Introduction
In this era of globalization, scientist had discovered various method of analysis. One of the methods of analysis is known as electrochemical method of analysis. Electrochemical method of analysis consists of coulometry, voltammetry and potentiometry. (Harvey, 2000) Coulometry is a method of analysis either with fixed current or constant current. Coulometry is also known as amperometry. In amperometry, current passes through a polarisable electrode. The current that passes through the cell is directly proportional to concentration of ion species that present in the electrochemical cell. Whereby, petentiometry is a method of analysis with zero or negligible current and the potential of the cell serve as a signal. During the process of recording for current change a graph of electrode potential versus time is being plot. These graphs could be categorized into two which is polarograhy and voltammetry. The different between polarography and voltammetry is that polarography used dropping mercury electrode and voltammetry used a solid metal electrode or other types of electrode. However in this assignment voltammetry will be discussed.
Voltammetry is taken from the original word of volt. The prefix volt means measurement involving potential. (Monk, 2001) Voltammetry can also be further divided into pulse voltammetry, square wave voltammetry, Stripping voltammetry, thin layer voltammetry, cyclic voltammetry and differential pulse voltammetry.
However, the topic of the assignment differential pulse voltammetry.
Differential Pulse Voltammetry
There is various technique of voltammetry present nowadays. For the topics to be discuss here is differential pulse voltammetry.
The diagram below shows the graph of differential pulse voltammetry.
It is being name differential pulse volatmmetry is because 2 current is being measured. Unlike on normal pulse voltammetry the current is being measured at a short time intervals and its stop after the current is dropped. In differential pulse voltammetry, 2 sample is being masured. When the 1st sample is added into the system the potential increased. As fast as the sample stop the 2nd sample is added into the system result in decreasing in current. The different of the current is being measured. It was because of the different in current is being measured it is name as differential pulse voltammetry. (Monk,2001)
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Differential pulse voltammetry is a beneficiary technique. It enable detection up to nanoscale to be done.(Girault,2004) It was because it uses a method of differentiation when there is a different even at a low current it could be observed. However, in classical method or normal pulse voltammetry it does not enable us to do so. It was because of the small scale of different could be observed it is very sensitive. (Skoog, 2006)
Importance of Differential Pulse Voltammetry
DPV usage is very important in examining the pH dependence of redox potential for a electron and proton transfer in tryptophan and tyrosine. The pH dependence is used to calculate the ∆G values for different reaction pathways and thus determine that the mechanism can be a one step or two step depending on several factor. DPV is also Important in examining quantized double layer charging of hexanethiolate coated monolayer protected Aurum clusters. It provides necessary resolving power, by suppressing background currents s to separate out all 13 peaks related to Aurum clusters core charging. This helps to make the tough peaks to become visible. This highlights the power of DPV.
Differential pulse voltammetry (DPV) is also important in the determination of Dapsone is 4,4′-diaminodiphenyl sulfone (DDS) in drug substance and product at carbon paste electrode and a glassy carbon electrode. Differential pulse voltammetry (DPV) is also important in the determination of ascorbic acid, pyridoxine and folic acid in a multivitamin preparation. The individual vitamins all gave well-defined peaks in the anodic region with a linear response of peak current to concentration. The DPV method was found to be generally applicable to the determination of the vitamins in several multivitamin preparations, or, in simplified form, to the determination of the individual vitamin preparations.
Differential pulse voltammetry (DPV), important for the determination of pharmaceuticals, dyes, insecticides and pesticides. In general, this methods offer high sensitivity, low limit of determination, easy operation, and the use of simple instrumentation. DPV also important for the quantization of phenols.
Difference and Similarity of Differential Pulse Voltammetry and Normal Pulse Voltammetry
DIFFERENCES
Differential Pulse Voltammetry
Normal Pulse Voltammetry
The current is taken before and after sample is added into the system.
After each redox reaction, the current return to its very own original point.
Range:
Pulse Amplitude= 5 – 250 mV.
Pulse Width= 3 – 1000 ms
(Polarography); 4 – 6550 ms (Voltammetry)
Range:
Pulse Width= 3 – 2000 ms
(Polarography); 4 – 6550 ms (Voltammetry)
The differential current is plotted as a function of potential to yield a voltammogram.
Current is plotted as a function of potential.
It can measured the difference in a small scale.
It is unable to measure at a small different of current.
The shape of the voltammetric graph increases as it proceed.
The voltammetric graph is not increasing through the time interval.
SIMILARITIES
All potential values are entered in mV, and thePulse WidthandPulse. Periodare entered in ms.
The Advantage and Disadvantage of Differential Pulse Voltammetry (DPV)
Advantage of Differential Pulse Voltammetry
Differential pulse voltammetry can distinguish faradaic waves better from the background due to the larger 2nd derivative of the current/potential relation for faradaic processescompared to the normal pulse technique. Besides that, since the modulation amplitude of differential pulse voltammetry is constant, capacitive current will be expressed as a more or less constant baseline. Electro -oxidizable and -reducible substances on the other hand, will appear as recognizable peaks. The detection limits of 10-8M are possible, though one should be aware of the increasing probability to encounter irreversible phenomena. The latter can be detected by a shift of the voltammetric peak to more negative (reduction) or positive (oxidation) potentials and by the lowering of the peak with decreasing modulation time(User manual for, 2001).
The main advantage over direct current (DC) polarography that differential pulse polarography (DPP) shares with other pulse methods is that there is little double layer charging contribution to the overall response, which allows the achievement o f a lower detection limit. An advantage that DPP has over both DC polarography and other pulse methods is that due to the differential measurement sequence, the output of this technique takes the form o f a symmetrical peak, which is more useful from an analytical perspective(O’Gorman, 1998). Differential pulse voltammetry (DPV) is a selective and sensitive technique, where the potential is changing linearly with the time (potential linear sweep) superimposed by the potential pulses of the amplitude between 10 and 100 mV for several milliseconds (Jiri Sochor, Jiri Dobes &Olga Krystofova, 2013).
Next, by using differential pulse voltammetry at stationary electrodes, excellent results can be obtained provided that oxidation and reduction are soluble, or with a mercury electrode if the resulting metal (if any) amalgamates; the voltammetric method can often be more rapid than the corresponding polarographic mode with its dependence on the drop time, provided that the delay time between pulses is not less than twice the pulse width (to avoid transient noise disturbances) and that the scan rate is not too fast ( to limit dc distortion) (E.A.M.F.Dahmen, 1986).
The Advantage and Disadvantage of Differential Pulse Voltammetry (DPV)
Advantage of Differential Pulse Voltammetryy
Differential pulse voltammetry can distinguish faradaic waves better from the background due to the larger 2nd derivative of the current/potential relation for faradaic processescompared to the normal pulse technique. Besides that, since the modulation amplitude of differential pulse voltammetry is constant, capacitive current will be expressed as a more or less constant baseline. Electro -oxidizable and -reducible substances on the other hand, will appear as recognizable peaks. The detection limits of 10-8M are possible, though one should be aware of the increasing probability to encounter irreversible phenomena. The latter can be detected by a shift of the voltammetric peak to more negative (reduction) or positive (oxidation) potentials and by the lowering of the peak with decreasing modulation time(User manual for, 2001).
The main advantage over direct current (DC) polarography that differential pulse polarography (DPP) shares with other pulse methods is that there is little double layer charging contribution to the overall response, which allows the achievement o f a lower detection limit. An advantage that DPP has over both DC polarography and other pulse methods is that due to the differential measurement sequence, the output of this technique takes the form o f a symmetrical peak, which is more useful from an analytical perspective(O’Gorman, 1998). Differential pulse voltammetry (DPV) is a selective and sensitive technique, where the potential is changing linearly with the time (potential linear sweep) superimposed by the potential pulses of the amplitude between 10 and 100 mV for several milliseconds (Jiri Sochor, Jiri Dobes &Olga Krystofova, 2013).
Next, by using differential pulse voltammetry at stationary electrodes, excellent results can be obtained provided that oxidation and reduction are soluble, or with a mercury electrode if the resulting metal (if any) amalgamates; the voltammetric method can often be more rapid than the corresponding polarographic mode with its dependence on the drop time, provided that the delay time between pulses is not less than twice the pulse width (to avoid transient noise disturbances) and that the scan rate is not too fast ( to limit dc distortion) (E.A.M.F.Dahmen, 1986).
The Disadvantage of Differential Pulse Voltammetry
Differential pulse voltammetry is slower technique compared to square wave voltammetry (O’Gorman, 1998).
Conclusion
As a conclusion, differential pulse voltammetry is a very useful method for analysis to be done compare with normal pulse volatmmetry due to its sensitive. It is a useful in various field of the industry like pharmaceuticals, dyes, insecticides and pesticides. Although differential pulse voltammetry is useful, however it must be used based on the condition of the when analysis is done.
References
(2001).User manual for electrochemical method for windows version 4.9.. (pp. 9-10). The Netherlands: Eco Chemie B.V. Retrieved from http://www.bioeng.nus.edu.sg/people/PI/trau/Lab_manuals/Autolab manuals/Electrochemical Methods 4.9.pdf
Ballentine. J. , & Woolfson,A.D, (1980). The application of differential pulse voltammetry at the glassy carbon electrode to multivitamin analysis.32(1), 353-356.
E.A.M.F.Dahmen. (1986). Electroanalysis:theory and application in aques and non-aques media and automated chemical control. (Vol. 7, p. 164). New York: Elsevier Science Publishing Company Inc. Retrieved from http://books.google.com.my/books?id=DpCWhuUMbdMC&pg=PA164&lpg=PA164&dq=advantages+of+differential+pulse+voltammetry&source=bl&ots=6iOU-xcP22&sig=_JDlOgIQ0Bs3Px5PqZMNXMwgAK0&hl=en&sa=X&ei=2AAkU5yAJsbZrQfJwoFQ&ved=0CEcQ6AEwAzgo#v=onepage&q=advantages of differential pulse voltammetry&f=false
Christian, G.D. (2004), Analytical Chemistry, 6th edition.
Girault, H.H.(2004) Analytical and Physical Electrochemistry.
Harvey, D.(2000). Modern Analytical Chemistry.
Jiri Sochor, Jiri Dobes,& Olga Krystofova, (2013). Electrochemistry as a tool for studying antioxidant properties. International Journal of Electrochemical Science, Retrieved from http://www.electrochemsci.org/papers/vol8/80608464.pdf
Miles, D. T.; Murray, R. W. Analytical Chemistry 2003, 75, 1251–1257
Mohammed A. E. R. , Nahla N. S, & Mohammed I.W, (2011). differential pulse anodic voltammetric determination of dapsone in pharmaceutical preparation using carbon paste and glassy carbon electrodes: Application to quality control l .6, 307-321. Retrieved from http://dspace.upce.cz/bitstream/10195/42522/1/ElRiesMA_DifferentialPulse_2011.pdf
Monk, P.M.S.(2001). Fundamentals of Electroanalytical Chemistry.
Ni, Y., & Wang, L . (2001). Simultaneous determination of nitrobenzene and nitro-substituted phenols by differential pulse voltammetry and chemometrics.431(1), 101-113. Retrieved from www.sciencedirect.com/science/article/pii/S0003267000013192
O’Gorman, J. (1998). Novel electroanalytical methods. (Master’s thesis, Dublin City University)Retrieved from http://doras.dcu.ie/19220/1/John_O’Gorman_20130717104801.pdf
Sjödin, M.; Styring, S.; Wolpher, H.; Xu, Y.; Sun, L.; Hammarström, L. J. Am. Chemistry Soc. 2005, 127, 3855–3863.
Skoog, D.A., Holler, E.J., and Crouch, S.R., (2007), Principles of instrumental Analysis, 6th edition.
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