CNTs-COOH Paste Electrode for Detection of Temozolomide
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The MWCNTs-COOH Paste Electrode (MCPE) was successfully used to study the electrochemical behavior of temozolomide in 0.2 M H2SO4 solution, phosphate buffer solution (0.1M PBS, pH 7.4) and 0.1M NaOH solution by Cyclic Voltammetry (CV) technique. The results exhibit that MCPE can remarkably enhance sensing and electrocatalytic activity towards the oxidation and reduction of temozolomide in acidic, neutral, and basic solutions. The effect of the scan rate exhibits the adsorption controlling process. The effect of pH range from 2 to 6 was investigated by cyclic voltammetry technique, from cyclic voltammetry study exhibits the peak current was pH-dependent with a slope of 68 mV/pH. The detection limit (LOD)) at MCPE were found to be 0.056 mM,0.069 mM and 0.065 mM in 0.1M H2SO4, 0.1M PBS (pH 7.4) and 0.1M NaOH solutions respectively by Cyclic Voltammetric (CV) technique. Similarly, from Linear Scan Voltammetric (LSV) technique, the detection limits (LOD) were found to be 0.050 mM, 0.021mM and 0.036 mM in acidic, neutral, and basic solution respectively. The proposed method was successfully applied for the determination of temozolomide in the clinical sample.Keywords:
Horizontal scan rate
Phosphate buffered saline
Buffer solution
Temozolomide
Adsorptive stripping voltammetry has been extended by
elimination voltammetry with the linear scan rate (EVLS). EVLS
offers the elimination of selected currents from the linear
scan voltammetry results. It can be achieved by an elimination
function formed by a linear combination of total currents
measured at different scan rates. The problem of substance
adsorption influence on the elimination voltammetry results has
been studied. Theoretical curves of an irreversible current
with adsorbed substance being electroactive were calculated for
three elimination functions. As a practical application, the
adsorptive stripping voltammetry of thermally denatured DNA on
a hanging mercury electrode has been developed. While the LSV
signal of single-stranded DNA at low concentrations gives a
slight hint of the cathodic peak, the EVLS provides quite a
clear signal in the form of the peak-counterpeak. It is
possible to determinate DNA at concentrations below of
micrograms per milliliter.
Horizontal scan rate
Linear sweep voltammetry
Adsorptive stripping voltammetry
Anodic Stripping Voltammetry
Stripping (fiber)
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Adsorptive stripping voltammetry has been extended by elimination voltammetry with linear scan rate (EVLS). EVLS offers the elimination of selected currents from the linear scan voltammetry results. It can be achieved by an elimination function formed by a linear combination of total currents measured at different scan rates, because the basic idea of elimination of chosen currents (for example the charging current, Ic, the reversible current for substances transported only by linear diffusion, Ir, and the purely kinetic current, Ik) consists of the different dependence of voltammetric current on the scan rate. In this article, the problem of substance adsorption influence on the elimination voltammetry results has been studied. Theoretical curves of an irreversible current with adsorbed substance being electroactive were calculated for three elimination functions. A: the function eliminating Ik and Ic and conserving Ir B: the function eliminating Ic and Ir, conserving Ik; and C: the function eliminating Ir and Ik and conserving Ic, where Ic, Ir, and Ik are the charging current, the reversible diffusion current, and the kinetic current, respectively. A larger difference between diffusion and adsorption was exhibited by the elimination function A. It provides a substantial increase in resolution and sensitivity as compared to the linear scan voltammetry current peak and clearly marks the adsorption. In case of the adsorption of electroactive substances this elimination function A can be useful for analytical applications, particularly for the adsorptive stripping voltammetry with electrochemical irreversible systems. As a practical application, the adsorptive stripping voltammetry of thermally denatured DNA on a hanging mercury electrode has been developed. While the LSV signal of single-stranded DNA at low concentrations gives a slight hint of the cathodic peak (due to the reduction of adenine and cytosine residues), the elimination A provides quite a clear signal in the form of the peak-counterpeak. It is possible to determinate DNA at concentrations below micrograms per milliliter by using this elimination function. The results received by the adsorptive stripping voltammetry in the mode of linear scan (LSV), square-wave (SWV) and elimination with linear scan (EVLS) are discussed.
Horizontal scan rate
Adsorptive stripping voltammetry
Linear sweep voltammetry
Stripping (fiber)
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Linear sweep voltammetry
Horizontal scan rate
Basis (linear algebra)
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Horizontal scan rate
Linear sweep voltammetry
Supporting electrolyte
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The effect of different concentration of phosphate buffer solution with pH=7.4 on hydrocarbonylation of 10-phenanthroline-Fe2+ to determine free radicals system was studied.The phosphate buffer solution of 0.1,0.15 and 0.2 mol/L were added to the system of 10-phenanthroline-Fe2+,with the increasing of buffer solution,ΔA536 decreased continually.When the buffer solution is more than 3 mL,ΔA536 remained stably.The system of 10-phenanthroline-Fe2+which contained the phosphate buffer solution with different concentration was eliminated by ascorbic acid.The result showed the effect of removal hydroxyl radicals changed with the concentration and addition of buffer solution.Therefore,the concentration and addition of phosphate buffer solution should be known on hydrocarbonylation of 10-phenanthroline-Fe2+ to determine free radicals system.The effectively comparison could be happened in one system.
Phenanthroline
Phosphate buffered saline
Buffer (optical fiber)
Buffer solution
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The influence of pH on the protective effect of phosphate buffer on the corrosion processes was studied by measuring the amounts of elements released from a dental amalgam. The analyses were conducted by means of atomic absorption spectrophotometry. The protective effect of phosphate buffer was reduced in solutions with low pH, and mercury could be detected in the solutions. Phosphate buffer maintained its aftereffect in the pH region 6.8-5.5. The flow rate of the solution did not influence the inhibiting effect of phosphate buffer.
Buffer (optical fiber)
Phosphate buffered saline
Buffer solution
Mercury
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Cyclic voltammetry,differential-pulse stripping voltammetry,and square wave voltammetry were used to investigate the electrochemical behavior of maquinox at a glassy carbon electrode and a new method for detection of maquinox was established.The maquinox showed a sensitive reductive peak at-0.8 5V(vs.SCE)using cyclic voltammetry in a B-R solution.The impact of buffer solution,pH,accumulation time and scan rate were discussed.The peak current was linear to the concentration of maquinox ranging from 2.0×10-6 mol/L-2.0×10-3 mol/L with a detection limit of 5.0×10-8 mol/L by DPV,and ranging from 2.0×10-6 mol/L-1.0×10-3 mol/L with a detection limit of 2.0×10-8 mol/L by SWV.The determination of maquinox has been performed and the possible mechanism for the electrode process was also proposed.
Differential pulse voltammetry
Horizontal scan rate
Buffer solution
Square wave
Stripping (fiber)
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The water soluble calixarene p-hexasulfonato-calix[6]arene (pSC6) was subjected to voltammetric oxidation studies in alkaline aqueous solution (pH 13) at glassy carbon (GC) working electrodes. Cyclic voltammetry revealed that the oxidation of pSC6 resulted in a narrower and more intense peak as the potential scan rate was decreased. This suggested a process whereby attachment of pSC6 to the electrode surface occurred during the time frame from initial application of potential to commencement of oxidation, in effect a potential- and/or time-controlled attachment process. Further investigations confirmed this behavior. Adsorptive voltammetry (AdV) studies at GC electrodes revealed a response attributed to the oxidation of pSC6 accumulated at the electrode surface. The intensity and behavior of this response were a function of the accumulation potential, the accumulation time, the scan rate, and the concentration of pSC6. The surface attachment process is discussed in terms of the applied potential with respect to the potential of zero charge and multilayer deposition of pSC6 on the surface.
Horizontal scan rate
Glassy carbon
Calixarene
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Objective Screen for the best buffer solution to improve the stability of the povidone-iodine gel.Method The influences of non-buffer and different buffers(phosphate buffer solution and Citrate buffer solution)on the stability of povidone-iodine gel were investigated by accelerated tests at 30 ℃and 40 ℃.Result After 6 months of accelerated tests,each of the parameters of povidone-iodine gel Ⅴ with Citrate buffer solution(0.2 mol/L) is eligible,the others are not eligible with the sharp decrease in pH values and the content of available iodine.Conclusion Citrate buffer solution is the best solution for the preparation of povidone-iodine gel and the solution is helpful to improve the stability of the gel.
Buffer (optical fiber)
Phosphate buffered saline
Buffer solution
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Abstract Voltammetric methods use a constant sweep rate during the course of a scan. This paper reports a study of the influence of a nonconstant sweep rate on the voltammetric response. In this approach, either continuously increasing or continuously decreasing potential scan rates can be employed, unlike presently available methods which rely on a constant sweep rate. The voltammetric response of potassium ferrocyanide at a glassy carbon electrode was used as a model system to test the new method. The responses obtained using traditional staircase voltammetry (linear staircase voltammetry) and the new approach (nonlinear staircase voltammetry) were compared by experiment and by simulation. The new approach offers capability for signal enhancement, whereby enhanced current or enhanced peak shape can be obtained by choice of appropriate waveform parameters.
Linear sweep voltammetry
Potassium ferrocyanide
Horizontal scan rate
SIGNAL (programming language)
Ferrocyanide
Constant (computer programming)
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