Comparison of high-performance liquid chromatography, supercritical fluid chromatography and capillary zone electrophoresis in drug analysis.

High-performance liquid chromatography (HPLC), supercritical fluid chromatography (SFC) and capillary zone electrophoresis (CZE) are compared with respect to their usefulness in drug analysis. Factors discussed include efficiency, performance, sensitivity, optimization parameters, method development time, sample preparation, technical difficulties, orthogonality of the information obtained and the possible application to various substance groups. It is concluded that HPLC can be applied successfully in virtually all areas of pharmaceutical analysis. CZE has a promising future in the analysis of drugs and in the field of biotechnological analysis, where a high number of plates is required together with a short analysis time. Nevertheless improvements in detection are still necessary for most applications. SFC is particularly suitable for moderately polar compounds or substances for which mass-sensitive detection is required. SFC and CZE can be considered as complementary to HPLC owing to the orthogonality of the acquired data, and as a result more information can be obtained from the analysis.

Use of high-performance liquid chromatography in the pharmaceutical industry.

Requirements for new pharmaceutical products and their impact on applications of high-performance liquid chromatography (HPLC) are discussed. The strengths and weaknesses of HPLC in this context are evaluated and compared with current trends and expectation in separation science.

Experience with routine applications of liquid chromatography-mass spectrometry in the pharmaceutical industry.

The combination of liquid chromatography and mass spectrometry (LC-MS) has been established to complement gas chromatography (GC)-MS in the analysis of non-volatile and labile drugs in complex materials. The possibilities of LC-MS in the pharmaceutical industry for the analysis of drug substances and dosage forms, metabolism studies and the elucidation of the structures of materials of biological origin are discussed. Instrumental requirements, limitations and applications of LC-MS are considered and experiences with LC-MS in routine applications are reported. Preliminary results obtained with thermospray LC-MS are compared with those using a direct liquid inlet interface.

Liquid chromatography-mass spectrometry in the pharmaceutical industry: objectives and needs.

The role of liquid chromatography-mass spectrometry (LC-MS) in the analysis of drugs is discussed. The main fields of application are thermally labile compounds, compounds with low volatility and compounds with rather high molecular weights, all of which are not generally suitable for analysis by combined gas chromatography-mass spectrometry. The objectives, needs, limitations and abilities of LC-MS for the analysis of by-products, degradation products, traces of drug substances for pharmacokinetic studies and metabolites in complex matrices are presented. The LC-MS coupling is discussed as a sophisticated LC detector for sensitive and selective quantitative determinations or as an on-line sample-introduction system for the mass spectrometer to obtain structural information for identification or structural elucidation. LC-MS combined with a flow-switching technique can be used for the analysis of mixtures containing large amounts of components which otherwise would be detrimental to the LC-MS technique. With flow-injection techniques the LC-MS interface is used as a sample-introduction system with possibilities for sample preparation, sample clean-up and chemical derivatization.

Utilization of direct liquid inlet LC/MS in studies of pharmacological and toxicological importance.

The temperature of the droplets produced at the tip of the direct liquid inlet liquid chromatography/mass spectrometry (DLI LC/MS) probe decreases to about -70 degrees during the adiabatic evaporation of the droplet in the vacuum of the mass spectrometer. Broadening of peaks eluting from the probe is acceptable, being about 80 microL in volume, as shown by the DLI LC/MS analysis of cortisone, dexamethasone, and corticosterone in both the positive and the negative chemical ionization (PCI and NCI) modes. The minimum amount of sample which can be injected is about 10 ng in the scanning mode and about 100 pg in the selected ion monitoring (SIM) mode as shown by the analysis of bromocriptine and bromocriptinine. Other thermally-labile and/or non-volatile compounds analyzed by this system in the PCI and/or the NCI modes included ergotamine, esculin, sulfamethazine, chloramphenicol, erythromycin, alpha-tocopherol, cocaine, 8-chloro-theophylline, and dicophol. Non-ultraviolet absorbing carbohydrates were also analyzed, including sucrose (NCI), permethylated maltotriose, and partially hydrolyzed, derivitized lichenan and starch. By a flow switching technique, bromocriptine in a Pariodel tablet, ergot alkaloids in a Hydergine drop solution, and bromocriptine and bromocriptinine in whole urine could be analyzed without prior extraction.

A comparison of reversed-phase and partition high-performance liquid chromatography of some digitalis glycosides.

Comparison of the data for adsorption and reversed-phase chromatography of digitalis glycosides shows the complementary nature of the two modes of separation. The correct choice for a particular problem should make possible a rapid and good separation with simple isocratic systems. Detection limits vary between 10 and 100 ng per injection and permit the analysis of by-products even in low-dosage pharmaceutical formulations. Quantitation is easily possible with both chromatographic techniques using external standardization. The reproducibility for repetitive chromatograms is about 1% relative standard deviation for manual injections by loop injectors and is even significantly better for automatic injection. Reversed-phase chromatography can offer some advantages with regard to sample preparation of pharmaceutical formulations.

A low-cost gradient system for high-performance liquid chromatography. Quantitation of complex pharmaceutical raw materials.

A device is described that makes use of an eight-port motor valve to generate step gradients on the low-pressure side of a piston pump with a low dead volume. Such a gradient device with an automatic control unit, which also permits repetition of previous steps, can be built for about half the cost of a gradient system with two pumps. Applications of this gradient unit to the separation of complex mixtures of glycosides and alkaloids are discussed and compared with separations systems using two high-pressure pumps. The gradients that are used on reversed-phase material with solvent mixtures of water and completely miscible organic solvents are suitable for quantitative routine control of pharmaceutical products. The reproducibility of retention data is excellent over several months and, with the use of loop injectors, major components can be determined quantitatively with a reproducibility of better than 2% (relative standard deviation). The step gradient selector valve can also be used as an introduction system for very large sample volumes. Up to 11 can be injected and samples with concentrations of less than 1 ppb can be determined with good reproducibilities.