Determination of total carbon dioxide in beer and soft drinks by gas diffusion and flow injection analysis

A gas diffusion FIA method for determination of total CO2 in beer and in soft drinks is described. The composition of the acceptor stream for diffused carbon dioxide is critical. Bromocresol purple has been selecled among a large number of tested pH indicators and if the detection is made at a wavelength of 430 nm, stable baseline conditions and positive deflections of the resulting FIA peaks are obtained. The selected indicator is combined with a linear pH buffer. A simple and practical graphical method for determining a suitable starting pH of the acceptor stream, as well as the expected dynamic range and the linearity of the calibration graph, is presented.