Evaluation of isotachophoresis as a method of identification and comparison with other methods by information theory

Abstract

Information theory is applied to estimate the identification power of isotachophoresis. Two approaches are used to estimate the information content of qualitative isotachophoresis. In the first, an expression is derived for the maximum number of compounds that can be distinguished in an isotachopherogram under realistic conditions; if equal probabilities of the incidence of the compounds are assumed, the maximum information content is 6.5–7 bit. In the second approach, the information content obtained by a retrieval procedure from a library of data on 263 anionic species in eight leading electrolyte systems in the pH range 3–10 is discussed; the information content is 3.5–5.7 bit for the individual electrolyte systems. When correlation between the systems is taken into account, the information content is reduced, e.g., to an average of 3.2 bit per system for the four systems with lowest correlation. Based on the information content, isotachophoresis is compared with mass spectrometry, infrared spectrometry, gas chromatography and thin-layer chromatography. It is shown that the identification power of isotachophoresis is in the range of that of packed-column gas chromatography.