ABSTRACT.A simple, rapid and sensitive spectrophotometric method has been developed for the determination of iodate (IO3 -) in table salt and sea water. The proposed method is based on the reaction of iodate with potassium iodide in an acid medium to liberate iodine. The liberated iodine bleaches the blue color of methylene blue and is measured at 665.6 nm. This decrease in absorbance is directly proportional to the iodate concentration and obeys Beer's law in the range of 0.5-14 µgmL -1 of IO3 -. The molar absorptivity, Sandell's sensitivity, detection limit and quantitation limit of the method were found to be 1.24 x 10 4 Lmol -1 cm -1 , 1.41 x 10 -2 µgcm -2 , 0.048 µgmL -1 and 0.145 µgmL -1 , respectively. The optimum reaction conditions and other analytical conditions were evaluated. The effect of interfering ions on the determination has been described. The proposed method has been successfully applied to the determination of the iodate in the table salt and sea water.

A simple spectrophotometric method has been developed for the determination of arsenic in various environmental and biological samples. The method is based on the reaction of arsenic(III) with potassium iodate in acid medium to liberate iodine. This liberated iodine bleaches the blue color of toluidine blue or pinkish red color of safranine O. The decrease in absorbance at 628 or 532 nm is directly proportional to arsenic(III) concentration and obeys Beer's law in the range of 1.2-10.5 or 0.4-11.5 microg mL(-1) for arsenic(III). The molar absorptivity, Sandell's sensitivity, detection limit and quantitation limit of the method using toluidine blue or safranine O were found to be 1.076 x 10(4) or 1.388 x 10(4) L mol(-1) cm(-1), 9.66 x 10(-3) or 7.49 x 10(-3) microg cm(-2), 0.308 or 0.250 microg mL(-1), 0.934 or 0.759 microg mL(-1) respectively. The relative standard deviation for five replicate analyses of 4 microg mL(-1) of As(III) using toluidine blue or safranine O were 0.60% or 0.80%. The optimum reaction conditions and other analytical conditions were evaluated. The effect of interfering ions on the determination is described. The proposed method is free from any interference. The method has been used for the determination of arsenic in various environmental and biological samples.

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Um método espectrofotométrico simples, rápido e sensível foi desenvolvido para a determinação de hipoclorito usando Rodamina B. O método proposto considera a reação de hipoclorito com iodeto de potássio em meio ácido, com liberação de iodo. O iodo liberado descora a solução vermelho-rosada de Rodamina B que pode ser medida em 553 nm. Este decréscimo na absorbância é diretamente proporcional à concentração de hipoclorito e obedece a lei de Beer no intervalo de 0,1 a 4,0 μg mL -1 de hipoclorito. A absortividade molar, sensitividade de Sandell, limite de detecção e de quantificação do método são 2,57×10 5 L mol -1 cm -1 , 2,01×10 -3 μg cm -2 , 0,070 μg mL -1 e 0,212 μg mL -1 , respectivamente. As condições ótimas de reação e outros parâmetros analíticos foram avaliados. O efeito dos íons interferentes na determinação é descrito. O método proposto foi aplicado com sucesso na determinação de hipoclorito em várias amostras de água de torneira, água mineral e leite.A simple, rapid and sensitive spectrophotometric method has been developed for the determination of hypochlorite using Rhodamine B. The proposed method reports the reaction of hypochlorite with potassium iodide in an acid medium with iodine liberation. The liberated iodine bleaches the pinkish red color of the Rhodamine B and can be measured at 553 nm. This decrease in absorbance is directly proportional to the hypochlorite concentration and obeys Beer's law in the range of 0.1 -4.0 μg mL -1 of hypochlorite. The molar absorptivity, Sandell's sensitivity, detection limit and quantitation limit of the method were found to be 2.57×10 5 L mol -1 cm -1 , 2.01×10 -3 μg cm -2 , 0.070 μg mL -1 and 0.212 μg mL -1 respectively. The optimum reaction conditions and other analytical parameters were evaluated. The effect of interfering ions on the determination is described. The proposed method has been successfully applied to the determination of the hypochlorite in various samples of tap water, natural water and milk.Keywords: hypochlorite determination, spectrophotometry, Rhodamine B IntroductionHypochlorite is very high tonnage chemical for sanitizing and bleaching purposes. 1 The determination of hypochlorite is industrially important in connection with water analysis. 2 Hypochlorite is inherently an unstable compound. Hypochlorite is widely used in textile industry as a bleaching agent 3 and disinfectant in fabrics, wood pulp food and milk 4 industries. A medical application of the compound is in the treatment of skin cancer. 5 Another application of the chemical has been a valuable tool for the narcotics department as it could be applied to track the banned drugs like cocaine. 6 Sodium hypochlorite is used as a screening agent 6 for the identification of cocaine.The lethal action of calcium hypochlorite on Bacillus anthracoides spores 7 appeared to result from alteration of the structural organization of the spores which led to disturbance of the normal permeability barrier with loss of life -sustaining components and unbalance of metabolic process. It is also used...

It is described the use of 1,3 dinitrobenzene or 2,4 dinitrophenyl hydrazine is used as coupling agent for the spectrophotometric determination of paracetamol. This method is easy and simple based on the reaction of acid hydrolysis of paracetamol to produce p-aminophenol, which in turn reacts with nitrite in acidic standard to form diazonium ion, which is coupled with coupling agent in basic standard to produce azo dyes. The formed dyes follow Beer’s law in the range of 0.8-20.5 mg mL-1 of paracetamol with 1, 3 dinitrobenzene or 0.5-18.4 mg mL-1 of paracetamol with 2,4 dinitrophenyl hydrazine with absorption maxima at 429 nm or 430 nm. The molar absorptivity and Sandell’s sensitivity of paracetamol with 1,3 dinitrobenzene or paracetamol with 2,4 dinitrophenyl hydrazine azo dyes were 1.965×104 L mol-1 cm-1 or 2.776×104 L mol-1 cm-1, and 7.692×10-3 mg cm-2 or 5.698×10-3 mg cm-3 respectively. The dyes formed are stable for more than 12 h. The optimal reaction circumstances and other analytical parameters are evaluated. Interference due to foreign organic compounds have been studied. The method has been effectively applied to the determination of paracetamol in pharmaceutical samples.