Carbon paste electrodes, or CPEs, are widely used to analyze trace amounts heavy metal ions. These electrodes offer a portable and simple way to detect these ions. CPEs are versatile, sensitive and selective in their detection because they can be easily modified using various modifier materials. Modifiers including organic polymers, inorganic exchangers of ions, nanoparticles, and several ligands can be used to improve the sensitivity, selectivity, and versatility of these electrodes.
The modification of carbon paste electrodes with a complexing agent improves their performance in the electrochemical determination of heavy metals. The type of carbonaceous materials used to prepare CPEs will determine the choice of complexing agents. In this paper three different types CPEs made from carbonaceous materials are examined: CPEs made of graphite, carbon microspheres and multiwall nanotubes. The characterizations of these CPEs were performed by SEM and EDAX using JEOL JSM-820 (scanning electron microscope) as well as Bruker AXS XFlash Detector (4010). The results showed the surface area of these CPEs varied according to the ratio carbon/Nujol, which was determined as 1:1 for G-CPE. 1:1.6 were found for mS - CPE. The mS CPE showed the best performance when it came to the electrochemical determination of heavy metals. It had a larger area than CNT CPE and G-CPE.
AgCl/KClSat was used as reference electrode. Cyclic voltammetric measurements were recorded with an EG&G PARC Model 263 potentiostat/galvanostat. The voltammograms obtained from the three electrodes made of carbon paste immersed in vanillic and catechol acids, gallic acid, l'ascorbic/l'glutathione, and 4 x10-4 moles*L-1 of vanillic or catechol showed that these antioxidants were detected with similar kinetics. Seven measurements were taken to determine the reproducibility. The RSD of anodic peak potentials was less than 4%.
The mS-CPE, CNT-CPE, and G-CPE were all able to distinguish between the antioxidants. G CPE presented the lowest detection threshold. Principal Component Analysis demonstrated the ability of CPEs to differentiate between antioxidants. The electrodes are able separate electrochemical signals in relation to their chemical structure. The potential of these CPEs to detect antioxidants in complex samples is discussed. This information can be utilized to develop an analytical methodology for the identification of antioxidants in real samples. This will be useful in the food industry to reduce loss of important antioxidants caused by oxidation and degrading. This will be beneficial to other industries that want to reduce the use of chemicals. This could lead to a healthier environment and better food quality. In addition, these CPEs can be used in the field of health care to improve patient monitoring. They are a better alternative to noble metallic electrodes when it comes to oxidation reactions. They can also be easily adapted to existing instruments. This will allow for the development of a more affordable and simpler way to determine trace levels of important antioxidants.
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