Sources of Uncertainty in Gas Chromatography

Abstract

One of the best analytical technique is Gas chromatography (GC) which suitable to gas, liquid, and solid samples (components must be volatile). When a mixed solution sample is injected into the GC system which consist of carrier gas (mobile phase) which carries the mixture through the stationary phase from the injection port through the column (where the sample is separated into individual components) to the detector resulting a chromatogram which demonstrating the retention time of each component ant the amount of that component. Measuring a number of readings and determining the mean would increase the amount of information (The extra results you use, the closer value to the true mean you get) regularly between 4 and 10 repeats is sufficient to best estimation of the mean and Standard deviation. There are several factors might cause uncertainty for example measuring instrument, the measured sample, Operator skills, Sampling issues or the environment which summarized in Ishikawa diagram. Uncertainty is estimated by two ways: Type A evaluation which estimate uncertainty statistically which can be reduced and type B evaluation which estimate uncertainty from professional judgment. In order to overcome the errors which might occur, all sources of uncertainty must be identified and the range of the uncertainty must be estimated from each source. After that, ultimately combined individual uncertainties to get an overall uncertainty.