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Keywords:

plasma/serum short-chain fatty acids, blood tubes, polyacrylamide gel, gas chromatography, flame ionization detection

Abstract:

Short-Chain Fatty Acids (SCFA; acetate, propionate and butyrate) are more and more recognised as mediators of local gut and systemic health. Quantification of SCFA in plasma and serum is challenging due to their low concentrations in human blood and the ubiquitous nature of acetate, requiring careful standardisation of the sample preparation procedure. Also the choice of the blood tube might affect the resulting concentrations. SCFA concentrations were measured in blood samples (10 mL), collected from 10 healthy subjects in 7 different blood tubes. Control samples included milliQ (MQ) water and standard SCFA solutions. After pre concentration and clean-up of the samples using a hollow fibre liquid membrane extraction, SCFA concentrations were measured using gas chromatography (GC) coupled to Flame Ionisation Detection (FID). Acetate concentrations were significantly higher (ANOVA, p<0.01) when blood was collected in an EDTA K2 tube, where as propionate and/or butyrate levels were significantly higher in plasma prepared in a PST tube and a Barricor tube and serum prepared in a SST tube (ANOVA, p<0.01 for all three tubes). Similar profiles of contamination were observed when analysing standard SCFA solutions that had been centrifuged in the different blood tubes. Lowest levels of contamination were observed when using red top glass serum tubes. A red top glass serum tube is the preferred tube to collect blood for the quantification of SCFA. When plasma is preferred over serum, a lithium heparin tube is the most appropriate test tube.