Biochemical and biomedical applications of capillary column GLC using SIM

Separation, quantification and identification of non-volatile organic acids in body fluids by gas chromatography

The present paper concentrates on the analysis of non-volatile organic acids in physiological fluids. The solvent extraction and DEAE-Sephadex extraction of organic acids, respectively, seem to be the most widely used methods for isolation of this group of compounds from the biological matrix. Gas chromatography-mass spectrometry (GC/MS) is the preferred method for the separation, quantification and identification. In three tables organic acids are divided into the classes according to a functional group, a survey of alkylation methods is given and retention indices of common urinary organic acids on various GC columns are summarized.

Determination of the beta-adrenergic blocker timolol in plasma by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

A method based on LC-MS-MS has been developed for the determination of timolol in plasma using the (CD3)3-labelled species as the internal standard. Timolol is isolated from plasma by a simple solid-phase extraction and converted to its oxazolidin-2-one prior to analysis on a 50 x 4.6 mm reversed-phase high-performance liquid chromatography column packed with SynChropak, C18, 5 microns. The column eluate is passed by means of a heated nebulizer interface into a corona discharge atmospheric pressure chemical ionization source where the analyte and its internal standard are detected using multiple reaction monitoring (MRM). The very high specificity of this technique permits chromatographic run times of less than 2 min. The method has a lower quantifiable limit of 0.5 ng ml-1, with intra- and inter-day relative standard deviations less than 10%, and enables the determination of timolol in plasma after ocular administration to volunteers.

Applications to analytic chemistry: an evaluation of stable isotopes in mass spectral drug assays

We evaluated stable isotope analogues (SIAs) as internal standards in mass spectral drug assays on the analytic parameters of accuracy, precision, specificity, and limit of quantitation. Only one literature report suggests that the use of an SIA made an assay more accurate, although theoretic considerations strongly support their use. There is substantial evidence, however, that their use made assays more precise. Potentially, the chromatographic peak shape and retention time of the SIA can be compared with those of the analyte to support assay specificity, and this type of comparison has been implemented as a new computer program (QSIMPS). There is some evidence that SIAs can serve in "carrier" substances to increase recoveries and thus lower the limit of quantitation of an assay. However, the use of large amounts of an SIA (relative to the analyte) leads to analytic imprecision, because of memory effects, large blank values, and unacceptable confidence limits.

Drug level monitoring: cardiovascular drugs

Methods for the determination of cardiovascular drugs in blood and plasma are critically reviewed with emphasis on gas and liquid chromatographic techniques. The importance of the various procedures is discussed, in particular sample work-up where the conditions for isolation and derivatization of the compounds are decisive for the accuracy and precision of the methods. Compared with other assay techniques chromatographic methods are generally to be preferred owing to their better selectivity. In the review the following groups are discussed: digitalis glycosides, antiarrhythmic agents, beta-adrenoceptor antagonists, vasodilating agents, antihypertensive compounds, and diuretics.

Separation and determination of the two components of glycerol formal by high-performance liquid chromatography

The two isomeric components of glycerol formal, 1,3-dioxan-5-ol and 1,3-dioxolane-4-methanol, are marginally separated (Rs = 1.0) by polar-bonded-phase high-performance liquid chromatography (HPLC) on a cyanopropyl column with acetone-hexane as the eluent. Esterification of these components with 3,5-dinitrobenzoyl chloride produces derivatives which are, however, completely resolved (Rs > 2) by normal-phase HPLC on silica; derivatization has the added advantage of introducing an ultraviolet-absorbing chromophore into each component. Preparative scale chromatography is used to isolate each of the derivatives, which are characterized by their UV, NMR and mass spectral properties. These esters are used as reference standards for an analytical method based on derivatization and normal-phase chromatography. In this way a sample of glycerol formal is calibrated for use as a standard in the direct determination of the two components by polar-bonded-phase HPLC.