Determination of impurities in remoxipride by capillary electrophoresis using UV-detection and LIF-detection; principles to handle sample overloading effects

Capillary electrokinetic separation techniques for profiling of drugs and related products

Capillary electrokinetic separation techniques offer high efficiency and peak capacity, and can be very useful for the analysis of samples containing a large variety of (unknown) compounds. Such samples are frequently met in impurity profiling of drugs (detection of potential impurities in a pharmaceutical substance or product) and in general sample profiling (determination of differences or similarities between samples). In this paper, the potential, merits, and limitations of electrokinetic separation techniques for profiling purposes are evaluated using examples from literature. A distinction is made between impurity profiling, forensic profiling and profiling of natural products, and the application of capillary zone electrophoresis, micellar electrokinetic chromatography, and capillary electrochromatography in these fields is discussed. Attention is devoted to important aspects such as selectivity, resolution enhancement, applicability, detection, and compound confirmation and quantification. The specific properties of the various electrokinetic techniques are discussed and compared with more conventional techniques as liquid chromatography.

Determination of enantiomeric excess by capillary electrophoresis

Capillary electrophoresis (CE) is becoming an established method for the determination of chiral trace impurities. This paper provides an overview of the state of the art of CE for such determinations. Detection limits of 0.1% impurity is widely accepted as a minimum requirement for chiral trace impurity determinations. This can be relatively easily achieved with CE. However, determination of lower concentrations requires careful optimization of the separation system. Four factors that are of particular significance for trace enantiomeric determinations: resolution, limit of detection, linear range and type of detection, are discussed. Further, the advantages and disadvantages of derivatization in this context are treated as well as the separation approach, ie., direct chiral separation or separation after the formation of diastereomers. It is concluded that the limit of impurity detection can be about 0.05% when UV detection is employed. Using laser-induced fluorescence detection, a quantitative determination at the 0.005% level is often possible.

Application of microemulsion electrokinetic chromatography to the analysis of a wide range of pharmaceuticals and excipients

Microemulsion electrokinetic chromatography (MEEKC) is a capillary electrophoresis (CE) technique in which solutes partition with moving oil droplets present in a microemulsion buffer. Ionised species will also separate by electrophoresis. In this paper MEEKC is shown to give highly efficient and relatively rapid separations for a wide range of pharmaceuticals, vitamins and excipients. A single set of operating conditions was used to resolve both water-soluble and insoluble compounds. The method was also used to separate both ionic and neutral compounds. The method was especially useful in the analysis of water-insoluble neutral compounds such as steroids and lecithin, which are difficult to analyse by CE. The method was found to be both quantitative and highly repeatable. The quality of the separation was found to be dependent upon the sample diluent used if large injection volumes are employed. The use of MEEKC for the determination of complex mixtures such as multi-ingredient formulations and drug-related impurities was successfully demonstrated. MEEKC offers significant advantages over many forms of CE and capillary electrochromatography (CEC) and should be considered as an extremely useful option in pharmaceutical analysis.

Optimisation, validation and application of a capillary electrophoresis method for the determination of ranitidine hydrochloride and related substances

Ranitidine hydrochloride is an H2-antagonist which is widely prescribed for the treatment of peptic ulcers. The drug is marketed in a variety of dosage forms including tablets, syrups and injection solutions. A range of synthetic and degradative impurities of ranitidine are known and currently, these impurities are routinely determined using thin-layer chromatography (TLC). Alternatively a high-performance liquid chromatography (HPLC) method has also been employed in the assay of the pharmaceutical preparation. Unlike TLC, capillary electrophoresis (CE) offers the capability to quantify simultaneously both the active drug content and the levels of the related substances. The advantages of simplicity, selectivity, versatility and ease of use of CE offers a complementary separation technique to the established methods of HPLC and TLC in the determination of ranitidine and its related substances. This work represents a comprehensive evaluation of the performance of a developed CE method in the determination of drug-related impurities in both drug substance and various pharmaceutical formulations. The data obtained clearly shows that the performance of an optimised CE method can be equivalent in terms of sensitivity and precision to that of a HPLC method employed for a similar purpose and offers better selectivity against TLC and HPLC.