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HOWARDSTROEBEL Duke University Durham NC 27706
Applications of Autosampling GC-MS in an Introductory Organic Chemistry Laboratory Gary L. Asleson, Marion T. Doig, and Frederick J. ~eldrich' College of Charleston, Charleston, SC 29424 Feature Editor's Note: Tn s account ofthe benefa ai resd tsof
ntrooucing complex lnstrdmentatlon n a slmpie way nto a beg~n-
nmg organlc chern stry laboratory oeserves attention as an am-
I aginative and, I believe, pedagogically sound innovation.
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Autosampling has obvious advantages for industrial laboratorie~,but the application of autosampling technology for the undereraduate curriculum has been lareelv overlooked (I).1n;his paper we will describe our use of an autosampling GC-MS system and discuss the pedagogical advantages that autosampling atfords. Our applications of an automated GC-MS instrument have been in the introductorv " oreanic laboratorv " seauence. the biochemistry laboratory, instrumental analysis, and stndent research projects. -
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Advantages of Autosampling in Large Classes In each case. the ~ r i m a r vadvantaee of autosam~line over manual iijection is thit it allows a large numder 07 individual students access to GC-MS instrumentation who would otherwise (in the case of manual injection) never have such exposure. In our introductory organic chemistry course wehave average enrollments o? 165 students in the firs&semester laboratory and 110 students in the second-semester laboratory. We also have off-sequence sections (i.e., second-semester laboratorv in the fall and first-semester laboratory in the spring) 90 that the total number of organic laboratory students in any one semester can easily exceed 200. This situation is clearly different from what might be encountered in a smaller liberal arts institution where having fewer students could make hands-on experience less onerous. It also is different from that of laree universities where ereater resources (space. . . , personnel, and instrumentation, usually are available ta handle the lurlrer student load. Yet. our situation is neither unique nor a sufficient reason to deny students the use of so~histicatedchemical instrumentation in problem-solving exercises. The instrument time that would be needed to provide all students individual access to a GC-MS can be estimated from the time for a sample injection, analyte retention times, and the recycle time needed between injections, assuming a ramped temperature program. With a relatively short 12-m column, modest final temperature of 200 'C, initial temperature set just below the boiling point of a common solvent, and average retention time of 3-8 min, a
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'Author to whom correspondence should be addressed. A290
Journal of Chemical Education
reasonably optimistic time for each stndent would be 15 min. With a 30-m column, the time would be much longer. This conservative estimate assumes that the student has prior experience with syringe technique, and that the stndent will not take up instrument time during laboratory hours for data manipulation. In a lab of 22 students the total time required would be about 5.5 h, and with 3-h laboratories, two instruments would be required. In addition the instructor would need to be available simultaneously in the wet laboratory and at the GC-MS to assist students in its use. For institutions without maduate assistants or unlimited budgets, these problems Gight preclude stndent use of a GC-MS at the introductorr level. were it not for the availability of antosampling. A com~elline~edaeoeicala m m e n t also can be made for the use bf auGmate2 & u m e n t s . Many modern instruments are viewed as "black boxes" that awe students without presenting an opportunity for teaching principles. Jones (2)stated that modem instruments are designed by manufacturers for operation "by a technician in an industrial lab who may need to run hundreds of samples daily; the instrument is designed to simplify his task. The result is a 'black box' arrangement." In a related paper, Hams and O'Bnen (3) contended that where the mission is education of a chemist, and not the training of a technician, that the appropriate focus for use of chemical instrumentation should be on principles and analysis assessment of methods, rather than on the training for use of a specific instrument (e.g., Hewlett-Packard GC-MS or a Perkin Elmer GC-MS). We concur with the opinions of Jones and Hams and O'Brien. Our application if automated instrumentation for introductory students takes advantage of designs that were intended primarily for industrial, high volume, low maintenance use. By having students focus on the interpretation of data obtained by various methods of using a GC-MS, we turn the "black box" into a "data generator". It is neither necessary nor practical to train intmductory stndents on the operation of a GC-MS in order for it to serve a useful pedaeoeical function. In each application d&ribed below the student is res~onsiblefor ore~arinehis or her sam~le.loading it in a sample tray, ie~oiding~ertinent data i n log sheet, and analyzing the data generated from the sample. The instructor loads the sample tray onto the antosampler, and initiates its operation for the problem at hand with a preprogrammed, optimized method. The total amount of time . spent by the student on data collection is less than five minutes, the time spent by the instructor for the class of
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topics in chemical instrumsntcrtion students is less than 15 minutes, and can be reduced even more if the students log in their samples into the sequence log table on the GC-MS computer. We have found that i t is easy enough for the instructor to generate the log table without burdening the students with this task. We also have found that nearly all of the students want to watch the instrument in operation and that a few of the more motivated students want to see how the data can be manipulated 'manually' by the operator. Such interest is accommodated easily on a formal or informal basis by the instructor.
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