Dopamine, selective/sensitive detection

Niwa O, Morita M, Tabei H (1991) Highly sensitive and selective voltammetric detection of dopamine with vertically separated interdigitated array eledrodes... 

ONiwa, MMonta, HTabei, Highly sensitive and selective voltammetnc detection of dopamine with vertically separated mterdigitated array electrodes. Electroanalysis, 3 (1991), 163-168... 

Other examples of important biomolecules that can be detected using carbon paste electrodes modified with phthalocyanines are the neimotransmitters dopamine, serotonin, and epinephrine. Oni et al. [37] described the utilization of CPE containing iron(II) phthalocyanine (PePc), and iron(II) tetrasulfonated phthalocyanine ([FeTSPc]" ]) for the detection of dopamine and serotonin. The presence of ascorbic acid did not interfere with the determination of both species, individually or in a mixture. Shahrokhian et al. [38] performed epinephrine determinations in pharmaceutical and clinical samples through voltammetric techniques with high sensitivity and selectivity, low detection limit (sub-micromolar), and high reproducibility. 

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 dynamics of the release and uptake of dopamine into brain extracellular space are currently under intense investigation[20-22]. Dopamine is a well-known extrasynaptic messenger that functions via volume transmission, escaping from the synaptic cleft to bind to extrasynaptic receptors and transporters. High sensitivity, chemical selectivity, and fast temporal resolution are all desirable characteristics in detecting neurotransmitters in vivo. In practice, it is difficult to achieve all of these with one method. 

For the detection of dopamine, controlled-potential (potentiostatic) techniques, which are concerned with the study of charge transfer processes at the electrode-solution interface, are favored due to a number of advantages. These include high sensitivity, selectivity towards electroactive species, wide linear range, portability and low cost of instrumentation, speciation capability and a wide range of electrodes which allow assays of unusual environments [29]. 

As low concentrations of dopamine are released and rapidly cleared from the extracellular space, the sensing electrodes must be sensitive, and selective and respond quickly[6]. For in vivo detection of neurotransmitters such as dopamine, physically small electrodes are advantageous due to their small size and high sensitivity to catecholamines[34]. There are currently no electrodes small enough to measure dopamine concentrations within the approximately 100-nm synapse, but considerable developments are being made in minimizing electrode size to approach synapses as closely as possible and also to minimize... 

It should be noted, that the Lacc-GDH recycling electrode does not distinguish between epinephrine, norepinephrine or dopamine. Nevertheless, the selectivity is sufficient for discriminating the catecholamine signal from other components of the stimulating buffer without any purification or separation step. If the ratio between epinephrine and norepinephrine shall be determined, on the basis of the bioelectrocatalytic substrate regeneration by GDH immobilized on a carbon electrode (15) norepinephrine can be detected 40 times more sensitive than epinephrine while 1 4 selectivity is observed for the Lacc-GDH electrode. The conventional HPLC procedure for determination of catecholamines requires complex and expensive devices since the electrochemical detector has only low selectivity. 

Lv M, Mei T, Zhang C, Wang X. Selective and sensitive electrochemical detection of dopamine based on water-soluble porphyrin functionalized graphene nanocomposites. RSC Adv 2014 4 9261-70. 

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