Construction And Testing Of LabVIEW Software To Interface .

2y ago
13 Views
2 Downloads
669.28 KB
5 Pages
Last View : 23d ago
Last Download : 2m ago
Upload by : Jewel Payne
Transcription

H-SC Journal of Sciences (2013) Vol. IINelson and AndersonConstruction and Testing of LabVIEW Software to Interface with a PrincetonApplied Research Model 273 Potentiostat and an HP Model 8452APhotospectrometerStephen Nelson and C. William AndersonDepartment of Chemistry, Hampden-Sydney College, Hampden-Sydney, VA 23943With LabVIEW, it was possible to create a program that could operate a Princeton Applied Research Model 273potentiostat, an HP Model 8452A photospectrometer, and a YSI Model 5000 Dissolved Oxygen Meter from a singleinterface. Such a program would solve the problems that diverted so much effort away from further experimentsand toward watching a potentiostat change potential over the course of several hours (in some cases up to twelvehours). Unfortunately, the dissolve oxygen detection was omitted due to the limits of the instrumentation. However,testing the program's viability with several samples whose redox potentials were given, a program was constructedthat could indeed consolidate the functions of a potentiostat and a spectrometer.INTRODUCTIONIn natural and in synthetic oxygen binders–compounds that carry oxygen through thebloodstreams of organisms– the binder itself containsa metal center to which oxygen can attach. Theseoxygen binders are essential to biological life forms,including humans, and more efficient and convenientbinders are a large topic in chemical industry(Fischer- ‐Fodoretal.,2011).One method of changingthe transition state of various metals in order todetermine the most efficient state for binding oxygenis a process of electrochemistry that involves applyingvoltages to samples using a potentiostat. A Princetonpotentiostat is an instrument that generates andmeasures voltage across a given sample. Thereference electrode used with the potentiostat cellwas a silver chloride electrode. Then, an HP Model8452A spectrometer, emitting both UV and visiblelight, actuates a shutter and allow the light to passthrough a sample and into a diode array. Thespectrum is displayed on the PC monitor, and oxygenreadings for the sample are taken from a connectedYSI 5000 oxygen meter. Utilizing these threeinstruments, the metals’ transition states are altered.Observable oxygen binding can be measured istry because of the use of both apotentiostat and a ment that uses “virtual instruments” (VIs) inplace of traditional written code to compile workinginstrument software.9 Instrument manufacturers aswell as independent individuals make available setsof basic VIs that can be customized and connectedas a framework for a more elaborate instrumentinterface. With the LabVIEW software, a virtualinstrument could be compiled that could operate apotentiostat in conjunction with an HP diode arrayspectrometer and a YSI oxygen meter. The combinedadvantages from applying LabVIEW to thecoordinated operation of the potentiostat, diode arrayhttp://sciencejournal.hsc.eduspectrometer, and oxygen meter equal an intuitiveprocess for analyzing oxygen binding samples thatreduces experiment time and possible errors in data.Fig1. Layout of the three instruments involved in oxygen carrierredox analysis.METHODSThe first focus of this project was to persuadethe Princeton potentiostat to receive and implementorders from a PC. A set of VIs written expressly forthe PAR Model 273 was downloaded and saved tothe PC hard drive (Jamalet al., 1991). While theseVIs were written to perform cyclic voltammetryexperiments – a different electrochemical processthan the one set as the goal of this project – theycontained components that had the potential to eter containing a 10 Ohm dummy cell wasconnected to the potentiostat and the main VI, “CyclicVoltammetry”, was initialized.Unfortunately, as it was written the VI would notinteract correctly with the potentiostat. The mostprobable cause of these errors was explicitlymentioned in the text written within the VI. Therelative age of the instrument supposedly made itsusceptible to errors if a modern PC attempted to1

H-SC Journal of Sciences (2013) Vol. IINelson and Andersonsend too many commands in a short period of time.To remedy this, short pauses of 100 millisecondswere placed between each VI. This solution correctedsome of the errors, but still allowed others to occur.Using LabVIEW's Highlight Execution function, the VIwas slowed so that step of the program was visible,errors included. Many errors were occurring inside ofsubVIs, so those subVIs were opened and modifiedto pause at key points to allow the potentiostat moretime to process its commands. This produced anoperational VI as well as the groundwork for the nextpotentiostat VI.Fig 2. HP 8452A NELSON v2: This version saves a text version ofthe spectrum.Once the Cyclic Voltammetry VI was deemedusable, the prefabricated VIs provided by themanufacturer of the spectrometer were opened. Themain VI, which allowed the user to take a singlespectrum across a range of wavelengths, wascomplete and required no modifications. A secondversion of the HP 8752A VI was created thatperformed the same function, but a series of functionswere added that allowed the VI to save the spectrumas a text file complete with a footer containing thedate and time the spectrum was taken as well as theoperator's name and the name of the sampleWith the completion of both the potentiostat'sVIs and the spectrometer VIs, a blank VI named“Experimental Potentio-Spec” was created. Severaliterations of this VI were completed, but the finalversion ultimately contained five major frames thatperformed different functions given proper directionfrom the operator. The first frame setup thespectrometer. The second frame tells thespectrometer to take a reference spectrum. The thirdhttp://sciencejournal.hsc.eduframe was compiled from a series of the modified VIsused during the cyclic voltammetry experiments Theprogression of this frame is as follows (with pausesomitted): the potentiostat is set to the default state,the current range is set, the potentiostat's status isdetermined, the initial potential for a cell is set andheld for the number of seconds specified, thepotential is stepped and the spectrometer takes tenspectra on the last tenth of the equilibration time, theresulting spreadsheet (the absorbance values areaveraged from the ten spectra) is saved with thepotential attached to the end of the filename, and thepotentiostat acts as it was directed to do oncompletion. Note that the functions that attach thefooters to the ends of the spectra files have beenseparated from the spectrometer VI and placed into astandalone VI to avoid VI malfunctions. The fourthframe of the “Potentio-Spec” VI is nearly identical tothe third frame. The only discrepancy is in the mannerby which the VI steps the potential. Whereas the thirdframe steps the potential in equal steps specified bythe operator, the fourth frame calculated each stepindividually by way of a modified Nernst equation andsteps the potential accordingly. This method ofstepping the potential is more useful because it cancalculate much smaller steps near the zero potentialof a sample. Relatively large steps, such as thosetaken by the third frame of the “Potentio-Spec” VI,can miss the zero potential completely and therebyruin a time-consuming experiment. The fifth frame ofthe VI resets any error codes generated by thespectrometer.Unfortunately, the YSI dissolved oxygen metersupplied was unable to correctly process commandsreceived from the PC and was therefore removedfrom service for the purposes of these experiments. Ithas been noted that the purpose of compiling virtualinstruments that operate the potentiostat and thespectrometer was to perform redox reactions. To thisend, several solutions of ferrocenecarboxylic acidwere produced. According to Hillier, et al. thetheoretical redox potential for the oxidation offerrocenecarboxylic acid is 0.4 V, or 400 mV(Hillieretal.,2004). That fact made ferrocenecarboxylic acidan excellent candidate for testing the “Potentio-Spec”VI. However, only solutions whose solvents – in thesecases, deionized water – contained a measure ofsodium bicarbonate were usable. Those solutions of0.1125 M ferrocenecarboxylic acid in approximately4 10-5 M sodium bicarbonate were clear with adistinct orange color. The other “solutions” wereactually suspensions of ferrocenecarboxylic acid.

H-SC Journal of Sciences (2013) Vol. IINelson and AndersonPrior to the completion of the “Potentio-Spec”VI, ferrocenecarboxylic acid samples were used totest the progress of the program. Using the Nernstequation and several spectra taken during thosetests, an experimental redox potential forferrocenecarboxylic acid was calculated. Thecalculated potential, 417 mV was inserted into the VIand the fourth frame was used to complete a series ofpotential steps on the sample. The resulting spectrashowed that the calculated potential was extremelyclose to the actual redox potential, and additionallyshowed that the VI and its components operated in amanner conducive to the successful reduction andoxidation of samples used in electrochemistry andspectroelectrochemistry.Figure 3. Frame three of the “Potentio-Spec” VI. This frame conducts an equal-step run.RESULTS AND DISCUSSIONThe “Cyclic Voltammetry” VI, though not itself a goalof this project, is important enough to beardiscussing. It began as a program developed by athird party who had occasion to work with thePrinceton Applied Research Model 273 potentiostat(National Instruments Developer Community).Because of the age of the potentiostat, it waspreviously meant to be controlled by way of itsphysical keys or, alternatively, by sending commandsthrough a PC via terminal emulator. Though its digitalfunctions are primitive compared to more moderninstruments, it is till controllable through the LabVIEWprogramming environment. After downloading thecyclic voltammetry package from the party whodeveloped it, it was discovered that the VI generatederrors that made impossible the running of a cyclicvoltammetry experiment. The subsequently modifiedVIs, fixed to cope with the hardware setup, werearranged in such a way that the eighth version (thelatest version to date) of the “Cyclic Voltammetry” VIwould take multiple scans of the same sample andsave each one to the same text file. By no means isthis latest version perfect – it still generates randomerrors on occasion – but it functions well enough tohttp://sciencejournal.hsc.eduuse as a standalone program. If the source of therandom errors could be identified and corrected, the“Cyclic Voltammetry” VI could potentially be a veryuseful program.The program also contributed to the“Experimental Potentio-Spec” VI by donating itssubVIs to the production. Once the experimental VIwas put together, it could run a full basic steppingroutine with either equal potential steps or stepsdetermined by a modified Nernst equation. Earlyversions of this program could only perform equalstepping runs and were somewhat difficult to test.Several different solutions were used to test thefunctionality of the “Potentio-Spec” VI: rophenolindophenol, and ferrocenecarboxylicacid. The external cell used to perform steppingexperiments was one of Dr. William Anderson'sinvention. It was a solvent-resistant shell with holedrilled to allow for the passage of a liquid sample. Athin, transparent layer of gold was sandwichedbetween Plexiglas plates and acted as the workingelectrode for the cell.3

H-SC Journal of Sciences (2013) Vol. IINelson and Andersonhttp://sciencejournal.hsc.eduB SG r e e nT r ia l20 m VA b s o rb a n c e( A U )20151050100200300400500600700800900W a v e le n g t h( n m )B SG r e e nT r ia l21 0 0 0 m VA b s o rb a n c e( A U )The Bindschedler's green samples seemedto give only a small peak of less than 0.5 AU near750 nm on its spectrum. Additionally, runs thatstepped the potential from negative potentials or zeroto high potentials in excess of 1.2 V failed to reduceor oxidize the samples; the redox potential of thegreen dye is theoretically 224 mV (Lewis et al., 1948).This could be due to impurities in the lot ofBindschedler's green used; it was also possible thatthe failure to affect the sample was due to technicalissues with the potentiostat's electrometer or with thepotentiostat itself. However, when a sample of RoseBengal sodium salt was used to test the “PotentioSpec” VI, the redox potential was between 1.7 V and1.8 V. These readings coincided with theexperimental redox potential of rose bengal accordingto Islam and Ito (Islam et al.,1999). The data seemedto discount the theory that an issue was occurringwithin the electrometer. Unfortunately, the samples ofDCPIP (dichlorophenolindophenol) tested alsoexhibited massive and erratic redox potentials.According to Whitaker et al. the redox potential ofDCPIP should be about 217 mV (Whitaker et al.,2012).To make certain that the electrometer andpotentiostat were in working order, a voltmeter wasapplied to the electrodes on a cell with a DCPIPsolution inside and the voltmeter returned the samevalues that the potentiostat displayed on its digitalfront panel. Based on these observations, there is astrong probability that the Bindschedler's green andDCPIP may be contaminated.The ferrocenecarboxylic acid solution wasused last because of its properties. It could be easilyoxidized and reduced and would give clear indicatorsof the status of its oxidation state such as the color ofthe solution. Since the overall goal of this project wasto create a program that could all but automate xylic acid appeared to be ideal forthese sorts of experiments. The redox potential of theferrocenecarboxylic acid coincided with researchconducted at 0.417 V (Hillier et al., 2004). Repeatedtests gave consistent results and confirmed that theprogram as indeed functioning as it should.With the completion of this program,any who wish to apply it to spectroelectrochemistryhave the opportunity to have an automated system inplace of a tedious repetition of key pressing. Ideally,the error and tedium of human action has beenremoved from the process of spectroelectrochemistry(at least in the areas to which the techniquesdiscussed herein can be applied). If an oxygen metercould be incorporated into the process, thenoperators would be able to measure the oxygencontent of a sample as well as its redox potential andanalyze how well that sample binds oxygen.2520151050100200300400500600700800900W a v le n g t h( n m )Fig 4. Top: spectrum of Bindschedler's green at 0 mV. Bottom:spectrum of Bindschedler's green at 1000 mV. Both spectra weretaken using the equal step method. The absorbance units havebeen multiplied by ten due to an error in the LabVIEW program.Note the miniscule peak at 720 nm.This is especially useful when syntheticbinders that utilize metal centers, such as hemoglobin(Berg et al., 2012). It has been noted that the originalintent of this project was to create a completelyautomatic system that combined the processes ofpotentiometry, UV-vis spectrometry, and dissolvedoxygen detection. It has also been noted that theoxygen detector was rendered inoperable by itsinability to correctly decode the commands sent to itfrom a PC interface. However, the main result of theproject, the “Experimental Potentio-Spec” VI didsuccessfully combine potentiometry and spectrometryto form a program suitable for performingspectroelectrochemistry. Even though the VI cannotanalyze the oxygen content of a sample, it canmanipulate the potential applied to a sample and itcan take spectra of a sample in order to determineredox characteristics of that sample. Again, if adissolved oxygen meter could be incorporated intothe program, a fantastic VI would come to be.REFERENCES1. Fischer-Fodor, E.; Mot, A.; Deac, F.; Arkosi, M.;Silaghi-Dumitrescu, R. Towards hemerythrin-basedblood substitutes: Comparative performance tohemoglobin on human leukocytes and umbilical veinendothelial cells. J. Biosci. 2011, 36, 215-221.

H-SC Journal of Sciences (2013) Vol. IINelson and Anderson2. Jamal, R.; Pichlik, H. LabVIEW Applications andSolutions; Prentice Hall PTR: New Jersey, 1991; pp4-6.3. Hillier, S.C.; Frost, C.G.; Jenkins, A.T.A.; Braven,H.T.; Keay, R.W.; Flower, S.E.; onucleotide digestion. Bioelectrochemistry. 2004,63, 307-310.4. National Instruments Developer Community.5. Lewis, P.R.; Hinshelwood, C.N. Adjustments inBacterial Reaction Systems. I. The Reducing Powerof Bact. Lactis aerogenes under Various Conditions.Proceedings of the Royal Society of London. SeriesB, Biological Sciences. 1948, 135, 301-316.6. Islam, S.D.M.; Ito, O. Solvent effects on rates ofphotochemical reactions of rose bengal triplet statestudied by nanosecond laser photolysis. Journal ofPhotochemistry andPhotobiology A: Chemistry.1999, 123, 53-59.7. Whitaker, G.T.; Belogay, E.A.; Smith, E.T.Spectroelectrochemical Determination of the RedoxPotential of Cytochrome C via Multiple Regression:An Undergraduate Instrumental Analysis orBiochemistryLaboratoryExercise.wise.fau.edu/ ebelogay/pub/tce07-bsw-cytc.pdf(accessed July 5, 2012).8. Hillier, S.C.; Frost, C.G.; Jenkins, A.T.A.; Braven,H.T.; Keay, R.W.; Flower, S.E.; onucleotide digestion. Bioelectrochemistry. 2004,63, 307-310.9. Berg, J.M.; Tymoczko, J.L.; Stryer, L. Hemoglobin:Portrait of a Protein in Action. In Biochemistry, 7thEd.; W.H. Freeman: New York, 2012; pp 196-201.http://sciencejournal.hsc.edu5

Department of Chemistry, Hampden-Sydney College, Hampden-Sydney, VA 23943 With LabVIEW, it was possible to create a program that could operate a Princeton Applied Research Model 273 p

Related Documents:

Certified LabVIEW Architect Exam LabVIEW Core 1 LabVIEW Core 3 LabVIEW Core 2 Managing Software Engineering in LabVIEW Advanced Architectures in LabVIEW LabVIEW Connectivity Object-Oriented Design and Programming in LabVIEW LabVIEW Performance LabVIEW Real-Time 1

examples. So launch LabVIEW and explore the LabVIEW environment as you read this section. 1.3.1 Starting LabVIEW . If your version of LabVIEW was installed using the default installation procedure, launch LabVIEW by selecting All Programs National Instruments LabVIEW 2013 (or LabVIEW 2014) LabVIEW 2013 (or LabVIEW 2014) from the Start menu .

Labview Exercises for Labview 7.0 Installation of Labview: 1. Install the Labview 7.0 software and drivers onto your computer. These files can be found by mapping a network drive to \\poohbah\labview, and by running the ‗autorun‘ file in the ‗Labview 7‘ folder. The serial num

Sound and Vibration Measurement Suite Sound and Vibration Toolkit LabVIEW Internet Toolkit LabVIEW Advanced Signal Processing Toolkit . LabVIEW Report Generation Toolkit for Microsoft Office LabVIEW Database Connectivity Toolkit LabVIEW DataFinder Toolkit LabVIEW S

in LabVIEW Object-Oriented Design & Programming in LabVIEW LabVIEW Learning Path LabVIEW Core 1 LabVIEW Getting Started LabVIEW LabVIEW Core 3 Core 2. Student Guide x ni.com C.What You Need to Get Started Befor

of the LabVIEW Arduino interface. What this book covers Chapter 1, Welcome to LabVIEW and Arduino, introduces you to the Arduino platform and the LabVIEW software. Chapter 2, Getting Started with the LabVIEW Interface for Arduino, shows you how to install and use the LabVIEW interface for Arduino via the LINX module.

Actor-Oriented Design in LabVIEW LabVIEW NXG Options LabVIEW NXG Core 1 LabVIEW NXG Core 2 Transitioning to LabVIEW NXG Proficiency Events LabVIEW Developer Days CLD Summit . This learning path is for users developing embedded control and monitoring systems to design smart machines or industrial equipment. It presents courses, exams, and .

Density (PSD), displaying the level of stress and LabVIEW Interface for Arduino (LIFA). Fig. 6. The overall LabVIEW programming for the study B. Graphical User Interface The graphical user interface (GUI) is designed in LabVIEW to help user to communicate with the LabVIEW and display the results. Fig. 7 describes the overall LabVIEW GUI of the