Dual-electrode Detection Research Articles

46] Determination of pterins by liquid chromatography/electrochemistry

Publisher Summary This chapter focuses on determination of pterins by liquid chromatography/electrochemistry. Pterins are of interest because of their possible involvement in a number of diseases. Pterins are obtained from the sources such as pterin, pterin-6-carboxylic acid, 6-methylpterin, and xanthopterin. A property of the pterins essential to their biological role as enzyme cofactors is their electrochemistry. Fully oxidized pterins can be reversibly reduced to 5,8-dihydropterins which rapidly tautomerize to 7,8-dihydropterins. These 7,8-dihydropterins can either be further reduced to 5,6,7,8-tetrahydropterins or be oxidized back to the fully oxidized state. Dual-electrode detector uses two working electrodes placed adjacent to each other and normal to the direction of flow—that is, in a parallel-adjacent configuration. Using this detector, one electrode is operated at an oxidizing potential to detect the dihydro- and tetrahydropterins while the other electrode is operated at a reducing potential to detect the oxidized pterins, thus the three stable oxidation states of the pterins can be detected simultaneously. For the determination of pterins in urine, a 25-cm chromatography column thermostatted at 30° is used. The mobile phase contains 5% methanol (v/v). A flow rate of 1.0 ml/min is employed.

Sensitive liquid chromatographic method for physostigmine in biological fluids using dual-electrode electrochemical detection

A liquid chromatographic method using dual-electrode detection has been developed for determination of physostigmine in biological fluids. The limit of detection is in the order of 25–50 pg mol −1 of plasma. A high sample throughput is obtained by a single solvent extraction step and autoinjection into the chromatograph. Data following oral doses of physostigmine are presented.

Determination of toxic azo dye metabolites in vitro by liquid chromatography/electrochemistry with a dual-electrode detector.

Aromatic amine and azo compounds are prevalent in the manufacture of common dyestuffs. The toxic actions of these substances are believed to be the result of metabolic activation and formation of labile products. Incubation techniques utilizing the liver microsomal fraction are a common method for studying the formation of these reactive intermediates. This study describes the use of liquid chromatography/electrochemistry (LCEC) for the determination of 4-nitroaniline, 2-amino-5-nitrophenol, and the labile N-hydroxy-4-nitroaniline in microsomal incubations. No prior extraction, preconcentration, or derivatization steps are necessary for the determinations which can be accomplished by a direct injection of the incubation. The dual-electrode detector in the parallel-adjacent configuration is used to confirm peak identity assignments. The series mode of this detector permits determination of 4-nitroaniline and its metabolites as products of the commonly used textile dye, Disperse Orange 3, in incubation media. Detection limits for the compounds of interest are all in the subpicomole range.

The use of liquid chromatography with dual-electrode electrochemical detection in the investigation of glutathione oxidatin during benzene metabolism

Liquid chromatography with electrochemical detection provides a powerful tool for the study of glutathione oxidation during benzene metabolism. The use of two dual-electrode detectors allows for the detection of oxidized and reduced glutathione and of phenol and quinone metabolites of benzene. The role of glutathione as a reductant is explored in this paper. Results indicate that hydrogen peroxide is the oxidizing agent primarily responsible for glutathione exidation during benzene, phenol and hydroquinone metabolism.

Gradient Elution of Biogenic Amines and Derivatives in Reversed Phase Ion-Pair Partition Chromatography with Electrochemical and Fluorometric Detection

Abstract The compatibility of gradient elution and reversed phase ion-pair partition systems combined with electrochemical and fluorometric detection has been investigated. The phase system consisting of buffers with perchlorate counter-ions as mobile phases and tri-n-butylphosphate as stationary phase allows the use of pH and counter-ion gradients. It appeared that (i) use of gradients is time saving and favourable with respect to detection limits and (ii) dual electrode detection may offer a solution to the problem of gradient-induced baseline shifting in electrochemical Electrochemical detectors are rather sensitive towards changes in the mobile phase. Applying the differential coulometric detection principle the gradient induced baseline shift is reduced and consequently the quantification of a number of compounds is facilitated, although noise levels are slightly increased. Future research will be devoted to noise investigations in order to minimize detection limits.

Determination of Common Analgesics in Serum and Urine by Liquid Chromatography/Electrochemistry

Abstract A reverse phase LC method with amperometric electrochemical detection is described for determination of several common analgesics in blood serum and urine. The retention properties as a function of organic mobile phase modifier and pH are graphically illustrated and discussed. Electrochemical properties of the analgesics and possible internal standards are also presented. Step-gradient elution was used to facilitate simultaneous determination of analgesics with a wide range of hydrophobicities. Parallel dual-electrode detection with two glassy carbon working electrodes enables acetaminophen to be selectively determined in the same chromatographic run at +0.75 V while several other analgesics are determined at +1.15 V.

Determination of the Oxidized and Reduced Forms of Biopterin in Tissue Samples

Abstract Biopterin, in its reduced form, is a cofactor to the enzymes catalyzing the rate-limiting reactions in the synthesis of both the catecholamines and serotonin. It has been suggested that it may serve a role in the regulation of these neurotransmitters. Altered biopterin concentrations have also been reported in various neural disorders. In this report, we describe a method using liquid chromatography/electrochemistry to quantitate both the oxidized and reduced forms of biopterin in mouse tissue samples. This method employs a dual-electrode amperometric detector in the parallel-adjacent configuration. Subpicomole detection limits were achieved for all oxidation states.

Determination of pterins in biological samples by liquid chromatography/electrochemistry with a dual-electrode detector.

Determination of pterins in biological samples by liquid chromatography/electrochemistry with a dual-electrode detector.

Dual electrochemical detection in HPLC, new trend in analytical chemistry

Several instrumental techniques of electrochemical detection have been applied in detectors for HPLC. Flow cells but also electronics have been subject to this process of development. Several authors describe successful experiences in evaluating amperometric and coulometric [1, 2] single electrode detectors. Flow cells based on different principles have been used, e. g. thinlayer [3-7], wall jet [8] and tubular cells [9, 10]. Blank constructed the basic dual amperometric detector [7], Kissinger et al. designed detectors for thin-layer dual electrode detection [11]. The same improvements are realized with the coulometric detector, the ESA 5100A Coulochem dual electrode, we use for our analytical investigations. The fundamental principle of the coulometric measuring technique is especially attractive because of its selectivity, high sensitivity and its conversion efficiency of 100%. Amperometrics detectors often react with an efficiency comprise between 1 and 10 %. The use of a low flow-through cell configuration (Fig. 1) makes possible to achieve a complete material conversion at the electrode surface providing a high coulometric yield. The results (signal response) are up to 15 times higher than in an amperometric system. In the past, in our lab, amperometric detection has been successfully used for the determination of urinary catecholamines as NE and E. Dopamine, another compound of interest which follows the same clean-up steps procedure, always appears on the catechol chromatogram, higher than the normal urinary value, this normal value being established by fluorimetry. The pH of the mobile phase, electrolyte concentration, the type o f column and the chemical procedure were modified in order to improve the separation of an possibly interfering substance which could be isographic with dopamine, but no significant results were obtained. Thanks to advances in analytical electrochemistry, dual electrode systems provide us with the chromatographic tool to solve this practical problem. As dopamine (E and NE) can be oxidized and reduced, this reversibility (redox mode) has been employed to confirm the identity of the compound in a urine extract.

Series dual-electrode detector for liquid chromatography/electrochemistry

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSeries dual-electrode detector for liquid chromatography/electrochemistryDaryl A. Roston and Peter T. KissingerCite this: Anal. Chem. 1982, 54, 3, 429–434Publication Date (Print):March 1, 1982Publication History Published online1 May 2002Published inissue 1 March 1982https://doi.org/10.1021/ac00240a019RIGHTS & PERMISSIONSArticle Views186Altmetric-Citations101LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (665 KB) Get e-Alerts Get e-Alerts

A dual ion-selective electrode detector for the simultaneous detection of bromine- and chlorine- containing compounds in gas chromatography

A dual ion-selective electrode gas chromatographic detector which allows the simultaneous detection of chlorine- and bromine-containing compounds through two-channel operation is described. Components eluted from the g.c. column are hydrogenated, the hydrogen chloride and hydrogen bromide produced being absorbed in a standard solution of halide; the ion concentrations in the resulting solution are monitored by chloride- and bromide-selective electrodes. The dual electrode detector gives two chromatograms simultaneously, one selective for chlorine- and bromine-containing compounds and the other for bromine-containing compounds. The response ratio, i.e., the peak area of the readout from the chloride channel divided by that from the bromide channel for the same compound, gives valuable information. The Cl/Br ratio in an eluted molecule can be determined accurately from the response ratio if a standard reference compound is injected simultaneously.