Advance in on-line two-dimensional liquid chromatography modulation technology

For some years now, multidimensional chromatography has been the focus of development in liquid chromatography in order to comprehensively analyze increasingly complex samples. It becomes clear that the molecular composition in biological samples is much more complex than previously assumed. Thus, the manifold variations of multidimensional chromatography allow a deeper understanding of the processes in nature. This review introduces the most important and creative modulators for the realization of two-dimensional liquid chromatography and discusses their advantages and disadvantages. One critical point in 2D-LC is, that the fractions from the D-1 are often eluted in an incompatible or non-optimal injection solvent for the D-2, which causes in no or low retention of analytes, loss of separation power or increasing peak broadening in the D-2. Therefore, in this review the modulators are considered with regard to their ability to combine orthogonal separation mechanisms. (c) 2019 Elsevier B.V. All rights reserved.