Introduction of mass spectrometry in a first- semester general chemistry laboratory course. 6
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ABSTRACT : An experiment has been developed to introduce first-semester general chemistry students to mass spectrometry. Students analyze water samples contaminated with a known compound, either DMSO or MTBE. Students are asked to determine the concentration of the compound in the water. In performing this experiment, students should learn (i) how the mass of an atom or molecule is determined, (ii) the effect of the presence of different isotopes on molecular mass, (iii) the role of an internal standard, and (iv) how mass spectrometry is used in answering various scientific questions. The ratio of the area of the peak generated by the contaminant over the area of the peak generated by the internal standard is plotted against the known concentration of the contaminant in the standards. The standard curves students typically produce on graphing software are quite good (R2= 0.99 or better). Students determine the concentration of the contaminant in the unknown sample algebraically using the equation for the best-fit line. The experiment involving MTBE has been used as part of a guided-inquiry activity in which students are presented with a hypothetical scenario involving the sudden decline of a waterfowl population.
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Mass spectrometry.;Isotopes.;Nuclear reactions. --------20--