Buffer composition suitable for determining very low fluoride concentrations using a fluoride ion-selective electrode and its application to the continuous analysis of rain water

In order to continuously analyze rain water with a fluoride ion-selective electrode (F− ISE), various buffer systems were examined in terms of the sensitivity enhancement. On the basis of the result that the sensitivity could be maximized at around pH 2.8 using the conventional acetate buffer, we proposed Sørensenʹs buffer (a mixture of glycine and hydrochloric acid, pH 2.8) to be most suitable for rain water analysis. The limit of linear response was 1 × 10−7 mol dm−3 and the detection limit was 1 × 10−8 mol dm−3 by optimizing the sample to buffer dilution rate as 10: 1. A good correlation was found between the results from the rain water analysis using this method and those of ion chromatography. A continuous analysis of rain water during a rainfall event was successfully carried out.