Abstract: An apparatus has been developed for the isolation of fluoride in biological samples through pyrohydrolysis. With this apparatus, it is possible to determine both organic and inorganic fluorocompounds with a recovery close to 100% and precision within 5%. The high recovery rate can be expected even for highly heat-resistant compounds such as CaF2, without using WO3 as a catalyst. For determination of the isolated fluoride, a separate apparatus was developed in which flow injection analysis was used in conjunction with a fluoride ion-selective electrode as a detector. With this apparatus, fluoride in a sample solution with a volume as small as 0.2 ml, and at a concentration as low as 0.5µg/l, can be determined within 3 minutes with a precision of several percent. Combined use of the two apparatuses makes it possible to determine fluoride in different biological samples within 10^-15 minutes with a precision of several percent, free from external contamination. By selecting suitable conditions for analysis and using a 1 g sample, it is possible to determine fluoride at a concentration as low as 5 ng/g. By employing these apparatuses, the fluoride content in different biological samples has been determine and the effectiveness of their use confirmed. An apparatus is described for the isolation of F-1 in biological samples through pyrohydrolysis and for its determination by flow injection analysis with detection by ion-selective electrode. The determination limit was 5 ng g-1 of F-1.

Abstract: An apparatus for flow injection analysis (FIA) was developed to measure very low fluoride ion concentrations (( µmol/l). The analytical conditions of the apparatus were investigated. and the instrument was used to determine fluoride ion concentrations in serum and urine. All interferences caused by serum and urine matrices were eliminated using the proposed method. The recovery was almost 100.0% for serum and urine samples. The precision was within 4%. The results of determination of fluoride ion concentrations in the NIST Standard Reference Material of urine, SRM 2671a, agreed with the certified values. The detection limits: in serum and urine were 0.016 and 0.16 µmol/l. respectively. The assay throughput was 15 samples/h in serum and 24 samples/h in urine. The mean fluoride ion concentrations in serum and urine samples from 53 young Japanese women were 0.383±0.158 µmol/l and 0.207±0.103 mg/g Cr, respectively, There was a significant correlation (r = 0.39, p < 0.01) between serum and urine fluoride ion concentrations. (C) 2001 Elsevier Science B.V. All rights reserved.