| Caesalpinia Sappan L is a traditional Chinese medicine.Hematoxylin andBrazilin are two important kinds of active ingredients that Caesalpinia Sappan Lcontains. Electrochemical methods were used to study the properties and the detectionof brazilin and hematoxylin.1. A linear sweep voltammetry determination of hematoxylin was developed,In asupporting electrolyte of Britton-Robinson of pH5.0, hematoxylin gives a sensitivereduction peak by linear sweep voltammetry. The voltammetric potential peak currentis proportional to the concentration of hematoxylin in the range of2.24×10-61.05×10-4mol·L-1, and the detection limit is7.41×10-7mol·L-1（S/N=3）, the working curveregression equation is:（A）=5.281×10-7+0.287c (mol·L-1), R=0.9981.2. A new method for the determination of Brazilin at the carbon nanotubesmodified glassy carbon electrode was described. The MWCNTS/GC was constructedby dropping the modified solution,which was prepared with the modified method ofcarbon nanotubes dispersion in the solution of DMF, on the surface of the electrode.The optimum compositions of the modified solution, MWNT:DMF=1mg:1mL,Theelectrochemical characteristics of brazilin at this modified electrode were studied bycyclic voltammetry in detail. Under the optimal conditions, the method showed goodlinearity for brazilin in the range of6.8×10-5-8.2×10-4mol·L-1in B-R buffersolution with a detection limit of2.2×10-5mol·L-1（S/N=3）.The proposed methodshowed high selectivity and sensitivity, and the disposal method of the sample wassimple. The method was applied to the determination of brazilin samples.3. Molecular imprinted over-oxidized polypyrrole （OPPy） modified glassycarbon electrode （hematoxylin-OPPy/GC） was prepared by electrochemicalpolymerization of pyrrole with cyclic voltammetry in the presence of templatemolecule hematoxylin, and was followed by over-oxidized at1.3V in phosphatebuffer solution （pH=9.05）. The modified electrode could successfully avoidpolymerization of oxidized hematoxylin and the interference of brazilin. A linearresponse curve was obtain from1.0×10-62.05×10-5mol·L-1, with the detection limit of5.0×10-6mol·L-1. The main driving force for recognition are hydrogen bonds andcomnlementarv cavity effect. In addition, hematoxylin-OPPy/GC was used todetermine the trace amounts of hematoxylin in stimulted samples with satisfactoryresults.4. We also used computational chemistry to study these electrochemicalproperties of the two substances, oxidant ability of brazilin is superior to hematoxylin.On the surface of over-oxidized polypyrrole （OPPy） modified glassy carbonelectrode,because of the strong interacted force between hematoxylin and polypyrrole,adsorption ability of hematoxylin on surface of electrode is better than brazilin.Sowith the incresing of the concentrade of hematoxylin,interference of brazilin wasweakened in the process of determing hematoxylin. |
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