Speciation of Arsenic in Environmental and Biological Samples

Abstract

A novel arsine generator glass assembly is constructed and reported for the spectrophotometric determination and speciation of arsenic in real samples. In an arsine generator, sodium borohydride is added dropwise to the acidic sample solution and arsine thus formed is reacted with silver diethyldithiocarbamate (Ag‐DDTC) ‐ Tritron‐X (TX‐100) solution in pyridine to form a red coloured complex. The complex showed the absorption maximum at λmax 540 nm. The molar absorptivity of the method was found to be (1.55) × 104 L mole−1 cm−1 at this wavelength. The presence of non‐ionic surfactant, i.e. TX‐100 in the Ag‐DDTC solution, makes the method ≈ 3 times more sensitive than the conventional Ag‐DDTC method. Beer's law is obeyed in the concentration range of 0.05–2.80 mg L−1 of arsenic. The detection limit of the method was calculated to be 20 μg L−1 As. Speciation of arsenite from other forms of arsenic in sample solutions was carried out by extraction of arsenite with Pb‐DDTC in chloroform, followed by spectrophotometric determination. After arsenite separation the sample is used for the arsenate determination. Total arsenic was determined by acid decomposition of the same sample. The speciation data were found to be comparable (±2%) with ICP‐MS, with better precision (< 1%). The method has been successfully applied for the speciation of arsenic in drinking water and dust samples of arsenic affecting the Rajnandgaon district of Chhattisgarh, India, and urine and blood samples of patients with arsenical diseases. Concentration of total arsenic in tube‐well water of this area was 3–6 times more than the permissible limit. Dust samples contained less amounts of arsenic than the ground water.

Determination of Arsenic in Environment by Spectrophotometric Technique using Hydroxamic Acids

“…Spectrophotometric determination of arsenic using hexamethylene ammonium-hexamethylenedithiocarbamate [19], silver diethylthiocarbamate [20], azure-B( [21], molybdate-iodine tetrachloride [22], variamine blue [23], rhodamine-B [24] have also been reported. Studies have been also done on determination of arsenic from aqueous solution by electro coagulation method using Al-Fe electrodes [25].…”

Overestimation of geogenic arsenic in landfill leachate: interference of humic and phosphinic acid in a commercial test kit

“…It is the most popular spectrophotometric method [14] and dates back to the work of Vašák and Šedivec in 1952 [15]. Since then, it has been continuously refined and modified with regard to different sample matrices [16][17][18][19], optimisation of the chromophoric [17,20,21] and hydride generation methods [22][23][24], the identification of interferences [17,[25][26][27][28] and As speciation [29][30][31][32]. Ultimately, a performance comparable to inductively coupled plasma mass spectrometry [33] was achieved.…”

Arsenic speciation in natural and contaminated waters using CZE with in situ derivatization by molybdate and direct UV‐detection

“…There are a few publications concerning the application of the chemical reactions of arsenate or arsenite ions for their photometric determination 10–23; as for MMA and DMA the similar reactions are not mentioned in literature. According to published data molybdoarsenic complexes of arsenate, MMA and DMA ions are synthesized and structurally characterized.…”