Quantitative determination of glycine in commercial dosage forms by kinetic spectrophotometry

A kinetic method for the determination of nanogram quantities of amino acid glycine (Gly) is described. The catalytic activity of cobalt in the reaction of oxidation of purpurin (1,2,4-trihydroxyantraquinone, PP) by hydrogen peroxide in alkaline buffer solution decreases in the presence of micro quantities of glycine. Operating conditions for the successful determination of glycine were optimized and yielded a theoretical detection limit of 6.5 ng/mL. Kinetic equations are proposed for the investigated process. The interference effects of certain foreign ions and amino acids upon the reaction rate were studied in order to assess the selectivity of the method. The procedure was successfully applied to the determination of glycine in various pharmaceutical samples. The unique features of this procedure are that the determination can be carried out rapidly at room temperature and analysis time is short. The procedure is simple, inexpensive and efficient for use in the analysis of a large number of samples. The article is published in the original.     

分光光度法定量测定柠檬酸及其盐的含量

酸性介质中,柠檬酸(或盐)与Fe3+形成的黄色络合物在光照条件下发生光致变色现象,生成紫红色络合物,采用分光光度法可定量测定柠檬酸及其盐的含量.在冰水浴中,日光照射20 min,阴凉处静置30 min,检测波长为490nm.线性范围为(0～300)mg/L,相对标准偏差(RSD)为0.46％(n=6),检测限为3.46...     

The determination of gold by atomic absorption spectrophotometry

Gold can be isolated from most other elements other than the platinum metals by the extraction of iron(II) 1,10-phenanthroline tetrabromoaurate in chloroform. After isolation gold can be determined in the organic solvent by atomic absorption spectroscopy or colorimetrically by decomposition of the complex and determination of the iron by bathophenanthroline.     

The determination of selenium by atomic absorption spectrophotometry

The problems involved in the determination of selenium by atomic absorption spectrophotometry are discussed. A practical method is described for which the sensitivity is approximately 1 p.p.m. Such concentrations can be determined in organic samples, but with mineral samples the preliminary treatment renders the procedure unsuitable for concentrations lower than 50 p.p.m. in a sulphide ore.     

Quantitative analysis of rabeprazole sodium in commercial dosage forms by spectrophotometry

The main aim of this work is to develop and validate two spectrophotometric methods for the quantitative analysis of rabeprazole sodium in commercial dosage forms. Method A is based on the reaction of drug with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) in the presence of ammonium cerium(IV) nitrate in acetic acid medium at room temperature to form red-brown product which absorbs maximally at 470 nm. Method B utilizes the reaction of rabeprazole sodium with 1-chloro-2,4-dinitrobenzene (CDNB) in dimethyl sulfoxide (DMSO) at 45+/-1 degrees C to form yellow colored Meisenheimer complex. The colored complex has a characteristic band peaking at 420 nm. Under the optimized reaction conditions, proposed methods are validated as per ICH guidelines. Beer's law is obeyed in the concentration ranges of 14-140 and 7.5-165 microg ml(-1) with linear regression equations of A=6.041 x 10(-4)+1.07 x 10(-2)C and A=1.020 x 10(-3)+5.0 x 10(-3)C for methods A and B, respectively. The limits of detection for methods A and B are 1.38 and 0.75 microg ml(-1), respectively. Both methods have been applied successfully for the estimation of rabeprazole sodium in commercial dosage forms. The results are compared with the reference UV spectrophotometric method.     

Quantitative analysis of irbesartan in commercial dosage forms by kinetic spectrophotometry

The objective of this work is to develop a new kinetic spectrophotometric method for the determination of irbesartan in pharmaceutical formulations. The method is based on the reaction of carboxylic acid group of the oxidized irbesartan with a mixture of potassium iodate (KIO(3)) and iodide (KI) to form yellow colored triiodide ions in aqueous medium at 30+/-1 degrees C. The reaction is followed spectrophotometrically by measuring the rate of change of absorbance at 352 nm. The initial-rate and fixed-time (DeltaA) methods are adopted for constructing the calibration curves, which were found to be linear over the concentration ranges of 10.0-60.0 and 7.5-60.0 microg ml(-1) respectively. The regression analysis of calibration data yielded the linear equations: rate=-2.138 x 10(-6)+1.058 x 10(-4)C and DeltaA=-3.75 x 10(-3)+3.25 x 10(-3)C for initial rate and fixed time (DeltaA) methods, respectively. The limit of detection for initial rate and fixed time methods are 0.21 and 2.40 mug ml(-1), respectively. The various activation parameters such as E(a), DeltaH++, DeltaS++ and DeltaG++ are also calculated for the reaction and found to be 70.95+/-0.43 kJ mol(-1), 68.48+/-0.21 kJ mol(-1), 16.54+/-0.24 J K(-1) mol(-1) and -4.94+/-0.07 kJ mol(-1), respectively. The proposed methods are optimized and validated as per the guidelines of International Conference on Harmonisation (U.S.A.). The point and interval hypothesis tests have been performed which indicate that there is no significant difference between the proposed methods and the reference method. The methods have been successfully applied to the determination of irbesartan in commercial dosage forms.     

The determination of uranium isotopes by atomic absorption spectrophotometry

The uranium isotopes, ²³⁵U and ²³⁸U, can be determined easily by atomic absorption techniques, employing relatively inexpensive and unsophisticated equipment. A water-cooled hollow-cathode discharge tube was used as an absorption tube. It was found that large amounts of uranium atoms, in the ground state, were produced by the discharge in the tube. Thus the inherently weak uranium resonance radiation coming from. an emission source and passing through the absorption tube was absorbed. For the first time in an atomic absorption technique, samples and related standards were used in the emission source instead of an absorption source, and a high degree of accuracy and precision was obtained. Valid results were also obtained by conventional techniques — that is, the samples and related standards were employed in the absorption source.     

The determination of trace elements in sulphide minerals by atomic absorption spectrophotometry with absorption tubes

A method for the determination of minor and trace elements (Zn, Cd, Pb, Cu and Ag) in sulphide minerals by atomic absorption spectrophotometry is described. For enhancing the sensitivity of the determination, the absorption tube technique is applied. Memory effects and background absorption influences on the measurement with absorption tubes are discussed.     

The determination of silver in sulphide minerals by atomic absorption spectrophotometry

Silver can be determined in sulphide minerals by atomic absorption spectrophotometry after decomposition with nitric and/or sulphuric acid with addition of tartaric acid to prevent precipitation of antimonic acid. The amount of silver retained in the residue is negligible if the acids used are completely chloride-free or if mercury(II) nitrate is added.     

The determination of iron in tungsten carbide by atomic absorption spectrophotometry

An atomic absorption spectrophotometric procedure for the determination of 0.005 to 0.20% iron in a phosphoric acid solution of tungsten carbide is described. The method is rapid, preliminary separations are not required and the results obtained have been compared with those obtained by X-ray fluorescence.     

The determination of strontium in coal ash by atomic absorption spectrophotometry

An atomic absorption spectrophotometric method for the determination of 0.01%–0.40% strontium in coal ashes is proposed. After suitable dissolution of the sample, 2000 p.p.m. of lanthanum are added to overcome interferences before the solution is atomized. The results obtained were compared with those obtained by flame-emission spectrophotometry. The method is rapid and no preliminary separations are necessary.     

The determination of sodium in pure limestones by atomic absorption spectrophotometry

The determination of sodium in pure limestones by atomic absorption spectrophotometry is described. The interferences of chloride and calcium ions are discussed; chloride affects the dissociation equilibrium, and calcium lowers the evaporation rate of sodium, thus lowering the concentration of free sodium atoms in the flame. The sensitivity achieved with a rather rough apparatus is 0.15 p.p.m. sodium.     

The rapid determination of barium in bone by atomic absorption spectrophotometry

A rapid and precise method for the determination of barium in bone is presented. Barium as the nitrate is directly separated from calcium by co-precipitation with added strontium using fuming nitric acid. Atomic absorption measurements are made at 553.6 nm using a nitrous oxide-acetylene flame in the presence of strontium and potassium, and being free from noise due to the emission of CaOH. In order to improve accuracy and speed a radioactive tracer is used.     

Quantitative determination of oxybutynin hydrochloride by spectrophotometry, chemometry and HPTLC in presence of its degradation product and additives in different pharmaceutical dosage forms

Simple, accurate, sensitive and validated UV spectrophotometric, chemometric and HPTLC-densitometric methods were developed for determination of oxybutynin hydrochloride (OX) in presence of its degradation product and additives in its pharmaceutical formulations. Method A is the first derivative of ratio spectra (DD¹) which allows the determination of OX in presence of its degradate in pure form and tablets by measuring the peaks amplitude at 216 nm. Method B and C are principal component regression (PCR) and partial least-squares (PLS) for determination of OX in presence of its degradate in pure form, tablets and syrup. While, the developed high performance thin layer chromatography HPTLC-densitometric method was based on the separation of OX from its degradation product, methylparaben and propylparaben followed by densitometric measurement at 220 nm which allows the determination of OX in pure form, tablets and syrup. The separation was achieved using HPTLC silica gel F₂₅₄ plates and chloroform:methanol:ammonia solution:triethylamine (100:3:0.5:0.2, v/v/v/v) as the developing system. The accuracy, precision and linearity ranges of the developed methods were determined. The results obtained were statistically compared with each other and to that of a reported HPLC method, and there was no significant difference between the proposed methods and the reported method regarding both accuracy and precision.     

New method for the determination of pentachlorophenol by atomic absorption spectrophotometry

A new application of atomic absorption is reported for the determination of pentachlorophenol. The method is based on solvent extraction into nitrobenzene of the ion-pair formed between tris(1,10-phenanthroline) iron(II) and the anion of pentachlorophenol, and the subsequent determination of the iron concentration m the extract by atomic absorption at the 2483 A iron line.