Automated dual two-dimensional liquid chromatography approach for fast acquisition of three-dimensional data using combinations of zwitterionic polymethacrylate and silica-based monolithic columns

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.

Liquid chromatography at the university of pardubice: a tribute to Professor Pavel Jandera

Pavel Jandera was a world-leading analytical chemist who devoted his entire professional life to research in the field of high-performance liquid chromatography. During all his scientific career, he worked at the Department of Analytical Chemistry at the University of Pardubice, Czech Republic. His greatest contribution to the field of liquid chromatography was the introduction of a comprehensive theory of liquid chromatography with programmed elution conditions. He was also involved in the research of gradient elution techniques in preparative chromatography, modeling of retention and selectivity in various phase systems, preparation of organic monolithic microcolumns and, last but not least, in the development of theory and practical applications of two-dimensional liquid chromatography, mainly in the comprehensive form. In this review article, we have tried to capture the highlights of his scientific career and provide the readers with a detailed overview of Pavel Jandera's contribution to the evolution of separation sciences. This article is protected by copyright. All rights reserved.

An off-line three-dimensional liquid chromatography/Q-Orbitrap mass spectrometry approach enabling the discovery of 1561 potentially unknown ginsenosides from the flower buds of Panax ginseng, Panax quinquefolius and Panax notoginseng

To comprehensively elucidate the herbal metabolites is crucial in natural products research to discover new lead compounds. Ginsenosides are an important class of bioactive components from the Panax plants exerting the significant tonifying effects. However, to identify new ginsenosides by the conventional strategies trends to be more and more difficult because of the large spans of acid-base property (the neutral and acidic saponins), molecular mass (400-1400 Da), and rather low content. Herein, an off-line multidimensional chromatography/high-resolution mass spectrometry approach was presented: ion exchange chromatography (IEC) as the first dimension of separation, hydrophilic interaction chromatography (HILIC) in the second dimension, and reversed-phase chromatography (RPC) for the third dimension which was hyphenated to a Q Exactive Q-Orbitrap mass spectrometer. By applying to the flower buds of P. ginseng (PGF), P. quinquefolius (PQF), and P. notoginseng (PNF), IEC using a PhenoSphere^TM SAX column could fractionate the total extracts into the neutral (unretained) and acidic (retained) fractions, while HILIC (an XBridge Amide column) and RPC (BEH Shield RP18 column) achieved the hydrophilic interaction and hydrophobic interaction separations, respectively. Q-Orbitrap mass spectrometry offered rich structural information and complementary resolution to the co-eluting components, particular to those minor ones by including precursor ion lists in data-dependent acquisition. We could characterize 803 ginsenosides from PGF, 795 from PQF, and 833 from PNF, and 1561 thereof are potentially unknown. These results can indicate the great potential of this multidimensional approach in the ultra-deep characterization of complex herbal samples supporting the efficient discovery of potentially novel natural compounds.

Strategies to circumvent the solvent strength mismatch problem in online comprehensive two-dimensional liquid chromatography

On-line comprehensive two-dimensional liquid chromatography is a powerful technique for the separation of highly complex samples. Due to the addition of the second dimension of separation, impressive peak capacities can be obtained within a reasonable analysis time compared to one-dimensional liquid chromatography. In online comprehensive two-dimensional liquid chromatography, the separation power is maximized by selecting two separation dimensions as orthogonal as possible, which most often requires the combination of different mobile phases and stationary phases. The online transfer of a given solvent from the first dimension to the second dimension may cause severe injection effects in the second dimension, mostly due to solvent strength mismatch. Those injection effects may include peak broadening, peak distortion, peak splitting or breakthrough phenomenon. They are often found to reduce significantly the peak capacity and the peak intensity. To overcome such effects, arising specifically in online comprehensive two-dimensional liquid chromatography, different methods have been developed over the years. In this review, we focused on the most recently reported ones. A critical discussion, supported by a theoretical approach, gives an overview of their advantages and drawbacks.

Configuration of the ion exchange chromatography, hydrophilic interaction chromatography, and reversed-phase chromatography as off-line three-dimensional chromatography coupled with high-resolution quadrupole-Orbitrap mass spectrometry for the multicomponent characterization of Uncaria sessilifructus

Herbs represent complex chemical systems involving various primary and secondary metabolites that are featured by large spans of acid-base property, polarity, molecular mass, and content, etc., which thus poses great challenges to characterize the metabolites contained. Here, the combination of multiple-mechanism chromatography coupled with improved data-dependent-MS² acquisition (DDA-MS²) is presented as a strategy to support the deep metabolites characterization. Targeting Uncaria sessilifructus, a reputable medicinal herb containing alkaloids and triterpenic acids (TAs) as the main pharmacologically bioactive ingredients, a three-dimensional liquid chromatography (3D-LC) system was established by integrating ion exchange chromatography, hydrophilic interaction chromatography, and reversed-phase chromatography (IEC-HILIC-RPC). The first-dimensional chromatography, configuring a PhenoSphere SCX column eluted by methanol/20 mM ammonium acetate-0.05% formic acid in water, could well fractionate the total extract into two fractions (unretained ingredients and alkaloids). The subsequent HILIC using an XAmide column and RPC by a CSH Phenyl-Hexyl column achieved the sufficient resolution of the total TAs and total alkaloids, respectively. A polarity-switching precursor ions list-including DDA approach by Q-Orbitrap-MS enabled the high-efficiency, coverage-enhanced identification of alkaloids and TAs. This 3D-LC/Q-Orbitrap-MS system was validated as precise (RSD < 5% for intra-day/inter-day precision), Up to 308 components were separated from U. sessilifructus, and 128 thereof (including 85 alkaloids, 29 TAs, and 14 others) were identified or tentatively characterized, exhibiting superiority over the conventional one-dimensional LC/MS. Conclusively, 3D-LC/MS in an off-line mode can facilitate the flexible configuration of multiple chromatography to accomplish the fit-for-purpose characterization of the metabolites from an herbal extract or a biosample.