Jan Christensen on Multidimensional LC for Environmental Screening

Non-targeted screening of environmental samples means working with complex mixtures in which trace-level compounds sit alongside far more abundant ones.¹ At ISC 2026, Jan Christensen of the University of Copenhagen sat down with LCGC International to discuss when adding a second dimension of separation can offer a clear advantage over one-dimensional liquid chromatography–high resolution mass spectrometry (LC–HRMS).² The first requirement, according to Christensen, is sample complexity. In complex environmental and biological samples, low-concentration compounds are present together with high-concentration ones, and a one-dimensional separation often fails to deliver a pure mass spectrum. Multidimensional separation resolves compounds that would otherwise coelute, producing purer spectra and, with them, more reliable identifications. Christensen is clear that it is not a technique to apply across thousands of routine samples, but for complex mixtures the cleaner spectra support greater confidence in feature identification and prioritization.

Matrix effects are the second argument. In complex mixtures, ion suppression in electrospray ionization is a persistent problem, and a second dimension of separation means fewer compounds coelute, which lowers that suppression. Presentations at ISC 2026 have shown clear reductions in matrix effects with multidimensional separation. Work from Christensen’s group with ion chromatography (IC), hydrophilic interaction liquid chromatography (HILIC), and supercritical fluid chromatography (SFC) points to salts as a major source of ion suppression for polar micropollutants, particularly once samples are preconcentrated by evaporation or freeze-drying, which enriches the salts along with the analytes. Separating those salts from the analytes in a second dimension lowers suppression, which in these techniques often appears in the middle or toward the end of the chromatogram. Christensen adds a caveat for gas chromatography (GC), where signal enhancement from active sites in the liner and column is more common, and more separation may mean more active sites rather than an improvement. That has not been investigated in detail, but for LC-type techniques, Christensen describes the benefit as clear.

Christensen answered the following questions:

• When does multidimensional chromatography offer a clear advantage over one-dimensional LC–HRMS for environmental non-targeted screening?
• How can chromatographic separation improve confidence in feature identification and prioritization?
• Can multidimensional chromatography significantly reduce matrix effects and ion suppression in complex environmental samples?

References

1. Zweigle, J.; Tisler, S.; Bevilacqua, M.; et al. Prioritization Strategies in Non-Target Screening of Environmental Samples by Chromatography with High-Resolution Mass Spectrometry. LCGC International 2026, 3 (2), 22–24. DOI: 10.56530/lcgc.int.hl3988l9
2. Christensen, J. H. Multidimensional Chromatography and LC-HRMS for Non-Target Screening of Environmental Contaminants: Strategies for Quantification, Prioritization, and Identification. Presented at ISC 2026, in Prague, Czech Republic. https://www.czech-in.org/cmPortalv15/Searchable/isc26/config/normal#!sessionschedule (accessed 2026-09-18).