Non-parametric linear regression of discrete Fourier transform convoluted densitometric peak responses.

The manuscript discusses the application of chemometrics to the handling of TLC response time data. Derivative treatment of chromatographic response data followed by convolution of the resulting derivative curves using 8-points sinx(i) polynomials (discrete Fourier functions) was found to be beneficial in eliminating the interference due to background noise in TLC-densitometric measurements. It also compares the application of Theil's method, a non-parametric regression method, in handling the response data, with the least squares parametric regression method, which is considered the de facto standard method used for regression. Theil's method was found to be superior to the method of least squares as it assumes that errors could occur in both x- and y-directions and they might not be normally distributed. In addition, it could effectively circumvent any outlier data points.