Determination of -Cysteine in Amino Acid Mixture and Human Urine by Flow-Injection Analysis with a Biamperometric Detector

Zhao, Chuan; Zhang, Juncai; Song, Junfeng

doi:10.1006/abio.2001.5332

Cited by 74 publications

(44 citation statements)

References 27 publications

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“…In the literature, there are many examples of biamperometric measurements of various analytes as components of complex biological samples (urine, blood) due to high selectivity of the method. Michalowski and Trojanowicz determined copper in blood [1] using biamperometry on platinum wire electrodes and Fe 3þ j Fe 2þ redox pair, while C. Zhao and colleagues determined l-cysteine in amino acid mixture and human urine using two pretreated platinum electrodes as a biamperometric detector [2]. A. Moreno Gá lvez et al studied various indicating redox systems for biamperometric determination of pharmaceuticals [3].…”

Section: Introductionmentioning

confidence: 99%

Use of DPPH⋅|DPPH Redox Couple for Biamperometric Determination of Antioxidant Activity

Milardović¹,

Iveković²,

Rumenjak³

et al. 2005

Electroanalysis

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A novel electrochemical method for selective determination of antioxidant activity based on 2,2-diphenyl-1-picrylhydrazyl j 2,2-diphenyl-1-picrylhydrazin (DPPH · j DPPH) redox couple and biamperometric technique is proposed. Two identical glassy carbon disk electrodes were mounted in a classic electrochemical cell and the tested working potential difference was between 50 and 200 mV. The DPPH · j DPPH redox couple exhibited a high degree of reversibility. Selectivity of detector was tested by different antioxidant compounds in ethanol-phosphate buffer solution, pH 7.40. The results of antioxidant activity of pure antioxidant compounds and of actual samples of beverages, expressed as Trolox equivalents and determined by proposed biamperometric and spectroscopic measurements, were in good correlation (R ¼ 0.9959). The detection limit for Trolox established by the applied biamperometry was 0.05 mM while the resulting current was linear up to 25 mM of Trolox.

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Section: Introductionmentioning

confidence: 99%

Use of DPPH⋅|DPPH Redox Couple for Biamperometric Determination of Antioxidant Activity

Milardović¹,

Iveković²,

Rumenjak³

et al. 2005

Electroanalysis

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“…Due to the importance of l-cysteine, its electroanalytical determination is based on its reducing properties. Whereas, it exhibits irreversible oxidation requiring positive overpotential at most conventional electrode surfaces [3]. Therefore, the electrochemical detection of lcysteine has been shown to be facilitated by electrode modification with substituted and unsubstituted transition metal phthalocyanines adsorbed or immobilized onto a graphite electrode [4,5] as well as when a glassy carbon electrode is coated with conductive polymeric films [6].…”

Section: Introductionmentioning

confidence: 99%

Electrocatalytic Characteristics of Ferrocenecarboxylic Acid Modified Carbon Paste Electrode in the Oxidation and Determination ofL-Cysteine

2005

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The electrochemical behavior of l-cysteine studied at the surface of ferrocenecarboxylic acid modified carbon paste electrode (FCMCPE) in aqueous media using cyclic voltammetry and double step potential chronoamperometry. It has been found that under optimum condition (pH 7.00) in cyclic voltammetry, the oxidation of l-cysteine is occurs at a potential about 580 mV less positive than that an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, a and catalytic reaction rate constant, K' h were also determined using electrochemical approaches. The electrocatalytic oxidation peak current of l-cysteine showed a linear dependent on the l-cysteine concentration and linear calibration curves were obtained in the ranges of 10 À5 M -10 À3 M and 4.1 Â 10 À8 M -3.7 Â 10 À5 M of l-cysteine concentration with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods respectively. The detection limits (2d) were determined as 2.4 Â 10 À6 M and 2.5 Â 10 À8 M by CV and DPV methods. This method was also examined for determination of l-cysteine in some samples, such as Soya protein powder, serum of human blood by using recovery and standard addition methods.

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“…6) because (FcM)TMA is easily decomposed [34] and l-Cys is rapidly oxidized by air or oxygen [9,45] when pH > 9. In the range of pH 6 -8.3, the variation of the catalytic peak current is slight, and in the range of pH 2 -6, the catalytic peak current increases with the increasing in pH.…”

Section: The Effects Of Experimental Conditions On Catalytic Peak Curmentioning

confidence: 99%

Study on Electrocatalytic Oxidation of L‐Cysteine at Glassy Carbon Electrode by (FcM)TMA and Its Electrochemical Kinetics

2005

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The electrocatalytic oxidation of l-cysteine by (ferrocenylmethyl)trimethylammonium at a glassy carbon electrode in 0.1 M Na 2 SO 4 aqueous solution has been studied. The rate constant for the catalytic reaction was evaluated as (4.28 AE 0.05) Â 10 3 M À1 s À1 by chronoamperometry. Experimental conditions, which maximize the current efficiency of the electrocatalytic oxidation, such as pH value and the concentration of the catalyst, were also investigated. The experimental results of electrocatalytic kinetics of l-cysteine oxidation on GCE in the presence of (ferrocenylmethyl) trimethylammonium obviously support the reaction mechanism proposed and the rate determining step assumed in scheme described in this work.

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Determination of -Cysteine in Amino Acid Mixture and Human Urine by Flow-Injection Analysis with a Biamperometric Detector

Cited by 74 publications

References 27 publications

Use of DPPH⋅|DPPH Redox Couple for Biamperometric Determination of Antioxidant Activity

Use of DPPH⋅|DPPH Redox Couple for Biamperometric Determination of Antioxidant Activity

Electrocatalytic Characteristics of Ferrocenecarboxylic Acid Modified Carbon Paste Electrode in the Oxidation and Determination ofL-Cysteine

Study on Electrocatalytic Oxidation of L‐Cysteine at Glassy Carbon Electrode by (FcM)TMA and Its Electrochemical Kinetics

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