HPCE determination of R(+) and S(-) mepivacaine in human serum using a derivatized cyclodextrin and ultraviolet detection

Solid-state study of mepivacaine hydrochloride

Different crystalline forms of the local anaesthetic mepivacaine hydrochloride (MH) were revealed by Fourier transform infrared spectroscopy (FT-IR), not by conventional differential scanning calorimetry (DSC). The existence of two polymorphic anhydrous modifications was discovered and further characterized by X-ray powder diffraction and thermal analysis: Form II, the commercial one, and the more stable Form I, obtained by re-crystallization from Form II. Two pseudopolymorphs were also obtained: Form III, a solvate crystallized from ethanol and Form IV, a solvate crystallized from methanol. Single crystal X-ray diffraction data for both solvates were collected and their structures were determined. Form II, metastable and monotropically related to Form I, generates through desolvation of Form III, very often present in industrial processing, where crystallization from ethanol solution is a common practice. For the sake of clarity, the presence of polymorphic forms should be reported in the drug master files of MH. However, since MH is readily water soluble, the observed polymorphism has no relevance to its typical clinical use as aqueous solutions.

Use of negatively charged cyclodextrins for the simultaneous enantioseparation of selected anesthetic drugs by capillary electrophoresis-mass spectrometry

The simultaneous enantioseparation of selected anesthetic drugs was studied by capillary electrophoresis (CE) in presence of three different negatively charged cyclodextrins (CDs). Among the chiral selectors tested, namely carboxymethyl, sulfobutyl ether and sulfated-beta-CD, the latter appeared to be the most effective to achieve the enantiomeric resolution of the investigated compounds. Beside CD type, resolution was greatly influenced by the buffer pH, the molecular structure of the anesthetic compounds, CD concentration and temperature. The optimum electrophoretic conditions for the stereoselective analysis of the studied anesthetics were obtained with a poly(vinyl alcohol) coated capillary (48.5 cm total length x 50 microm I.D.), a 50 mM Tris-phosphate buffer at pH 2.5 containing 6 mg ml(-1) of sulfated-beta-CD, an applied voltage of 30 kV and a temperature of 30 degrees C. Under these optimized conditions, four drugs, namely bupivacaine, mepivacaine, ketamine and prilocaine, were simultaneously enantioresolved in less than 12 min. Furthermore, the method was applied to the stereoselective analysis of mepivacaine in a pharmaceutical preparation. Finally, the method was on-line coupled to electrospray ionization mass spectrometry using the counter current partial-filling technique.

Enantiospecific analysis by capillary electrophoresis: applications in drug metabolism and pharmacokinetics

Enantiospecific analysis has an important role in drug metabolism and pharmacokinetic investigations and its now no longer acceptable to determine total drug, or metabolite, concentrations following the administration of a racemate. Inspite of the fact that capillary electrophoresis (CE) has become an essential technique in pharmaceutical and enantiospecific analysis, the chromatographic methodologies remain the most commonly used approach for the determination of the enantiomeric composition of drugs in biological fluids. The application of CE to bioanalysis has been slow, which is in part associated with the complexity of biological matrices together with the relatively poor concentration limits of detection achievable. However, as a result of its versatility, high separation efficiency, minimal sample requirements, speed of analysis and low consumable expense CE is likely to play an increasingly significant role in the area. This review present an overview of enantiospecific CE in bioanalysis in which the approaches to enantiomeric resolution and the problems associated with biological matrices are briefly discussed. The application of enantiospecific CE to samples of biological origin is illustrated using examples where the methodology has either solved an analytical problem, or provided a useful alternative to the currently available chromatographic methods. Such improvements in methodology are associated with either the high separation efficiency and/or microanalytical capabilities of the technique. Enantiospecific CE will not replace the chromatographic methodologies but does provide the bioanalyst with a useful addition to his armamentarium.

Enantioselective determination of drugs in body fluids by capillary electrophoresis

During the past decade, chiral capillary electrophoresis (CE) emerged as a promising, effective and economic approach for the enantioselective determination of drugs in body fluids, hair and microsomal preparations. This review discusses the principles and important aspects of CE-based chiral bioassays, provides a survey of the assays developed and presents an overview of the key achievements encountered. Applications discussed encompass the pharmacokinetics of drug enantiomers, the elucidation of the stereoselectivity of drug metabolism and bioanalysis of drug enantiomers of toxicological and forensic interest.

Capillary electrophoresis of drugs: current status in the analysis of pharmaceuticals

The current status of capillary electrophoresis (CE) in pharmaceutical analyses is reviewed with about 300 references, mainly from 1996 until 1999. This article covers the use of CE for assay and purity determination of the main component, analysis of natural medicines, antisense DNA, peptides, and proteins. Analysis of hydrophobic and/or electrically neutral drugs by electrokinetic chromatography, capillary electrochromatography and nonaqueous CE is critically evaluated. Detailed techniques for the separation of enantiomers are given in the text with some actual applications. Furthermore, this review includes sensitivity and regulatory aspects for the actual use of CE in new drug applications (NDA). The analytical validation required for CE in NDA is also treated.

Capillary electrophoresis in clinical and forensic analysis: recent advances and breakthrough to routine applications

This paper is a comprehensive review article on capillary electrophoresis (CE) in clinical and forensic analysis. It is based upon the literature of 1997 and 1998, presents CE examples in major fields of application, and provides an overview of the key achievements encountered, including those associated with the analysis of drugs, serum proteins, hemoglobin variants, and nucleic acids. For CE in clinical and forensic analysis, the past two years witnessed a breakthrough to routine applications. As most coauthors of this review are associated with diagnostic or forensic laboratories now using CE on a routine basis, this review also contains data from routine applications in drug, protein, and DNA analysis. With the first-hand experience of providing analytical service under stringent quality control conditions, aspects of quality assurance, assay specifications for clinical and forensic CE and the pros and cons of this maturing, cost-and pollution-controlled age technology are also discussed.

Capillary electrophoresis as a versatile tool for the bioanalysis of drugs--a review

This review article presents an overview of current research on the use of capillary electrophoretic techniques for the analysis of drugs in biological matrices. The principles of capillary electrophoresis and its various separation and detection modes are briefly discussed. Sample pretreatment methods which have been used for clean-up and concentration are discussed. Finally, an extensive overview of bioanalytical applications is presented. The bioanalyses of more than 200 drugs have been summarised, including the applied sample pretreatment methods and the achieved detection limits.

A literature assessment of sample pretreatments and limits of detection for capillary electrophoresis of drugs in biological fluids and practical investigation with some antimalarials in plasma

A literature survey on published reports of the determination of drugs in biological fluids shows that all methods of sample pretreatment have been used and that the limits of detection achieved vary widely, ranging from low ngcm(-3) to microgcm(-3). The most widely used injection method was hydrodynamic and, in the majority of cases, whenever low detection limits were achieved, this was a result of preconcentration during the sample pretreatment. Only a small proportion of the reported methods employed electrokinetic injection and utilised the field amplified sample injection (FASI) techniques. An experimental investigation of the alternative hydrodynamic and electrokinetic injection methods for a small set of antimalarial drugs is reported. It was found that electrokinetic injection with FASI from an acetonitrile-water matrix produced dramatic improvements in detection limits. This improvement could not, however, be achieved when the drugs were in plasma using protein precipitation, liquid-liquid extraction or solid phase extraction pretreatment methods. This highlights the importance of sample pretreatment in utilising the potential sensitivity of capillary electrophoresis with electrokinetic injection.