Colorimetric determination of tetracycline hydrochloride in pharmaceutical preparations

A simple, sensitive, and rapid colorimetric method is presented for the estimation of tetracycline hydrochloride as the pure drug and in formulations. The proposed method is based on the reaction of tetracycline HCl with cupric chloride in an alkaline medium to give a yellowish green solution whose absorbance is measured at 400 nm against a reagent blank. The color obeys Beer's law in the concentration range of 0-20 micrograms/mL. Molar absorptivity and Sandell's sensitivity of the yellowish-green copper complexes of tetracycline HCl are 1.99 X 10(4) L X mol-1 X cm-1 and 0.0241 ppm, respectively.     

Colorimetric determination of tetracycline derivatives in pharmaceutical preparations

A quick colorimetric method is reported for the determination of tetracycline derivatives such as oxytetracycline hydrochloride (OTCH), chlortetracycline hydrochloride (CTCH), methacycline hydrochloride (MCH), and doxycycline hydrochloride (DCH). The method involves complexation of the above derivatives with cupric chloride in alkaline medium. The yellowish green copper complexes of OTCH, CTCH, MCH, and DCH show maximum absorbance at 395, 410, 400, and 400 nm, respectively. The color intensity obeys Beer's law in the concentration range of 0-20 micrograms/mL.     

Colorimetric determination of diazepam in pharmaceutical preparations.

A colorimetric method is presented for the estimation of diazepam as the pure drug and in formulations. Diazepam is hydrolyzed with 6N HCl to 2-methylamino-5-chlorobenzophenone, which is extracted with chloroform to give a yellow solution whose absorbance is measured at 410 nm against a solvent blank. The color obeys Beer's law in the concentration range of 0-30 mug/ml. In 5 determinations, recovery was 99.0 +/- 1.9%. The method is applicable to pure diazepam and its formulations for oral and parenteral use. No interferences were observed from pyridoxine hydrochloride and commonly used preservatives, vehicles, and colors.     

Colorimetric and volumetric assays of colchicine in galenicals and in pharmaceutical preparations.

In the method described the amide group in the colchicine molecule is reduced with lithium aluminum hydride to the corresponding secondary amine. The latter is extracted with chloroform and then determined either colorimetrically by the copper dithiocarbamate reaction or volumetrically by dissolving in acid and titrating with sodium hydroxide or perchloric acid. The results were comparable with those obtained by the Egyptian Pharmacopoeia spectrophotometric method.     

Colorimetric determination of stanozolol in pharmaceutical formulations

In acidic medium, stanozolol reacts with phenoldisulfonic acid to form a stable yellow chromophore, which is quantitated by spectrophotometry at 385 nm. The reaction gives a linear response at concentrations from 5 to 50 micrograms/mL. The method is suitable for routine analytical control of stanozolol and its formulations.     

Titrimetric assay of pancreatic lipase in pharmaceutical preparations

Lyophilized pancreas and pancreatic extracts are widely used in therapy of pancreatic exocrine function deficiencies. Among the measures for quality of the extracts, assay for lipolytic activity appears to be one of the best. However, assay precision is poor, because the specificity and mode of action of lipase requires careful optimization of the assay parameters, especially substrate and measurement conditions. In the method proposed here, substrate quality is improved by the use of sodium desoxycholate and a high-speed stirrer for more reproducible emulsions. Fatty acids are assayed by a titrimetric method, using an electronically monitored pH meter. A comparative statistical study of the U.S. Pharmacopeia method, the International Pharmaceutical Federation (FIP) method, and a modified FIP method showed the latter to have improved accuracy and reproducibility.     

分光光度法测定树脂包衣尿素溶出的研究

研究了对二甲氨基苯甲醛分光光度法应用于树脂包衣尿素养分溶出测定的可行性。对二甲氨基苯甲醛与尿素在酸性条件下生成黄色物质,其吸光值与尿素溶液的浓度成正比。结果表明,该方法与蒸馏后滴定法测定尿素相关性非常好,测定过程中缩二脲和硝态氮、铵态氮的干扰少。树脂包衣尿素养分溶出测定期间,尿素样品分解量少,分光光度法与蒸馏后滴定法的测定结果相关性非常好。试验证明两种方法测定包衣尿素溶出均可给出满意的结果,但分光光度法更快速、简便,适合于大批量样品的测定。     

Gas chromatographic determination of histapyrrodine hydrochloride in pharmaceutical preparations

A simple gas chromatographic method is described for the determination of histapyrrodine HCl in marketed formulations. Chlorpheniramine maleate is used as the internal standard. The amount of histapyrrodine HCl found by the proposed method averaged 19.91 mg/tablet, compared with the label claim of 20 mg/tablet. The method was statistically evaluated for accuracy and precision.     

Simple colorimetric method for determination of terbutaline sulfate from pharmaceutical preparations

A simple colorimetric method is described for the determination of terbutaline sulfate. The method is based on measurement of a colored species formed when terbutaline sulfate is treated with diazotized dapsone and p-nitroaniline at room temperature. Compounds such as starch, talc, and common excipients do not interfere in the reaction. Statistical validation showed that the method was highly precise and accurate. The results agree well with those obtained by other methods reported in the literature.     

Thin layer chromatographic identification and quantitation of niacin and niacinamide in pharmaceutical preparations

A safe and simple thin layer chromatographic method has been developed for the estimation of niacin and niacinamide in pharmaceutical preparations containing other vitamins, enzymes, herbs, antiamoebic drugs, etc. The method involves removal of excipients from the preparation by ethanol precipitation and isolation of niacin or niacinamide from other ingredients by TLC on silica gel with water as developing solvent, followed by extraction in 0.1N HCl, and spectrophotometric estimation of the vitamin at 262 nm. The percent recoveries for niacin and niacinamide were 100.1 +/- 1.9 and 100.2 +/- 1.5, respectively.     

Colorimetric method for the estimation of total limonoid aglycones and glucoside contents in citrus juices

A method for estimating the total limonoid aglycone and glucoside concentrations in Citrus samples in terms of limonin and limonin glucoside equivalents is presented. The method consists of extraction followed by colorimetric quantification. The colorimetric quantification was based on the formation of red to orange colored derivatives resulting from the treatment of limonin, limonin glucoside, or a fruit extract with 4-(dimethylamino)benzaldehyde (DMAB) in the presence of perchloric and acetic acids. Absorbance maxima for the limonin and limonin glucoside derivatives were found to be 470 and 503 nm, respectively. The influence of DMAB concentration, reaction time, and solvent composition on color development and sensitivity were investigated and optimal assay conditions established. With a microplate format under these conditions, the limits of detection and quantification were determined to be 0.25 and 0.50 microg/mL for limonin and 0.50 and 1.0 microg/mL for limonin glucoside.     

Polyvinyl chloride matrix membrane electrodes for manual and flow injection analysis of chloroquine in pharmaceutical preparations.

Two types of polyvinyl chloride (PVC) matrix membrane electrodes responsive to the antimalarial drug chloroquine have been constructed, electrochemically evaluated, compared and used in pharmaceutical analysis. Type 1 is the classic PVC model with chloroquine-tetraphenylborate (TPB) sensor; Type 2 is a coated silver disk without internal filling solution. Both electrode types exhibited rapid linear potentiometric response to the logarithmic concentration of diprotonated chloroquine cation in the 10(-1) - 10(-6)M range with calibration slopes 28-30 mV/concentration decade over the pH range 1.8-6.2. These electrodes were sensitive enough to permit determination of chloroquine phosphate at concentrations as low as 5 microgram/mL with good accuracy and precision. Determination of chloroquine in various pharmaceutical preparations using direct potentiometry and potentiometric titration with NaTPB gave an average recovery of 98.8% of the nominal values (SD 0.5%). The Type 2 electrode was also assessed in a flow-through sandwich cell for flow injection analysis. Results were compared with data obtained by the U.S. Pharmacopeia method.     

Determination of vitamin B1 in pharmaceutical preparations using a lead ion selective electrode and atomic absorption spectroscopy.

Simple, rapid, and accurate methods have been developed for determining vitamin B1 in pharmaceutical preparations without prior separation of the vitamin. The methods are based on the desulfurization reaction with potassium plumbite and measurement of the unreacted lead(II) ions at 217 nm using atomic absorption spectroscopy (AAS), or by titration with EDTA at pH 4.5 with the lead ion selective electrode and Gran's plot. The results compare favorably with those obtained using the USP fluorometric method. Recoveries of pure vitamin B1 averaged 99.1%, with a standard deviation of 0.8%, and 99.0%, with a standard deviation of 0.7%, for the AAS and ion selective electrode procedures, respectively.