Accurate determination of fluorine, chlorine, and sulphur at trace level (<100 ppb)

Combustion Ion Chromatography enables the determination of speciated halides and sulphur compounds by a single analysis. TE Instruments developed a fully automated, extremely compact sample preparation system covering the pyrohydrolytic combustion, fraction collection, and sample injection towards any IC. The XPREP C-IC is the only configuration capable of introducing liquid samples both via optimised direct injection module and conventional boat-inlet system into a horizontal furnace. Sample introduction by direct injection improves the analytical results for trace level applications such as aromatic hydrocarbons and ultrapure chemicals.    

A larger sample volume (100 µL) can be introduced into the direct injection module compared with boat-inlet systems. Controlled sample evaporation at 1 µL/s eliminates the need for a boat program and decreases the time of sample combustion dramatically. Multiple sample combustions can be collected in the same absorption tube, which increases the concentration of analytes in the absorbance medium. The analytical results at trace level are significantly improved by adjusting the number of sample combustions, volume of absorbance liquid, size of the IC sample loop, and use of a pre-concentrator.

The XPREP C-IC sample preparation system was connected to a high-end IC to generate a fully automated C-IC configuration. Calibration standards made from fluorobenzene (F), chlorobenzene (Cl) and Dibenzothiophene (S) in Xylene were analysed, covering a range of 25 – 100 ppb for each element. Excellent calibration line fits (>0.999 r2) were created by optimizing the number of sample combustions for each analysis. The table below demonstrates high precision of analysed results at trace level (<100 ppb), which is well below the scope of international test methods currently available such as ASTM D7359 and UOP 991.

The direct injection module allows faster and more controlled combustion of larger sample volumes in comparison with boat-inlet systems. A higher concentration of analytes will be trapped in the absorbance medium, providing the best possible results for analysing liquid samples with combustion-IC at trace level.   

The recently launched XPREP C-IC has a small footprint, which saves bench space. It enables speciated halide and sulphur analysis by any of the well-established ICs, offering controlled sample introduction compatible with direct injection and boat-inlet. This sample system features a 65 position fraction collection unit facilitating the immediate analysis or storage of combusted samples and performs oxidative pyrohydrolitic combustion of solids, liquids, gas and LPG