A Facile Spectrophotometric Method for the Determination of Selenium

Abstract

Selenium is widely distributed in nature in relatively small concentrations in rocks, plants, coal and other fossil fuels. Selenium compounds are extensively used in paints, dyes, glass, electricals, rubber and insecticides, and in many other industries. 1 The determination of selenium is of considerable interest because of its contrasting biological effects; selenium is a toxic element as well as a trace element for animals and humans.2 Its efficiency causes pulmonary edema, abdominal pain, jaundice, chronic gastrointestinal diseases, hair loss and fatigue in humans, 3 and its deficiency causes Keshan and Kaschin beck diseases in humans, which have been frequently reported in China. 4 It also plays a major role in the life cycle of plants (Cruciferae family) which absorb organoselenium compounds accumulated in the soils of semiarid areas, and may poison livestock that graze on them. Selenium enters into natural water through seepage from seleniferrous soil and industrial waste. Water drained from such soil may cause severe environmental pollution and wildlife toxicity.2 Selenium is also reported to be present in cigarette paper, tobacco, 5 and various cosmetic samples. 6 Because of its significance, several analytical techniques have been reported concerning the determination of selenium. 7-10Many spectrophotometric methods for the determination of selenium have been reported with some chromogenic reagents, such as 3,3-diaminobenzidine, 11 dithiozone, 12 8-hydroxyquinoline, 1-naphthylamine-7-sulfonic acid 16 and Leuco Crystal Violet. 17 Of these reagents, some have been reported to be carcinogenic, while few others are less selective; the latter reagent system required heating and 25 min for full color development. There is thus a need to develop an entirely new method, which would overcome the existing inadequacies in the determination of trace amounts of selenium.In the present investigation, a facile, sensitive and selective method has been reported for the determination of selenium with a new reagent Variamine Blue (VB), based on the liberation of iodine by the reaction of selenium with potassium iodide in an acidic medium and a subsequent oxidation of VB by the liberated iodine to form a violet-colored species. The developed method has been successfully employed for the determination of selenium in water, soil, plant materials, human hair, cosmetic and pharmaceutical preparations. Experimental ApparatusJasco (Model UVIDEC-610) and Elico (Model CL-27) spectrophotometers with 1 cm matched quartz cells were used for all absorbance measurements. ReagentsAll of the chemicals used were of analytical-reagent grade, and distilled water was used throughout the study. Standard selenium(IV) solution (1 mg/ml).Prepared by dissolving 0.219 g of Na2SeO3 in 100 ml water. A working standard solution was prepared by a suitable dilution of the standard solution. Variamine Blue (VB), (0.05%). Prepared by dissolving 50 mg of Variamine Blue (E. Merck, Germany) in 25 ml methanol and made up to 100 ml with distilled water, and s...

Multi-pumping mechanised determination of selenium in natural waters by light emitting diode (LED) spectrometry

“…The proposed method provides a limit of detection of the same order than that obtained by using NPDPTC after a previous separation of the gas phase generation, 9 and clearly lower than other photometric procedures. 3,7,8 It seems that kinetic spectrophotometric approaches provide an enhancement of the LOD and astonishing the sensitivity reported for FIA spectrophotometric determination with MBTH is one order of magnitude better than that obtained by us. However, on looking through the aforementioned study, 12 it can be seen that authors reported a sensitivity of 0.1875 for the concentration range between 0.050 and 0.500 mg L -1 which is clearly lower than the value of 0.501 obtained in this study for the range between 0.010 and 0.500 mg L -1 and thus it is surprising that they could found a LOD of 0.00025 mg L -1 nor for using a 2σ criterion.…”

A rapid assessment method for determination of iodate in table salt samples

“…In this work, the liberated iodine was allowed to react with the VB dye in the presence of sodium acetate (reaction 2). Variamine blue is known to be a suitable chromogenic reagent for iodine (Revansiddapa and Kumar 2001;Narayana and Cherian 2005;Coo and Martinez 2004). The liberated I 2 oxidizes the dye to a violet color whose absorbance maxima is at 550 nm.…”

<b>Microwave assisted spectrophotometric method for the determination of copper using leucocrystal violet</b>

“…The slope of the calibration curve leads to a molar absorptivity of 1.47 x 10 6 L mol -1 cm -1 . The Sandell's sensitivity [18], detection limit (D L = 3.3 σ/m) and quantitation limit (Q L = 10 σ/m), where σ = standard deviation of the reagent blank and m = slope of calibration curve [19] were found to be 4.3 x 10 -5 µg cm -2 , 0.001 µg mL -1 and 0.0043 µg mL -1 , respectively.…”