SpecUV-Vis is a Windows compatible computer program that simulates an ultraviolet (UV)-visible spectrophotometer (1-4) with a wavelength range of 350 to 750 nm. The program has two operational modules.

The Single-Beam Spectrophotometer (SBS) Module (see Fig. 1) enables the user to make separate absorbance or transmittance measurements at 1-nm intervals within the wavelength range of the simulated instrument. The procedure for operating the SBS Module mimics that required for most single-beam instruments. The user must switch on the light source, select the wavelength, set the transmittance zero reading, use a reference to set the absorbance zero reading, prepare a sample, and place it in the instrument to make a reading, not forgetting to close the cover of the cell compartment before taking the reading.

Figure 1. The Single-Beam Spectrophotometer (SBS) Module

The Double-Beam Spectrophotometer (DBS) Module (see Fig. 2) enables the user to scan through the entire wavelength range of the instrument and produces either an absorbance or transmission spectrum of the selected sample. Data are recorded at 1-nm intervals and the displayed spectrum can be saved as an ASCII data file for import into a suitable graphics program such as Microsoft Excel. Both modules incorporate a Sample Preparation Area (SPA) that contains five acid-base indicators: thymol blue, methyl orange, bromophenol blue, bromothymol blue, and phenol red. The concentration and pH of a selected indicator can be varied and the software reproduces accurately the color of the indicator under the set conditions.

Figure 2. The Double-Beam Spectrophotometer (SBS) Module

The instruction manual that accompanies the software includes:

• Detailed notes for using the simulator.
• Background information on UV-visible spectrophotometry and instrumentation.
• Suggested exercises for each module.
• Notes for instructors that relate to the exercises.

The software and its accompanying manual can be used to illustrate the recording of an absorption spectrum and the Beer-Lambert law (5-7) as well as various aspects of acid-base indicators such as the spectrophotometric determination of pK_a (8), the isosbestic point (6, 9), and distribution diagrams (10, 11).

Literature Cited

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3. Piepmeier, E. H. J. Chem. Educ. 1973, 50, 640.
4. Lott, P. F. J. Chem. Educ. 1968, 45, A89, A169, A182, A273.
5. Skoog, D. A.; West, D. M.; Holler, F. J. Fundamentals of Analytical Chemistry, 7th ed.; Saunders College Publishing: Fort Worth, TX, 1996, Chapters 22-24.
6. Christian, G. D. Analytical Chemistry, 5th ed.; Wiley: New York, 1994; Chapter 14.
7. Kennedy, J. H. Analytical Chemistry--Principles, 2nd ed.; Saunders College Publishing: New York, 1990; Chapters 11,12.
8. Patterson, G. S. J. Chem. Educ. 1999, 76, 395.
9. Harris, D. C. Quantitative Chemical Analysis, 5th ed.; Freeman: New York, 1997; Chapters 19, 20.
10. Butler, J. N. Ionic Equilibrium--A Mathematical Approach; Addison-Wesley: Reading, MA, 1964; Chapter 5.
11. Sawyer, C. A.; McCarty, P. L.; Parkin, G. F. Chemistry for Environmental Engineering, 4th ed.; McGraw-Hill: Singapore, 1994; Chapter 4.