[Comparison and optimization of total ionic strength adjustment buffer during detecting fluoride in trace serum sample by fluoride ion selective electrode method].

Objective: To probe on the influence by four kinds of total ionic strength regulating buffer (TISAB) in establishing the standard curve and determining the level of fluoride in trace serum sample (rats serum and the calf serum) by fluoride ion selective electrode, and further explore the optimal volume ratio among TISAB and serum samples.
Methods: Standard curve equations of four TISAB were established to clarify the influence of TISAB kinds. And the trace serum samples (rats and calf) were diluted to 1 times by TISAB, and then levels of fluoride in the samples that added by the standard sodium fluoride were detected, subsequently the influence of TISAB kinds on recovery rate were analyzed. Finally, the optimal ratio among serum sample and each TISAB in different serum was determined according to the recovery rate of the serum sample with different volume ratio.
Results: The standard curve of TISAB III sample exhibited best fitting effect (R2 = 0.9926 ), and it also showed the overwhelming superiority with the scope of recovery rates ranged from 90% to 105% in the rat serum standard addition recovery experiments. As calf serum, TISAB IV (recommended by health industry standard) performed superior than others with the scope of recovery rate ranged from 90% to 110% in standard addition recovery experiment. When the volume ratio changed, every kinds of TISAB had an optimal proportion with good recovery rate, only TISAB III with the proportion as 1: 1, nevertheless, those change little affected on the recovery rate in calf serum.
Conclusion: The method recommended by health industry standard is only suitable for detecting the trace amounts of fluoride in the serum sample as calf, but not the serum sample as rats.