Shift of a peak apex and decrease in apparent peak height due to baseline drift in chromatograms

Abstract

The effects of baseline drift on a peak maximum point (apex) and apparent peak height are estimated from mathematical models, assuming that the peak shape is a normal or a gamma (so called Poisson) type and that the drift is straight. The inclination of baseline drift is expressed in the ratio of the apparent peak height (h) and the difference (d₁) of two points (C and E) on the vertical axis (detector response) ; where C and E are the intersections in the baseline with the tangent line at the inflection point in the leading half of a peak, and with the perpendicular from the apparent apex to the horizontal axis (time), respectively. The shift of a peak apex and the decrease of apparent peak height increase with d₁/h and with the skewness of the peak shape. The peak apex moves about the region between the two inflection points which are half of the peak width. The decrease rate {(h_o/-h)/h_o} of peak height exceeds 10 % in d₁/h> 0.7 (upward drift) or in d₁/h> 0.6 (downward), where h_o is the true peak height in no drift. However, the rate is less than 1 % in d₁/h<0.2, which is negligible in most cases.