## 4 Discussion  
This review summarises the published literature on the use of CV for the measurement of antioxidant status in biological samples. The aim is to provide practical information to help clinicians or researchers faced with implementing CV in their research. The technical aspects of CV were systematically examined with particular emphasis on sample collection and handling, experimental and parameter setup, and the various methods used to determine the antioxidant and voltammetric peak connexion. The findings demonstrate the impressive flexibility of CV in being able to analyze a wide range of biological specimens, including blood, homogenized tissue, body fluids and skin (via direct skin-electrode contact). Despite the relative simplicity of the procedure, the use of CV in measuring antioxidant status remains limited and restricted to just a few highly focussed research groups. Collection of blood through venpuncture is one of the most common and safe clinical procedures, and blood plasma has been used in most of the human studies included in this review. However, poor phlebotomy pracises can lead to in vitro haemolysis affecting the quality of the sample and incorrect interpretation of the result [79; 80]. Erythrocytes are known to carry both non-enzymatic and enzymatic antioxidants [81], and haemoglobin can interfere with CV analysis [82]. Thus, in vitro, haemolysis may have an impact on the interpretation of CV. It was therefore a surprise, that no group reported quality assurance measures to detect haemolysis. It is recommended that haemolysis tests are done because of the potential confounding by the contamination by intracellular antioxidants and haemoglobin. While both EDTA and Heparin have been used for anticoagulation of blood sample, EDTA has been reported to interfere with CV readings by oxidizing at a potential of over 900 mV and masking the intrinsic voltammetric peaks. On the contrary, Heparin is not CV sensitive and can be used reliably [29]. Additionally, Heparin has been shown to provide superior preservation capability for ascorbic acid (a key constituent of the first voltammetric peak) over EDTA plasma, serum, citric acid and Stabiltye (r) [83]. As a result, Heparin is the ideal anticoagulant for the treatment of blood samples for the measurement of CV. In addition to compensating for the volume needed for experiments, and preventing coagulation [84], sample dilution can be used to modify the CV sensitivity to identify additional redox-active molecules by altering the surface interaction of the electrodes with the test solution. A study conducted by [PERSON] et al. reported that dilution of red/white wine improves the sensitivity of CV to phenolic groups by enhancing the diffusion of the redox-active molecule to the electrode surface [25]. While the voltammetric peak height of the serum (rat) reported by [PERSON] et al., is proportional to the sample dilution [31; 32], the effect of serial dilution of plasma was not assessed. Both tissue and plasma samples (at \(-75\)\({}^{\circ}\)C) can be stored for at least six months without impact on the CV results [29], with the degradation of frozen brain samples and poor voltammetry signals after that time [28]. Antioxidant stability during storage is an important aspect which has not been adequately addressed in the design of the studies covered by this review. For example, if the plasma sample is insufficiently acidified or if an inadequate temperature is used for long-term storage, plasma ascorbic acid can degrade rapidly [83]. Most of the studies covered in the review used the three standard electrode configurations. Two research groups departed from this convention and introduced microelectrodes and SPEs. Key attributes of the microelectrode are smaller currents, steady-state response, and short response time. This was reported with the measurement of skin antioxidant status by direct skin-electrodes contact.