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Indirect spectrophotometric determination of hydrogen peroxide
Abstract
A method for the indirect spectrophotometric determination of H2O2 is based on its oxidation with chlorine in basic medium and measurement of the unreacted Cl2 by the colour reaction with o-tolidine at 438 nm. The effective molar absorptivity for H2O2 with o-tolidine is 5.37104 mol–1 cm–1 at pH 1.7. The lower limit of determination is 1.8510–7 mol/l or 6.29 ppb. Br–, I–, NO–
2, Pb2+ and Sn2+ interfere even in small amounts, but are not present in commercial H2O2.
A simple indirect sequential injection spectrophotometric method for the determination of the UV-filter p-aminobenzoic acid (PABA) in sunscreen formulations is proposed. The determination is based on the reaction of PABA with hypochlorite in acidic medium and the subsequent measurement of the residual chlorine by using the well-known reaction with o-tolidine.The experimental variables involved in the sequential injection analysis (SIA) system (sandwich arrangement, volumes of sample and reagents, propulsion flow rate, reaction coil length) and adequate concentrations of reagents were studied.The SIA method has a linear range up to 20 μg ml−1 (3sy/x/b detection limit) of 1.0 μg ml−1 and a measurement throughput of 55 injections h−1.Sunscreen cosmetics containing PABA were analyzed by the proposed method and the results were validated by comparison with those obtained by a liquid chromatographic procedure used as reference.The analytical features of the proposed method make it suitable for quality control of final products.
A Spectrofluorometric method for microdetermination of H2O2 has been developed. The method is based on the oxidation of hydrogen peroxide with ceric ion in acid solution and measurement of the fluorescence during titration of the Ce(III) ions produced. The fluorescent species have excitation and emission maxima at 260 and 360 nm, respectively. The detection limit of measurement by this method was 0.1 ppm hydrogen peroxide.
Flow-injection analysis system (FIA system), which was based on Fe(II)-catalyzed oxidation of chromotropic acid with hydrogen peroxide, was developed for the determination of hydrogen peroxide. The chromotropic acid has a fluorescence measured at lambda(em)=440 nm (emission wavelength) with lambda(ex)=235 nm (excitation wavelength), and the fluorescence intensity at lambda(em)=440 nm quietly decreased in the presence of hydrogen peroxide and Fe(II), which was caused by Fe(II)-catalyzed oxidation of chromotropic acid with hydrogen peroxide. By measuring the difference of fluorescence intensity, hydrogen peroxide (1.0 x 10(-8)-1.0 x 10(-3) mol L(-1)) could be determined by the proposed FIA system, whose analytical throughput was 40 samples h(-1). The relative standard deviation (RSD) was 1.03% (n=10) for 4.0 x 10(-8) mol L(-1) hydrogen peroxide. The proposed FIA technique could be applied to the determination of hydrogen peroxide in rain water samples.
A biosensor for the specific determination of hydrogen peroxide was developed using catalase (EC 1.11.1.6) in combination with a dissolved oxygen probe. Catalase was immobilized with gelatin by means of glutaraldehyde and fixed on a pretreated teflon membrane served as enzyme electrode. The electrode response was maximum when 50 mM phosphate buffer was used at pH 7.0 and at 35 degrees C. The biosensor response depends linearly on hydrogen peroxide concentration between 1.0x10(-5) and 3.0x10(-3) M with a response time of 30 s. The sensor is stable for >3 months so in this period >400 assays can be performed.
A simple and sensitive fluorescent quenching method for the determination of trace hydrogen peroxide (H(2)O(2)) has been proposed to determine hydrogen peroxide in rain water sample. The method is based on the reaction of H(2)O(2) with 3,3'-diethyloxadicarbocyanine iodide (DI) to form a compound which has no fluorescence in acetate buffer solution (pH 3.09). The maximum emission wavelength of the system is located at 604 nm with excitation at 570 nm. Under the optimal conditions, the calibration graph was obtained between the quenched fluorescence intensity and hydrogen peroxide concentration in the range of 5.0 x 10(-7) to 9.0 x 10(-4) mol L(-1). The proposed method was applied to determine H(2)O(2) in rain water samples, and the result was satisfactory. The mechanism involved in the reaction was also studied.
Hydrogen peroxide reacts with iron(II) in acidic medium, and the unreacted iron(II) forms a stable complex with 1,10-phenanthroline that absorbs at 508 nm. This indirect spectrophotometric method, based on the absorbance reduction of tris(1,10-phenanthroline)iron(II) was utilised for the determination of hydrogen peroxide. The effective molar absorptivity for H2O2 is 2.22 × 104 l mol–1 cm–1. The proposed procedure is sensitive and has been applied to the analysis of commercial peroxide samples. Possible interferences are discussed.
Analyst 115:99 1:1 volume ratio into a graphite furnace and heated upto 1200 °C, according to the temperature programme given in Table 1. This process was repeated until about 100 mg compound had
- H Af~ar
- R Apak
- Tor
Af~ar H, Apak R, Tor I (1990) Analyst 115:99 1:1 volume ratio into a graphite furnace and heated upto 1200 °C, according to the temperature programme given in Table 1. This process was repeated until about 100 mg compound had