Development of a method for the direct determination of fluorine in solid samples using electrothermal vaporization coupled to inductively coupled plasma optical emission spectrometry
For the first time, electrothermal vaporization (ETV) coupled to inductively coupled plasma optical emission spectrometry (ICPOES) was used to directly detect fluorine (F) in solid samples. Atomic emission was employed for the determination of F by ICPOES, due to the high ionization potential of F. Small amounts (2 mg) of NIST 8432 (Corn Starch) standard reference material were weighed into the graphite boats for direct insertion into the ETV furnace. The optimized ETV program included a pyrolysis step (250 °C for 15 s) and a vaporization step (2200 °C for 20 s). The Ar 404.442 nm emission line was employed for point-by-point internal standardization, to compensate for sample loading effects on the plasma. The resulting peak area of the transient F emission signal during the vaporization step was then integrated for F determination. External calibration was performed using DUWF-1 (Durum Wheat Flour) standard reference material. To further broaden the applicability of ETV-ICPOES, an alternative method was developed enabling calibration with standard solutions based on the peak area of the F peak observed during the drying step. This was then used to quantify F in solid DUWF-1 using the sum of the peak areas observed during the pyrolysis and vaporization steps. This method allows quick screening of F in plant-based materials using ETV-ICPOES.