Estimation of Total Fluoride in Foodstuffs

rlstuffs J. I. READ AND R. C0LLINS Deporlment of Industry, Laboratory of the Government Chemist’ Cornrtqll House, Stamford Slreet, London A procedure is described for estimation of total fluoride in foodstuffs for levels down to 0 3 mg/kg. The sample is mixed with a prepared calcium hydroxide, as an ashing additive to immobilise volatile fluoride, and ashed in a staintess-steel lined mume. Fluoride is separated by steam-distillation lrom a sulphuric acid medium and collected, when necessary) on an anion-exchange resin After elution. the fluori<le is measllled potentiometrically using a fluoride ion- sensilieelectrode- Staodard deviations of the resr-tlts for leve)s normally found in foodstuffs have been calculated and derived confldence intervals ar e gjven. Introduction Few method.s have been described for the estimation oftotal fluoride in food- stuffs. The procedure used historically has been decomposition of organic material by ashing with an ashing additive to immobilise volatile fluoride and to break do*ln complex fluoride minerals, isolation of the fluoride by a Willard- Winter rype distiliation and measurement of fluoride in the distillate. A typical method i; describ ed t