Optimization of ion selective electrode method in detection of urinary fluorine

Abstract

Objective: To optimize the ion selective electrode method of measuring urinary fluorine in WS/T 30-1996. Methods: The volume of 5 mol/L NaOH solution was fixed to confect the TISAB buffer solution. The samples were prepared by mixing 5 ml urine and equal volume of TISAB solution. Fluorine electrode and calomel electrode was used to test. When the potential value changed less than ±0.5 mV in one minute, it could be recorded. The standard curve method was selected as a quantitive method. Results: The linear range of this method was 0.07~50.0 mg/L, E=238.96-57.50lgC, r=0.999 8. The LOD and LOQ were 0.02 mg/L and 0.07 mg/L (with 5 ml urine) , respectively. The RSD of intra -and inter-batch precision were 0.80%~2.82% and 2.17%~2.86%, respectively. The recovery rate was 102%~107%. The urine sample could be preserved stably for 14 days at room temperature, and for 30 days at 4 ℃ and -20 ℃. Conclusion: In this method, the preparation process of TISAB buffer solution was simplified, and the linear range was expanded. It could meet the needs of occupational population detection.