Pérez-Olmos R, Soto J C, Zárate N, Díez I
Lab. de Química Analítica, EUITI, Universidad del País Vasco, Plaza de la Casilla 3, 48012 Bilbao, Spain.
J Pharm Biomed Anal. 2008 May 12;47(1):170-6. doi: 10.1016/j.jpba.2007.11.028. Epub 2007 Nov 26.
A sequential injection analysis (SIA) system has been developed for the first time to quantify potassium and total fluoride in toothpastes and gels used to prevent both dentinal hypersensitivity and dental caries. To enable this simultaneous determination, potentiometric detection, using a conventional fluoride electrode and a tubular potassium selective electrode, formed by a PVC membrane containing valinomycin as ionophore, was carried out. A manifold that uses a three-way solenoid valve was designed. The former under binary sampling conditions, provides reproducible mixing ratios of two solutions. This fact facilitates that the system automatically generates, on-line, the calibration curves required by the analytical procedure. The calibration ranged from 1.0 x 10(-4) to 1.0 x 10(-3) mol L(-1) for both potassium and total fluoride determinations. The R.S.D. (11 readings) resulted to be less than 1.5% for both determinations. Off-line studies related to the dissolution of the solid samples, the transformation of monofluorophosphate in fluoride, the elimination of organic matrix interference onto the plastic membrane of the potassium electrode, and the selection of the most adequate TISAB solution for fluoride determination, were also considered. A sampling rate of 18 samples h(-1) for both determinations was attained, their precisions and accuracies being statistically indistinguishable from those achieved by atomic emission spectroscopy (for potassium determination) and by a conventional batch potentiometry (for total fluoride determination) adopted as reference techniques.
首次开发了一种顺序注射分析（SIA）系统，用于定量测定用于预防牙本质过敏和龋齿的牙膏和凝胶中的钾和总氟含量。为实现这种同时测定，采用常规氟电极和管状钾选择性电极进行电位检测，管状钾选择性电极由含有缬氨霉素作为离子载体的PVC膜制成。设计了一种使用三通电磁阀的流路。前者在二元进样条件下，可提供两种溶液可重现的混合比例。这一事实便于系统在线自动生成分析程序所需的校准曲线。钾和总氟测定的校准范围均为1.0×10⁻⁴至1.0×10⁻³ mol L⁻¹。两次测定的相对标准偏差（11次读数）均小于1.5%。还考虑了与固体样品溶解、一氟磷酸根转化为氟、消除有机基质对钾电极塑料膜的干扰以及选择最适合氟测定的总离子强度调节缓冲溶液相关的离线研究。两种测定的进样速率均达到18个样品/小时，其精密度和准确度与作为参考技术的原子发射光谱法（用于钾测定）和常规批量电位分析法（用于总氟测定）所获得的结果在统计学上无显著差异。
