The role of assay methods in characterizing the quality of bulk pharmaceuticals.

This study presents the role of assay methods in characterizing the quality of bulk substances in pharmaceutical analysis. High-performance liquid chromatography (HPLC) is the most remarkable development and the technique has become very significant in the quality control of bulk drugs and pharmaceutical formulations, even at the pharmacopoeial level. Development of HPLC and other chtromatographic techniques, coupled with mass spectrometry, is also useful in the determination of drugs and their metabolites in biological samples. The role of electrophoretic, spectroscopic, and other methods in pharmaceutical analysis are discussed here. There are separate sections devoted to microscopy techniques that are useful in the pharmaceutical field, as also the regulatory aspects of drug analysis, with emphasis on questions related to validation.

Applications of the extractive methods in chemical analysis of some psychotropic drugs.

The review is devoted for the solid phase extraction and the extractive spectrophotometric methods for the determination of some psychotropic drugs, e.g. phenothiazines, thioxanthenes, dibenzothiazines, fluoxetine, fluvoxamine, trazodone.

Sensitive extractive spectrophotometric methods for the determination of nortriptyline hydrochloride in pharmaceutical formulations.

Two simple, sensitive and rapid extractive spectrophotometric methods have been developed for the assay of the antidepressant drug nortriptyline (NOR) hydrochloride in pure form and in different dosage forms. The methods involve the formation of colored ion-pairs between the drug and the complex of niobium(V)-thiocyanate (Nb-SCN) or iron(III)-thiocyanate (Fe-SCN) followed by their extraction with butanol or a mixture of butanol and chloroform and quantitative determination at 360 nm and 490 nm, using Nb-SCN and Fe-SCN, respectively. The experimental conditions were optimized to obtain the maximum colour intensity. The methods permit the determination of nortriptyline over a concentration range of 15-100 microg/ml and 5-24 microg/ml with the detection limit of 0.84 microg/ml and 0.32 microg/ml, using Nb-SCN and Fe-SCN, respectively. The proposed methods are applicable for the assay of the investigated drug in different dosage forms and the results are in good agreement with those obtained by the official and HPLC methods. No interference was observed from common excipients present in pharmaceutical formulations. The proposed procedures were applied to determine the amount of nortriptyline hydrochloride as active ingredient in the presence of its degradation product, dibenzosuberone. The extractive spectrophotometric methods can also be used to determine the amount of nortriptyline hydrochloride in tablets after its solid phase extraction (SPE).

Sensitive spectrophotometric methods for quantitative determination of chlorprothixene in pharmaceutical dosage form.

Simple and sensitive UV-VIS spectrophotometric methods for the determination of chlorprothixene hydrochloride have been developed. One of them is based on the oxidation of chlorprothixene (CPT) by ammonium metavanadate with the formation of colourless product. The second method involves the formation of ion-pair between the drug under investigation and inorganic complexes of titanium (IV) thiocyanate followed by its extraction with mixture of butanol-chloroform (1:9, v/v). The optimum conditions for the oxidation of CPT or ion-pair formation are established. The studies are examined by UV-VIS, IR or NMR spectroscopy. The methods permit the determination of CPT over the concentration range of 2.5-25 mug/ml and 4-35 mug/ml using ammonium metavanadate or the titanium (IV) thiocyanate complex, respectively. The methods are rapid, highly reproducible and accurate with +/- 0.8%. The methods are applicable to the assay of the drug under investigation in different dosage forms and the results are in good agreement with those obtained by the official methods. Common excipients used as additives to active ingredient in pharmaceutical preparations do not interfere in the proposed methods. The extractive spectrophotometric method can be applied to the determination of chlorprothixene hydrochloride in tablets after solid phase extraction (SPE).

Extractive spectrophotometric methods for the determination of doxepin hydrochloride in pharmaceutical preparations using titanium (IV) and iron (III) thiocyanate complexes.

Two simple, precise, and accurate extractive spectrophotometric methods have been developed for the determination of doxepin hydrochloride in pharmaceutical preparations. The methods are based on the formation of ion association complexes of doxepin with titanium (IV) and iron (III) thiocyanate complexes in acidic medium. The produced compounds are insoluble in water but well soluble in some organic solvents. They are extracted with mixtures of butyl alcohol-chloroform (2:3, v/v) and (1:4, v/v) and measured spectrophotometrically at 400 and 490 nm for DOX-Ti-SCN and DOX-Fe(III)-SCN methods, respectively. Beer's law was obeyed in the concentration ranges of 5-50 and 3-30 microg/ml with molar absorptivity of 7.12 x 10(3) and 1.36 x 10(4) l mol(-1) cm(-1) for DOX-Ti-SCN and DOX-Fe-SCN systems, respectively. The proposed methods have been successfully applied for the analysis of the drug in dosage forms. No interference was observed from common pharmaceutical adjuvants. The methods have been also used for the determination of the drug in the presence of its degradation product. Statistical comparison of the obtained results with the reference methods shows excellent agreement and indicates no significant difference in accuracy and precision.