Systematic Deviations due to Random Noise Levels in Size Exclusion Chromatography Coupled With Multi Angle Laser Light Scattering

Starting from a theoretical molar mass distribution (generalized exponential distribution), the concentration and light scattering chromatograms of a size exlusion chromatography coupled with multi angle laser light scattering experiment are constructed with random noise levels. From these noisy curves, a log M versus retention volume plot is created. This plot shows a systematic deviation in the low and high molar mass region. In the low molar mass region (poor light scattering signals), the log M signals are systematically too high. In the high molar mass region (poor concentration signals), the log M signals are constantly too low. We show that this systematic error is due to the fact that the logarithm of negative numbers is not defined.