Optimization of the Micro-Scale Determination of Arsenates by Direct Potentiometric Titration with Silver Ions and its Application to the Determination of Arsenic in-Organic Compounds

Abstract

A micro-scale argentimetric method for the determination of orthoarsenates by potentiometric detection of the end-point has been developed. The optimal results were obtained when this titration was carried out in water-methanol medium, buffered at pH 7.50. This method minimizes the error of old methods arising from the small coprecipitation of silver oxide near the equivalence point and the data obtained are characterized by good accuracy and reproducibility. The procedure to perform the titration with an automatic apparatus is described as well as the optimum concentration range and titration rate. The method was then applied to the determination of arsenic in organic compounds after mineralization in the Schöniger flask using a quartz spiral.

Key Words:

• Arsenate determination
• argentimetric titration
• potentiometric titration
• micro-scale analysis
• organoarsenic determination