Rapid communications in mass spectrometry : RCM
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Rapid Commun. Mass Spectrom. · Jan 2004
Comparative StudyUse of isotopically labelled octanoic acid to assess the effect of meal size on gastric emptying.
It has been proposed that the (13)C-octanoic acid breath test (OBT) provides a safe, non-radioactive means of measuring gastric emptying. However, deuterated octanoic acid provides a better marker when compared with scintigraphy, as the kinetics are less complex than those of the (13)C label. The appearance of (2)H in saliva is modelled as a two-compartment body water system, using an asymmetric triangular gastric emptying function. ⋯ These trends were mirrored in the OBT data, with significant differences between 1 MJ and 2 MJ (DeltaT(1/2) (C) = -0.63 h vs. 2 MJ, p = 0.013) and non-significant increases with the larger 3 MJ meal (DeltaT(1/2) (C) = +0.10 h vs. 2 MJ). Total meal calorie content was shown to have an effect on gastric emptying using both the OBT and the OST. The deuterium method allows the direct calculation of the gastric emptying function and could be used as an alternative to gamma scintigraphy, allowing further validation of the (13)C-octanoic acid breath test.
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Rapid Commun. Mass Spectrom. · Jan 2004
Quantification of hydrogen cyanide in humid air by selected ion flow tube mass spectrometry.
Following our recent observation that Pseudomonas bacteria in vitro emit hydrogen cyanide, we have found it necessary to investigate the ion chemistry of this compound and to extend the kinetics database for selected ion flow tube mass spectrometry (SIFT-MS) to allow the accurate quantification of HCN in moist air samples, including exhaled breath. Because of the proximity of the proton affinities of HCN and H2O molecules, the presence of water vapour can significantly distort HCN analysis in the presence of water vapour and a more sophisticated analytical procedure has to be developed. Thus, the reactions of H3O+(H2O)0,1,2,3 ions with HCN molecules have been studied in the presence of varying concentrations of water vapour, reactions on which SIFT-MS analysis of HCN relies. The results of these experiments have allowed an analytical procedure to be developed which has extended the kinetics database of SIFT-MS, such that HCN can now be quantified in humid air and in exhaled breath.
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Rapid Commun. Mass Spectrom. · Jan 2004
Determination of carnitine and acylcarnitines in plasma by high-performance liquid chromatography/electrospray ionization ion trap tandem mass spectrometry.
A high-performance liquid chromatography/mass spectrometry method was developed for the determination of carnitine, its biosynthetic precursor butyrobetaine, and eight acylcarnitines in plasma. The procedure includes a solid-phase extraction for carnitine and short- and medium-chain acylcarnitines, and a liquid-liquid extraction for protein-bound long-chain acylcarnitines, followed by separation on a reversed-phase column in the presence of a volatile ion-pairing reagent. Detection was achieved using an ion-trap mass spectrometer run in the tandem mass spectrometry (MS/MS) mode. ⋯ Application of the method to the diagnosis of pathological acylcarnitine profiles of metabolic disorders in a patient suffering from methylmalonic aciduria is presented. The method allows quantification of carnitine, butyrobetaine, acetylcarnitine and propionylcarnitine, and semiquantitative analysis of medium- and long-chain acylcarnitines. In contrast with other methods, no derivatization step is needed.