Liquid chromatography on a monolithic column microfluidic chip coupled with “three‐T” sample injection mode and amperometric detection

Abstract

An LC microfluidic chip (LC chip) with amperometric detection was developed. The LC chip employed a 7.5 cm long reversed-phase polymethacrylate monolithic column as a stationary phase and a "three-T" injection mode. A convenient interface was designed to conduct pump pressure into the microfluidic chip to drive solution, and a home-made device was used to control the distance between the working electrode and the LC chip accurately. The "three-T" sample injection mode completely avoided the problem of sample dilution and sample leakage during separation, which is usually observed in traditional and "T" type LC chip, without the using of valve and finally results in a better resolution, reproducibility and relatively high sensitivity. Using the proposed LC chip system, we have successfully separated two isomers, catechol and hydroquinone, within 12 min with a RSD (n=3) <3.0% for retention time and <2.4% for peak area. We have also successfully separated and determined 5-hydroxy-L-tryptophan, dopamine and 5-hydroxytryptamine within 25 min with a RSD (n=3) <5% (for peak area) and a detection limit of 0.16-0.51 μmol/L.

Advances in monoliths and related porous materials for microfluidics

“…Device performance was analyzed in terms of peak capacity, and the LMA monolith with 15 min gradient elution gave the highest peak capacity. Wang et al 51 developed a three-T shape glass microchip with a LMA-based monolith for separation with electrochemical detection. The three-T injection shape avoided sample leakage and dilution by improving focusing.…”

Microfluidic Size Exclusion Chromatography (μSEC) for Extracellular Vesicles and Plasma Protein Separation

“…Two major technical challenges faced in miniaturized SEC are on‐chip sample injection and chip material suitable for high pressure flow operation. Successful miniaturization of commercial rotary valve injector [ 28,29 ] and microfluidic passive injector using cross junction [ 30–32 ] or T‐junction [ 33 ] channel designs have been reported. However, the former method requires costly valve components, while the latter on‐chip flow modules are sensitive to small pressure changes at low flow rates.…”

Toward higher extraction and enrichment factors via a double‐reservoirs microfluidic device as a micro‐extractive platform

“…So far, numerous microfluidic devices have been used for extraction purposes on a wide variety of samples including aqueous, biological, and food samples . For instance, liquid–liquid micro–extraction technique has been implemented by means of microfluidic devices.…”