Limits of the internal standard technique in chromatography

Improved quantification of prostaglandins in biological samples by optimizing simultaneously the relationship eicosanoid/internal standard and using liquid chromatography tandem mass spectrometry

“…The ideal internal standard is an isotopically labelled version of the analyte that will be coeluted with the analyte but will be resolvable by mass spectrometry or an alternative detection method [1]. Although the validity of the internal standard technique relies among others on the assumption of linearity of the detector response towards the analyte and the internal standard [2,3], a review of the current literature on eicosanoids quantification has revealed that details on the detector linearity towards the internal standard are generally omitted. In addition a key weakness in the majority of the literature on quantification is that it does not deal sufficiently with the contextual issue concerning the strategies behind the selection of a particular amount of internal standard especially in cases where the analytes can have a wide span of concentrations.…”

Stochastic Utility of Internal Standard Method in Liquid Chromatography

“…[2][3][4][5][6] As demonstrated by Haefelfinger4, however, the internal standard method is not always preferable to the external calibration. In some instances, the latter yields more precise results.…”

“…In some instances, the latter yields more precise results. 4 The aims of this paper are to comprehend the uncertainty structure (i.e., stochastic properties) of the internal standard method and to predict the total precision or RSD of experimental results from the sample preparation, measurement and signal processing. The common but often elusive question concerning which is more precise, the internal standard method or external calibration, is answered mathematically for some typical examples.…”

“…Statistics elicits useful knowledge from experimental data, e.g., a strong correlation between measurements of analyte and IS material which leads to a precise result or small RSD in the IS method. 4 If raw data (e.g., concentration measurements) are obtained from repeated experiments, this approach can treat any problem without prior knowledge or model of the cause and effect of error. However, it cannot estimate the precision (or RSD) of another pair of analyte and IS from the knowledge of a pair examined already.…”

Deductive Prediction of Measurement Precision from Signal and Noise in Photomultiplier and Photodiode Detector of Liquid Chromatography

“…The precision is usually expressed in statistical terms as RSD or SD and is a universal criterion for evaluating the analytical fulfillment of a newly developed method as well as diverse traditional methods.1 In HPLC, however, relatively few publications can be found describing and discussing the statistical aspect and its cause and effect. [2][3][4][5][6][7][8][9][10][11][12][13][14][15] To the authors' knowledge, only three reviews have treated the HPLC precision from the theoretical viewpoint. 2,3,15 Quite recently, a theory to predict the actual RSD values in an analytical instrument has been proposed and the application to an HPLC apparatus equipped with a photomultiplier has been demonstrated.…”