Determination of Ten Kinds of Alpha-2 Agonists Residues in Animal Derived Food by UHPLC-Triple Quadrupole/Composite Linear Ion Trap Mass Spectrometry

[Objectives]The paper was to establish an ultra high performance liquid chromatography-quadrupole/linear ion trap complex mass spectrometry for the determination of 10 kinds ofα2-receptor agonists in animal derived food.[Methods]The samples were extracted with sodium carbonate buffer solution and ethyl acetate,and analyzed by mass spectrometry after solid phase extraction and high performance liquid chromatography separation.[Results]Ten kinds ofα2-receptor agonists showed a good linear relationship in the range of 1-100μg/mL,with the average recovery of over 69%and the relative standard deviation less than 8.32%.The detection limit of 10 kinds of α_(2)-receptor agonists was up to 1μg/kg.[Conclusions]The method has good selectivity and strong anti-interference ability,and can meet the requirements of 10 kinds ofα2-receptor agonists residues in animal derived food.

Application of Liquid Nitrogen Cold Trap for Purification of Hydrogen Gas Stream Generated from NaBH4

The feasibility of using liquid nitrogen cold trap （LNCT） for the removal of water vapour and alkaline mist from the hydrogen gas stream which is generated from the catalytic and acidic decomposition of sodium borohydride is investigated. Practically, the target application is mobile fuel cells based on hydrogen production from storage in chemical hydrides. The LNCT would be used as a one step purification method with less cost and space requirements instead of applying the conventional purification techniques. Two catalysts were investigated for the production of hydrogen from the aqueous solution of NaBH4 in a small scale packed bed reaction column. The hydrogen generated from the catalytic decomposition of NaBH4 was accompanied by limited quantity of water vapour and alkaline mist. Nonetheless, higher quantities were generated when applying the acidic decomposition of NaBH4 and consequently the utilization of LNCT for H2 purification has proved useful and lead to a reduction in the content of these impurities; thereby the concentration of hydrogen in the outlet stream has increased.

Role of trapped liquid in flow boiling inside micro-porous structures:pore-scale visualization and heat transfer enhancement

Flow boiling is an important heat dissipation method for cooling high heat flux surfaces in many industrial applications.The heat transfer can be further enhanced by using porous media surfaces due to their high specific surface areas.However,although flow boiling in channels is well understood,the phasechange behavior with the additional capillary effect induced by the porous structures is not well understood,and the design of the porous structures is difficult to avoid dryout and over-temperature accidents.A pore-scale lab-on-a-chip method was used here to investigate the flow boiling heat transfer characteristics inside micro-porous structures.The flow patterns,captured in the two-phase region with a uniform pore-throat size of 30 lm,showed that liquid was trapped in the pore-throat structures as both dispersed liquid bridges and liquid films.Moreover,the liquid film was shown to be moving on the wet solid surface by laser-induced fluorescence and particle tracking.A theoretical analysis showed that the capillary pressure difference between adjacent liquid bridges could drive the liquid film flows,which helped maintain the coolant supply in the two-phase region.The pore-throat parameters could be designed to enhance the capillary pressure difference with multiple throat sizes of 10–90 lm which would enhance the heat transfer 5%–10%with a 5%–23%pressure drop reduction.This research provides another method for improving the flow boiling heat transfer through the porous structure design besides changing the surface wettability.