Validation of an ion selective electrode system for the analysis of serum fluoride ion

A high impedance unit was developed for use with a fluoride/pH electrode system for the measurement of serum fluoride. The linearity, accuracy, precision and detection limit of the system is reported. At a pH of 1.55, the system was linear over a range of serum fluoride concentrations up to 100 mumol l(-1), with a lower limit of detection of 0.3 mumol l(-1). Recoveries at this pH were 94-105% in the range 2.6-100 mumol l(-1). Within-run CVs ranged from 4.2% at a level of 2.3 mumol l(-1) to 1.2% at a level of 55.7 mumol l(-1), while day-to-day CVs ranged from 12.8% at a level of 2.2 mumol l(-1) to 4.6% at a level of 51.7 mumol l(-1). The system demonstrated a rapid response time and has the potential for a smaller sample size requirement with alternative electrode shape. Continued development of this unit into an automated fluoride ion selective electrode system is recommended, since the measurement of serial serum fluoride samples is of greatest importance in assessing the impact of new anaesthetic agents on renal function.