Direct spectrometric determination of total fluorine in geological materials by continuous powder introduction into helium microwave induced plasma

Abstract

A sensitive, direct, spectrometric method for the determination of total fluorine content in a wide variety of geological materials has been developed. Solid samples were ground in a mill and sieved prior to continuous powder introduction microwave induced plasma optical emission spectrometry (CPI-MIP-OES) determination with a helium plasma. The effects of operating conditions and sample particle size on the analytical signal were evaluated. Materials were introduced as a solid–gas aerosol. The amount of fluorine was measured using calibration standards prepared by dropping of a standard fluoride solution on a suitable powdered support (silica or activated carbon) with matrix matching. The experimental detection limit for fluorine at line 685.6 nm, obtained with the CPI-He-MIP-OES method, was of the order of 3–6 μg g⁻¹; the uncertainty was about 5–17%. The developed method was validated by carrying out the analysis of different certified reference materials including soils, fly ash and coals.