Various implementations of two-dimensional high-performance liquid chromatography are increasingly being developed and applied to the analysis of complex materials, including those encountered in the analysis of foods, beverages, and nutraceuticals. Previously, we introduced the concept of selective comprehensive twodimensional liquid chromatography (sLC×LC) as a hybrid between the more conventional, but extreme opposite sampling modes of heartcutting (LC-LC) and fully comprehensive (LC×LC) 2D separation. The sLC×LC approach breaks the link between first dimension (1D) sampling time and second dimension (2D) analysis time that is faced in LC×LC and allows very rapid (as low as 1 s) sampling of highly efficient 1D separations, while at the same time allowing efficient 2D separations on the timescale of tens of seconds. In this paper, we improve upon our previous sLC×LC work by demonstrating the ability to perform the processes of 1D sampling and 2D separation in parallel. This significantly improves the flexibility of the technique and allows targeted analysis of analytes that elute close together in time in the 1D separation. To demonstrate the value of this added capability, we have developed a sLC×LC method using multiwavelength ultraviolet absorbance detection for the quantitative analysis of six target furanocoumarin compounds in extracts of celery, parsley, and parsnips. We show that 2D separations of 1D effluent containing the target compounds of interest reveal the presence of unanticipated interferent peaks that would otherwise compromise the quantitative accuracy of the method. We also demonstrate the application of the chemometric method iterative key set factor analysis with alternating least-squares to sLC×LC to mathematically resolve target compounds that are only slightly separated chromatographically but not sufficiently resolved for accurate quantitation.
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Acknowledgments All of the HPLC columns used in this work were generous gifts from their respective manufacturers. The flow selector valves were generous gifts of Cadence Fluidics, LLC. DRS, EDL, and DCH were supported by a Faculty Startup Award from the Camille and Henry Dreyfus Foundation. EDL was also supported by a research scholarship from the Howard Hughes Medical Institute. RCA was supported by an Altria Fellowship from VCU, and the work of SCR and RCA was supported by NSF grant CHE-0911330. SPT was supported by NCI grant 5K07CA128952-03. We would also like to acknowledge Jae Kyeom Kim, Scott Simpkins, Noemia Strapazzon, and Lindsay Young for providing vegetable samples.
- Liquid chromatography
- Selective comprehensive
- Targeted analysis