Comparison of different methods to estimate the uncertainty in composition measurement by chromatography

Abstract

Natural gas is a mixture that contains hydrocarbons and other compounds, such as CO2 and N2. Natural gas composition is commonly measured by gas chromatography, and this measurement is important for the calculation of some thermodynamic properties that determine its commercial value. The estimation of uncertainty in chromatographic measurement is essential for an adequate presentation of the results and a necessary tool for supporting decision making. Various approaches have been proposed for the uncertainty estimation in chromatographic measurement. The present work is an evaluation of three approaches of uncertainty estimation, where two of them (guide to the expression of uncertainty in measurement method and prediction method) were compared with the Monte Carlo method, which has a wider scope of application. The aforementioned methods for uncertainty estimation were applied to gas chromatography assays of three different samples of natural gas. The results indicated that the prediction method and the guide to the expression of uncertainty in measurement method (in the simple version used) are not adequate to calculate the uncertainty in chromatography measurement, because uncertainty estimations obtained by those approaches are in general lower than those given by the Monte Carlo method.

The Quality Control Laboratory

“…Ariza et al, 2015 [178] The role of uncertainty regarding the results of screening immunoassays in blood establishments. Pereira et al, 2015 [179, 180] Determination of polybrominated diphenyl ethers in water by a simple dispersive liquid-liquid microextraction-gas chromatography-mass spectrometry method.…”

Separation Science in Latin America

“…An example of the widespread use of SPME is the work presented by Gómez, Reyes, and Pawliszyn [5], who evaluated the performance of a system designed to sequentially desorb multiple SPME fibers in automatic chromatographic analyses. Ayala and coworkers [6] compared the various approaches used to estimate the uncertainty in the quantitative analysis of permanent gas mixtures. The problem of overloading in GC analysis and the approaches to control it were examined by Zenkevich and Pavlovskii [7].…”