THE CHN (carbon, hydrogen, nitrogen) elemental analyser is a mainstay of many analytical laboratories, and a new white paper from Exeter Analytical helps to throw some light on the factors affecting the performance of these instruments.
Looking at the way CHN analysers are operated in a typical laboratory environment, the report considers the advantages and disadvantages of the two main instrument configurations – horizontal or vertical combustion. Perhaps not surprisingly, considering that the company’s own instument, the Model 440, is a horizontal furnace device, it finds that this arrangement “allows analysts to produce accurate and precise data on wide ranging sample types without system re-optimisation, saving time and reducing running costs”.
Samples are introduced to a horizontal furnace analyser via a quartz ladle, enabling the removal of post-combustion residues, whereas in a vertical combustion arrangement the new sample is introduced on top of previously used samples. The white paper observes that the resulting build-up of sample residue in vertical furnace analysers “increases the potential for poor analytical data”.
Accuracy and precision are the main criteria for most analytical laboratories, but the reality is that busy workloads and constantly-changing sample types mean that the operational parameters need to be set-up afresh for each sample run. Again, the white paper finds that better accuracy and precision is achieved with a horizontal furnace arrangement than a vertical or hybrid design, and the inherently more stable set-up reduces the need for recalibrations and sample re-runs
Copies of the white paper ‘How instrument design affects CHN micro-analytical performance‘ are available from Exeter Analytical.
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