Microchip gas chromatography column using magnetic beads coated with polydimethylsiloxane and metal organic frameworks

Micro gas chromatography (μGC) using microfabricated silicon columns has been developed in response to the requirement for portable on-site gas analysis. Although different stationary phases have been developed, repeatable and reliable surface coatings in these rather small microcolumns remains a challenge. Herein, a new stationary phase coating strategy using magnetic beads (MBs) as carriers for micro column is presented. MBs modified with organopolysiloxane (MBs@OV-1) and a metal organic framework (MBs@HKUST-1) are deposited in on-chip microcolumns assisted with a magnetic field with an optimized modification process. MBs@OV-1 column showed a minimum HETP of 0.074 cm (1351 plates/m) of 62 cm/s. Mixtures of volatile organic compounds are successfully separated using MBs carried stationary phase which demonstrates that this technique has good chromatographic column efficiency. This method not only provides a novel coating process, washing and characterization of the stationary phases but also establishes a straightforward strategy for testing new absorbent materials for μGC systems.

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

Isoprene is a typical physiological marker that can be used to screen for chronic liver disease. This work developed a portable micro-integrated chromatography analysis system based on micro-electromechanical system technology, nanomaterials technology and embedded microcontroller technology. The system integrated components such as graphene oxide quantum dots modified semi-packed microcolumn, In2O3nanoflower (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 of the peak areas and retention times obtained for the separated gases were in the range of 0.95%-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.

NiO nanocomposites/rGO as a heterogeneous catalyst for imidazole scaffolds with applications in inhibiting the DNA binding activity

Herein, we report a facile approach to synthesize a new highly versatile heterogeneous catalyst by spontaneous aerial oxidation based on nickel oxide nanocomposites immobilized on surface-functionalized reduced graphene oxide sheets. NiO nanocomposite/reduced graphene oxide (rGO-NiO-NC) is a highly efficient, cost-effective, reusable, selective, and eco-friendly nano-catalyst that does not lose any activity even after five reaction cycles. Nickel loading on the rGO-NiO nanocomposite was found to be 3.3 at%, which contributes to the effective and efficient use of rGO-NiO-NCs as a nano-catalyst for the synthesis of imidazole derivatives. Consequently, a series of imidazole derivatives were synthesized, catalyzed by rGO-NiO-NCs, in 60 min with high yields (86% to 96%) under green conditions. Furthermore, the present synthetic methodology was used for the synthesis of highly aromatic imidazole derivatives (B1-B3) whose calf thymus-DNA binding affinities suggest their superior inhibition ability to displace ethidium bromide (EB), which was further confirmed by molecular docking studies. Additionally, the green chemistry matrix of the synthesis reaction was found to be very close to ideal values, such as carbon efficiency (82.32%), E-factor (0.51), atom economy (77.86%), process mass intensity (1.51), and reaction mass efficiency (66.14%).