A method for gas chromatographic/mass spectrometric analysis of low-molecular-weight organic acids in liver tissue is described. The method involves formation of methoximes of 0x0 acids, preventing exchange of hydrogen by enolization. The acids are separated as methyl esters by gas chromatography on an SP-1000 capillary column. The origin of fragment ions in the mass spectrometric analysis was studied by analysis of deuterated analogs.Lactate, pyruvate, 3-hydroxybutyrate, fumarate, succinate, malate, 2-oxoglutarate and citrate were analyzed in freeze-clamped livers of rats given [l No deuterium was incorporated in succinate and the 0x0 acids analyzed. The incorporation of deuterium from [l,l-2H2]ethanol in one position of malate and fumarate was about the same as in lactate (18 -23 "/, of the atoms), but the deuterium in lactate originated to a larger extent from the 1-pro-R position than in malate and fumarate. This indicates lack of equilibration of the NADH pools utilized by cytosolic malate dehydrogenase and lactate dehydrogenase, and that the former pool is more closely related to cytosolic acetaldehyde oxidation. 3-Hydroxybutyrate incorporated the 1-pro-S hydrogen of ethanol to a larger extent than the 1-pro-R hydrogen. This is in agreement with the presence of 3-hydroxybutyrate dehydrogenase and aldehyde dehydrogenase in the mitochondrial compartment. Hydrogen in citrate appears to be derived from C-1 of ethanol both via oxaloacetate and via intramitochondrial isocitrate dehydrogenase.

A nonaqueous capillary electrophoresis/electrospray mass spectrometry method for the separation of lidocaine (LID) and two of its metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), has been developed. The separation medium was: 70 mM ammonium formate and 2.0 M formic acid in acetonitrile/methanol (60:40 v/v). With a sheath liquid of methanol/water (80:20 v/v) containing 2% formic acid and positive ion detection, reproducible determinations (8-11% relative standard deviation (RSD)) of lidocaine and its metabolites were performed in spiked human plasma. The limits of detection (LODs) were between 69.1 and 337 nM. The influences of sheath liquid composition, nebulizing gas pressure and drying gas temperature on the separation were examined.

SummaryA method for preparation of capillary columns and traps with a very thick film (up to 100 pm) of stationary phase is described. The principle of this method is based on an immediate fixation of a film of prepolymer, formed during dynamic coating. Thus, the development of film irregularities, such as are caused by Rayleigh instability i s avoided. Fixation of the film is conveniently accomplished by heat-accelerated crosslinking as was demonstrated in this work, where a commercially available silicone prepolymer (Sylgard 184, Dow Corning) was employed.The low phase ratio columns which thus can be prepared are interesting both in chromatography with dense mobile phases and as enrichment devices. Examples of the latter application are shown, where trace organic components from air and water were concentrated.

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Two methods for sampling and concentration of volatile organic compounds are reported. In the first method, traps coated with a very thick film (ca. 100 pn) of cross-linked silicone stationary phase are employed. Such thick films can be prepared with a modified dynamic coating procedure, which is briefly described. The low phase ratio traps can be utilized for enrichment of volatiles from gaseous as well as aqueous matrices.The second technique is based on chromatographic evaporation of a solvent in a capillary tube,where the process is sustained bya repeated sample injection and a cyclic flow reversal. In this way, large solvent volumes can be handled by a small volume system. Under optimal conditions, when using a solvent barrier, quantitative recovery is possible even for compounds of comparatively high volatility. Another important application of the technique is extraction of trace components from gases such as headspace samples, polluted air, etc.