Extraction-Spectrophotometric Determination of Arsenic in Environmental Samples with Iodide and Amidines

A simple and rapid method for the spectrophotometric determination of traces of total arsenic present in industrial waste waters is described. It is based on the reaction of As(III) with I− in 5 –6 M HCl, and extraction of the iodo-arsenite complex formed into chloroform with amidines. The molar absorptivity of AsI4 − with 11 different amidines is in the range (3.9 –7.9) × 103 lmol−1 cm−1 at λmax = 380 –395 nm; the simplest compound, N,N′-diphenylbenzamidine (DPBA) has been chosen for further studies. The limit of detection with DPBA is 0.1 μg As/ml. The method is highly selective with almost no interference from all anions and cations tested.