Chemical Education Today edited by
NSF Highlights
Susan H. Hixson
Projects Supported by the NSF Division of Undergraduate Education
National Science Foundation Arlington, VA 22230
Curtis T. Sears, Jr.
New Quant: A Quantitative Analysis Laboratory Curriculum Using an Analyzed Complex Matrix
Georgia State University Atlanta, GA 30303
R. Cameron Dorey,* Jeffery A. Draves, and Conrad L. Stanitski Department of Chemistry, University of Central Arkansas, Conway, Arkansas 72035; *
[email protected] New Quant is a project to introduce students to issues faced in contemporary analytical chemistry in the laboratory portion of the quantitative analysis (“Quant”) course by utilizing an analyzed complex matrix (ACM). At this point in a student’s experience, the “wet” chemistry involved in chemical analysis is usually emphasized in the course. The laboratory courses in common use today can be described as “traditional” and “naturalistic”. Each of these has advantages and disadvantages, and our ACM laboratory design is intended to maximize the advantages. The traditional quantitative analysis laboratory samples typically contain high concentrations of a single analyte in an inert matrix, and the experiment consists of dissolution followed by a titration, precipitation, or one-step instrumental analysis. Although the laboratory experiments emphasize analytical precision and the “wet” chemistry involved in the particular experiment, the experiments themselves by and large do not resemble what a student is faced with after he or she graduates. “Real-world” samples require varying degrees of preanalytical preparation to convert the sample into a physical or chemical form that is readily analyzed, to remove or mask interferences, and to adjust the concentration of analytes to fit the analytical technique. Other common characteristics of real-world samples not simulated in typical laboratory samples are that they may contain more than one substance for analysis, and the sample size may be limited. The traditional samples are still widely used, however, because they provide the instructor with the “true value” of the analyte concentration, which can then be used to judge student technique. One method for addressing these deficiencies in quantitative analysis is to use consumer products, water or soil samples, industrial products, or similar materials for analytes. This scheme has the advantage of simulating for the student the complexity found in real-world samples, but does not provide the instructor with the “true value” for the analyses. A common technique for grading an experiment involves averaging the student determinations and taking this average as the “true” value. This has merits, but is flawed when the analysts are students attempting the particular analysis (or any analysis) for the first time. Not only may large errors arise from unfamiliarity with the analysis, but the average of the results may be highly skewed owing to unknown interferences in the analyte matrix. Our solution to this problem involves using a complex matrix, which has been professionally analyzed, in order to
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simulate a real-world sample. The sample/matrix we have chosen is the clinical control serum used in laboratories to calibrate instruments and perform quality control. This matrix has a mixture of inorganic and organic ions, hydrophobic and hydrophilic organic molecules, and enzymes and other proteins, available at two or more levels per analyte. This enables us to assay a much larger variety of analytes than is normally available. Our laboratory procedures have been adapted from manual procedures used in clinical laboratories, so that the chemistry behind working analyses can be studied by the student through the experiment. Most of the analytes found in this matrix are present at fairly low concentrations, so most of the experiments use instrument-based detection; however, only a spectrophotometer and a potentiometer are required. Modern spectrophotometers and potentiometers are easily interfaced to a personal computer for data acquisition (often through a serial port), which opens the possibility of computer-aided data acquisition. We are using Labview (National Instruments) for acquisition; data reduction is performed using one of the common spreadsheet programs. Using a biologically derived matrix also enables us to emphasize safety considerations, which are important with this kind of material—a point not often made in undergraduate chemistry laboratories because most work is done with synthetic substances. The experiments have a significant advantage over the traditional experiments in that they elicit much more enthusiasm from the students because of both the relevance of the sample and a reduced level of tedium in the analytical technique. They also have the advantage over naturalistic experiments that there is an accepted value for the analyte. This enables the instructor to use the students’ accuracy for grading purposes and to determine when an analysis is adversely affected because of reagent or instrument problems. More information on the project can be found on the World Wide Web at http://chemistry.uca.edu/Projects. By June 2000, publication of a laboratory manual containing the experiments is anticipated. Acknowledgment This work was partially supported by a grant (DUE 9650845) from the National Science Foundation, Division of Undergraduate Education, Instrumentation and Laboratory Improvement Program.
Journal of Chemical Education • Vol. 76 No. 6 June 1999 • JChemEd.chem.wisc.edu
