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HPLC methods were developed for the analysis of pharmaceutical creams containing binary drug mixtures (betamethasone valerate-chlorocresol; hydrocortisone-miconazole nitrate; desonide pivalate-chlorhexidine; dexamethasone-clotrimazole; triamcinolone acetonide-econazole nitrate). The chromatographic separations were performed on C-18 and cyano columns under reversed-phase conditions. A post-column on-line photochemical reactor (irradiation at 254 nm) was arranged between the analytical column and the diode-array detector to enhance the performance of the method. Two UV spectra (photoreactor on and off) were obtained for each analyte and these additional sources of information proved to be useful for the unambiguous identification of the various analytes. The method was applied to the quality control of commercial creams using a solid-phase extraction procedure for the sample clean-up.

HPLC analyses of pharmaceutical dosage forms containing analgesics and related compounds (acetylsalicyclic acid, paracetamol, propyphenazone, caffeine and chlorpheniramine) were performed on C18 and cyano columns under reversed-phase conditions. The performance of the methods was enhanced by introducing postcolumn on-line photochemical derivatization in combination with a diode-array detection. The column effluents were subjected on-line to UV irradiation (254 nm) and the characteristic photo-induced spectral modifications were useful for the unambiguous identification of the various analgesic compounds. The proposed HPLC methods were successfully applied to the analysis of commercially available analgesic dosage forms.

Solid-phase extraction (SPE) using C-18, diol and ion-exchange sorbents followed by UV spectrophotometric (conventional and derivative mode) assay was applied to the analysis of basic, acidic and neutral drugs commercially available in creams. A representative set of drugs (promethazine, chlorhexidine, benzydamine, ketoprofen, ibuprofen, fentiazac, piroxicam, fluorouracil, crotamiton and hydrocortisone acetate) was selected, and for each drug the appropriate SPE conditions (adsorption, washing and elution) were investigated to obtain a practical and reliable sample clean-up. It was shown that the developed SPE procedures were capable of removing interfering cream components (excipients including preservatives) allowing accurate spectrophotometric analyses to be performed. In some applications, derivative spectrophotometry was advantageous over the conventional absorption mode with respect to higher selectivity and versatility.

2-Bromoacetyl-6-methoxynaphthalene has been found to be a useful prechromatographic fluorescent labelling reagent for the analysis of dicarboxylic acids. The derivatization reaction of azelaic acid and meglutol with this reagent yieded stable and highly fluorescent diesters which could be analysed by reversed-phase HPLC with fluorescence detection. According to the nature of the sample, the derivatization reaction could be carried out in acetonitrile or in an aqueous micellar system. The proposed methods proved to be suitable for the quality control of various complex pharmaceutical and cosmetic formulations of the azelaic acid and meglutol.

A reversed-phase HPLC method is proposed for the separation of five liquorice triterpenoids, 18 beta glycyrrhetic acid (beta GA), 18 alpha glycyrrhetic acid (alpha GA), 24-hydroxy-18 beta-glycyrrhetic acid (24-OH-beta GA), alpha and beta liquiritic acid (alpha and beta LA), with potentially different biological activities. The method has been developed by studying the influence of the type of stationary phase, pH, amine modifier and organic modifier on the resolution of the five compounds. The optimized chromatographic conditions were then successfully applied to the analysis of alpha- and beta-GA in pharmaceutical preparations (toothpaste and creams) on a reversed-phase Phenomenex Ultracarb 5 ODS (30) column (150 x 4.6 mm i.d.), using as the mobile phase acetonitrile-THF-0.010 M dioctylammonium phosphate buffer (pH 6.5) (25:20:55, v/v/v) at a flow-rate of 0.8 ml min-1. SPE methods with diolic and C18 sorbents were developed to isolate and concentrate the analytes and to enhance the sensitivity for the determination of alpha-GA as an impurity in the beta-GA preparations. The method was found to be reliable and suitable for the quality control of beta-GA preparations.

A selective and sensitive high performance liquid chromatographic (HPLC) method has been developed for the determination of reduced glutathione (GSH) in biological samples (rat liver, spleen and plasma). The method involved a prechromatographic thiol derivatization with methyl 4-(6-methoxynaphthalen-2-yl)-4-oxo-2-butenoate; the reaction was rapid (5 min) under mild conditions (pH 7.5 and ambient temperature) and selective for the sulphydryl group. The thiol adducts were separated on a reversed-phase C-18 column using acetonitrile: 0.05 M triethylammonium (TEA) phosphate (pH 4) solution 32:68 (v/v) as the mobile phase. Fluorescence detection (lambda em = 450 nm; lambda exc = 310 nm) was used and the detection limit (S/N = 3) was about 0.5 pmole of the injected GSH adduct. The method was also applied to the determination of total glutathione in rat plasma after a preliminary reduction with dithiothreitol.

Derivative and difference spectrophotometric methods are described for the direct simultaneous analysis of combinations of Trimethoprim with sulfonamide drugs (sulfadiazine, sulfamethoxazole, sulfamethoxypyridazine) in commercial dosage forms. The more advantageous approach (derivative and difference mode) is suggested for each binary mixture. The assay results are compared with those obtained by a new chromatographic (HPLC) method, involving a C-18 column and a mobile phase (pH 6.5) containing 1.8 diaminooctane as amine modifier and sodium heptansulfonate as ion pairing agent.

Ethacrynic acid and its methyl ester are proposed as useful pre-chromatographic derivatization reagents for the HPLC analysis (UV detection) of reduced glutathione (GSH) and L-cysteine. The optimum experimental conditions for the thiol derivatization, the removal of the excess reagent by liquid-liquid or solid-phase extraction and the reversed-phase chromatographic separations of the thiol adducts were investigated. The method was applied to the HPLC determination of GSH and L-cysteine in commercial formulations and proved to be suitable for the HPLC determination of oxidized glutathione (GSSG) after reduction to GSH using dithiothreitol (DTT).

Reversed-phase HPLC on different column packing materials (Hypersil C-18, Spherisorb-CN, Chromspher-B) is used to obtain selective separations of imidazole antimycotic drugs, such as ketoconazole, clotrimazole, tioconazole, bifonazole, isoconazole, econazole, miconazole and fenticonazole. The use of a post-column on-line photochemical reactor is shown to be useful for the enhancement of the sensitivity of the HPLC analysis with UV detection. The proposed HPLC methods are applied to the analysis of commercial dosage forms (creams) with solid-phase extraction (SPE) procedure, using a diol sorbent, being found to be a convenient technique for the sample preparation giving quantitative drug recovery.

The synthesis, diastereomeric separation, assignment to erythro- and threo-configuration by 1HNMR, and optical resolution of 3-(p-trifluoromethyl-phenyl)- and (p-thioanisyl)-2-biphenylyl-3-hydroxypropionic acids are described. The enantiomers were submitted to a preliminary assay to determine antiinflammatory activity.

We present a chromatographic method for the separation and determination of the optical purity of the enantiomers of WB 4101 [(+/-)-1], one of the most potent and selective alpha 1-adrenoreceptor antagonists. (+/-)-1 was converted into the amide of N-tosyl-(S)-proline. The two diastereoisomers were separated on silica gel and analysed by HPLC reversed phase. The analytical method described is both accurate and sensitive and allows the optical purity to be determined at very low concentrations and to obtain WB 4101 enantiomers with a purity of more than 99.95%.

Synopsis Limits imposed on the usage of thioglycolic acid, its salts and esters in cosmetic formulations require selective and sensitive analytical methods for their determination. In this study a convenient and reliable method based on high-performance liquid chromatography (HPLC) has been developed. The method involves a precolumn reaction of the thiol compounds with ethacrynic acid to give thiol adducts which can be separated by reversed-phase liquid chromatography and detected at lambda= 273 nm. The derivatization reaction proved to be quantitative under mild conditions (20 min at pH 7.4 and room temperature) and the chromatographic conditions allowed thioglycolic acid, glyceryl monothioglycolate, thiolactic acid, and thioglycolic acid ethyl ester to be discriminated. The proposed method was successfully applied to the analysis of commercial cosmetic formulations containing thioglycolic acid and glyceryl monothioglycolate, fulfilling the requirements of a general and selective method for the analysis of aliphatic thiols in cosmetics.

The optically active diastereometric erythro- and threo-3-thienyl-analogues 6a-d of 3-aryl-2-biphenylyl-3-hydroxy-propionic acids have been prepared. Some stereoisomers of 3-(3-thienyl)derivative 6b showed inhibition around 40% in the carrageenan-induced rat paw edema test.