Research Journal of Recent Sciences _________________________________________________ ISSN 2277-2502 Vol. 1(10), 51-54, October (2012) Res.J.Recent Sci. International Science Congress Association 51 Quantitative Determination of Selenium and Development of Chemical Sensing Indicator Plates via New Synthesized Dye and its Application in Water and Plant Samples Sharma Ruchi Dubey, Joshi Smita and Amlathe Sulbha3* Department of Chemistry BUIT, Barkatullah University Bhopal, MP, INDIA Department of Chemistry, Sarojini Naidu Govt. Girls PG College, Bhopal, MP, INDIA Department of Chemistry BUIT, Barkatullah University, Bhopal, MP, INDIA Available online at: www.isca.in Received 27th July 2012, revised 4th August 2012, accepted 29th August 2012Abstract A selective, simple, inexpensive and a new reagent for determination of selenium is proposed. This method is based on oxidation of hydroxylamine hydrochloride with selenite ions to nitrous acid, which in turn diazotizes sulfanilic acid which subsequently couples with NEDA to form magenta colored azo dye. The dye thus formed shows a maximum absorbance at 550 nm. The method obeys Beer’s law in the range of 0.05 to 0.26 ppm of Se. Its molar absorptivity, Sandell’s sensitivity, standard deviation and relative standard deviation were found 9.04x10, 8.73x10-3, 0.002, and 0.87% respectively. All the reaction parameters have been optimized. Interferences between the azo reaction and non targeted ions often present in environmental samples were investigated. The method has been successfully applied to the analysis of waste water and plant material. Chemical sensing strips were also been prepared and were successfully applied for detection of selenium in air and semi quantitative determination in water. The advantages of method are its high sensitivity, reproducibility, and the fact that measurement is simple, rapid and low cost. Keywords: Diazotization, coupling, azodye, selenium, chemical sensing device, NEDA. Introduction Heavy metals are priority toxic pollutants that severely limit the beneficial use of water for domestic and industrial application. There are over fifty elements that can be classified as heavy metals, but only seventeen that are considered to be both very toxic and relatively accessible. Mercury, lead, arsenic, cadmium, selenium, copper, zinc, nickel, and chromium should be given particular attention in terms of water pollution. Heavy metals are present in the soil, natural water and air, in various forms and may contaminant food and drinking water. Selenium is a naturally occurring element considered a link between metals and nonmetals because of its unique properties. It is found in nature in small concentration in rocks, plants, coal and fossil fuels. Volcanic eruptions, insecticides, fertilizers, smelting ceramics, metallurgical operations, glass rubber accelerators and electronic goods are major environmental sources of Se. Selenium enters into natural water through seepage from seleniferous soil and industrial waste. The automobile spare part market represents a potential source of selenium. Certain industrial and agricultural- processes releases selenium as a byproduct. The maximum tolerance limit value (TLV) for human being is 0.1mg/m in air and 4ppm for water. Currently, low concentration of aqueous Se concentration or speciation is analyzed either by ICP-MS, Hydride generation graphite furnace AAS or Ion chromatography hydride generation AES8-9. However, these techniques, although they provide high sensitivity are rather challenging and rely on complex instruments and thus are expensive for regular analysis, particularly true for developing countries, where selenium toxicity is a well known problem. Several methods for determination of selenium through complexation10-13, oxidative coupling14-15 and diazotized coupling16 have been reported. This paper describes the detailed reaction scheme mechanism of a reliable and sensitive method based on a three step reaction (oxidation, diazotization and coupling) which produces a magenta colored azo dye that can be analyzed spectro- photo metrically at 550nm along with description of development of chemical sensing strips for detection of selenium in air and semi quantitative determination of water. Material and Methods Apparatus: All spectral measurements have been carried on digital spectro- photometer: - Systronic-166, BSM-13 and UV-visible spectrophotometer 2201. Reagents: All reagents used were analytical grade chemicals. Double distilled water is used throughout the experiment. Selenium solution: 80 g mL-1 stock solution of Se was prepared by dissolving 219.015 mg of NaSeO containing 80 g of selenium in 100 ml of distilled water.1 g mL-1 working standard was prepared by appropriate dilution of stock daily. Research Journal of Recent Sciences ______________________________________________________________ ISSN 2277-2502Vol. 1(10), 51-54, October (2012) Res. J. Recent Sci. International Science Congress Association 52 Hydroxylamine Hydrochloride (HA): 10% aqueous NHOH.HCl was prepared by dissolving 10g of HA in 100ml of distilled water. Sulfanilic acid (SA): 1% Sulfanilic acid was prepared by dissolving 1g SA in hot water. Hydrochloric Acid: 1ml of 85% pure concentrated HCl was used for diazotization, 4M HCl was used for making up the final volume. N-(1-naphthyl) Ethylene diamine dihydrochloride (NEDA): 1% NEDA was prepared by dissolving1g NEDA in 2ml HCl and then made up to 100ml by distilled water. . Procedure: 1-4ml of sample is taken in 30ml graduated tube, 2ml of 10% hydroxylamine hydrochloride, 1ml of conc. HCl and 3ml of 1% sulfanilic acid were added to it. The solutions are shaken and heated at 50-60C for 10-15 min kept for few seconds, then, 4ml of 1% NEDA are added and diluted to 15ml by 4M HCl and the absorbance is measured at 550nm. The reagent blank prepared in the same fashion shows negligible absorbance at 550nm. Results and DiscussionReaction mechanism: The color reaction for the proposed system may be as follows: I Step: Selenite ions (Se IV) oxidizes NHOH.HCl to HNOHSeO- +H +NHOH.HCl Se + HNO +2HO II Step: HNO produced diazotizes sulfanilic acid producing a diazonium salt OOC NH+NO- +2HHOOCN Diazotized SA III Step: Coupling takes between NEDA and diazotized SA, thus forming a stable magenta dye. The method is based on the oxidizing property of selenite ions in acid media. HOOCN + NH-CH-CH-NH2 HOOCN=NNH CH-CH-NH2 (Magenta dye) Spectral Characteristics: The magenta colored dye formed exhibit maximum absorbance at 550nm. Reagent blank shows negligible absorbance in this range as shown by figure- 1. Reaction conditions: Molarity: 4M HCl was found optimum for diazotization and color development, no color develops below 3M of HCl and reading increases above 4M of HCl if used. For making up the final volume 0.5 to 1.5M HCl was used. Temperature: The reaction was studied for 0C-100C. Absorbance decreases below and above 50C-60C. On boiling absorbance increases but blank reading too. Thus 50C- 60C was found optimum for color development. The dye was found stable for more than 20 hr. Time: Absorbance was measured instantly, after 5 minutes heating, 10 minutes heating,15 minutes, 20 minutes, 25 minutes and continuous increase in absorbance was observed till 10min, remains nearly constant till 15 minutes and then it start decreasing. Thus 10-15 minutes time was found optimum. Reagent concentrations: Following concentrations of reagents were found optimum when reaction was studied for 1-5ml of each reagent: Sulfanilic acid: 3ml of 1% Sulfanilic acid. Hydroxylamine hydrochloride: 2ml Hydroxylamine hydrochloride NEDA: 4ml of 1% NEDA HCl: 1ml of 4M HCl for diazotization and 3-5ml of 1.5M final volume make up. Effect of Co-pollutants: The method has been checked for its validity in presence of various co-pollutants and other foreign species. Interference of nitrite is masked by addition of sulphamic acid/sodium arsenite prior to analysis. The method was found to be free from most of the co-pollutants. The results obtained were given in table-1. Table-1 Tolerance limit to various interfering ionic species S. No. Interfering ions (co-pollutant species) Tolerance limit g mL-1) 1 K + , Cr + 6 10 5 2 Mn ++ , Ca ++ , Mg ++ , Na + ,Cl - , CO3 -- 1 10 5 3 Al +++ 1.5 10 5 4 NH3 2.5 10 5 5 Zn ++ 2 10 5 6 Fe +++ , NH + , SO -- 5 10 5 7 Cu ++ 6 10 6 8 Hydrazine 1 10 3 Application: The method found its applicability in various real samples as described, data are given in table -2. Selenium in polluted water: - To an aliquot (150-250ml) of sample contained in distillation flask, 1g of KI and 10ml of SO treated with 0.5 ml of saturated bromine water were added and the solution distilled under vacuum till copious fumes of SO vapor were evolved. By this process all other forms of selenium are converted into selenium (IV). The distillate was collected in 10 ml of 5% hydroxyl amine chloride solution and made up to a fixed vol. (50ml) and analyzed by the described procedure. H + N + N + ´ ´ ´ ´ ´ ´ ´ ´ Research Journal of Recent Sciences ______________________________________________________________ ISSN 2277-2502Vol. 1(10), 51-54, October (2012) Res. J. Recent Sci. International Science Congress Association 53 Selenium in plant material: 5g cabbage (spikes) was taken. 10 ml of conc. nitric acid was added and gently heated for 20 min. Then 0.5 ml of per chloric acid was added and contents were gently heated for 10 min. until the evaluation of ample fumes per chloric acid. 10 ml of water was added to the cooled residue and heated again for 10 min. then 5 ml of conc. HCl was added and heating continued for 10 min. the contents were diluted to 50 ml after adding 10 ml. of EDTA solution. An aliquot (1 ml) of sample was taken and selenium was determined as recommended. Table- 2 Presence and Recovery of selenium in various real samples S. No. Sample (amt. g) Se added g ) Total Se g ) % 1 Cabbage(5g) 10 9.43 94.3 2 20 18.85 94.2 3 30 28.75 95.8 4 Waste water(250ml) 10 9.8 98 5 20 19.7 98.5 6 30 29.5 98.3 Preparation of Test Paper: The method has been used to prepare test papers for detection and semi quantitative determination of selenium in air and water. Whatman no. 41 filter paper stripes (1x5 cm) were cut, dipped in HA and Conc. HCl, dried in a temperature controlled oven at 50C- 60C, then dipped in SA, again dried at 50C-60C, finally dipped in NEDA and again dried at the same temperature. These test papers were found to be stable for about three weeks, if kept in a well stoppered bottle. Detection in air: At the time of testing selenium in air, the test papers were exposed to vapors of selenium sample for a few seconds. The paper turned magenta indicating the presence of selenium. As little as 0.2 g of selenium can be detected by using test paper strips. Detection and semi quantitative determination in water: The test papers had also been successfully used for water to detect as low as 0.02g selenium. Semi quantitative determination had been done by comparing the color with standard samples prepared. Indicator Tubes: Detection and semi quantitative determination of Se in water has been done using above method. Simple glass plates of size (2 x 6 cm) having uniform thickness were taken and a slurry of silica was pasted of about 1mm thickness. After drying the plate in oven at 100C for an hour it was impregnated with HA and Conc. HCl, dried in a temperature controlled oven at 50C-60C, then impregnated with SA, again dried at 50C-60C, finally impregnated with NEDA and again dried at the same temperature. These indicator plates were found to be stable for about10 days if kept in a well stoppered bottle. A single drop of water containing Se will indicate its presence on these plates in form of magenta color appearance. As little as 0.02 g of selenium can be detected using these plates. Conclusion The proposed method is cheap, rapid and environment friendly, highly sensitive and easily employable as compared with the method based on same principle as reported in table-3. AcknowledgementThe authors are grateful to Principal, and Govt. Sarojini Naidu Girls College Bhopal Director BUIT, BU and HOD, Dept. of Chemistry BUIT for providing lab facilities. Figure-1 Absorbance Spectra of Sample with respect to Blank   \n  \r       \n   \r\n \n \r   Research Journal of Recent Sciences ______________________________________________________________ ISSN 2277-2502Vol. 1(10), 51-54, October (2012) Res. J. Recent Sci. International Science Congress Association 54 Table-3 Comparison with other reported methods S. No. Reagents used Medium/pH max. Beer’s Law range(ppm) Special remarks 1 3,3’Diaminobenzidine 17 Aqueous/2-3 420 0.1-10 Colored salts interfere 2 J-acid 10 Acidic/ 1-2.5 520 .03-0.3 Less sensitive 4 HA, PNA, NEDA 16 Acidic/ 2 545 0.1-2.5 Sensitive but more amount of chemicals is used, time consuming, High blank 5 HA, SA,NEDA (Proposed method) Acidic /2 550 0.05-0.26 Highly sensitive, cheap, rapid, negligible blank References1.Murhekar G.H., Trace Metals Contamination of Surface Water Samples in and Around Akota City in Maharashtra, India, Res.J.Recent Sci., 1(7), 5-9(2012) 2.Choudhary R., Heavy Metal Analysis of Water of Kaliasote Dam of Bhopal, MP, India, Res.J.Recent Sci., 1 (ISC-2011), 352-353 (2012)3.Vaishnav V., Daga K., Chandra S. and Lal M., Adsorption Studies of Zn (II) ions from Wastewater using calotropis procera as an Adsorbent, Res.J.Recent.Sci., 1(ISC-2011), 160-165 (2012)4.Shapira J.R., in organic selenium compounds, Their Chemistry and Biology, Klayman D.L. and Gunther W.H., Wiley Interscience, New York, 701 (1971)5.Sitting M.I., Toxic metal, Pollution control and Worker Protection, Noyes Data Corporation, Park Ridge, USA (1976) 6.Nwajei G.E., Okwagi P., Nwajei R.I. and Obi-Iyeke G.E., Analytical Assessment of Trace Elements in Soils, Tomato Leaves and Fruits in the Vicinity of Paint Industry, Nigeria,Res.J.Recent Sci.,1(4), 22-26 (2012) 7.Patty F.A., Industrial Hygiene and forecasting, Wiley Interscience New York, , 886 (1962)8.Adhkins R.L., Walsh N., Edmunds M. and Trafford J.M., Inductively-Coupled Plasma-Atomic Emission Spectrometric Analysis of Low-Levels of Selenium in Natural-Waters, Analyst, 120, 1433-1436 (1995) 9.Norheim G., Determination of Selenium in Biological Material using Automated Wet Digestion and an Automated Hydride Generation Atomic Absorption System,Application Note,Agilent Technologies © Agilent Technologies, Inc., 1988, November 1, (2010) AA086 10.Ramachandran K.N., Kaveeshwar R., and Gupta V.K., Spectrophotometric determination of selenium with 6amino-1-naphthol-3-sulphonic acid (J-acid) and its application in trace analysis,Talanta,40, 781 (1993)11.Johansson K., Luo X. and Olin A., Rapid one-step derivatization of Se(VI) to a piazselenol for the spectrofluorimetric determination of selenium in biological material,Talanta, 42, 1978 (1995)12.Ramanchandran K.N. and Kumar G.S., Modified spectrophotometric method for the determination of selenium in environmental and mineral mixtures using 2,3-diaminonaphthalene,Talanta,43(10), 1711-1715 (1996)13.Pursynska K.,Spectrophotometric Determination of Selenium with 1-Naphthyloamine-7-sulfonic Acid, Analytical Science,13(4), 629-632 (1997)14.Krishniah L.K., Kumar S., Suvardhan K. and Chiranjeevi P., Simple Spectrophotometric Determination of Traces of Selenium in Environmental Samples,3rd International Conference on Environment and Health, Chennai, York Uni, 217-225,15-17 Dec (2003)15.Subrahmanyam P., Krishnapriya B., Suvardhan K., Rekha D., Murali Krishna P., Rao G.C., Lingappa Y., Venkata Reddy B.C., Jayaraj B. and Chiranjeevi P., Spectrophotometric Determination of Se (IV) in Environmental Samples Using a Novel Oxidative Coupling Reagent, Environmental Monitoring and Assessment, 136(1-3), 1-7 (2005)16.Matamoros A. and Benning L.G., Spectrophotometric Determination of Low Level Concentrations of selenium in Aqueous Solutions, Mineralogical Magazine, 72, 451-454 (2008)17.Afkhami Aand Madrakian T., Kinetic–spectrophotometric determination of selenium in natural water after preconcentration of elemental selenium on activated carbon, Talanta, 58, 311-317 (2002)