Artefactual pyruvate and 2-oxobutyrate produced by trimethylsilylation of methylmalonic and ethylmalonic acids in the presence of oxygen
Trimethylsilylation of methylmalonic and ethylmalonic acids in the presence of headspace atmospheric oxygen is shown to produce the trimethylsilyl derivatives of pyruvic and 2-oxobutyric acids, along with 2-hydroxy-2-methylmalonic and 2-hydroxy-2-ethylmalonic acids, respectively. This may lead to overestimation of these keto acids, if they were not oximated in the original sample, and the mistaken reporting of the 2-hydroxymalonates.
Experiment-originated variations, and multi-peak and multi-origination phenomena in derivatization-based GC-MS metabolomics
Gas chromatography combined with mass spectrometry (GC-MS), in particular derivatization-based GC-MS, is one of the most commonly used analytical methods in metabolomics. However, experiment-derived variations and originations of chromatographic peaks are two fundamental issues that could influence interpretation of metabolic pathways. Here, we focus on some pitfalls and limitations, especially the commonly ignored multi-origination and multi-peak phenomena in derivatization-based GC-MS metabolomics. We use examples to illustrate that ignoring these two factors could lead to wrong interpretations of results and serious metabolic implications. We also discuss strategies to overcome some of these confounding factors.
Accelerated selective short column chromatography of neutral and acidic amino acids on a beckman-spinco analyzer, modified for simultaneous analysis of two samples
Summary o 1. Acidic and neutral amino acids can be chromatographed selectively on a22-cm column of spherical resin using the Beckman-Spinco amino acid analyzer. Four procedures will elute four different groups of amino acids, each with satisfactory resolution of the individual amino acids. Only the regular buffers, or simple modifications thereof, and regular operating conditions are used for these accelerated procedures. 2. Amino acids in physiological fluids can be analyzed quantitatively over a concentration range of 0.01–0.2 umoles ; the accuracy is equivalent to that obtained on the 55-cm resin column. Accelerated chromatography can therefore be used for the investigation and management of patients with disorders of acidic and neutral amino acid metabolism. 3. Simple, economical mechanical modifications of the analyzer are alsodescribed whereby two resin columns may be eluted and analyzed simultaneously, thus further increasing the efficiency of analyzer operation.