Potentiometric detection of carboxylic acids by flow injection analysis using a tungsten oxide electrode

Potentiometric flow injection (PFI) analysis of carboxylic acids based on a tungsten oxide electrode is described. The electrode is shown to offer high sensitivity and a stable baseline for the detection of carboxylic acids. The parameters affecting the electrode response such as the concentration of buffer, the pH and flow rate were studied in detail. The electrode exhibited a linear response for propionic acid in the concentration range of 2.5 x 10-4 M-5 x 10-3 M using a 5 x 10-4 M phosphate buffer at pH 6.5 as a carrier. The detection limits were found to be in the range of 1.0 x 10-5 M-5 x 10-5 M with a 20 μl injection.