PCCP May 2011 SI

Electroanalysis, 2001

The capacity of chemometric multivariate calibration methods, partial least square (PLS) and principal component regression (PCR), to extract quantitative analytical information from overlapping peaks in anodic stripping voltammetry is illustrated in the simultaneous analysis of synthetic mixtures containing Pb(II), In(III), Cd(II), and Tl(I). The influence of raw and first derivative data in the predictive ability of the calibration models was discussed and the results obtained in the analytical performance of synthetic mixtures by PLS and PCR were compared. The analytical results show no observable differences between the two methods and the utilization of derivative data did not improve the prediction step.

Analytical Chemistry, 2004

It has been found empirically that, for an E rev C irrev process, the forward/backward ratio of the peak height magnitudes in cyclic voltammetry equals 1 + kτ, where k is the rate constant of the chemical reaction and τ is the time required for the scan to travel between the half-wave and reversal potentials. The relationship is largely independent of the scan rate and the reversal potential, except insofar as these influence τ. Though not exact, the relationship is obeyed closely enough to provide accurate rate constants under favorable conditions. The utility of this simple formula in extracting homogeneous kinetic information is demonstrated using experimental data for the electron-transfer-induced isomerization of an octahedral manganese complex. An explanation of the relationship is presented, as is a more exact formula that reduces to 1 + kτ when k is small. A semiquantitative explanation of the relationship is provided.

Analytical Chemistry, 1971

Analytica Chimica Acta, 1995

A model is presented that is applicable to a wide range of peak-shaped voltammetric signals. It may be used, via curve-fitting, to resolve severely overlapped peaks, irrespective of the degree(s) of reversibility of the electrode processes. The resolution procedure has been thoroughly tested for several voltammetric and polarographic techniques (differential pulse, square wave and pseudo-derivative normal pulse), using reversible, quasireversible and irreversible electrochemical systems.

bio.ilstu.edu, 2007

Introduction .................................................................................................................................. 234 Overview................................................................... ... ... 4075—CHAPTER 12—6/11/2006—13:42 —BSARAVANAN—15180—XML MODEL C – pp. 233–259 ... A new instrument for the ...

Carbon-fiber microelectrodes allow for high spatial and temporal measurements of electroactive neurotransmitter measurements in vivo using fast-scan cyclic voltammetry (FSCV). However, common instrumentation for such measurements systems lack patient safety precautions. To add safety precautions as well as to overcome chemical and electrical noise, a two-electrode FSCV headstage was modified to introduce an active bandpass filter on the electrode side of the measurement amplifier. This modification reduced the measured noise and ac-coupled the voltammetric measurement and moved it from a classical direct current response measurement. ac-coupling not only reduces the measured noise, but also moves FSCV toward compliance with IEC-60601-1, enabling future human trials. Here, we develop a novel ac-coupled voltammetric measurement method of electroactive neurotransmitters. Our method allows for the modeling of a system to then calculate a waveform to compensate for added impedance and capacitance for the system. We describe how first by measuring the frequency response of the system and modeling the analogue response as a digital filter we can then calculate a predicted waveform. The predicted waveform, when applied to the bandpass filter, is modulated to create a desired voltage sweep at the electrode interface. Further, we describe how this modified FSCV waveform is stable, allowing for the measurement of electroactive neurotransmitters. We later describe a 32.7% sensitivity enhancement for dopamine with this new measurement as well as maintaining a calibration curve for dopamine, 3,4dihydroxyphenylacetic acid, ascorbic acid, and serotonin in vitro. We then validate dopamine in vivo with stimulated release. Our developed measurement method overcame the added capacitance that would traditionally make a voltammetric measurement impossible, and it has wider applications in electrode sensor development, allowing for measurement with capacitive systems, which previously would not have been possible.

Analytical Chemistry, 1977

principal component analysis-are utilized in selecting the wavelengths for monitoring, by reflectance spectroscopy, color-generating reactions invoMng uric acidand cholesterol In serum. The data base we used was accumulated by a rapid-scanning reflectance spectrophotometer that measured reflectance at 16 wavelengths every 5 s after the reaction was initiated. The data were then analyzed in multidimensional space by a mainframecomputerwith commercial statistical software packages. The most appropriate wavelengthswere those that yielded the largestgeneralized distance between analyte concentration by discriminant analysis and the largest weighting coefficient by principal component analysis. For uric acid, taking the ratio of reflectance measured at two wavelengths instead of at a single wavelength much better separates the clinicallysignificantconcentrations. For cholesterol, the spectral region that is sensitive to the presence of interference, e.g., hemoglobin, can be clearly demonstrated by the "pattern" generated with principal component analysis.

Madridge J Anal Sci Instrum, 2017

Based on the hypothesis related to fractal structure of electrode one can develop the quantitative theory for description of the measured voltammograms (VAGs). We suppose that at least two percolation channels take part in the process of its formation. One channel can be associated with the fractal structure of electrodes while the second one can be related to the heterogeneous structure of the double electric layer. Based on the obtained fitting function that follows from the suggested theory it becomes possible to differentiate the state of two measured electrodes (with regeneration or without application of this procedure). This result obtained directly from the measured data can find a wide application in electrochemistry for analysis of other VAGs, especially in detection of possible traces of substances that take place in chemical reactions in the vicinity of heterogeneous electrodes.

Electroanalysis, 2003

A novel application of Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS) method for the background correction and for the resolution and quantitation of coeluted analyte mixtures in liquid chromatography with voltammetric detection is presented. The selected voltammetric technique for analyte detection was Linear Sweep Voltammetry (LSV), which provides richer multivariate information than the more widespread employed univariate amperometric detection. Use of other voltammetric detection techniques was also attempted but they gave much poorer results because of instrumental and software limitations concerning data acquisition times. The method is tested in the resolution and quantitation of mixtures of pyrocatechol, ascorbic acid and epinephrine coeluting mixtures. In spite of the extremely large background current contributions observed using this voltammetric technique, MCR-ALS was shown to be able to model this background contribution satisfactory as well as to resolve and give good quantitative estimations of these three analyte in their mixtures. The proposed approach is recommended for resolution and quantitation of complex coeluted mixtures using liquid chromatography with voltammetric detection and also for fast initial screening of optimal potential when amperometric detection is preferred.

Journal of Electroanalytical Chemistry, 2010

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are