Portable Liquid Chromatography

Abstract

The development of miniaturized systems has opened the possibility of the introduction of hand‐portable liquid chromatography ( LC ), but this kind of LC has evolved slowly although it has significant potential for solving analytical challenges in various applications in situ or at situ monitoring, due to their ability to perform measurements at the point of the potential analytical problem occurs. This article provides an overview of the current state of the art of portable LC technology and its context. The first LC reported as portable was the OB‐4 or Milichrom, developed by Baram et al. in 1983, but this system is far away from the contemporary idea of portability although served as a basis for the later developed portable LCs. It was not until 2015, after notable advancements in pumps, detectors, column technology, and batteries that a new wave of portable LCs surged. A timeline with relevant portable LC contributions is given and their main features are described in the article. The Axcend Focus was the first commercialized capillary/nano portable LC. Sharma et al. in 2015 proposed a number of requirements that an LC system must achieve to be considered as portable and Rahimi et al. in 2020 developed criteria to assess LC portability named portaBle fiEld Testing sTandard framEwoRk ( BETTER ) criteria, which evaluates: the system cost, performance, robustness, operation time, portability, and weight. To date, portable LC systems meet some of the grade 2 and 3 criteria for almost all assessments. The grade 4 and 5 criteria are deemed a challenge to be met by next‐generation devices. The capabilities of different pumping systems have been tested in several studies being the most popular option the syringe pumps. Injectors have not presented a major obstacle when they come to adapting to portable equipment. The downscaling of LC has been closely related to the dimensions of the analytical column, particularly to its internal diameter, capillary packed and monolithic columns have been employed. On‐column light‐emitting diode ( LED ) detection configurations, which do not make use of flow cells eliminating the associated dead volumes were proposed. Electrochemical detectors were also used in portable LC. Almost all portable LCs are homemade and were not commercialized, for most of them only a single paper was published and the number of real applications is scarce. New knowledge is necessary for advancing in portable LC.