A colorimetric determination of acetylcysteine, penicillamine, and mercaptopropionylglycine is described. The method is based on the oxidation of mercapto-compounds with iron(III) in the presence of 1,10-phenanthroline. The iron(II) formed was quantitatively and rapidly converted to the stable tris(1,10-phenanthroline)iron(II) complex measured spectrophotometrically at 515 nm. The results obtained from various commercial formulations indicate that the method proposed allows a simple, sensitive determination of these mercapto-drugs with good accuracy (99.5-101% recovery) and remarkable precision (RSD +/- 0.6-1.6%).

Acetylcysteine↗

PubMed1981

Colorimetric determination of miconazole nitrate in pharmaceutical preparations.

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Imidazoles↗

PubMed1980

[Effect of aging on stability and dissolution velocity of controlled-release ferrous sulfate tablets].

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Delayed-Action Preparations↗

PubMedDate not supplied

HPLC determination of glutathione and other thiols in human mononuclear blood cells.

A simple and sensitive HPLC method is proposed for the determination of glutathione (GSH) in human mononuclear cells, based on the derivatization of the tripeptide with Ellman's reagent. The mobile phase was composed of a mixture of methanol and ammonium formate (10:90 v/v, with a flow rate of 1 mL/min). The stationary phase was a C18 (4.6 microns, 250 x 4 mm) reversed phase column. The detection of GSH was performed at 280 nm, resulting in a neat chromatographic peak at 5.8 min. A calibration curve showed good linearity over the concentration range 3 x 10(-6) - 6 x 10(-5) M, with a satisfactory precision. The method was found to yield a quantitative recovery of glutathione (96%), to be sensitive (down to 30 pmol of glutathione per injection) and to have a high precision (R.S.D.% approximately equal to 2). The proposed HPLC method allows for the separation and quantitation of cysteine and N-acetylcysteine, if present in biological samples. Furthermore, the method allows for the determination of total thiol present in human mononuclear cells.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

Fluorimetric determination of aluminum traces in hemodialysis solutions using Mordant Red 19.

A sensitive and accurate method for the spectrofluorimetric determination of trace levels of aluminum in hemodialysis solutions using Mordant Red 19 as the complexation reagent has been developed. The optimal experimental conditions for the concentration of fluorimetric reagent, pH, temperature, and the specific type of matrix are reported. The emission of the fluorescent metal chelate was measured at 555 nm, excitation at 478 nm. Linearity between emission intensity and aluminum concentration was found in the 2-20 ppb range in standard aluminum solutions. Limit of detection was 0.4 ppb. The aluminum amounts in some commercial hemodialysis solutions were determined by means of the extrapolation method. The proposed method proved to be suitable in terms of sensitivity and accuracy for the determination of aluminum in dialysis fluids.

Aluminum↗

PubMedDate not supplied

Simultaneous determination of all-trans-retinoic acid, beta-carotene, and vitamin A in galenic preparations by liquid chromatography.

The concentrations of vitamin A, beta-carotene, and all-trans-retinoic acid in oral preparations were determined in a single analysis by a method based on isocratic, reversed-phase liquid chromatography (LC). The LC system consisted of a C18 column, a mobile phase of acetonitrile, dichloromethane, methanol, and water and a UV detector set at 330 nm. The linearity ranges were 25-250 ng/mL for trans-retinoic acid and vitamin A, and 100-1,000 ng/mL for beta-carotene. This LC method for the determination of retinoids is simple, precise, and accurate. No extraction procedure is required before the chromatographic analysis; only a suitable dilution is necessary. The method proved to be reliable, fast, and economical. Furthermore, this method is indicative of stability, because it allows for the determination of degradation products such as 13-cis-retinoic acid.

Chromatography, Liquid↗

PubMedDate not supplied

Comparison of three analytical methods for quality control of clozapine tablets.

Three different analytical methods for the quality control of clozapine in commercial formulations were developed and compared: a liquid chromatographic (LC) method with UV detection, a capillary zone electrophoretic (CZE) method, and a linear scan voltammetric (LSV) method. The isocratic LC procedure used a C18 reversed-phase column; the CZE method used an uncoated fused-silica capillary and phosphate buffer containing polyvinylpyrrolidone as the background electrolyte; the LSV method analyzed clozapine solutions with acidic phosphate buffer as the supporting electrolyte. The 3 methods gave similar and satisfactory results, in terms of precision and accuracy. Repeatability and intermediate precision were good (RSD% < 2.2) and accuracy, resulting from recovery studies, was between 98 and 102%. The rapidity of analysis was high for all 3 methods, especially for the LSV.

Antipsychotic Agents↗

PubMedDate not supplied

Extractive spectroscopic insulin determination in pharmaceutical formulations.

Two methods are proposed, one spectrophotometric and one spectrofluorimetric, for the determination of insulin in several pharmaceutical formulations. The methods were found to be fairly simple, sensitive and accurate, and thus suitable for this purpose. Both methods involve an extractive step with diethyl ether for the elimination of excipient interference, and subsequent direct spectrometric analysis. Spectrophotometric determinations were carried out at lambda = 276 nm; spectrofluorimetric determinations were carried out at lambda em = 306 nm with lambda exc = 277 nm.

Amino Acid Sequence↗