Validation of specificity in quantitative thin layer chromatography—is spectral correlation a reliable measure of spot purity?

Abstract

Summary.The current guidelines of quantitative method development establish a requirement to validate a set of method parameters and the selectivity is one of the most important parameters to be proven. Currently, one of the most frequently used approaches is to measure the spectrum of a spot together with some reference spots and to correlate them. Additionally, several places of the spot (start, middle, end) can be measured and also correlated. In the current paper we perform a simulation done on 170 real spectra with different levels of contamination and noise, establishing the distribution of correlation coefficient. It can be concluded that contamination up to 10% almost cannot be detected by simple correlation measurement, regardless of the noise level. Moreover, at a high noise level there is a very low margin between correlation of different compounds and the correlation of the same (but noisy) spectra. These observations suggest that the spectral correlation cannot be a reliable measure of method specificity and some another chemometric methods need to be searched in further research.