Assessment of peak purity in liquid chromatography using condition index and singular value evolving profiles

A new method for peak purity control in liquid chromatography with diode array detection is proposed, based on both the concept of condition index evolving profiles (CIEPs) and singular value evolving profiles (SVEPs) and the technique of moving fixed-size window along the Chromatographic retention time axis. The CIEPs and SVEPs are produced by singular value decomposition (SVD) on data matrices constrained by the moving window which contains a fixed number of spectra and moves along the Chromatographic profile. Visual inspection of the singular values and condition indices, as they evolve along the Chromatographic retention time, enable to detect small amounts of a spectrally similar impurity under a major peak with zero Chromatographic resolution. No assumptions are made about the shape of the spectra of the compounds involved or about the degree of spectral similarity of the major compound and the impurities. The method was checked using simulated experiments.