The traditional voltammetric sensor is a mercury drop electrode. Mercury is not only poisonous but also cannot be used in the positive potential area, so its application is greatly limited.  Since the 1950s, noble metal electrodes, semiconductor electrodes, and various carbon electrodes have been successively developed. Among carbon electrodes, carbon paste electrodes are widely used. The so-called carbon paste electrode (CPE) is a paste made by mixing conductive graphite powder and hydrophobic binders (such as paraffin wax, silicone oil, etc.), and then coating the surface of the electrode rod or filling into the electrode tube to make a type of electrode.

The performance of carbon paste electrodes mainly depends on their preparation method, materials used, electrode surface state, and service time. Therefore, the preparation of carbon paste electrodes is a basic and important work. The main materials required to prepare carbon paste electrodes are graphite powder and binders, and binders are mainly divided into two categories.

1. Non-conductive adhesive

1. Organic liquid adhesives, such as paraffin, silicone oil, mineral oil, epoxy resin, etc. On this type of electrode, the electrochemical reaction occurs at the interface between the electrode and the test solution.

2. Solid binders, such as solid paraffin, PVC ( ), etc. CPE with solid paraffin as a binder has the advantages of a smooth and stable electrode surface, good reproducibility, low background noise, high sensitivity, and good selectivity compared with ordinary CPE, etc., and can be applied to flow systems.

2. Electrolyte binder

NaOH is the electrolyte solution binder. The CPE prepared by using this binder can carry out electrochemical reactions in the electrode body, thereby expanding the application range of CPE, the electrode surface is easy to renew, and the positive potential residual current is low. However, due to poor electrode robustness and large background current in the negative potential region, CPEs prepared with this binder are rarely used in electrochemical studies.

Because carbon paste electrodes have outstanding characteristics such as low electrode residual current, simple preparation method, non-toxicity, easy surface renewal, wide potential application range, and low price, this type of electrode is widely used in various fields such as inorganic and inorganic. Substance analysis, organic matter analysis, drug analysis, electrochemical, and biosensors have been developed rapidly.

However, so far, CPE has only stayed in the stage of laboratory research and has not entered the stage of industrial production, mainly because the preparation technology of CPE is still immature. At this stage, most carbon paste electrodes are prepared by manual grinding. The disadvantage of this method is that the carbon powder, binder, and modifier cannot be mixed well. However, carbon paste electrodes still have great development potential.

This article was scientifically tested by Han Sujuan, a senior teacher at the No. 9 Middle School in Gaocheng District, Shijiazhuang City.

Xinhuanet Science Popularization Department

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