## 4 Discussion
The immunity of microelectrodes to 'ohmic drop' phenomena make it possible to conduct electrochemical experiments in previously inaccessible samples such as non-polar solvents, supercritical fluids and solids [85]. With reference to SPEs, the sample volume required for SPEs is significantly smaller than for standard CV. Another important advantage of SPEs is that they are intended for single-use applications,eliminating the arduous de-fouling process between each measurement. This also makes them ideal for clinical applications, as SPEs reduce the risk of cross-contamination between the hazardous biological samples and operators [86]. RE is crucial to the accuracy of electrochemical measurements by providing a known stable potential that can be referenced by WE. The ideal RE, such as the Standard Hydrogen Electrode (SHE) has a stable potential set at 0, reversible and non-polarisable with high exchange current density to minimize the risk of noise superimposing the measurement signals [87]. However, as SHE is cumbersome to use and maintain, most researchers chose to use SCE and Ag/AgCl electrodes instead, as we have shown in this study. While SCE has a stable potential at +0.244 V (against SHE) and is simple to construct and maintain, due to the presence of hazardous elemental mercury and Hg2 CI2 (calomel), it has fallen out of fashion [88]. The Ag/AgCl consists of a silver wire dipped in a chloride solution with a standard potential of 0.230 V (\(\pm\)10 mV). Ag/AgCl electrode non-toxic and easy to use; however, it has some disadvantages, including chlorine ions, that may leak out of the junction and interfere with certain electrode surfaces, such as gold and incompatibility with organic solvents [88]. Such deficiencies have led to an increase in the demand for pseudo-reference electrodes (pseudo-RE) in recent years. These electrodes are mainly structurally solid and made from materials such as elemental silver, platinum or gold wires. They are generally used either in miniaturized electrochemical cells (i.e., portable biosensors) or when organic solvents are used as the measurement media [87]. Some of the advantages of pseudo-RE, including simplicity, no liquid gap junction potential, low ohm resistance, no standard RE solvent contamination. However, the inherent potential of pseudo-RE cannot be measured due to the lack of thermodynamic equilibrium, potential shifts occur because many of them are not ideally nonpolarisable and have limited operating pH or temperature range [89]. Overall, different RE varieties and their respected characteristics could have an impact on and shift the potential of the sample. The RE selection should, therefore, take into account the working electrode, the oxidation potential of the sample and the nature of the measurement environment. Scanning range and scan rate are two of the most critical parameter setups for CV. It is ideal to scan over a wide range of voltages so that more antioxidants can be measured in the sample. However, a balanced approach must be taken to avoid overoxidation of the electrode surface in aqueous samples at a high potential range. As shown in the result section, most studies included in this review set the scanning range between 0-1.3 V. The exact value will have to be adjusted according to the type of WE and RE used and the antioxidants of interest. The scan rate is one of the key determinants of current amplitude. In a voltammetry cell, there are two types of electric current: (1) Faradic current (generated when redox-active molecules are oxidized or reduced) and (2) Non-Faradic current (charge between electrode and analyte). Non-Faradic current can be regarded as background noise that limits the sensitivity of the voltammetry system because it can mask the Faradic current. According to the Randles-Sevcik equation [90, 91], Faradic current is proportional to the square root of scan rate, whereas the non-Faradic current is directly proportional to the scan rate [92].