Three-dimensional derivative spectrochimatograms in high-performance liquid chromatography and their implications for peak homogeneity validation

The full ultraviolet spectra generated by a photodiode-array detector are transformed to the nth derivative (dⁿA/d?ⁿ). The bipolar, three-dimensional data matrix (dⁿA/d?ⁿ, ?, t) is presented with computer-aided graphics as an extension of the spectrochromatogram concept to aid peak validation. Existing display algorithms are modified to yield several presentations which reveal the full topography of the elution profile. These include rotation in three-dimensional space and inspection of the positive and negative data planes. A novel contour-plot representation is proposed to enable the derivative spectrochromatographic data to be presented in a two-dimensional format. Two planes of data (i.e., positive and negative amplitudes of (dⁿA/d?ⁿ) in the (?, t) plane) can be displayed as required for derivative data presentation. The technique is used to assess the homogeneity of overlapping peaks of ethynyloestradiol and norethisterone. © 1986.