Assessing stability-indicating methods for coelution by two-dimensional liquid chromatography with mass spectrometric detection

Development of a rapid screening method utilizing 2D LC for effect-directed analysis in the identification of environmental toxicants

Effect-directed analysis (EDA) is a crucial tool in environmental toxicology, effectively integrating toxicity testing with chemical analysis. The conventional EDA approach, however, presents challenges such as significant solvent consumption, extended analysis time, labor intensity, and potential contamination risks. In response, we introduce an innovative alternative to the conventional EDA. This method utilizes the MTT bioassay and online two-dimensional liquid chromatography (2D LC) coupled with high-resolution mass spectrometry (HR-MS), significantly reducing the fractionation steps and leveraging the enhanced sensitivity of the bioassay and automated chemical analysis. In the chemical analysis phase, a switching valve interface is employed for comprehensive analysis. We tested the performance of both the conventional and our online 2D LC-based methods using a household product. Both methods identified the same number of toxicants in the sample. Our alternative EDA is 22.5 times faster than the conventional method, fully automated, and substantially reduces solvent consumption. This novel approach offers ease, cost-effectiveness, and represents a paradigm shift in EDA methodologies. By integrating a sensitive bioassay with online 2D LC, it not only enhances efficiency but also addresses the challenges associated with traditional methods, marking a significant advancement in environmental toxicology research.

Two-dimensional liquid chromatography with reversed phase in both dimensions: A review

Two-dimensional liquid chromatography (2D-LC), and in particular comprehensive two-dimensional liquid chromatography (LC×LC), offers increased peak capacity, resolution and selectivity compared to one-dimensional liquid chromatography. It is commonly accepted that the technique produces the best results when the separation mechanisms in the two dimensions are completely orthogonal; however, the use of similar separation mechanisms in both dimensions has been gaining popularity as it helps avoid difficulties related to mobile phase incompatibility and poor column efficiency. The remarkable advantages of using reversed phase in both dimensions (RPLC×RPLC) over other separation mechanisms made it a promising technique in the separation of complex samples. This review discusses some physical and practical considerations in method development for 2D-LC involving the use of RP in both dimensions. In addition, an extensive overview is presented of different applications that relied on RPLC×RPLC and 2D-LC with reversed phase column combinations to separate components of complex samples in different fields including food analysis, natural product analysis, environmental analysis, proteomics, lipidomics and metabolomics.

Dealing with Wandering First-Dimension Peaks in 2D-LC Separations

The retention of large molecules, such as peptides and proteins, is strongly dependent on mobile-phase composition and temperature. Consequently, the retention times (tR) of these molecules often fluctuate from one separation to the next. In two-dimensional liquid chromatography (2D-LC), this fluctuation can be challenging to deal with, especially if only one or a few specific peaks in the first dimension (1D) separation are targeted for further separation. In this installment, we describe instrumental concepts that are useful for coping with this challenge.