Interactive Computer Models for Analytical Chemistry Instruction

Tom O'Haver
Professor Emeritus
Department of Chemistry and Biochemistry
The University of Maryland at College Park

Last updated: January, 2016

Spectroscopy Instrumentation and methodology

Color Temperature of a Blackbody Source

Animated Diffraction 

Photomultiplier Light Measurement System


Comparison of Analytical Calibration Methods

Multiwavelength Spectrometry

Lock-in Amplifier

Wavelength modulation system

Molecular spectrometry

U.V.-Visible Spectrophotometer

Dual Wavelength Spectrophotometer

Instrumental Deviations from Beer's Law

Calibration Curve Fitting Methods in Absorption Spectroscopy 

Signal-to-Noise Ratio of Absorption Spectrophotometry

Effect of Slit Width on Signal-to-Noise Ratio in Absorption Spectroscopy

Scanning Fluorescence Spectrometer 

Fluorescence Spectroscopy Signal-to-Noise Ratio

Atomic spectrometry

Signal and Photon SNR of Atomic Emission Spectrometer

Effect of Slit Width on Emission Spectroscopy SNR

Line Wing Overlap
Spectroscopy of Atomic Absorption 

Classical, electrical, and computational methods

Worksheets for Analytical Calibration Curves 

Calcium Ion Selective Electrode model

Resolution of Capillary Chromatography

Discrete Equilibrium 
Chromatography Model

Triprotic Titration Data Analysis 

Monoprotic Titration Curve model 

This is a collection of free, downloadable, interactive computer models of common analytical instruments and techniques. Most have a point-and-click interface; you click buttons and drag sliders to control variables and the model responds dynamically, often much faster than real time. Note that these are not really simulations of particular commercial instruments. They are rather interactively manipulable mathematical models that are essentially sets of linked equations that describe various parts of or aspects of each system. The advantage of linking these equations in spreadsheet is that it gives the students and instructor an opportunity to explore how these textbook relationships interact with one another. My models give you the ability to change many of the chemical and instrumental variables that effect the outcome, including not only the variables that are conventionally adjustable in the laboratory (such as the wavelength of a spectrometer or the concentration of a chemical solution), but also the instrumental design variables that are determined by the instrument manufacturer and can not normally be adjusted by the experimenter (such as the ruling density of a grating or the focal length of a spectrometer).

Most of the spreadsheets produce graphs and charts that illustrate the internal operation of, or mimic the output generated by, these systems. Because they are just spreadsheets, it's easy for instructors and students to inspect the equations that drive these models. Unlike closed proprietary programs, the mathematical basis of these models is not hidden but rather easily accessible and can be viewed, modified, corrected, or extended by any instructor who is familiar with the basics of modern spreadsheet construction.

I originally designed these models for courses I used to teach during the 1990's at the University of Maryland at College Park: Instrumental Analysis (an upper-division undergraduate laboratory course) and Spectrochemical Methods (a graduate lecture course). The spreadsheets were based on the level of treatment in the textbooks for those courses and were designed to be used by individual students either as homework assignments, for in-class use in a computer lab environment, in the laboratory for the analysis of student-generated data, or as a supplement to laboratory experiments, to allow investigations into the fundamentals of system behavior for which time is not available in the laboratory. The spreadsheets can also be used by the instructor in lecture-demonstration environments. Student-assignment handouts and suggested experiments are included for most of them.

The mathematical basis for each model is described in PDF files, including all cell definitions and equations that relate the variables. The equations themselves are usually taken directly from the typical textbook treatment for each topic, sometimes with additions from other sources or with the addition of small amounts of random variability to make the behavior closer to real measurement systems.

Instructors are able to, and are invited to, modify these spreadsheets in any way for their students. See the unsolicited user comments below from actual users of these spreadsheets. 

OpenOffice Calc Versions
Calc is the Open Document spreadsheet format, part of the OpenOffice Suite, which students and faculty can download and use without cost, from for Windows, Macintosh, and Linux. Calc is basically the same as Excel. To run these Calc spreadsheets, you have to first download the OpenOffice installer (download from, then install it (by double-clicking on the installer file that you just downloaded), and then download my spreadsheets from this site.  Once OpenOffice is installed, you can run my spreadsheets just by double-clicking on them. The OpenOffice suits also includes a full-featured word processor, a presentation program, and other components. There is no need for students to buy the expensive Microsoft Office suite; the latest version of OpenOffice is always available for free download. Note: Downloading the individual spreadsheet .ods files with some versions of Interent Explorer will change the file types from ".ods" to ".zip"; you will have to edit the file names and change the extensions back to ".ods" for them to work properly. This problem does not occur in Firefox or in Chrome.

  The Calc versions of these models will also run on LibreOffice Calc, for example running on a Raspberry Pi 3.

Microsoft Excel Versions
To run the Excel versions (.xls or .xlxs) you must have a recent version of Excel installed, preferably 2013 or later. Interoperability between Excel ".xls" and OpenOffice Calc ". ods" files have been improved in Excel 2013 and OpenOffice version 4, which can read and save in each other's formats, but there are still some problems relating to fonts, forms controls (particularly radio buttons, check boxes, and sliders), and named variables. I am gradually trying to fix those problems and provide customized xls version that have been tested in Excel 2013. If you don't find what you want here, let me know. I also recommend Scott Sinex's excellent collection of Interactive Excel Spreadsheets.

WingZ Versions
These models were originally developed in the early 90's in WingZ (.WKZ) format, the first object-oriented spreadsheet with a built-in scripting language called HyperScript., but that program is now obsolete. This is still a useful format, because the HyperScript language has some has some unique capabilities that are useful in this sort of simulation and because the WingZ player program has a very modest memory footprint and runs very quickly even on older, smaller, or slower 32-bit computers (but not unfortunately on 64-bit Windows). I am gradually re-writing these models in the industry-standard, non-proprietary Open Document format (using OpenOffice Calc) and in Excel, but until that work is complete, some of them will be available only in the original WingZ format. To open the WKZ files you'll need the "player" application that  is included in the following file archives for both PCs and Mac:

PC users: Click to download a basic set of WingZ models and the player application as a ZIP file (700 Kbytes)
Mac users: Shift-click to download a basic set of WingZ models and the player application as a SIT file (500 Kbtes)

How to open WKZ files: Both of the file archives above include the WingZ player application that is needed to open the WKZ files. Make sure that ALL of the files in this download are kept in the same folder. Put any separately downloaded model files (.wkz files) in the same folder. To run a model, first launch Wingz.exe, then open the WKZ files from within Wingz (File => Open). (To get WingZ to launch when you double-click a WKZ file, you'd have to enter WKZ as a new file type in Tools => Folder Options => File types). Note: It is best to download the basic set of models initially, to make sure that you have all the pieces needed, then check back here occasionally for new models, which can be downloaded individually and then moved into the folder with wingz.exe.

If you have suggestions for other models like these that you would like to see developed, please email me at

What do the students have to say about these models?

Unsolicited Comments from Users at Other Institutions

"Thank you for such a fantastic resource and for the obvious effort that went into creating it....You are a true steward of our discipline."

"...your carefully explained website ... helped me tremendously.... It is an excellent resource."

I was thrilled to find your website...!

What a godsend it was to find your cheat-sheets on calibration curves."

your paper and experiment [is] very useful for me."
"They are very easy to use and helped me a lot."

"It’s a remarkable piece of work...your “Interactive Computer Models for Analytical Chemistry Instruction”

"This stuff is really impressive work...."

"...easy to use and understand....saved me many hours of work...."

...fascinating free interactive softwares. "

"Your website helped me very much and clarified a lot to me."
"I’m happy I have found your site since it has some very valuable information relevant to the projects I’m currently working on."

"Your models and write ups are excellent. It is an outstanding contribution for students and faculty members from developing countries."

" deep gratitude for the wonderful interactive diffraction grating models; they are in so many words instructive and indispensable."

"I was able to get everything working nicely and can promise you they will be helpful with my students."

"Today I had the first simulation experiment and the students were excited...."

"The [simulated] lab was much more interesting than the lecture, this is for sure!...I had very good feedback from students..."

"...thank you so much for your website!!! "

"...I have found [your worksheets] of great use whilst working on my current project."

"Wow! Nice work … and lots of it. Your stuff is wonderful!"

"I found your website very informative."

"What I like about your grating demo is that it clearly shows how increased dispersion causes the different wavelengths to have to travel different distances to the sensor...."

"Let me congratulate you on a fine web page! I'm a technical support engineer for Wingz ... and I rarely run across such sophisticated use of our products."

1. Scott Sinex, Chemical Excelets:  Interactive Excel Spreadsheets for General Chemistry. (
2. Chemistry PhET Simulations (
3. Brian Tissue, Spreadsheet Simulations for Analytical and Physical Chemistry (
4. Gizmos. Commercial web-based interactive simulations, billed as "the world's largest library of math and science simulations":
5. Flick Coleman, "Interactive Spreadsheet Demonstrations for Introductory, Inorganic, Analytical and Physical Chemistry,"

View this page in Romanian courtesy of azoft.   Italian Translation Courtesy of Search-Sos. Russian translation courtesy of Prof. Alexander Nikiforov. Translation into Portuguese for .

Created by T. C. O'Haver , Department of Chemistry and Biochemistry, The University of  Maryland at College Park. Comments, suggestions and questions should be directed to Prof. O'Haver at

Copyright © 2017, Thomas C. O'Haver
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

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