Determination of Aqueous Fluoride by Continuous Powder Introduction Microwave-Induced Plasma Optical Emission Spectrometry after Preconcentration on Various Sorbents

Abstract

ABSTRACT A spectrometric determination of aqueous fluoride has been improved by coupling of continuous powder introduction microwave-induced plasma optical emission spectrometry with separation of the analyte onto powdered sorbents. A selective solid phase extraction method for preconcentrating trace fluoride from aqueous environmental samples on calcium hydrogenphosphate dihydrate in batch operation was employed while, for flow operation, the zirconium modified activated carbon method was adopted. The fluoride could be readily excited in helium plasma at 685.6 nm. Using a 1-L sample volume and a preconcentration factor of 1000, practical detection limit with respect to water sample is in the range 4.0–4.7 ng mL−1, depending on the sorbent used. External calibration was done using standards obtained by the dropping of standard fluoride solution on the powdered sorbent covering fluoride content from 50 to 5000 µg g−1. The procedure was applied to the determination of fluoride in mineral waters and certified reference material (CRM) drinking water.