Characterization of the interlaboratory reproducibility of results in quantitative gas-chromatographic analysis using the internal normalization method

Abstract

A comparison of the results of gas-chromatographic analysis performed for the same samples with the use of various instruments with flame-ionization detectors and different (packed and capillary) columns indicates statistically significant differences in the results of data processing by the internal normalization method. Such variations in relative peak areas were detected on the same instrument on a comparison between data obtained under isothermal conditions and with temperature programming. Conceivable reasons for the observed changes in relative peak areas and procedures for the evaluation of errors due to this effect in the analysis of various samples on particular instruments are considered.

Internal Standards for Quantitative Analysis of Chemical Warfare Agents by the GC/MS Method: Nerve Agents

“…When using the internal standard method, the response factor value needs to be known in order to arrive at reliable analytical results. Additionally, the concentration range where the analyte and internal standard chromatographic peak area is a linear function must be known, as only then, the constant value of the response factor is ensured [ 1 , 3 ]. This explains why many articles focusing on internal standard applications begin by a detailed validation, especially testing linearity of the function and the limit of quantification and repeatability of the analysis [ 4 – 16 ].…”

“…In case the sample is modified before the analysis (extraction, distillation, and solvent evaporation), maximum similarity of chemical and physical characteristics of the analyte and of the internal standard should be ensured [ 1 , 3 ]. Close retention times of the analyte and the internal standard are also required in order to eliminate peak area discrimination at varying temperatures under temperature-programmed conditions [ 1 , 3 ]. On top of these published requirements for the internal standard selection, one needs to consider the requirement that the internal standard must neither react or interact with the analyte nor constitute a decomposition product or other admixture of the analysed compounds.…”

“…When using the internal standard method, the response factor value needs to be known in order to arrive at reliable analytical results. Additionally, the concentration range where the analyte and internal standard chromatographic peak area is a linear function must be known, as only then, the constant value of the response factor is ensured [1,3].…”

“…is explains why many articles focusing on internal standard applications begin by a detailed validation, especially testing linearity of the function and the limit of quantification and repeatability of the analysis [4][5][6][7][8][9][10][11][12][13][14][15][16]. In case the sample is modified before the analysis (extraction, distillation, and solvent evaporation), maximum similarity of chemical and physical characteristics of the analyte and of the internal standard should be ensured [1,3]. Close retention times of the analyte and the internal standard are also required in order to eliminate peak area discrimination at varying temperatures under temperature-programmed conditions [1,3].…”