This work showed a flow system designed with solenoid valves for preconcentration of fluoride using SPADNS method in water samples. The analyte was preconcentrated in a mini-column coated with Layered Double Hydroxides (LDH) used as adsorbent. Then, the fluoride ions were eluted with 0.5 mol L⁻¹ sodium hydroxide and determined by spectrophotometry. The variables that affect the system such adsorbent mass, type of eluent, solutions flow rate, reagent concentration and pH effect were critically evaluated. Under optimized conditions, the detection limit, coefficient of variation, linear range and preconcentration factor were estimated at 15 µg L⁻¹ (99.7% confidence level), 0.8% (500 µg L⁻¹, n = 10), 50–500 µg L⁻¹ and 10, respectively. The accuracy of the method was evaluated by analysis of ALPHA APS 1076 (Simulated Rain Water) certified material, the values were not significantly different at a 95% level of confidence. The method was applied for fluoride determination in water samples and the levels found were below the maximum values established by Brazilian environmental and health legislations.

这项工作显示了一种设计有电磁阀的流量系统，该流量系统使用SPADNS方法对水样品中的氟进行了预浓缩。将分析物在一个微型柱中进行预浓缩，该微型柱涂有用作吸附剂的分层双氢氧化物（LDH）。然后，用0.5mol L ^-1氢氧化钠洗脱氟离子，并通过分光光度法测定。严格评估影响系统的变量，例如吸附剂质量，洗脱液类型，溶液流速，试剂浓度和pH值影响。在最佳条件下，估计的检出限，变异系数，线性范围和预浓缩系数分别为15 µg L ^-1（99.7％置信度），0.8％（500 µg L ^-1，n = 10），50–500 µg L ^-1和10。该方法的准确性通过对ALPHA APS 1076（模拟雨水）认证材料的分析进行了评估，在置信度为95％时，这些值没有显着差异。该方法用于水样中的氟化物测定，发现的含量低于巴西环境与健康法规规定的最大值。