable for over 24h. The absorbance vs arsenic (III) concentration calibration graph shows a rectilinear relationship for a wide range 1-250 μg mL~(-1) of As (III). Large amount of about 50 cations, anions and complexing agents do not interfere in the determination. The method was successfully used for the determination of arsenic in several standard reference materials (alloys and steels) as well as in some environmental waters (underground and surface), biological samples (human blood, urine, hair and nails) and soil samples. Solution containing both arsenic (III) and arsenic (V) and complex synthetic mixtures were also successfully analysed using the proposed method. The method has high precision and accuracy (s = ±0.01 for 5 μξ mL~(-1)) of analyte.