Analytical Study of an Environmentally Hazardous Element, Arsenic, by Indirect Spectrofluorimetric Method in Diverse Fields

Abstract

An inexpensive and virtually specific non‐extractive method for the determination of arsenic(III) at trace and ultra trace levels (5 ng mL⁻¹–1 µg mL⁻¹) in 0.09–0.45 (M) sulphuric acid has been developed. The method is based on the quantitative oxidation of arsenic(III) by chromium(VI) in the presence of iodine as catalyst. A known excess of chromium(VI) was taken and after oxidation of arsenic (III) the leftover chromium(VI) quantitatively quenches the fluorescence developed by murexide in acid medium. Measurement of the fluorescence intensity was carried out at 424 nm with excitation at 336 nm. The measurement is repeated without arsenic(III) addition and the increase in fluorescence intensity gives arsenic(III) concentration with the help of a calibration graph. The method is very precise and accurate [s.d. = ±0.71 and r.s.d. = 0.71% for the determination of 0.1 µg mL⁻¹ of arsenic(III) in 11 replicates]. Relatively large excesses of over 35 cations and anions do not interfere. The method has been successfully applied for arsenic determination in various complex matrices, certified reference materials (alloys), and environmental and biological samples.

Keywords:

• Murexide
• Fluorimetric determination
• Arsenic
• Ultra‐trace analysis