CHARACTERIZATION OF OVERLAPPED CHROMATOGRAPHIC PEAKS BY THEIR 2ND DERIVATIVE - THE LIMIT OF THE METHOD

The second derivative of a chromatographic signal can aid In the recognition of composite peaks. In the case of a two-component composite, the second derivative has three maxima and two minima. The time position of the second of the three maxima is indicative of the point where the peak envelope of each component cross each other. This second maximum can be used to trigger the end of integration of the first component and the beginning of the integration of the second component. In theory, the second derivative approach works well. The present paper Investigates the limits of the method. It was found that, depending on the separation between the two components in the composite, there is a peak height ratio below which the method falls to recognize the existence of a composite system. The greater the separation, the smaller the height ratio. At 4σ separation, the minimum height ratio that the method can still recognize as a composite Is around 10−5. However, the useful range of the approach may extend to a lower range of height ratios due to the small changes in the area with relatively large changes In the peak height ratio. Noise also affects the useful range of the method. In general, as the noise increases, the method fails at higher peak height ratios. A surface describing the useful range of the method is given as a function of the signal-to-noise ratio, the separation, and the height ratio. © 1990, American Chemical Society. All rights reserved.