G. Nagendrappa

A simple spectrophotometric method for the determination of phosphate in soil, detergents, water, bone and food samples through the formation of phosphomolybdate complex followed by its reduction with thiourea

A simple spectrophotometric method is developed here for the determination of phosphate present in the samples of soil, detergents, water, bone and food based on the formation of phosphomolybdate complex with the added molybdate followed by the reduction of the complex with thiourea in aqueous sulfuric acid medium. The system obeys Beers law at 840 nm in the phosphate concentration range, 0.5-10.0 μg/ml. Molar absorptivity, correlation coefficient and Sandells sensitivity values are found to be 1.712 mol(-1) cm(-1), 0.9769 and 0.0555 μg cm(-2) respectively. For a comparison of the results determined from the developed method, phosphate present in the same set of samples is determined separately following an official method. The results of the developed method are agreeing well with those of the official phosphomolybdate method.

A Simple Spectrophotometric Determination of Phosphate in Sugarcane Juices, Water and Detergent Samples

A simple spectrophotometric method is developed for the determination of phosphate in sugar cane juice, water and detergent samples. The method is based on the formation of phosphomolybdate with added molybdate followed by its reduction with sodium sulphide in aqueous sulfuric acid medium. The system obeys Lambert-Beer’s law at 715 nm in the concentration range 0.3-12.24 ppm. Molar absorptivity, correlation coefficient and Sandell’s sensitivity values were found to be 6.1x103 mol-1 cm-1, 0.999 and 0.0156 µg cm-2 respectively. The results obtained were reproducible with acceptable standard deviation 3.7% and relative error 3.4%. For a comparison of the method phosphate present in various samples were also determined separately following an official method. The results of the developed method compare well with those of the official method.

Assessment of Heavy Metals in Water Samples of Certain Locations Situated Around Tumkur, Karnataka, India

Surface water and groundwater samples of certain locations namely Kallambella, Bugudanahalli, Maidala, Honnudike, Kunigal, Kadaba and Hebbur, situated around Tumkur were assessed in the month of September 2008 for pH, EC and heavy metals Cd, Cu, Fe, Hg, Mn, Zn and Ni. The pH vales of surface waters were in alkaline range of 7.8-8.2 and are well within safe limits for crop production. The pH of ground- water was in the range of 7.6-8.4. The conductivity was in the range of 0.20-0.68 mS/cm and 0.34-2.44 mS/cm for surface and groundwaters respectively. High EC value of Kallambella groundwater accounts for its salinity. All surface waters except Honnudike and Hebbur samples contain low concentrations of these metals and are ideal for irrigation. Though the samples from Honnudike, Kadaba and Hebbur have high iron concentration, only Honnudike and Hebbur samples have exceeded the limit of 5 mg/L required for irrigation. In groundwaters the concentrations of all these heavy metals except copper are also well in permissible limits and suitable for drinking. Cu, Fe, Ni and Zn were detected in all the samples and found in the range of 0.094-0.131, 0.958-12.537, 0.020-0.036 and 0.082-1.139 mg/L respectively in surface waters and these are in the range of 0.132-0.142, 0.125-1.014, 0.028-0.036 and 0.003-0.037 mg/L in ground- waters. The elements cadmium, mercury and manganese are absent in all the samples.

Iron(III) oxidized nucleophilic coupling of catechol with o-tolidine/p-toluidine followed by 1,10-phenanthroline as new and sensitivity improved spectrophotometric methods for iron present in chemicals, pharmaceutical, edible green leaves, nuts and lake water samples

A nucleophile formed from iron(III) oxidized catechol in 0.1M hydrochloric acid couple with o-tolidine, system 1/p-toluidine, system 2 to produce dye product, λ max 520 nm. The system 1/2 obeys Beers law in the range 0.08-8.0 μg ml(-1) with molar absorptivity, Sandell sensitivity and regression coefficient values, 4.225 × 10(3)/3.140 × 10(3) l mol(-1) cm(-1), 0.0132/0.0178 μg cm(-2) and 0.9987/0.9981. Iron(II) formed from iron(III) in system 1/2 reacts with 1,10-phenanthroline, λ max 510 nm, will constitute sensitivity improved iron determinations with values 0.08-1.6 μg ml(-1), 2.4136 × 10(4)/2.2511 × 10(4) l mol(-1) cm(-1), 0.0023/0.0025 μg cm(-2) and 0.9980/0.9997 corresponding to range, molar absorptivity, Sandell sensitivity and regression coefficient. The results of the systems for iron present in chemicals, pharmaceutical, edible green leaves, nuts and lake water samples are satisfactory since they are comparable with the results of iron determined separately from 1,10-phenanthroline method.

New spectrophotometric methods for the determinations of hydrogen sulfide present in the samples of lake water, industrial effluents, tender coconut, sugarcane juice and egg

The new methods are working on the principle that iron(III) is reduced to iron(II) by hydrogen sulfide, catechol and p-toluidine the system 1/hydrogen sulfide the system 2, in acidic medium followed by the reduced iron forming complex with 1,10-phenanthroline with λ(max) 510 nm. The other two methods are based on redox reactions between electrolytically generated manganese(III) sulfate taken in excess and hydrogen sulfide followed by the unreacted oxidant oxidizing diphenylamine λ(max) 570 the system 3/barium diphenylamine sulphonate λ(max) 540 nm, the system 4. The increase/decrease in the color intensity of the dye products of the systems 1 and 2 or 3 and 4 are proportional to the concentration of hydrogen sulfide with its quantification range 0.035-1.40 μg ml(-1)/0.14-1.40 μg ml(-1).

Simple spectrophotometric method for the determination of sulfur dioxide by its decolorizing effect on the peroxovanadate complex

A simple, rapid, and economical spectrophotometric method is developed for the determination of sulfur dioxide in sugar and air samples. The developed method is based on a red-brown peroxovanadate complex (λmax = 470 nm) produced in 2 M sulfuric acid when ammonium metavanadate is treated with hydrogen peroxide. Under fixed concentrations of hydrogen peroxide and ammonium metavanadate, when sodium metabisulfite (Na2S2O5 = 2SO2) is added, it preferentially reacts with hydrogen peroxide producing sulfuric acid, and the unreacted hydrogen peroxide then reacts with ammonium metavanadate; therefore, the concentration of sulfur dioxide is directly proportional to a decrease in the concentration of the peroxovanadate complex. The stoichiometric ratio between hydrogen peroxide and ammonium metavanadate as well as the stability constant of the complex are determined by the modified Job’s method and the respective values are found to be 1: 1 and 2.5 × 104 mol−1 L, respectively. The system obeys Lambert-Beer’s law in the concentration range 3.57–64.26 ppm of sulfur dioxide. The molar absorptivity, correlation coefficient, and Sandell’s sensitivity values are found to be 0.649 × 103 L mol−1 cm−1, 0.9908, and 0.1972 μg cm−2, respectively. The method is applied to the determination of sulfur dioxide present in commercial sugars and air samples. The results obtained are reproducible with a standard deviation of 0.02–0.05. For method validation, sulfur dioxide is also determined separately following the AOAC method for an air sample and the ICUMSA method for commercial sugars. The results obtained by the developed and official methods are in good agreement.

A New Spectrophotometric Method for Hydrogen Sulphide Through Electrolytically Generated Mn(III) With O-Tolidine

A simple, sensitive and economical spectrophotometric method for the determination of hydrogen sulphide is developed. The method is based on a redox reaction in that Mn(III) generated electrolytically is taken in excess, which is oxidizing a known but a less quantity of hydrogen sulphide and the unreacted oxidant will oxidize further o-tolidine to produce an orange yellow quinonediimine absorbing cation (λ max. 455 nm). Therefore, in principle, the decrease in color intensity of the absorbing system is proportional to the concentration of hydrogen sulphide. The stoichiometry between Mn(III) and o-tolidine and stability constant of the complex were determined by Jobs continuous method, the corresponding values were found to be 2:1 and 1.42X105 Lmol-1. The system was obeying Lambert-Beers law in the range 0.2-1.4 μg mL-1 of hydrogen sulphide. Molar absorptivity, correlation coefficient and Sandells sensitivity values were also calculated and found to be 4.2062X103 L mol-1 cm-1, 0.999 and 0.0012 μg cm-2 respectively. The method was employed for the determination of hydrogen sulphide in water samples. The results obtained were reproducible with acceptable standard deviation 0.01-0.068 and relative standard deviation, less than 3.21%. For a comparison, hydrogen sulphide present in water samples were also determined separately following the methylene blue official method. The results of the proposed method compare well with the official method.