Noradrenaline determination using electrochemical

The determination of catecholamines requires a highly sensitive and selective assay procedure capable of measuring very low levels of catecholamines that may be present. In past years, a number of methods have been reported for measurement of catecholamines in both plasma and body tissues. A few of these papers have reported simultaneous measurement of more than two catecholamine analytes. One of them utilized Used UV for endpoint detection and the samples were chromatographed on a reversed-phase phenyl analytical column. The procedure was slow and cumbersome because ofdue to the use of a complicated liquid-liquid extraction and each chromatographic run lasted more than 25 min with a detection Umit of 5-10 ng on-column. Other sensitive HPLC methods reported in the literature use electrochemical detection with detection limits 12, 6, 12, 18, and 12 pg for noradrenaline, dopamine, serotonin, 5-hydroxyindoleace-tic acid, and homovanillic acid, respectively. The method used very a complicated mobile phase in terms of its composition while whilst the low pH of 3.1 used might jeopardize the chemical stability of the column. Analysis time was approximately 30 min. Recently reported HPLC methods utilize amperometric end-point detection. 

The flow cell built from solid PTFE, placed in a light-proof steel box was used for the determination of gallic acid. Luminol and KCl solutions were run continuously at 3.5 mL min by the peristaltic pump to the mixing valve, which was mixed further with the carrier water stream pumped at 3.5 mL min [84]. Sensitive ECL inhibition effects in the presence of adrenaline [85], noradrenaline, and DA were observed for Ru(bpy)3 /TPA and Ru(phen)3 /TPA systems. The method was made practical for the determination of commercial pharmaceutical injection samples with satisfied results. Two phenomena, namely potential-dependent ECL and ECL-inhibition, were observed for both Ru(bpy)3 /TPA and Ru(phen)3 /TPA systems. It was found that the Ru(phen)3 /TPA ECL system offers many benefits over Ru(bpy)3 VTPA system including higher ECL intensity, better reproducibility, and larger inhibition sensitivity to bofli noradrenaline and DA. Compared with most conventional spectrometry, electrochemical, and HPLC or CE methods in both the sensitivity and LR, the proposed method is very simple, rapid, and sensitive and is possibly applied for trace analyses of biological samples [86]. 

---