Wavelet analysis of the baseline noise in HPLC

Baseline noise has a significant contribution to the repeatability of chromatographic measurements. In this study, baseline noise is characterized by calculating its power spectrum and wavelet transform using frontal chromatograms. Wavelet analysis is a very powerful means to detect the heteroscedastity or homoscedasticity of the baseline. Usually, it is assumed that noise level is proportional to signal intensity. This is, however, a rather rough estimation. Our calculations show that noise intensity is neither constant nor directly proportional to the signal intensity.