Dopamine determination using

Biogenic amines, such as histamine [131], adenine [132], dopamine [133] and melamine [134], have been determined using chemosensors combining MIP recognition and PM transduction at QCM. Electronically conducting MIPs have been used in these chemosensors as recognition materials. Initially, functional electroactive bis(bithiophene)methane monomers, substituted either with the benzo-18-crown-6 or 3,4-dihydroxyphenyl, or dioxaborinane moiety, were allowed to form complexes, in ACN solutions, with these amines as templates. Subsequently, these complexes were oxidatively electropolymerized under potentiodynamic conditions. The resulting MIP films deposited onto electrodes of quartz resonators were washed with aqueous base solutions to extract the templates. 

An imprinted poly[tetra(o-aminophenyl)porphyrin] film, deposited on a carbon fibre microelectrode by electropolymerization, was used for selective determination of dopamine [208] in the potential range of —0.15 to 1.0 V. This chemosensor has been used successfully for dopamine determination in brain tissue samples. The dopamine linear concentration range extended from 10 6 to 10-4 M with LOD of 0.3 pM. However, this LOD value is very high compared to that of the dopamine voltammetric detection using polyaminophenol MIPs prepared by electropolymerization [209]. Dopamine was determined by CV and DPV at concentrations ranging from 2 x 10 s to 0.25 x 10 6 M with LOD of 1.98 nM. This LOD value is lower than that of PM dopamine detection [133]. 

After the behavioral experiments, the brains were removed 1 h after the last injection, and dissected into four parts the cortex, diencephalon, brain stem, and cerebellum. The levels of dopamine, serotonin, noradrenalin, and histamine were determined using HPLC methods as previously described. 

C. Spegel, A. Heiskanen, J. Acklid, A. Wolff, R. Taboryski, J. Emneus and T. Ruzgas, On-chip determination of dopamine exocytosis using mercapto-propionic acid mothfied microelectrodes. Electroanalysis, 19(2-3), 263-271 (2007). 

In order to demonstrate specificity, investigators have quantified samples using the radioreceptor assay and some other method of analysis, on the premise that if the values obtained are similar, then the radioreceptor assay is appropriate under the conditions employed. For example, the serum concentration of neuroleptics can be determined using a radioreceptor assay based on the dopamine receptor binding procedure (Creese and Snyder, 1977). To demonstrate the specificity of this assay, some samples were analyzed using both the radioreceptor assay and a radioimmunoassay (Table 3). The results obtained were virtually identical, indicating that the radioreceptor assay was measuring the same substance as that detected by radioimmunoassay. 

Pre-column enaymlc conversion to glucuronldes was used to determine the eneintiomeric purity of some novel chiral phenolic dopamine antagonists, using reversed-phase HPLC. 2... 

A. Pietrzyk et al. reported an imprinted poly[bis(2,2 -bithienyl)methane] film for a piezoelectric microgravimetry of dopamine. The MIP film contained either a 3,4-dihydroxyphenyl or benzo-18-crown-6 substituent, for selective determination of dopamine and was electropolymerized on an imderlayer of poly(bithiophene) on a Pt/ quartz resonator. The detection limit of the method was reported to be 10 nM [401]. Kan et al, on the other hand, developed a composite of multiwalled carbon nanotube (MWCNTs) and MIP with dopamine templates using the copolymerization reaction of methacrylic acid and trimethylolpropane trimethacrylate (copoly(MAA-co-TRIM)) on the vinyl functionalized MWCNT surface and used the composite for the thermo-gravimetric analysis of the template. The composite was found to be selective towards dopamine in comparison with epinephrine and the response was linear in the range of 5.0 X 10 "-2.0 X 10 M [427]. 

MAINTAINING ADEQUATE TISSUE PERFUSION. When a patient is in shock and experiencing ineffective tissue perfusion tiiere is a decrease in oxygen resulting in an inability of die body to nourish its cells at die capillary level. If die patient has marked hypotension die administration of a vasopressor (a drug diat raises die blood pressure because of its ability to constrict blood vessels) is required. The primary health care provider determines die cause of die hypotension and then selects the best mediod of treatment. Some hypotensive episodes require die use of a less potent vasopressor, such as metaraminol, whereas at other times a more potent vasopressor, such as dobutamine (Dobutrex), dopamine (Intropin), or norepinephrine (Levoplied) is necessary. 

It is appropriate at this juncture to illustrate the power of chemiluminescence in an analytical assay by comparing the limits of sensitivity of the fluorescence-based and the chemllumlnescence-based detection for analytes in a biological matrix. The quantitation of norepinephrine and dopamine in urine samples will serve as an illustrative example. Dopamine, norepinephrine, and 3,4-dihydroxybenzy-lamine (an internal standard) were derivatized with NDA/CN, and chemiluminescence was used to monitor the chromatography and determine a calibration curve (Figure 15). The limits of detection were determined to be less than 1 fmol injected. A typical chromatogram is shown in Figure 16. 

Because LCEC had its initial impact in neurochemical analysis, it is not, surprising that many of the early enzyme-linked electrochemical methods are of neurologically important enzymes. Many of the enzymes involved in catecholamine metabolism have been determined by electrochemical means. Phenylalanine hydroxylase activity has been determined by el trochemicaUy monitoring the conversion of tetrahydro-biopterin to dihydrobiopterin Another monooxygenase, tyrosine hydroxylase, has been determined by detecting the DOPA produced by the enzymatic reaction Formation of DOPA has also been monitored electrochemically to determine the activity of L-aromatic amino acid decarboxylase Other enzymes involved in catecholamine metabolism which have been determined electrochemically include dopamine-p-hydroxylase phenylethanolamine-N-methyltransferase and catechol-O-methyltransferase . Electrochemical detection of DOPA has also been used to determine the activity of y-glutamyltranspeptidase The cytochrome P-450 enzyme system has been studied by observing the conversion of benzene to phenol and subsequently to hydroquinone and catechol... 

Biochemical analyses of 6-OHDA-injected animals revealed a 93 percent depletion of dopamine. The tissue was assayed using electrochemical detection following separation by high-pressure liquid chromatography (Felice et al. 1978). recorded as ng/mg protein in the nucleus accumbens and compared to control rats with sham lesions (sham=65.5 4.4, lesion=4.9 1.5 t(39)=23.4). A lesion was defined as complete if 75 percent or more of the dopamine was determined to be depleted from the nucleus accumbens compared to mean sham group values. 

A particular interest for clinical applications was a possibility for detection of dopamine by its oxidation on nickel [19], cobalt [65], and osmium [66] hexacyanofer-ates. Except for oxidation of dopamine, cobalt and osmium hexacyanoferrates were active in oxidation of epinephrine and norepinephrine. For clinical analysis it is also important to carry out the detection of morphine on cobalt [67] and ferric [68] hexacyanoferrates, as well as the detection of oxidizable amino acids (cystein, methionine) by manganous [69] and ruthenium [70] hexacyanoferrate-modified electrodes. In general, oxidation of thiols was first shown for Prussian blue [71] and nickel hexacyanoferrate [72], This approach has been used for the detection of thiols in rat striatum microdialysate [73], Alternatively, the detection of thiocholine with Prussian blue was employed for pesticide determination in acetylcholine-esterase test [74],... 

Figure 15.14 illustrates a typical voltammetric result for the determination of dopamine in the presence of ascorbic acid with a CNT-modified electrode. The selective voltammetric detection of uric acid [82] or norepinephrine [83] in the presence of ascorbic acid has been demonstrated with a (3-cyclodextrin-modified electrodes incorporating CNTs. Ye et al. [84] have studied the electrocatalytic oxidation of uric acid and ascorbic acid at a well-aligned CNT electrode, which can be used for the selective determination of uric acid in the presence of ascorbic acid. The simultaneous determination of dopamine and serotonin on a CNT-modified GC electrode has also been described [85],... 

The CL enhancement of the lucigenin reaction with catecholamines in the presence of HTAH micelles was used for determination of dopamine, norepinephrine, and epinephrine [42], However, the presence of an anionic surfactant, SDS, inhibits the CL of the system. The aforementioned CL enhancement in the presence of HTAH can be explained in the following way the deprotonated forms of the catecholamines are expected to be the principal species present in aqueous alkaline solution due to the dissociation of the catechol hydroxyl groups, and to react with lucigenin to produce CL. The anionic form of the catecholamines and the hydroxide ion interact electrostatically with and bond to the cationic micelle, to which the lucigenin also bonds. Therefore, the effective concentration of the... 

Naphthalene-2,3-dicarboxaldehyde (NDA), which reacts with primary amines to give highly fluorescent cyanobenz[/]isoindole (CBI) derivatives, has also been used for determination of amphetamine-related compounds [70], dopamine, and norepinephrine [72] sub-fmol to fmol amounts of these were detected by HPLC with the PO-CL detection. 

HPLC on a Cosmosil 5 Cis column, using a perchloric acid-acetonitrile eluent (pH 7.6), followed by CLD in the presence of hydrogen peroxide and bis(2,4,6-trichlorophenyl) oxalate (42), was applied to the determination of 1-aminopyrene (43a) and various diaminopyrenes (43b-d). Ascorbic acid was added to avoid oxidative degradation of the aminopyrenes in the presence of metals LOD in the sub-fmol range (SNR 3)147. A fast (less than 10 min) HPLC-ELCD method was proposed for determination of dopamine (19b) and its metabolites in microdialysates, using packed fused silica capillary columns LOD 0.05 Xg/L of dopamine in a 2 XL sample, RSD 3% (n = 10)148. 

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