Automated indirect fluoride determination by ICP-OES using discontinuous-flow analysis

Abstract

An automated method for the indirect determination of fluoride by inductively coupled plasma atomic emission spectrometry using discontinuous-flow analysis has been developed. A modified flow injection analysis system was used for sample preparation. The method is based on the determination of excess cerium(III) ion after precipitation of CeF₃. Separation of the precipitate is performed online on a syringe membrane filter that is cleaned each analysis cycle by 1 M nitric acid, ensuring a long life-time for the filter. As a result of the short reaction time, a detection limit of 9.5 mg L⁻¹ was obtained. The precision (RSD) of the proposed method is 1.02% at fluoride concentration of 28 mg L⁻¹. The applicability of the technique for groundwater monitoring of fluoride-contaminated area is demonstrated.

Keywords:

• fluoride
• inductively coupled plasma optical emission spectrometry (ICP-OES)
• cerium(III) fluoride
• precipitation
• automation