G. Gamberini

Solid-state study of polymorphic drugs : carbamazepine

Polymorphs of a compound have solid crystalline phases with different internal crystal lattices; in pharmaceuticals, differences due to polymorphism and pseudopolymorphism can affect bioavailability and effective clinical use. The aim of this work was to obtain the different polymorphic modifications of the anticonvulsant drug, carbamazepine, and to characterise them by means of typical structure-sensitive analytical techniques, such as FT-IR spectroscopy, XRPD and DSC. Further investigations were also performed by Hot Stage FT-IR thermomicroscopy, which permitted the visible and spectroscopic characterisation of the polymorphic forms during heating. Our results confirm the existence of three different polymorphic forms for anhydrous carbamazepine: Form III, the commercial one, Form I, obtained by heating Form III and Form II, crystallised from ethanolic solution. Substantial differences were detected among the polymorphs with regard to solid-state properties. Moreover, Hot Stage FT-IR thermomicroscopy proved its analytical potential to characterise the drugs polymorphism.

Analysis of cannabinoids in fiber hemp plant varieties (Cannabis sativa L.) by high-performance liquid chromatography

SummaryAn analytical procedure was developed for the detection of neutral and acidic cannabinoids in herbal cannabis without the need of any preliminary derivatization. The method was used to assay cannabinoid content of over one hundred fiber hemp samples grown in different Italian localities and harvested at different maturation level degrees during the summer. No interferences were observed due to the vegetal matrix.The influence of genetic factors and environmental conditions on cannabinoid content is discussed; the results may be of interest to enhance potential of fiber hemp in compliance with law enforcement purposes.

Simultaneous separation and identification of hashish constituents by coupled liquid chromatography-mass spectrometry (HPLC-MS)

SummaryThis paper reports the use of liquid chromatography for the separation and determination of the major cannabinoids extracted from hashish samples. The direct coupling to the mass spectrometer enables the selective identification both of neutral and acidic cannabinoids. The developed method does not require any preliminary derivatization and should, therefore, be of interest in forensic analysis for simple and unequivocal determination of hashish constituents.

Properties of the racemic species of verapamil hydrochloride and gallopamil hydrochloride

It is well known that the stereoselective actions associated with the enantiomeric constituents of a racemic drug can differ markedly in their pharmacodynamic or pharmacokinetic properties. Nevertheless, molecular chirality manifests itself in the solid, that is, crystalline state. The aim of this work was to characterize the solid-state properties of verapamil HCl and gallopamil HCl, two well-known chiral calcium channel antagonists. The characterization of the solid state for the single enantiomers and equimolecular mixtures for both the calcium antagonists was performed by solid-state techniques such as Fourier transform infrared (FT-IR spectroscopy), X-ray powder diffractometry (XRD) and differential scanning calorimetry (DSC). The FT-IR spectra and XRD of the single enantiomers are different from those of the corresponding equimolecular mixture owing to their different crystalline structure. The thermal behavior of the racemates and pure enantiomers were examined by DSC, and the resultant experimental and theoretical binary phase diagrams are discussed. Spectroscopic solid-state techniques, such as FT-IR and XRD, are useful in combination with thermal analysis for characterizing the racemic species of chiral drugs. The data obtained prove that the equimolecular mixtures of both verapmil hydrochloride and gallopamil hydrochloride exist as racemic compounds. Determination of the enantiomeric purity of the enantiomers and racemic compounds of both the calcium antagonists analyzed was performed by DSC.

Resolution of the enantiomers of verapamil and gallopamil by chiral liquid chromatography-mass spectrometry

SummaryAn HPLC-CSP method has been developed for the separation of enantiomers of verapamil and gallopamil using the improved version of the α1-acid glycoprotein, chiral stationary phase as selector with a volatile mobile phase. The results of the investigation provide the conditions which allow direct coupling to a mass spectrometer. In addition, the simultaneous enantioseparation of both the enantiomeric pairs of verapamil and gallopamil was achieved.

A high-performance liquid chromatographic method for the analysis of adenosine and some metabolites in the brain tissue of rats

SummaryAn analytical procedure has been developed for the assay of adenosine and some metabolites in brain tissue extracts of rats. This paper reports the extraction method, the technique adopted to avoid enzymatic transformations and the chromatographic conditions for the identification and quantitation of these nucleosides and bases.Peaks in the chromatograms of brain tissue extracts were identified by retention times, absorbance ratios of reference compounds and by enzymatic peak-shift.

Analytical Characterisation of Hashish Samples

SummaryThis report describes the analytical characterisation of two hashish samples to establish if they belong to a common lot, although their physical appearance is quite different. The samples were extracted and subjected to HPLC and GC for the separation and quantitation of the main cannabinoids. GC-MS enabled the selective identification of minor cannabinoids and terpenes.Hashish samples were also mineralised and analysed for metal traces by atomic absorption spectrometry (AA).

ANALYSIS OF PYRITHIONES BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

SummaryAn analytical procedure has been developed for the determination of zinc pyrithione in antidandruff formulations. Zinc pyrithione was converted into a stable copper complex and then analysed by reversed-phase HPLC.The proposed method allows the separation of the analyte from related pyrithiones and therefore is able to verify the compliance of cosmetic preparations with current legislation.

Enantiomeric separation of local anaesthetic drug by HPLC on chiral stationary phases

SummaryHigh-performance liquid chromatographic methods on chiral stationary phases have been developed for the stereoselective separations of the enantiomers of articaine hydrochloride and its metabolite articainic acid.Complete separations of articaine enantiomers have been achieved on a Chiralcel OD analytical column using mobile phases containing n-hexane and 2-propanol, while articainic acid enantiomers were resolved with n-hexane and ethanol.Good results were also obtained on a Chirobiotic V analytical column with 5% acetonitrile in triethylammonium acetate solution (7 mM; pH 6.5); the column showed good chemioselectivity and stereoselectivity, allowing simultaneous separation of both the enantiomeric pairs of articaine and articainic acid.

High-performance liquid chromatography of dihydroxyacetone as its bis-2,4-dinitrophenylhydrazone derivative

SummaryA rapid and simple HPLC method for the identification and determination of dihydroxyacetone, a tanning agent widely used in a variety of preparations, is presented. The method consists of the analysis of the formulated products after a derivatization reaction which enhances the response and the detection limit of the chromatographic analysis. The characterization and the elucidation of the spacial geometry of the synthesized derivative are described.