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Fitting Curves to Data (autofind) peak selector, a flexible interac- the installation procedure and given detive peak selector, and statistical and fault settings, which can be easily modigraphic reporting. fied to suit any situation. The minimum system requirements for PeakSolve are an 80386 SX CPU, U math co- Fitting data processor, VGA video resolution, 4 MB oo PeakSolve uses afileslot system, which is RAM (8 MB is recommended)) a hard disk simply a positional indicator of thefile,to with 3-5 MB of available disk space, a handle data in memory. For example, floppy disk drive, and a mouse. MS-DOS when a file is loaded, it is assigned slot version 3.1 or later and MS Windows 3.0 oo #1. When a second file is loaded, the first higher are required as well. For the purfile ii moved to slot #2, and the second file PeakSolve poses of this review, the PeakSolve software is assigned slot #1. This process can be Galactic Industries was loaded onto a Dell computer with a continued for up to 30 files. Loading files 395 Main St. 80486 DX2,66-MHz central processing unit, is accomplished through the "File/Open" Salem, NH 03079 but we found that the software worked also dialog box if one has already converted or 603-898-7600; Fax: 603-898-6228; on systems ranging up to a 100-MHz Penimported afileinto PeakSolve format. If sales@galactic. com tium. The main test computer is outfitted the file is in ASCII however the "File/ImVersion 3.03; $495 with 8 MB of RAM. port" command must be used. All file function manipulations proceed through PeakSolve is a Windows-based curveBecause PeakSolve is s Windows-based standard Windows dialog boxes. Once a fitting application that is ssed tofitvarious application, installation is very simple. types of chromatographic and steadyPeakSolve erovides sn-screen instructions file is loaded into memory ,he program is prepared tofitthe data state spectroscopic data such as that from for the user to follow; one is led through GC, HPLC, UV-vis, fluorescence, or NMR. Using PeakSolve, one models ideal peaks to a complex set of overlapping data peaks. In the deconvolution process, one has several choices of the lineshapes to be used, including Gaussian, Lorentzian, mixed Gaussian-Lorentzian, and log normal The software also fits a baseline US ing an offset linear quadratic or cubic model. Peak parameters and baselines may be optionally locked or constrained. One of PeakSolve's most powerful features is its ability to interface with a wide variety of data formats Galactic Industries supports instrument data types through either direct conversion of binary files generated by the instrument-control software or throurii other conversion and PC transfer utilities Common x v ASCII pair formats mav be used with the option to select varv.n? degrees of data prerision h e a d e r information and nonsvstpmari'c * axis increments T h e nrimher nf neaks fit
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PeakSolve allows manual entry of values for each peak, peak type selection, and settind of constraint limits sn any peak parameters.
Additional features include an automatic 426 A Analytical Chemistry News & Features, July 1, 1996
3000 cm-1 from the excitation wavelength of 458 nm. We conclude from this analysis that the shoulder in the 525-nm fluorescence peak is due to Raman scatter by the C-H stretching mode in CF3H. Thus PeakSolve has proven to be an extremely useful tool in identifying an additional contribution to the data. PeakSolve in action We used PeakSolve to ouantify the emisIn summary, PeakSolve is an exceptionsion characteristics offluorescencespecally user-friendly peak-fitting application. tra of iV,A^'-bis-(2,5-f«rt-butylphenyl)- The wide range offittingoptions makes it 3,4,9,10-perylenecarboxodiimide (BTBP) simple to tailor the use of the software to in supercritical fluoroform (CF3H). In a broad spectrum of users. Moreover, Gaparticular, we analyzed the data to deterlactic Industries has ensured that Peakmine whether there was any spectral shift Solve can recognize more than 100 differin the emission spectra as well as changes ent instrument data formats, which saves in spectral characteristics such as peak valuable time by avoiding the necessity of intensity and full-width-at-half-maximum. converting data into a specified format. We also used PeakSolve to oeconvolve the Finally, thefittingroutine implemented by data and determine the presence of any PeakSolve is sowerful and efficient, which Raman scatter contribution to the fluores- results in quick, accurate solutions. cence signal. Reviewed by Mark P. Heitz and Frank V. Bright, State University ofNew York at In comparison to conventional liquids, the distinctive BTBP vibronic bands Buffalo are clearly present and most pronounced T11C CUllUl |jf! \JVlUCo g r ClU IlcUlUlCb lAJl at high reduced-fluid densities. Howeach peak (one at the maximum and one ever, at low reduced-fluid densities we at each side of the full-width-at-half-maxiSOFTWARE RELEASED observed an additional shoulder in the mum location) to be used for shaping the peak. This provides the software with the 535-nm region that is most readily obSCULPT served at the lowest reduced density Interactive Simulations, Inc. best initial guess from which to begin the fit. In actually fitting the data, PeakSolve where the BTBP solubility is limited. 5330 Carroll Canyon Rd. We obtained the best fit results when a uses an iterative nonlinear curve-ntting San Diego, CA 92121 log-normal lineshape was assumed for routine based on the Marquardt-Leven619-658-9462; fax 619-658-9463; the two peaks from BTBP and the third berg method to model the data. To judge intsim-sales@intsim. com; the goodness of fit, the reduced % 2s peak (~ 535 nm) was fitted to a Lorenthttp://www. intsim. com zian lineshape, the expected lineshape calculated where n is the number of data $1195 for a Raman peak. points;/is the total number of degrees of freedom; and Exp{ and Calct ara the meaPeak analysis as a function of reduced SCULPT real-time molecular simulator for density in supercritical CF3H shows that the Macintosh PowerPC is designed for there is no variation in fluorescence spec- interactively visualizing and manipulating " / Exp{ - Calc; V tral characteristics (peak position and 3-D molecules by picking and dragging width) within the uncertainty in the data. atoms with the mouse. Features include vi^ [ RMSnoise I 9 »-0 \ / In addition, the contribution of the Raman sual feedback of steric clashes, the abilx2 (i) scatter to the fluorescence data is clearly ity to copy to and paste from ChemDraw, 7-F{ resolved by recovered value of the emis- Chem3D, Microsoft Word, and PowerPoint, (n-f) sion maximum for the ~ 535-nm peak. A stereo display and movies, and the ability sured and the calculated values, respectively. RMSnoise is the root mean nquared recovered value of 532 nm was obtained, read standard Brookhaven Protein Data which corresponds to a shift of nearly Bank files. noise over the region fitted and is estiThe hrst procedure necessary to begin thefittingprocess is to establish a baseline. One of the strong points 01 the PeaRSolve software is that one can easily generate a level baseline for each data set and eliminate the need to nt baseline parameters along with the adjustable peaks. The preprocessing technique reduces the fitprocessing time. Each peak to befitis then selected either manually or by using the PeakSolve autofind "tility, which searches the spectrum and locates potentially hidden peaks within the data. Another user-friendly feature is the peak editor, which is conveniently acce&oed froiii une LOOI bar or fr0111 uic pulldown curveni menu and auows one 10 edit any or all peaks. A variety of actions may be undenaken wnne in the peak ecutor. For example, one can denne the number of peaks, peak parameters, and peak functions as well as add or delete peaks as needed to best characterize the data being fit.
mated based on a single data set. A smoothed version of the original data is created by using the Savitsky-Golay algorithm, and the difference between the original and smoothed data is used to determine the RMSnoise parameter.
Analytical Chemistry News & Features, July 1, 1996 4 2 7 A
