Measurement of VFA in anaerobic digestion: The five-point titration method revisited

The 5-point titration method proposed by Moosbrugger et al. (1993) provides a cheap and rapid means for measuring inter alia short-chain volatile fatty acids. However, output from the analysis requires invoking a 'systematic pH error'. The authors ascribed this to either residual liquid junction potential effects or pH calibration errors. However, from a scientific standpoint this detracts from confidence in the method. In this paper, it is shown that Moosbrugger et al's 'systematic pH error' is an artefact of the numerical techniques employed in their analysis. An alternative numerical approach is presented which also gives excellent results, without invoking the pH error affect.