UV derivative spectrophotometric study of the photochemical degradation of nisoldipine.

The photodecomposition of nisoldipine ((+/-)3-isobutyl-5-methyl-1,4- dihydro-2,6-dimethyl-4-(2-nitrophenyl)-pyridine-3,5-dicarboxylate), whereby its 4-(2-nitrosophenyl) pyridine analogue is obtained as the photolytic product, was investigated under daylight exposure by means of UV derivative spectrophotometry. The optimal instrumental parameters (120 nm/min scan speed; 2 nm slit width; delta gamma = 10 nm and 5 s response time) for analogue derivative spectra were established for amplitudes 1D285 and 2D291 (measured to the baseline) of the nitroso analogue assay, as well as for 1D386 of the parent compound-nisoldipine assay. Using the first-order derivative spectrum, the minimum detectable amount of nitroso analogue in the presence of nisoldipine was equivalent to an impurity level of 5% and by the second-order derivative spectrum, the determination limit was equivalent to an impurity level of 2%.

Quantitative analysis of sulpiride and impurities of 2-aminomethyl-1-ethylpyrrolidine and methyl-5-sulphamoyl-2-methoxybenzoate in pharmaceuticals by high-performance thin-layer chromatography and scanning densitometry.

A simple and reliable thin-layer chromatographic method for determining sulpiride and impurities of 2-aminomethyl-1-ethylpyrrolidine and methyl-5-sulphamoyl-2-methoxybenzoate was developed and validated. A methylene chloride-methanol-ammonia solution (25%; 18 + 2.8 + 0.

HPTLC determination of ceftriaxone, cefixime and cefotaxime in dosage forms.

The objective of this investigation was to develop a HPTLC method for the determination of ceftriaxone, cefixime and cefotaxime, cephalosporins widely used in clinical practice. High performance TLC of cephalosporins was performed on pre-coated silica gel HPTLC plates with concentrating zone (2.5 x 10 cm) by development in mobile phase ethyl acetate-acetone-methanol-water (5:2.

HPTLC assay of cephalexin and cefaclor in pharmaceuticals.

A simple and reliable HPTLC method for the simultaneous determination of cephalexin and cefaclor is developed and validated. The methanol-ethyl acetate-acetone-water (5:2.5:2.

Gas chromatography-mass spectrometry determination of isosorbide 5-mononitrate and related impurities in raw materials and dosage formulations.

A straightforward quantitative method for gas chromatography-mass spectrometry determination of isosorbide 5-mononitrate (IS5MN) and its related impurities such as isosorbide (IS), isosorbide diacetate (ISDA) and isosorbide 2-acetate-5-nitrate (IS2A5N) in raw materials as well as in dosage formulations is developed. The recovery of these materials was found to be 100.4 +/- 2.

High-performance liquid chromatographic assay of 8-hydroxyquinoline sulfate and its stability in immunobiological preparations.

Because of the ability of 8-hydroxyquinoline sulfate (8-HQS) to irreversibly bind metals from rubber stoppers, the stability of 8-HQS in tuberculin solutions was investigated. For the determination of 8-HQS, a simple and sensitive reversed-phase HPLC method with detection at 240 nm was developed and validated. Rapid decreases in concentrations of 8-HQS were found in samples stored in original vials which were exposed to different temperatures and vial positions.

Spectrophotometric determination of desoximetasone in ointment using 1,4-dihydrazinophthalazine.

The proposed method is based on coloured hydrazone formation with 1,4-dihydrazinophthalazine as a reagent. Heating at 85 degrees C for 2 h was found necessary to ensure optimal hydrazone formation in the presence of hydrochloric acid. The yellow hydrazone product has an absorption maximum at 380 nm.

Densitometric determination of urinary 4-hydroxy-3-methoxymandelic acid (vanillylmandelic acid).

We propose a simple and precise densitometric method for measuring vanillylmandelic acid (VMA). The method comprises direct urine application, thin-layer chromatographic (TLC) separation, postchromatographic derivatization, and in situ reading of the formed derivative at 560 nm. Quantitation was done by measuring peak area with a computer-controlled TLC Scanner and applying a five-point calibration function.

Dissolution assay of theophylline, diprophylline and proxyphylline from a sustained release dosage form by high performance thin layer chromatography.

The content and dissolution rate of theophylline, diprophylline and proxyphylline from a sustained release formulation were determined by UV in situ densitometry. After separation the chromatographic zones corresponding to the spots of theophylline, diprophylline and proxyphylline on the high performance thin layer chromatographic plates were scanned in reflectance/absorbance mode at 275 nm. Quantification was performed with a second degree polynomial function over the range 40-200 ng for theophylline and 60-300 ng for diprophylline and proxyphylline.

Spectrophotometric determination of diltiazem in dosage forms.

A simple and reproducible method for determination of diltiazem in bulk and in dosage forms is presented. The method is based on formation of hydroxamic acid, which reacts with iron (III), forming a complex with a maximum absorption at 525 nm. Assay procedure for diltiazem dosage form requires thin-layer chromatographic separation prior to colorimetric analysis.

The urinary dehydroepiandrosterone, androsterone and etiocholanolone excretion of healthy women and women with benign and malignant breast disease.

The 24-h urinary excretion of dehydroepiandrosterone, androsterone and etiocholanolone was followed in healthy women (n = 50) and in women with benign-fibroadenoma (n = 32), microcysts (n = 32), macrocysts (n = 25) and malignant (n = 35) breast disease aged 35-50 years. The data were analysed in three groups each covering 5 years (35-39, 40-44 and 45-49). A significant decrease in the excretion of etiocholanolone and dehydroepiandrosterone was found in women with benign and malignant breast disease when compared to controls.

Spectrophotometric determination of clonidine in dosage forms using bromocresol green.

A simple and sensitive method for the determination of clonidine in dosage forms is presented. The method is based on colour reaction of clonidine with bromocresol green, whereby a yellow coloured ion pair is formed.

Determination of triamcinolone, triamcinolone acetonide and fluocinonide in dosage forms.

The colorimetric method for determination of triamcinolone, triamcinolone acetonide and fluocinonide in tablets, ointments and cream using isonicotinic acid hydrazide is proposed. This method provides a precise and reproducible results (recovery ranged within 97.42-101.

Densitometric determination of conjugated oestrogens in the raw material and in pharmaceutical preparations.

A densitometric method for determination of complex mixtures of conjugated oestrogens in raw material and tablets was developed. The proposed procedure comprised hydrolysis of sodium sulphate esters of oestrone, equilin, 17 alpha-oestradiol, equilenin, 17 alpha-dihydroequilin and 17 alpha-dihydroequilenin, the chloroform extraction of free oestrogens and methyltestosterone (internal standard) and separation on TLC plates using chloroform-cyclohexane-dioxane-triethylamine (4.5:4.

High-performance liquid chromatographic determination of tilidine in pharmaceutical dosage forms.

A reversed-phase high performance liquid chromatographic method for the determination of tilidine in bulk drug and its liquid and solid dosage forms is described. The method uses reversed-phase column RP-8 with methanol -0.2% water solution of ammonium carbonate (75:25,v/v) as the mobile phase and UV detector.

Determination of lidocaine in pharmaceutical preparations using thin-layer chromatographic densitometry.

A thin-layer chromatographic (TLC)-UV-densitometric method has been developed for the analysis of lidocaine in ointments, suppositories and gels. The method is quantitative, rapid and able to separate lidocaine from other components in the pharmaceutical dosage forms investigated without preliminary extraction. The method gave precise and reproducible results.

Interference by analgesic and antirheumatic drugs in 25 common laboratory assays.

Twenty five different analytical procedures, commonly used in clinical laboratories, were investigated for interference by eight analgesic and antirheumatic drugs. Ten of the investigated assays showed no statistically significant interference. Acetylsalicylic acid interfered in six assays (for glucose, uric acid, protein and cholesterol).

Effects on analgesic and antirheumatic drugs on the assay of serum enzymes.

Interference by some commonly used analgesic and antirheumatic drugs in the spectrophotometric and colorimetric assays of serum enzymes was examined. None of the investigated methods was significantly influenced by caffeine, phenacetin, ibuprofen or indomethacin. Acetylsalicylic acid affected the continuous assays of creatine kinase and lactate dehydrogenase (with pyruvate as substrate), and the colorimetric assay of alanine aminotransferase.