Evaluation of different SIA sample-buffer configurations using a fluoride-selective membrane electrode as detector

The peak profiles of four different buffer-sample SIA configurations, e.g. buffer-sample; sample-buffer; buffer-sample-buffer and sample-buffer-sample with the last two in the sandwich mode were evaluated with a fluoride-selective membrane electrode as detector. The best response characteristics and peak shapes as well as recovery and precision values were obtained for the buffer-sample configuration. For low concentration levels, sandwich SIA configurations are more suitable, when optimum buffer and pH are used. The utilisation of a cheap electrolyte with a minimum consumption of buffer and a cheap, robust instrumentation made the SIA system suitable for on-line determination of fluoride.