A novel approach to evaluate the extent and the effect of cross-contribution to the intensity of ions designating the analyte and the internal standard in quantitative GC-MS analysis

Abstract

In gas chromatography-mass spectrometry methods of analysis adopting the analyte's isotopic analog as the internal standard (IS), the cross-contribution (CC) phenomenon-contribution of IS to the intensities of the ions designating the analyte, and vice versa-has been demonstrated to affect the quantitation data. A novel approach based on the deviations of the empirically observed concentrations of a set of standards was developed to assess the accuracy of the empirically derived CC data. This approach demonstrated that normalization of ion intensities derived from the analyte and the IS generates reliable CC data. It further demonstrated that an ion-pair (designating the analyte and the IS) with ϳ5% or higher CC will result in a very limited linear calibration range. (J

An analytical investigation of 24 oxygenated-PAHs (OPAHs) using liquid and gas chromatography–mass spectrometry

“…S1 , Electronic supplementary material). As nonlinearity occurs throughout the calibration curve, detector fatigue is not responsible nor is cross-contribution likely [ 36 ] as there are no other ions detected to interfere with quantitation in clean matrices from the internal standard, 2F-FLUO- 13 C. Quadratic curves had an average linear coefficient ( R 2 ) over 0.99 for all compounds including those OPAHs that were listed as not quantifiable in a previous study [ 17 ]. Variability between each calibration set is reduced by over 40 % when modeled as quadratic curves compared with linear models using the same data.…”

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

“…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 ].…”

“…Similarly, some deuterized components of gasoline were used for the determination of aliphatic and aromatic hydrocarbons in water by the SPME method [ 7 ]. Additional examples of the internal standard use are [2H4]-1,2-dichloroethane for the determination of 26 halogenated compounds in water [ 24 ], [2H5]-3,4-methylenedioxyamphetamine and [2H6]-hydromorphone for the determination of narcotics and their metabolites in biological samples [ 4 ], and [2H14]-trifluarine, [2H6]-transpermethrine, and [2H4]-nitrophenol for the determination of 28 pesticides in the air [ 25 ]. This makes labelled analyte analogues ideal as internal standards for the determination of compounds by the GC/MS methods; however, their disadvantage is poor availability and high price.…”

“…The TIC area is usually considered [ 1 ]. More precise results can be achieved when considering the peak area of a particular ion [ 2 , 4 ], although the TIC area of the chromatographic peak can be sometimes more useful [ 5 ]. This is discussed in detail in publication [ 4 ].…”

“…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].…”