Chemometric resolution and quantification of four-way data arising from comprehensive 2D-LC-DAD analysis of human urine

Two-dimensional liquid chromatography (LC × LC) is quickly becoming an important technique for the analysis of complex samples, owing largely to the relatively high peak capacities attainable by this analytical technique. With the increase in the complexity of the sample comes a corresponding increase in the complexity of the collected data. Thus the need for chemometric methods capable of resolving and quantifying such data is ever more urgent in order to obtain the maximum information available from the data. To this end, we have developed a chemometric method that combines iterative key set factor analysis and multivariate curve resolution-alternating least squares analysis with a spectral selectivity constraint that is shown to be capable of resolving chromatographically rank deficient, non-multilinear data. (spectrally rank deficient compounds can only be quantified if the peaks having the same spectra are chromatographically resolved). Over 50 chromatographic peaks were found in a relatively small section of a LC × LC-diode array data set of replicate urine samples (a four-way data set) using the developed method. The relative concentrations for 34 of the 50 peaks were determined with % RSD values ranging from 0.09% to 16%.