Electrochemical detection determination

Rice JR, Kissinger PT. 1982. Liquid chromatography with precolumn sample preconcentration and electrochemical detection Determination of aromatic amines in environmental samples. Environ Sci Technol 1695) 263-268. 

Koch, D. D., and Kissinger, P. T., 1980a, Liquid chromatography with pre-column sample enrichment and electrochemical detection. Determination of serotonin in small amounts of serum and plasma. Anal. Chem. 52 27-29. 

E. Koyama, Y. Kikuchi, H. Echizen, K. Chiba and T. Ishizaki, Simultaneous high-performance liquid chromatography-electrochemical detection determination of imipramine, desipramine, their 2-hydroxylated metabolites, and imipramine V-oxide in human plasma and urine preliminary application to oxidation pharmacogenetics, Ther. Drug Monit., 1993, 15, 224-235. 

High performance Hquid chromatography with electrochemical detection has been used to determine 2—7 ppb of carbamate pesticides in water (40). The investigated pesticides were aminocarb, asulam, j -butylphenyknethylcarbamate (BPMC), carbaryl, carbenda2im, chlorpropham, desmedipham, and phenmedipham. 

Therefore, hplc methods seem more effective. By usiag a combiaed uv and electrochemical detection technique (52), the gem-chlotinated cyclohexadienones, the chlorophenols, and the phenoxyphenols present ia the chlorination mixtures can be determined with great accuracy. 

DETERMINATION OF CLARITHROMYCIN IN HUMAN PLASMA USING RP-LC WITH ELECTROCHEMICAL DETECTION... 

H. Fujimoto, I. Nishino, K. Ueno and T. Umeda, Determination of the enantiomers of a new 1,4-dihydropyridine calcium antagonist in dog plasma achiral / chiral coupled high performance liquid cliromatography with electrochemical detection , 7. Pharm. Sci. 82 319-322(1993). 

B.-M. Eriksson, B.-A. Persson and M. Wikstrom, Determination of urinary vanillyl-mandelic acid by direct injection and coupled-column clrromatography with electrochemical detection , 7. Chromatogr. 521 11-19 (1990). 

The on-line measurement of reducing capacity can be performed with either a single or a series of electrochemical detectors, and linear correlations have been demonstrated between total antioxidative activities determined by the electrochemical detection and those determined by DPPH- reduction or by the ORAC assay (Guo et al, 1997 Peyrat-Maillard et al, 2000). The reducing capacity must also be quantified by post-column reactions, either with DPPH- or by the reduction of phosphomolybdenum complexes followed by UV-VIS-detection (Bandoniene and Murkovic, 2002 Cardenosa et al, 2002). A combination of HPLC and semi-automatic ORAC analysis has also been described (Caldwell, 2001). 

Many drugs are electroactive, and as such, have been determined using LCEC. Space does not permit a discussion of the relevance of electrochemical detection to each class of drug. Table 4 lists several compounds of pharmaceutical interest (by therapeutic type and electroactive functionality) which have been determined by LCEC. 

Monitoring enzyme catalyzed reactions by voltammetry and amperometry is an extremely active area of bioelectrochemical interest. Whereas liquid chromatography provides selectivity, the use of enzymes to generate electroactive products provides specificity to electroanalytical techniques. In essence, enzymes are used as a derivatiz-ing agent to convert a nonelectroactive species into an electroactive species. Alternatively, electrochemistry has been used as a sensitive method to follow enzymatic reactions and to determine enzyme activity. Enzyme-linked immunoassays with electrochemical detection have been reported to provide even greater specificity and sensitivity than other enzyme linked electrochemical techniques. 

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... 

Sontag, G., Friedrich, O., Kainz, G., and Jorg, E. (1989). Determination of phenolic compounds by HPLC with electrochemical detection. Proc. EUR 5th Food Chem. Conference, Agric. Food Chem. Consum. 2, 703-707. 

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. 

Residues of alachlor and acetochlor are determined by similar methods involving extraction, hydrolysis to the common aniline moieties, and separation and quantitation by reversed-phase FIPLC with electrochemical detection. The analytical method for acetochlor is included as a representative method for residue determination of alachlor and acetochlor in plant and animal commodities. Propachlor and butachlor residues, both parent and metabolite, are determined by similar analytical methods involving extraction, hydrolysis to common aniline moieties, and separation and quantitation by capillary GC. The analytical method for propachlor is included as a representative method. The details of the analytical methods for acetochlor and propachlor are presented in Sections 4 and 5, respectively. Confirmation of the residue in a crop or... 

Mishin, V. M., Koivisto, T., and Lieber, C. S., The determination of cytochrome P450 2E1 -dependent p-nitrophenol hydroxylation by high-performance liquid chromatography with electrochemical detection, Anal. Biochem., 233,212,1996. 

Electrochemical detection is extremely selective and is consequently useful for determination of known components in complex mixtures. The nomenclature... 

Mayer, W. J. and Greenberg, M. S., Determination of some carbamate pesticides by high-performance liquid chromatography with electrochemical detection, ]. Chromatogr., 208, 295, 1981. 

Feubolt, R. and Klein, H., Determination of sulphite and ascorbic acid by high-performance liquid chromatography withe electrochemical detection,. Chromatogr., 640, 271, 1993. 

Hardcastle JL, Compton RG (2001) The electroanalytical detection and determination of copper in heavily passivating media ultrasonically enhanced solvent extraction by N-benzoyl-N-phenyl-hydroxylamine in ethyl acetate coupled with electrochemical detection by sono-square wave stripping voltammetry analysis. Analyst 126 2025-2031... 

Couto et al. [11] developed a flow injection system with potentiometric detection for determination of TC, OTC, and CTC in pharmaceutical products. A homogeneous crystalline CuS/Ag2S double membrane tubular electrode was used to monitor the Cu(II) decrease due to its complexation with OTC. The system allows OTC determination within a 49.1 1.9 x 103 ppm and a precision better than 0.4%. A flow injection method for the assay of OTC, TC, and CTC in pharmaceutical formulations was also developed by Wangfuengkanagul et al. [12] using electrochemical detection at anodized boron-doped diamond thin-film electrode. The detection limit was found to be 10 nM (signal-to-noise ratio = 3). 

UV detection, diode-array detector (DAD) and fluorescence have been the detection techniques used, coupled to HPLC for the analysis of OTC. UV detection is set at 355 nm [49-51], 350 nm [40], or at 353 nm [52], Using the diode array detector [49] offers advantages that the target peak can be identified by its retention time and absorption spectrum. Compared to UV detection, fluorescence detection is generally more specific and is less interfered by other compounds in the sample matrix [51]. A HPLC method with electrochemical detection has also been suggested recently. Zhao et al. [53] described HPLC with a coulometric electrode array system for the analysis of OTC, TC, CTC, DC, and methacycline (MC) in ovine milk. An amper-ometric detection coupled with HPLC was developed by Kazemifard and Moore [54] for the determination of tetracyclines in pharmaceutical formulations. 

Dean et al. [93] used a high performance liquid chromatographic method for the simultaneous determination of primaquine and carboxyprimaquine in plasma with electrochemical detection. After the addition of the internal standard, plasma was deproteinized by the addition of acetonitrile. Nitrogen-dried supernatants, resuspended in mobile phase were analyzed on a C8 reversed-phase column. Limits of detection for primaquine and carboxyprimaquine were 2 and 5 ng/mL with quantitation limits of 5 and 20 ng/mL, respectively. The assay sensitivity and specificity are sufficient to permit quantitation of the drug in plasma for pharmacokinetics following low dose (30 mg, base) oral administration of primaquine, typically used in the treatment of malaria and P. carinii pneumonia. 

Aniline, methyl aniline, 1-naphthylamine, and diphenylamine at trace levels were determined using this technique and electrochemical detection. Two electrochemical detectors (a thin-layer, dual glassy-carbon electrode cell and a dual porous electrode system) were compared. The electrochemical behavior of the compounds was investigated using hydrodynamic and cyclic voltammetry. Detection limits of 15 and 1.5nmol/l were achieved using colourimetric and amperometric cells, respectively, when using an in-line preconcentration step. 

Shea and MacCrehan [322] and Duane and Stock [323] determined hydrophilic thiols in marine sediment pore waters using ion-pair chromatography coupled to electrochemical detection. 

If the substance of interest appears to be electrochemically detectable, the optimum detection potential can be determined experimentally with the same set-up as described in Figure 4-1. 

Rocklin RD, Johnson DL. 1983. Determination of cyanide, sulfide, iodide, and bromide by ion chromatography with electrochemical detection. Anal Chem 55 4-7. 

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