Multiple Electrochemical Impedance SpectraParameterization (MEISP +). Version 2.0 . KumhoPetrochemical Co. Ltd., Kumho Chemical Laboratories,P.O. Box 64, Yuseong, Taejeon, 305-600, Korea. Fax: 8242 862 5651. http://powergraphy.com. Contact Kumho forprice.

The purpose of this software is to fit electrochemicalimpedance spectra to equivalent circuit models by the nonlinearleast-squares method and to deduce the values of the circuitelements that best fit the data. Competing software includes“ZSimpWin” from Perkin-Elmer and “Zplot/Zview” fromScribner Associates, but I will only compare this software withthe latter (v 2.3d), since it is the one with which I haveexperience. The program’s Web site and documentation saynothing about hardware and operating system requirements, andI was unable to install it under Windows 2000, although it didrun successfully under Windows NT4 on a 400 MHz machine.The program has hardware “dongle” copy protection, requiringthe dongle always to be present. (Zplot requires the dongle tobe inserted only every six months, which is a reasonablecompromise between adequate copy protection and the incon-venience of moving the dongle between home and work.)

I began by creating some equivalent circuits. Circuits aregenerated by a subprogram (CEDIT) that can also be run instand-alone mode. It can create circuits of arbitrary connectivity,made from resistors, capacitors, inductors, and special elements,and output them in standard SPICE file format. The elementsare connected by dragging wires between them in an obviousway that kept my six-year-old amused for some time. Fordistributed elements, I had to sort out the distinction betweentitles (must be X1, X2, ...), names (leave alone unless user-defined) and parameter names (must be no duplicates), but onceI had done this I had no problem constructing my circuit. Thespecial elements can be any of 26 types of distributed elementsused in fitting electrochemical impedance spectra (I could notthink of any missing ones), or they can be impedance functionsdefined by the user. User-defined functions are entered as linesof a subprogram in a text file and can use a variety of functionssuch as sqrt, tanh, or the predefined distributed elements. Thisis a nice feature for anyone with rudimentary programmingknowledge. However, my first attempt to create my ownconstant-phase element raised several questions not answeredby the documentation: Could I put a complicated expressionin the return line? Should I use ** or∧ to raise powers, or didI have to use the “pow” function, even though the exponentwas not complex? As in other places in the software, the userneeds to experiment a little before things will work. The userwho has an impedance function so arcane that it cannot behandled by any of the above methods can write and compilehis or her own .dll files and use them with MEISP+ (a featureI did not test). MEISP+ is certainly ahead of other softwarepackages in terms of the ultimate flexibility in creating circuits.Zplot is restricted to parallel/serial combinations and preselected

simple or distributed elements, although it might be argued thatyou are not practically limited unless you are a specialist whowants to make some very exotic circuits.

I evaluated this software using two experimental impedancespectra. One was for thallium electrodeposition at a single-crystal platinum electrode, which obviously fit the circuit witha parallel Rct/Cdl combination in series with the solutionresistance; the second was of a small fuel cell stack. The firststep was to read in the data file, which can be in Zplot, EG&GM398, BAS/Zahner, Gamry, Powergraphy, or plain ASCIIformat. It read the Zplot fuel cell file without difficulty. Forthe thallium data, I tried the ACSII format (three columns forfrequency, real part, and imaginary part, separated by commasor spaces), but the program crashed. I eventually found thatthe format is very fussy: a single space separator worked, buta comma and a space did not.

Having loaded in my thallium data set and selected mypremade circuit, I hit “prefit” to automatically choose initialvalues of the circuit elements, then “fit” to refine the values bynonlinear least squares, and presto, I had convergence to thesame values as I had obtained previously using Zplot. Theagreement of the results was not so surprising, since bothMEISP+ and Zplot use Macdonald’s LEVM as the underlyingnonlinear least-squares engine and use similar default fittingoptions (the LEVM report can be output for diagnosticpurposes). Not having to select initial values for the parametersis a very nice feature. Zplot and LEVM users know that poorinitial guesses for the parameters can easily lead to the dreaded“singular matrix” problem. Consequently, the user may needto know a lot about circuit impedance behavior just to makegood guesses for initial values. My fuel cell spectrum provedto be a more difficult test of this feature. The equivalent circuitwas a difficult one, since it had two CPE elements in paralleland inductive behavior at low frequencies. This time theprogram’s initial guesses led to a spectrum that correctly hadtwo loops above the axis at higher frequencies but that failedto go below the axis at lower frequencies to model the inductor.The documentation suggests the prefit algorithm is not set upfor inductive behavior. In this case, the initial guesses were nothelpful, and the subsequent fitting led to convergence to a wildlyincorrect result. I did not further test the guessing ability ofMEISP+, but even if it fails sometimes, it is a useful feature.

Another competitive advantage claimed for this program isthat it can fit sets of impedance spectra. Aside from the abilityto plot a parameter vs the variable changing from spectrum tospectrum (e.g., potential) or to produce a 3-D plot of all thespectra, this worked identically to Zplot’s “batch” mode.(Apparently ZSimpWin also has this feature.) Another claim isfor the program’s generic battery impedance function with 10parameters, which is supposed to fit all possible batterychemistries. The model seems physically reasonable, but I amnot sufficiently versed in battery impedance to support or refutethis rather bold claim. No doubt this would be useful for routine

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battery testing, where variation in a parameter may be adiagnostic signal for a certain failure mode.

I occasionally got fits that bore no resemblance to the data,came across incomprehensible error messages, or crashed theprogram, so the user is certainly not shielded from all problems.There are several minor annoying points, for example, thespelling “Nuquist” for “Nyquist”, the “Bode” plot option onlyshows log real and log imaginary parts of impedance vs logfrequency and not log magnitude and phase vs log frequency,and the main window is slightly larger than the screen (at leaston my system) and has to be shifted over to see the plots intheir entirety. The documentation covers all topics and is quitegood on the use of the various distributed elements; however,it is still short on some details and could use some thoroughediting. Most of my complaints are in the category of roughedges rather than fatal problems and will no doubt be remediedin a future release. In general, the features of this program havebeen well thought out. I liked the ability to force the timeconstant order and the ability to force several circuit elementsto have the same value (useful for transmission line models).These sorts of features, and especially the ability to definearbitrary impedance functions, make it a good choice for thespecialist. For most users and especially for the naive user, theautomatic choice of initial parameter values is the most usefulfeature, which makes MEISP+ a competitive choice.

David Harrington,UniVersity of Victoria

JA015328M

10.1021/ja015328m

KnowItAll Analytical System . Bio-Rad Laboratories,Sadtler Division, 3316 Spring Garden St., Philadelphia,Pennsylvania 19104. www.sadtler.com.

In most analytical laboratories, organizing vast amounts ofdata from myriad sources can be both an administrativechallenge and an impediment to scientific discovery. All toooften, key details remain obscured simply because of thedifficulty of extracting them from the overwhelming wealth ofinformation available. A new software package released by theSadtler Division of Bio-Rad Laboratories, the KnowItAllAnalytical System, seeks to help scientists overcome thisproblem by providing them with a coherent collection of toolsfor extracting valuable facts from data and easily forming theminto appealing reports.

The KnowItAll software consists of a common graphicalinterface containing various plug-ins, each designed to performa specific function. With such a structure, Bio-Rad has suc-ceeded in creating a program with nearly seamless interoper-ability between the different components. Practically any typeof information can be transferred from one plug-in to anothersimply by clicking on one of the context-sensitive buttons thatdirects the user to typical functions. The interface also containsa pane of user-configurable menus at the left of the main windowthat let the user easily switch between plug-ins. By default, themenus are sorted by analysis type, grouping all of the toolsrelevant to IR analysis, for instance, into one panel.

Overall, the interface is fairly intuitive, and anyone withexperience in a windowing operating system should face only

a modest learning curve before becoming comfortable with theprogram’s basic features. The software was installed easily, butthe product activation scheme, which requires a custom licensekey from Bio-Rad, could be problematic should the softwareneed to be moved to a different computer. Although the softwaredid not ship with a printed manual, the online help system offersthorough explanations of most topics. This help system isaugmented by an online support page on the Internet thatcontains, among other things, a series of tutorial movies thatreasonably introduce the user to the program’s various aspects.Additionally, KnowItAll also has a context-sensitive helpfunction that offers concise but sometimes vague descriptionsof the visible functions.

At the core of the KnowItAll system are the basic datahandling tools in the DrawIt and ReportIt plug-ins. In DrawIt,Bio-Rad presents an advanced and full-featured chemicaldrawing program that supports most common file types, elim-inating the need for any additional chemical drawing software.Similarly, the ReportIt plug-in allows for good handling of data,text, and graphics, making feasible the complete generation ofscientific reports and documents. Despite support for a largerange of file formats, however, formats used by some notableinstrument manufacturers are absent, potentially causing com-patibility problems in some laboratories.

Although KnowItAll touts its applicability to NMR, IR, MS,UV/vis, and GC data, the actual functionality seems somewhatskewed toward NMR and IR spectra. The generally excellenttools for analyzing these spectra allow for easy manipulationand processing as well as analysis based on database look-upsand comparison of multiple spectra. The AnalyzeIt plug-in forIR spectra, in particular, allowed for nearly effortless functionalgroup analysis and can interface with Sadtler’s extensive libraryof IR spectra. Additionally, the PredictIt plug-in proved able topredict the locations of both1H and 13C NMR peaks from amolecular structure on the basis of a database search for atomssimilarly situated.

Unfortunately, KnowItAll’s handling of data from otheranalytical sources was less impressive. Users dealing with datafrom MS, UV/vis, and GC are limited to database searches basedon molecular structure, observed peaks, or a wide range ofphysical properties. For these types of data, KnowItAll lacksany ability to process spectra or chromatograms. By purchasingthe optional MineIt Database Building plug-in, the useful-ness of the software can be increased with time, however, byallowing the user to create custom, searchable databases ofspectra or chromatograms of any type. Nevertheless, thisshortcoming could mitigate the software’s usefulness to manylaboratories.

Fortunately, the modular structure of KnowItAll opens thedoor for the development of third-party add-ins that will allowfor further customization of the software and offer the possibilityof more specialized analyses. Bio-Rad currently offers severaloptional plug-ins of its own. In addition to the Database Buildingoption mentioned above, the AssignIt option allows the user tobuild databases of NMR spectra containing a great deal ofadditional peak data, including factors such as intensities andcoupling constants. In addition, the Socrates’ IR Power Packoffers direct links from the AnalyzeIt plug-in to an electronicversion of George Socrates’Infrared Characteristic GroupFrequencies. For those interested in IUPAC naming, the IUPAC

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NameIt and IUPAC DrawIt offer the ability to generate a namefor a chemical structure and vice versa. Beyond software plug-ins, Bio-Rad also offers subscriptions to its online databases ofIR, NMR, and MS spectra, accessible through the samestraightforward interface as its local databases.

Overall, the KnowItAll Analytical System’s usefulness iseasily apparent, particularly in laboratories that generate largeamounts of IR and NMR data. Furthermore, its breadth offers

potential cost and time savings by eliminating the need formultiple software packages and streamlining the data reportingprocess.

Courtney Sherman and Jennifer Brodbelt,The UniVersity of Texas

JA015371+

10.1021/ja015371+

B O O K R E V I E W S

1556 J. AM. CHEM. SOC. 9 VOL. 124, NO. 7, 2002