The effect of hydrogen on fluorine detection in solid sampling electrothermal vaporization-inductively coupled plasma optical emission spectrometry

Abstract

The effect on the detection of fluorine (F) in solid samples of adding H₂ to the carrier gas in electrothermal vaporization (ETV) coupled to inductively coupled plasma optical emission spectrometry (ICPOES) is studied for the first time. By incorporating H₂ as the reaction gas through the ETV graphite furnace, H₂ is introduced into the Ar plasma through the central channel of the ICP. An optimal flow rate for H₂ was determined to be 3 mL min⁻¹, with a pyrolysis temperature of 200 °C and a vaporization temperature of 2200 °C for the ETV program. Two reference materials, NIST 8432 Corn Starch and 8437 Hard Spring Wheat, were used to observe the changes in sensitivity and limit of detection (LOD) for F, following the addition of H₂. These materials were also used to verify the accuracy of the method through external calibration of both following internal standardization with an Ar 404.442 nm emission line to compensate for sample loading effects on the plasma. Compared to a previous ETV-ICPOES method that was optimized without H₂, LODs were improved 17–140 fold, depending on the F emission line, in plant-based materials. Additionally, similar or improved LODs resulted for Cd and Hg in NIST 8437 under the conditions optimized for the determination of F compared to those previously obtained with methods optimized for multi-elemental detection (excluding F).