Real-time detection of isoprene marker gas based on micro-integrated chromatography system with GOQDs-modified μGC column and metal oxide gas detector

Abstract

Isoprene is a typical physiological marker that can be used to screen for chronic liver disease (CLD). This work developed a portable micro-integrated chromatography analysis system based on micro-electromechanical system (MEMS) technology, nanomaterials technology and embedded microcontroller technology. The system integrated components such as graphene oxide quantum dots (GOQDs) modified semi-packed microcolumn, In2O3 nanoflower (NF) gas-sensitive detector and 3D printed miniature solenoid valve group. The effectiveness of the separation effect of the micro-integrated system was verified by gas mixture test; the laws of the influence of carrier gas pressure and column temperature on the chromatographic separation performance, respectively, were investigated, and the working conditions (column temperature 90 °C and carrier gas pressure 7.5 kPa) for system testing were determined. The percentages of relative standard deviation (RSD) of the peak areas and retention times obtained for the separated gases were in the range of 0.95% to 6.06%, indicating the good reproducibility of the system. Meanwhile, the microintegrated system could detect isoprene down to 50 ppb at small injection volume (1 mL). The system response increased with increasing isoprene concentration and was linearly correlated with isoprene concentration (R2 = 0.986), indicating that the system was expected to be used for trace detection of isoprene, a marker gas for liver disease, in the future.

Programmable and Modularized Gas Sensor Integrated by 3D Printing

“…The protective package reduced the influence of contaminants on the sensors, extending the lifespan of the sensing system and enabling operation in contaminated environments. In a gas chromatography system reported by Han et al, 214 3D-printed components can serve as valve mounting blocks, featuring a three-dimensional microchannel distribution, to facilitate the assembly of miniature solenoid valve groups. A microcontroller unit regulated the activation and deactivation of these solenoid valves, enabling precise control over the channel pathways.…”

“…Furthermore, this approach obviated the need for conventional six-way valves and their associated motors, thereby enhancing the potential for portable integration of microdevices. 214 The flexibility of 3D printing in dimensions and shapes enables customized cells and chambers to be used as structural parts simultaneously to assemble various modules. For example, a 3D-printed chamber with a specially designed structure can efficiently accommodate commercial sensors and functional components in arrays while optimizing the physical and chemical processes of gas sensing.…”

“…This configuration offered considerable flexibility in gas testing. Furthermore, this approach obviated the need for conventional six-way valves and their associated motors, thereby enhancing the potential for portable integration of microdevices …”