Particle-based liquid chromatographic separations in microfluidic devices - A review.

The research and applications of liquid chromatographic (LC) chips receive more and more attention due to the numerous advantages over the traditional and larger analytical systems, e.g. requirement for small sample and reagent volumes, fast and inexpensive analysis, dead-volume free connections and the ability to multiplex measurements. Since LC is one of the most powerful separation techniques, its miniaturization seems an obvious target of lab-on-a-chip developments. However, the common procedures used in the preparation of chromatographic columns are not well applicable at the microscopic level. Additionally, implementing sample injection of (sub)nanoliter volumes (with sensitive detection) is still a challenge. This review deals with microchips incorporating particle-based stationary phases and focuses on the lab-made and commercialized chromatographic separations discussing the particle retention methods, the designs/constructions of LC chips, the separation performances and possible applications. A survey about microfluidic chips - capable of efficient separations and high-throughput sample pretreatment - hyphenated with electrospray mass spectrometric devices to achieve sensitive detection has also been made. The merits and limitations of different commercial LC chips were compared with other published approaches, as well.