Highly sensitive and rapid method for determination of fluoride ion concentrations in serum and urine using flow injection analysis with a fluoride ion-selective electrode.

An apparatus for flow injection analysis (FIA) was developed to measure very low fluoride ion concentrations (<1 micromol/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 micromol/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 micromol/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.