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2007
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In the Laboratory
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Quantitative Comparison of Three Standardization Methods Using a One-Way ANOVA for Multiple Mean Comparisons
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Russell D. Barrows
Department of Chemistry, Metropolitan State College, Denver, CO 80217
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May 2007
Vol. 84 No. 5
p. 839
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| Abstract |
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The use of an external standard calibration curve, standard addition, and internal standard methods for quantitatively determining the concentration of analytes is important to the study of analytical chemistry, especially in the area of instrumental analysis. To give students exposure to these methods in a non-traditional, guided-inquiry exercise that can be performed in a single laboratory period, the experiment reported here asks students to determine the concentration of three long-chain hydrocarbons by all three standardization methods using an experimental procedure of their own design by gas chromatography (GC). To persuade students to compare and contrast the experimental requirements of the three standardization methods, they are given only ten GC vials and a single unknown sample containing the three paraffin analytes. Although the students do not know the concentrations of the three analytes in their unknown sample, they do know that each of the three standardization methods should generate similar values for each analyte because they are given a single unknown sample. To test whether they have been successful, the students perform a one-way ANOVA statistical analysis on their results to see if the null hypothesis should be accepted or rejected.
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| Supplement |
The following materials are available:
i) The instructional handout given to students, which gives a simple explanation on how to perform a one-way ANOVA analysis using Microsoft Excel, and use of the Tukey multiple-comparison method; ii) one-way ANOVA analysis with a student's data that does not reject the null hypothesis; iii) A mathematical description of a one-way ANOVA analysis using the lab data shown in Table 1; iv) Appendix A gives individual steps from standard and unknown sample preparation to the final one-way ANOVA analysis, including steps for calculating the concentrations of the three analytes by the three standardization methods.
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| More Information |
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Citation |
Barrows, Russell D. J. Chem. Educ. 2007, 84, 839.
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Keywords |
Alkanes / Cycloalkanes; Analytical Chemistry; Gas Chromatography; Hands-On Learning / Manipulatives; Inquiry-Based / Discovery Learning; Laboratory Instruction; Quantitative Analysis; Statistical Mechanics; Student-Centered Learning; Upper-Division Undergraduate
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History |
Created:
Last Updated: |
3/22/2007
3/27/2007
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 Caution! | | Experiments, laboratory exercises, lecture demonstrations, and other descriptions of the use of chemicals, apparatus, instruments, computers, and computer interfaces are presented in the Journal of Chemical Education as illustrative of new or improved ideas or concepts in chemistry instruction and are directed at qualified teachers. Although every effort is made to assure and encourage safe practices and safe use of chemicals, the Journal of Chemical Education cannot assume responsibility for uses made of its published materials. Many chemicals are hazardous. Precautions for the safe use of hazardous chemicals and directions for their proper disposal are described in the Material Safety Data Sheets and on the labels. We strongly urge all those planning to use materials from our pages to make choices and to develop procedures for laboratory and classroom safety in accordance with local needs and situations. |
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2007
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May
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839
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