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We developed a cost-effective and sensitive spectrophotometric method for the determination of arsenic at trace level using a new reagent, leuco malachite green. Here we show that, arsenic reacts with potassium iodate in acidic conditions to liberate iodine, and the liberated iodine selectively oxidizes leuco malachite green to malachite green dye. We studied the Beer's law at 617 nm, which showed linearity over the concentration range 0.09-0.9 lg ml -1 of arsenic. We show that the molar absorptivity, Sandell's sensitivity and detection limit of the method are 6.1 · 10 4 l mol -1 cm -1 , 0.0012 lg cm -2 and 0.025 lg ml -1 , respectively. We applied the developed method for the determination of arsenic in environmental samples.

Highly sensitive and simple spectrophotometric determination of selenium is described for the determination of selenium(IV) using a new reagent leuco malachite green. The method is based on the reaction of selenium(IV) with potassium iodide in an acidic condition to liberate iodine, the liberated iodine oxidizes leuco malachite green to malachite green dye. The green coloration was developed in an acetate buffer (pH 4.2–4.9) on heating in a water bath (∼ 40 °C). The formed dye exhibits an absorption maximum at 615 nm. The method obeys Beer’s law over a concentration range of 0.04–0.4 µg mL−1 selenium. The molar absorptivity and Sandell’s sensitivity of the color system were found to be 1.67 × 105 L mol−1 cm-1 and 0.5 ng cm−2, respectively. The optimum reaction conditions and other analytical parameters have been evaluated. The proposed procedure has been successfully applied to the determination of selenium in real samples of water, soil, plant material, human hair, and cosmetic samples. The results were compared to those obtained with the reference method. Statistical analysis of the results confirms the precision and accuracy of the proposed method. In addition, the developed method is cost-effective and involves easily accessible instrumentation technique which can be used by ordinary research laboratories.

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A facile, sensitive and rapid spectrophotometric method for the determination of nitrite is presented. The method involves the reaction of nitrite with 4-aminoazobenzene under acidic conditions in the presence of a bromide ion allowing to complete the diazotization reaction almost instantaneously. The formed diazonium ion is then coupled with acetyl acetone to give bisazo dye in an aqueous alkaline medium having maximum absorption at 500 nm. The molar absorptivity and Sandell’s sensitivity of the method were found to be 4.2 × 104 dm3 mol−1 cm−1 and 1.1 ng cm−2, respectively. The system obeys the Beer’s law within the concentration range of 0.1–9 µg of nitrite in the final sample volume of 10 cm3. Optimum reaction conditions were evaluated and the influence of ionic interference on the determination of nitrite has been studied. The developed method has been applied in the determination of nitrite in water and soil samples, and the results were statistically evaluated.

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