Assessing chromatographic peak purity using condition index and singular value evolving profiles

A new method for determining chromatographic peak purity is presented. The method uses condition index evolving profiles (CIEPs) and singular value evolving profiles (SVEPs). To produce a CIEP or a SVEP, singular value decompositions are performed on data matrices containing the analyte's pure-component spectrum and sample spectra as they evolve over a chromatographic time profile. Visual inspection of condition indices and singular values as they evolve over time enables detection of less than 0.5% of a spectrally similar impurity with no chromatographic resolution (R_s = 0). Additionally, the CIEPs and SVEPs allow estimation of chromatographic pure regions. This method represents an extension of CIEPs which have been used in successful library searches of multicomponent mixtures based on gas chromatography-Fourier transform infrared spectra and liquid chromatography-UV-visible spectra.