Interactive Computer Models for Analytical Chemistry Instruction

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

http://terpconnect.umd.edu/~toh/models/
Last updated: May, 2001

A Links²Go Key Resource Award in the Simulation Models topic

This is a collection of interactive computer models and simulations 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, usually faster than real time. I originally designed these models for students in my courses in Instrumental Analysis (an undergraduate laboratory course) and Spectrochemical Methods (a graduate lecture-based course).They were designed to be used by individual students either as homework assignments, for in-class use in a computer lab environment, or in the laboratory for the analysis of student-generated data. Some can be used by the instructor in lecture-demonstration environments. Student assignment handouts are attached to most of them. The mathematical basis for each model, including cell definitions and equations, are described on the accompanying pages.

Recent additions and improvements. May 19, 2000. Version 2.0 of Fluorescence Spectroscopy model; new grating model Grat2.wkz; Version 1.1 of Instrumental Deviations from Beer's Law. June 6: Version 1.1 of Multiwavelength Spectrophotometry and addition of 3-component model CLS3.wkz. June 9, Fluorescence version 2.1. June 11: addition of two new models to Multiwavelength Spectrophotometry. June 21: versions 1.2 and 1.3 of UV-Visible spectrophotometer. June 24: version 1.0 of Lock-in Amplifier. June 29: Version 1.0 of Dual Wavelength Spectrometer. July 9: Version 1.1 of Dual Wavelength Spectrometer. July 14: Version 1.0 of Wavelength modulation spectrometry. Sept 5: Version 1.1 of Wavelength modulation spectrometry.

Mac users: Shift-click to download complete set of models as a SIT file (500 Kbtes)

Note: It is best to download the complete set of models initially, then check back here occasionally for additions and updates, which can be downloaded individually. Put all the model files (.wkz files) in the same folder as your Wingz program. First launch Wingz (Wingz.exe), then open the desired model files from within Wingz.

Spectroscopy Instrumentation and methodology

Color Temperature of a Blackbody Source	Animated Diffraction Grating	Photomultiplier Light Measurement System

Error propagation in Analytical Calibration	Multiwavelength Spectrometry	Lock-in Amplifier	Wavelength modulation system

Molecular spectrometry

U.V.-Vis. Photometer	Dual Wavelength Spectrophotometer	Instrumental Deviations from Beer's Law	Fluorescence Spectroscopy

Atomic spectrometry

Signal and Photon SNR of Atomic Emission Spectrometer	Effect of Slit Width on Signal-to-Noise-Ratio	Line Wing Overlap	Spectroscopy of Atomic Absorption

Classical and electrochemical methods

Calcium Ion Selective Electrode model	Resolution of Capillary Chromatography	Discrete Equilibrium Chromatography Model

Triprotic Titration Data Analysis	Monoprotic Titration Curve model

What do the students have to say about these models?

How these models were Developed

These models were created using WingZ, an object-oriented spreadsheet with a built-in macro language that is available from Investment Intelligence Systems Corp. To use these models, you must have access to the WingZ 1.1 program (Windows or Mac version). However, no knowledge of WingZ is required to operate the models. The advantage of WingZ, as compared to more popular spreadsheets such as Excel, is that WingZ 1.1 requires much less computer capacity - needing only about 1 MByte of RAM and 700K of disk space to run. It's also faster than Excel on small, older machines. The models themselves are quite small - about 10 to 40K bytes each; several can be open at once if desired. The disadvantage of WingZ is that it is not Excel and hence is doomed to obscurity.

Why didn't I make these models as Java applets, so they would run directly on the Web pages? Two reasons. First, a Java-compatible browser requires a larger and faster computer than WingZ 1.1; you can run most of my models on those old 486's that are too slow for recent Web browsers. Second, and more important, my models are just spreadsheets, which much more easily modified by instructors. You don't have to know programming to make simple changes in a spreadsheet. Some of the following Web pages include specific suggestions for things that can be readily customized by the instructor.