A.M. Di Pietra

Application of high-performance liquid chromatography with diode-array detection and on-line post-column photochemical derivatization to the determination of analgesics

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.

On-line post-column photochemical derivatization in liquid chromatographic—diode-array detection analysis of binary drug mixtures☆

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 analysis of imidazole antimycotic drugs in pharmaceutical formulations

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.

Analysis of miconazole and econazole in pharmaceutical formulations by derivative UV spectroscopy and liquid chromatography (HPLC)

Methods based on derivative UV spectrophotometry and high-performance liquid chromatography (HPLC) have been developed for the selective determination of miconazole and econazole in pharmaceutical dosage forms. A solid-phase extraction (SPE) procedure using a diol column gave quantitative drug extraction from formulated creams and provided purified sample solutions suitable for assay by the derivative UV spectrophotometric and HPLC methods. The proposed methods gave comparable accurate results, whereas a conventional UV spectrophotometric method was found to be seriously affected by excipients.

HPLC Analysis of Oxidation Hair Dyes in Permanent Hair Colorants

Abstract The reversed-phase liquid chromatographic separation of several hair dyes (diamines, aminophenols, phenols, etc.), using mobile phases containing 1,8-diaminoctane as new amine modifier and sodium heptansulfonate, is described. The combined effect of the amine and of the alkylsulfonate enabled very good separation of all the dyes studied. The proposed chromatographic system was found to be selective, rugged and therefore suitable for the reliable quality control of commercial permanent colorants. A preliminary solid phase extraction (SPE) procedure using SCX sorbents, was found useful to enhance detectability of low concentrated dyes and to isolate phenol compounds from the basic dyes.

HPLC analysis of aspartame and saccharin in pharmaceutical and dietary formulations

SummaryA reversed-phase HPLC method has been developed suitable for a reliable quality control of pharmaceutical and dietary formulations containing the synthetic sweeteners aspartame and saccharin. The proposed method is able to separate acesulfame, aspartame and saccharin, and their impurities such as 5-benzyl-3,6-dioxo-2-piperazineacetic acid (the major degradation product of aspartame) and 4-sulphamoylbenzoic acid,o- andp-toluenesulphonamides (the synthesis impurities of saccharin). A convenient solid-phase extraction (SPE) procedure using C-18 sorbent, was also developed for the determination of potential saccharin impurities.

High-pressure liquid chromatographic (HPLC) analysis of imidazole antifungals in commercial dosage forms

Abstract A high-pressure liquid cliromatographic (HPLC) method is presented for determining clotrimazole, miconazole nitrate and econazole nitrate in various commercial formulations. The analysis was performed on a reversed-phase column (RP 18) under isocratic conditions using a UV detector (230 nm). The described procedure proved to be more specific and versatile than the pharmacopoeia methods.

HPLC determination of glutathione and l-cysteine in pharmaceuticals after derivatization with ethacrynic acid

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).

HPLC-fluorescence determination of unconjugated estrogens in pharmaceuticals.

A fluorimetric liquid chromatographic method (lambda(ex) = 280 nm; lambda(em) = 312 nm) was developed for measurements of unconjugated estrogens (estradiol and estriol) in pharmaceutical dosage forms using a reversed-phase column with water acetonitrile at different composition as mobile phase. The in vitro release profiles of three different estradiol transdermal therapeutic systems were determined through a medical-grade silicone rubber subdermal implant material membrane, using a modified Franz diffusion apparatus at 37 degrees C in presence of PEG 400. The HPLC method possesses advantages of rapidity, simplicity and accuracy.

GC-MS analysis of incenses for possible presence of allergenic nitromusks.

A Gas chromatographic method with mass detector was developed to identify and determine nitromusks in incense sticks of different origin (India, China, Tibet). The proposed method was found useful to correlate dermatological allergic reactions with the use and composition of commercial incense sticks. The incense sticks were powdered, extracted with methanol and after the addition of 1-eicosanol as internal standard, injected into the GC-MS, using 25 m bonded phase fused capillary column methyl, 5% phenyl silicone (0.32 mm I.D., 0.25 microns film thickness). Musk ambrette was identified and determined in one kind of chinese incense together with musk ketone and musk xylene. The latter compound was also found alone in another kind of chinese incense.