7 research outputs found
Determination of bismuth and zinc in pharmaceuticals by first derivative UV-Visible spectrophotometry
A first order derivative spectrophotometric method has been developed for the simultaneous determination of bismuth and zinc by dithizone without time-consuming extraction step. The reactions of bismuth and zinc with dithizone in a three component solution prepared in water, acetone and n-propanol mixture have been investigated. These cations react with dithizone in this mixture at pH 5.0, forming coloured complex that is stable for at least 2 h. The linear range in D evaluation was between 3.0 x 10(-6) and 1.8 x 10(-5) mol 1(-1) for Zn and 2.4 x 10(-6) and 1.2 x 10(-5) Mol 1(-1) for Bi. The limits of detection for the analytical procedure were found 0.05 mg 1(-1) for both cations. The relative standard deviations for the determination of 0.5 mg 1(-1) bismuth and 0.5 mg 1(-1) zinc were 1.2 and 1.1%, respectively, for five determinations. The procedure is simple, rapid and reliable. This method was applied to the determination of bismuth and zinc in the pharmaceutical materials successfully. Good agreement was achieved between the results obtained by the proposed and comparative methods. (c) 2005 Elsevier B.V. All rights reserved
Simultaneous spectrophotometric determination of cyanide and thiocyanate after separation on a melamine-formaldehyde resin
A simple indirect spectrophotometric method for the determination of cyanide, based on the oxidation of the cyanide with chlorine (Cl-2) is described. The residual chlorine is determined by the color reaction with o-tolidine (3,3'-dimethylbenzidine). The maximum absorbance for Cl-2 is at 437 nm. A linear calibration graph (0-4.0 x 10(-5) M CN-) is obtained under optimal reaction conditions at room temperature and pH 11-12, The stoichiometric mole ratio of chlorine to cyanide is 1:1. The effective molar absorptivity for cyanide is 5.87 x 10(4) l mol(-1) cm(-1) at pH 1.6. The limit of quantification (LOQ) is 3.6 x 10(-7) M or 9.4 ppb. Effects of pH, excess reagent, sensitivity, reaction time and tolerance limits of interferent ions are reported. The method was applied to the determination of cyanide in a real sample. The basic interferent usually accompanying CN-, i.e. thiocyanate, is separated from cyanide by sorption on a melamine-formaldehyde resin at pH 9 while cyanide is not retained. Thiocyanate is eluted with 0.4 M NaOH from the column and determined spectrophotometrically using the acidic FeCl3 reagent. The initial column effluent containing cyanide was analyzed by both the developed chlorine-o-tolidine method and the conventional barbituric acid-pyridine (Spectroquant 14800) procedure, and the results were statistically compared. The developed method is relatively inexpensive and less laborious than the standard (Spectroquant) procedure, and insensitive to the common interferent, cyanate (CNO-). (C) 2000 Elsevier Science B.V. All rights reserved
Spectrophotometric determination of organic nitrogen by a modified Lassaigne method and its application to meat products and baby food
A modified Lassaigne method was developed for N determination based on fusion of the organic substance with metallic Na, conversion of the cyanide in the aqueous leachate to thiocyanate by ammonium polysulfide treatment, and colorimetric measurement of the thiocyanate formed by the addition of excessive ferric ions in acidic medium. The mean molar absorptivity of the Fe(NCS)(2+) complex at 480 nm is 2.96 x 10(3) L/mol(.)cm, enabling quantitation of 0.25-7.72 ppm N (linear range) in the final solution. The relative amounts of Na, (NH4)(2)S-2, and Fe(III) with respect to nitrogen in the analyte were optimized. The developed method was successfully applied to the determination of N in various brands of baby food, and it was compared statistically with the conventional Kjeldahl and elemental analysis methods. Protein nitrogen in a number of meat products was also precisely determined by the developed method. Thus, the total digestion time of the conventional Kjeldahl method was reduced considerably (e.g., to approximately 15 min for a dried sample) with a relatively simple spectrophotometric method requiring no sophisticated instrumentation
Simultaneous determination of chlorophyll a and chlorophyll b by derivative spectrophotometry
Chlorophyll a (Chl a) and chlorophyll b (Chl b) plant pigments, which are important in the food industry and are beneficial as environmental pollution indicators, have been. extracted with a novel solvent mixture (1: 1 v/v acetone-propanol) not containing chloroform and simultaneously determined by first-derivative spectrophotometry. The results were statistically compared to those obtained by the ordinary absorption spectrophotometric reference utilizing the principle of additivity of absorbances. The testing of the developed method in synthetic mixtures of Chl a and Chl b and in real plant material samples (grass, spinach, chard, purslane, black cabbage, crisp lettuce, rocket, dill and seaweed) proved successful in that the developed extractive derivative spectrophotometric method was both rapid and precise, and was not dependent on the Chl a/b ratio in contrast to the reference method which was adversely affected by the latter parameter
Spectrofluorometric determination of hydrogen peroxide
A spectrofluorometric method for microdetermination of H2O2 has been developed. The method is based on the oxidation of hydrogen peroxide with eerie ion in acid solution and measurement of the fluorescence during titration of the Ce(III) ions produced. The fluorescent species have excitation and emission maxims at 260 and 360 nm, respectively. The detection limit of measurement by this method was 0.1 ppm hydrogen peroxide