Determinação de fluoreto em baixas concentrações: validação de método com eletrodo íon seletivo para análise da água utilizada na preparação de soluções de diálise Determination of fluoride at low concentrations: validation of method using ion selective electrode to analyze the water used in the preparation of dialysis solutions

This paper describes the development and validation of an analytical methodology for determining the concentration of fluoride in water used for the preparation of dialysis solutions, by means of potentiometry with ion selective electrode. The investigated validation parameters were: selectivity, homoscedasticity, linearity, limit of detection, limit of quantification, reliability of measurement and precision. The optimized conditions of analysis were: HOAc/-OAc/NaCl/CDTA buffer (pH = 5.0 ± 0.1), in ratio of 10:1 (sample/buffer); concentrations of the standard solutions in the analytical curve: 0.05-0.80 mg/L. The evaluated method exhibited suitable validation parameters with detection and quantification limits equal to 0.020 and 0.050 mg/L, respectively. Also, an electronic spreadsheet was developed and validated for monitoring the quality of analytical curve of the methodology that calculates the decision limit to 0.20 mg/L.