Direct Determination of Six Cytokinin Nucleotide Monophosphates in Coconut Flesh by Reversed-Phase Liquid Chromatography-Tandem Mass Spectrometry

Electrochemical biosensor for cytokinins based on the CHASE domain of Arabidopsis histidine kinases 4

In this study, An AHK4 CHASE domain was used to construct an electrochemical cytokinin biosensor using ferrocene as the electrochemical mediator. Upon addition of cytokinin, the binding of cytokinin and AHK4 led to dimerization, which blocked electron transfer between ferrocene and the electrode, and the redox peak current of ferrocene was gradually reduced. Cytokinin was detected by recording the change of the ferrocene redox peak current. The biosensor shows a linear range of 50-400 nM with a linear regression equation of i_p = 0.0086c + 0.732 (R² = 0.993) with i_p in μA and c in nM and a detection limit (LOD) of 1.5 nM (S/N = 3). The biosensor exhibits excellent performance that avoids interference of other types of plant hormones and was successfully applied to the detection of cytokinins in bean sprouts.

Novel nanofibers mat as an efficient, fast and reusable adsorbent for solid phase extraction of non-steroidal anti-inflammatory drugs in environmental water

Core-shell polyaniline/polyacrylonitrile nanofibers mat (PANI/Pan NFsM) was prepared for extraction of hydrophilic non-steroidal anti-inflammatory drugs (NSAIDs) in environmental water. Superior adsorption and desorption performance of PANI/Pan NFsM was confirmed by both static and dynamic adsorption/desorption experiments. These properties proved PANI/Pan NFsM was a potentially efficient and fast solid phase extraction (SPE) adsorbent for NSAIDs. Under the optimized conditions, only 3 mg of PANI/Pan NFsM could easily extract eight target analytes in 10 mL of water sample without any pre-treatment, and the analytes retained on NFsM could be easily eluted by 500 μL of 1% acetic acid methanol for direct UPLC-MS/MS analysis. In addition, each piece of PANI/Pan NFsM could be reused for at least 20 times without performance decline. Possible adsorption mechanisms were also proposed. Practical feasibility was validated through the actual sample analysis.

Simultaneous Determination of Oleanolic Acid and Ursolic Acid by in Vivo Microdialysis via UHPLC-MS/MS Using Magnetic Dispersive Solid Phase Extraction Coupling with Microwave-Assisted Derivatization and Its Application to a Pharmacokinetic Study of Arctiumlappa L. Root Extract in Rats

Simultaneous detection of oleanolic acid and ursolic acid in rat blood by in vivo microdialysis can provide important pharmacokinetics information. Microwave-assisted derivatization coupled with magnetic dispersive solid phase extraction was established for the determination of oleanolic acid and ursolic acid by liquid chromatography tandem mass spectrometry. 2'-Carbonyl-piperazine rhodamine B was first designed and synthesized as the derivatization reagent, which was easily adsorbed onto the surface of Fe3O4/graphene oxide. Simultaneous derivatization and extraction of oleanolic acid and ursolic acid were performed on Fe3O4/graphene oxide. The permanent positive charge of the derivatization reagent significantly improved the ionization efficiencies. The limits of detection were 0.025 and 0.020 ng/mL for oleanolic acid and ursolic acid, respectively. The validated method was shown to be promising for sensitive, accurate, and simultaneous determination of oleanolic acid and ursolic acid. It was used for their pharmacokinetics study in rat blood after oral administration of Arctiumlappa L. root extract.