Voltammetric detection

Lunte et al. have recently developed a unique voltammetric detector using 

Voltammetric techniques have also been employed for on-chip EC detection. For instance, anodic stripping voltammetry (ASV) was used to detect Pb in a Si-Pyrex chip [770] or a polyimide chip [229]. 

Another voltammetric method, sinusoidal voltammetry (SV), was also employed. This was a frequency-based electrochemical method, which was found to be more sensitive than the usual constant potential (DC) amperometric detection method. SV has been achieved to detect on-chip separated catecholamines. This method is very similar to fast-scan cyclic voltammetry (CV), except that a 

SV detection was also achieved to detect catecholamines on a PDMS-quartz chip. Pyrolyzed photoresist films (PPF) were used as planar carbon electrodes. Since the photoresist (AZ4330) must adhere on a substrate for pyrolysis at 1000°C, a quartz plate that could withstand high temperature was selected. The LOD of dopamine decreased from 160 nM to 100 nM when the PPF was treated by piranha solution (HjSOyHjOj). It was because such a treatment increased the surface oxygen/carbon ratio, and hence the oxidation kinetics of dopamine wave improved [765]. 

FIGURE 7.25 Manipulation of the applied potential window to enhance selectivity of SV detection. Separation of 5 lM dopamine and 5 pM isoproterenol produced a resolution of 0.9. A 3-Hz sine wave with a 500-mV amplitude with a variable offset was applied for S V detection. 1. Excitation offset centered on the half-wave potential of isoproterenol (180 mV vs. silver/AgCl). (a) First harmonic (3 Hz) time course and (b) fourth harmonic (12 Hz) time course. 2. Excitation offset centered on the half-wave potential of dopamine (134 mV vs. Ag/AgCI). (c) Third harmonic (9 Hz) time course and (d) second harmonic (6 Hz) time course [765]. Reprinted with permission from the American Chemical Society. 

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PVSA-SG film was used for determination of Fe(Phen) + and Zn + as ternary complex Zn +-Phen-bengal rose by spectrophotometric method. The calibration graph was linear in the concentration 5T0 -5T0 mol/lfor Fe(II) and FlO - 5T0 mol/1 for Zn(II). The film can be regenerated and reused. LG-PDMDA-SG film was shown to be perspective modificator of the PG electrode surface and used for voltammetric detection of Mo(VI) at ppb level. 

C.A. Scolari and S.D. Brown, Multicomponent determination in flow-injection systems with square-wave voltammetric detection using the Kalman filter. Anal. Chim. Acta, 178 (1985) 239-246. 

Kafil, J. B. and Last, T. A., Liquid chromatography with voltammetric detection for quantitation of phenolic acids,. Chromatogr., 348, 397, 1985. 

Burlet, S. Cespuglio, R. (1997). Voltammetric detection of nitric oxide (NO) in the rat brain its variations throughout the sleep-wake cycle. Neurosci. Lett. 226 (2), 131-5. 

Capillary zone electrophoresis coupled with fast cyclic voltammetric detection was developed by Zhou et al. [27] for the separation and determination of OTC, TC, and CTC antibiotics. All compounds were well separated by optimization of pH and complexation with a boric acid sodium tetraborate buffer. The detection limit using fast on-line cyclic voltammetric detection with Hg-film-microm electrode was 1.5 x 10-6 mol/L for OTC (signal to noise ratio > 2). A continuous flow manifold coupled on-line to a capillary electrophoresis system was developed by Nozal et al. [28] for determining the trace levels of OTC, TC, and DC in surface water samples. 

B. Fabre, S. Burlet, R. Cespuglio, and G. Bidan, Voltammetric detection of NO in the rat brain with an electronic conducting polymer and Nafion bilayer-coated carbon fibre electrode. J. Electroanal. Chem. 426, 75-83 (1997). 

J.D. Guo, Y. Yuan, and S. Amemiya, Voltammetric detection of heparin at polarized blood plasma/1,2-dichloroethane interfaces. Anal. Chem. 77, 5711—5719 (2005). 

R. Cespuglio, H. Faradji, Z. Hahn, and M. Jouvet, Voltammetric detection of brain 5-hydroxyindo-lamines by means of electrochemically treated carbon fiber electrodes chronic recordings for up to one month with movable cerebral electrodes in die sleeping or waking rat, in Measurements of Neurotransmitters Release in Vivo (C.A. Marsden, ed.), Wiley, Chichester (1984). 

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],... 

S.B. Hocevar, J. Wang, R.P. Deo, M. Musameh, and B. Ogorevc, Carbon nanotube modified microelectrode for enhanced voltammetric detection of dopamine in the presence of ascorbate. Electroanalysis 17, 417-422 (2005). 

We have demonstrated a new method for preparing electrodes with nano-scopic dimensions. We have used this method to prepare nanoelectrode ensembles with individual electrode element diameters as small as 10 nm. This method is simple, inexpensive, and highly reproducible. The reproducibility of this approach for preparing nanoelectrodes is illustrated by the fact that NEEs given to other groups yielded the same general electrochemical results as obtained in our laboratory [84]. These NEEs display cyclic voltammetric detection limits that are as much as 3 orders of magnitude lower than the detection limits achievable at a conventional macroelectrode. 

Kennedy, R. T. and Jorgenson, J. W., Quantitative-analysis of individual neurons by open tubular liquid-chromatography with voltammetric detection. Analytical Chemistry 61(5), 436 441, 1989. 

Several different types of electrodes have been employed for voltammetric detection. As stated earlier, the background current is directly related to the... 

Because of the more extensive data array obtained by voltammetric detection, other data manipulation techniques to improve selectivity or sensitivity can also be devised. One example is to measure the difference in response at two different potentials in order to gain selectivity for compounds that are more difficult to oxidize. Compounds that are easily oxidized will give the same response at both potentials, and the difference signal will therefore be zero. Only... 

Electrochemical binding assays have also been applied for testing computational predictions which render the highest stabilization energy for the pre-polymerization mixture of several formulations traditionally used in non-covalent MIPs [119]. The batch binding assays and voltammetric detection confirm the theoretically best monomer-porogen solvent mixture for preparation of a recognition material for the dopamine metabolite homovanillic acid. 

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]. 

E. Palecek, S. Billova, L. Havran, R. Kizek, A. Miculkova and F. Jelen, DNA hybridization at microbeads with cathodic stripping voltammetric detection, Talanta, 56 (2002) 919-930. 

Pneumolysin Sandwich immunoassay with ALP or HRP labelled antibody using 3-indoxyl phosphate (3-IP) as substrate Cyclic voltammetric detection of indigo carmine (Ey 2 =-0.15 V)... 

Voltammetric detection of indigo carmine formed by ALP from 3-indoxyl phosphate... 

J. Wang, S. Thongngamdee and A. Kumar, Highly stable voltammetric detection of nitroaromatic explosives in the presence of organic surfactants at a polyphenol-coated carbon electrode, Electroanalysis, 16 (2004) 1232-1235. 

Single-nucleotide polymorphisms (SNPs) have been analysed on a capillary gel electrophoresis (CGE) microchip with EC detection [150]. The genetic section that contained the SNP was amplified by PCR and purified. Then, it was used in a single-base extension (SBE) reaction with a redox-labeled chain terminator, ferrocene-acycloATP. Products of the SBE, ferrocene-labeled SNP and free ferrocene-acycloATP, were separated employing CGE on microchip and detected using sinusoidal voltammetric detection at a pyrolysed photoresist film (PPF) electrode. 

N.E. Hebert, B. Snyder, R.L. McCreery, W.G. Ruhr and S.A. Brazill, Performance of pyrolyzed photoresist carbon films in a microchip capillary electrophoresis device with sinusoidal voltammetric detection, Anal. Chem., 75 (2003) 4256-4271. 

Abbreviations AOD, Acousto-optical deflection BCB, bisbenzyocyclobutadiene CCD, indirect contact conductivity detection CL, chemiluminescence ECD, electron capture detector FCS, fluorescence correlation spectroscopy FRET, fluorescence resonance energy transfer ICCD, integrated contact conductivity detection GMR, giant magnetoresistive LED-CFD, light emitting diode confocal fluorescence detector LIF, laser-induced fluorescence LOD, limit of detection MALDI, matrix-assisted laser desorption ionization PDMS, poly(dimethylsiloxane) PMMA, poly(methylmetha-crylate) SPR, surface plasmon resonance SVD, sinusoidal voltammetric detection TLS, thermal lens spectroscopy. 

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