Differential Pulse Voltammetry

Differential Pulse Voltammetry 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) 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 à ¢Ã‹â€ Ã¢â‚¬  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 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(OGorman, 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(OGorman, 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 (OGorman, 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=DpCWhuUMbdMCpg=PA164lpg=PA164dq=advantages+of+differential+pulse+voltammetrysource=blots=6iOU-xcP22sig=_JDlOgIQ0Bs3Px5PqZMNXMwgAK0hl=ensa=Xei=2AAkU5yAJsbZrQfJwoFQved=0CEcQ6AEwAzgo#v=onepageq=advantages of differential pulse voltammetryf=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 OGorman, J. (1998). Novel electroanalytical methods. (Masters thesis, Dublin City University)Retrieved from http://doras.dcu.ie/19220/1/John_OGorman_20130717104801.pdf Sjà ¶din, M.; Styring, S.; Wolpher, H.; Xu, Y.; Sun, L.; Hammarstrà ¶m, 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. 1

What Dilemma Did to Him :: Free Essay Writer

What Dilemma Did to Him We realize our dilemma goes deeper than shortage of time; it is basically a problem of priorities. We confess, We have left undone those things that ought to have done; and we have done those things which we ought not to have done. Charles E. Hummel. In a time of national dilemma what better way then a good book about over coming a dilemma. â€Å"The Crucible† By Arthur Miller does just that you could almost center the word dilemma around Arthurs’ character John Proctor. Only Miller could show how dilemmas reveal much about some persons personality or how it affects the lives of all. The Salem witch trail well there’s a dilemma and for Proctor as soon as he got over a dilemma wham bam another one is thrown into to his face. How do you describe John? Well he’s a simple man, stay out of his business and he’ll stay out of yours. As soon as the girls of Salem get busted of â€Å"witchcraft† John faces the first of many new events that would show John as more then anyone would have thought. When Abigail tells Proctor what really was going on in the woods that night, â€Å"We were dancin’ in the woods last night, and my uncle leaped in on us. She took fright, is all.† the right thing for everyone would be for him to tell them all the truth about what happened. If it wasn’t for the fact that John himself was no angel: Stopped going to church, and the big thing that makes everything that much more complicated is that Abigail and John who is a married man have had tender moments. Now how can he rat her out without busting h imself in an act that would kill his wife’s heart and muddy his name. So he does what any man would do, nothing, nothing at all just goes home and leaves it to the towns people. Well so far Mr. Proctor doesn’t sound much like a guy I like too out with but this story is only just begun. Not soon after John goes home to his wife, pushing the whole thing out of his mind. Was this the right thing to do for him or for the town or really for anyone involved in this stupid lie this was a dilemma only he could make right and everyone is involved in it is affected in a different way but most their very lives relied upon the truth Proctor knew.

Imperialism during the Progressive Era Essay

Imperialism is defined as the policy of extending a nation’s authority by territorial acquisition or by the establishment of economic and political domination over other nations. Throughout the time period many people considered Imperialism as another way of reform and Progression. Economics, the military, and the countries nationalism were all ready for the change. This idea of expanding was called the New Manifest Destiny. At this time period, Imperialism was getting very popular, and many began to think that the more land a country annexed, the more powerful it was. Expansionists believed that European countries were already rapidly growing spreading across the globe. Also, they saw that if Americans did not join the imperialism rule, it would end up missing out on power, and may be considered a weaker nation. Imperialism was needed for economic gain and America urgently needed foreign trade, especially with China at this time period. In addition, The United States was cons idered to be a great empire and by not showing their strength and power they might be envisioned as a weak nation. At the same rate, many Americans also saw that if the United States started to take other countries by force, it would go against the ideals of our own country. If economic growth occurred, we would need to build and protect our new empires, and this could very easily be a problem. Three presidents at this time period were very influential in their progressive views. One of these was Theodore Roosevelt. â€Å"Speak softly and carry a big stick†, a quote by Roosevelt himself, expresses his â€Å"Big-stick† diplomacy, stating that the threat of military force would be used to influence politics in other countries. Next, Taft’s dollar diplomacy states that money can influence decision-making and that America should expand and invest out of the country. Finally, Wilson believed that Americans should spread the beliefs of human rights, democracy, and word peace. This idea was called the â€Å"Humanity† diplomacy. Another important factor was the Panama Canal. This canal was a very key factor in both trade, and military strategy. For many years, travelers looked for an easier way to trade from the Atlantic to the Pacific, and this was it. One of the weaknesses of Imperialism, is that whenever the United States saw problems in one of the local areas, such as Cuba having problems with Spanish rule, America felt  the need to intrude. Eventually, this lead to the Mexican revolution and the Philippine revolt.

Race And Racial Inequality During The Civil Rights Of...

â€Å"Racism[ˈrÄ Ã‹Å'sizÉ™m]prejudice, discrimination, or antagonism directed against someone of a different race based on the belief that one s own race is superior†. Race and racial inequality have strongly shaped American history from its beginning up until now . Americans like to think of the founding of the American colonies and, later, the United States, as driven by liberty and freedom .However, from the start America was founded on inequality which involved the absolute oppression for not only the Native peoples who were often attacked, relocated, and forcibly assimilated into European culture,African slaves ,and for almost every race that has called this country â€Å"home†.Although the civil rights of everyone has improved over the last†¦show more content†¦Majority of the natives were then forced to attend residential schooling system that sought to re-educate them in white settler culture and economy. The forceful teaching of a new culture sought to undermine the natives’ culture and to form a new image of white supremacy and predominant role as the superior race. Despite years of change in society in the United States , no matter how rich and diverse the United States population is racism and discrimination has been held onto .After an end was put to slavery in the late 1860’s the federal government started to enforce Black Codes legislation that was discriminatory to African Americans. The codes made it illegal to be homeless and unemployed which led to mass imprisonment of African Americans being that there was not much financial stability for them post slavery. Civil rights activists in the 1960’s advocated for a more fair society that was â€Å"color blind†. Martin Luther King Jr, a major figure within this movement s, biggest goal was to have American society judge a person by character rather than by their color. 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