| Benzoquinone and hydroquinone are typical redox couples and are commonly used to study protoncoupled electron transfer（PCET）reactions.When benzoquinone is reduced benzoquinone accepts two protons and two electrons to form hydroquinone at the electrodesurface.During the electrochemical reduction of benzoquinone in an unbuffered solution,the proton concentration near the electrode surface decreases rapidly after the proton donor is depleted,that is,the pH value sharply increases,which causes the reduction potential of benzoquinone decreases rapidly,and a new peak is formed.The peak height of the new peak is proportional to the concentration of the proton donor,while the peak potential is dependent on the pKa of the proton donor.We investigated the effects of proton donors,PPi,ATP,ADP and CTP,on the electrochemical behavior of benzoquinone in unbuffered solutions cyclic voltammetry,and their changes after hydrolysis.We found that the peak current of the new peak is independent of the concentration of benzoquinone.PPi releases protons to form hydroquinone during electrochemically reducing benzoquinone.However,the hydrolysate H2PO4-of PPi can release more protons than PPi itself,which promotes the reduction of benzoquinone at higher potentials.Therefore,the increase of proton depends on the concentration of PPi.Moreover,ATP,ADP,and CTP release protons to form a pH gradient after hydrolysis,which provides more protons forthebenzoquinonereduction,so the increase in protons depends on the PPi concentration.The increase of new peak current is consistent with the increase in the concentration of the proton donor.According to this relationship,we established differential pulse voltammetry to determine the content of PPi,ATP,ADP and CTP,and realized the direct detection of PPi content in toothpaste using bare glassy carbon electrode.The test method has the advantages of simple operation,high sensitivity,strong anti-interference ability and so on. |
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