A Sensual Demonstration of Gas Chromatography We have recently conducted a. series of lecture, demonstration, and laboratory sessions with selected secondary school students.' A part of one of these sessions, devoted to organic chemistry, has been to demonstrate modern separation and analytical methods commonly utilized by organic chemists. I t is unfortunately easy to show operating instruments with countless glittering knobs which are too remote from the students experience to hold their interest or even effectively illustrate the point. In particular, a demonstration of gas chromatography for the separation and snalysis of organic compounds is unrewarding from a student interest standpoint. In an attempt to make this demonstration more memingful we have done the following demonstration: First, a fairly small sample of a mixture of n-pentyl acetate, bensaldehyde, and camphor (1: 1: 1mixture) was injected into agas chromatograph and the separation indicated by the usual recorder presentation of the output of a thermal conductivity detector. Next, a massive sample' was injected and a fan', positioned a t ttheexit port and directed toward the audience, was turned on. The emergence of each compound from the column is then shown not only by the recorder deflection, but also very vividly by the characteristic smell of each compound. We have been able to aromatize an elevated lecture hall capable of seating 120 students. A nearly unanimous response from participants was achieved. I t should be pointed out that although the bensaldehyde and camphor were not separated as shown by the recorder when using the massive sample, there was s sharp odor boundary as the two components were eluted from the column, Uustratiug the advantage of a specific detector over s. universal detector. A more complex mixture of materials would be more impressive, although it is important to select compounds thrtt are not persistent. The success of the experiment, particularly on a high school level, is enhanced if compounds are chosen with which the students have some associat~on,i.e., benzaldehyde and cosmetics. Like many lecture demonstrrutions, this demonstration can be pure entertainment, the scientific value rests with the correlation between the demonstration and the lecture.
' Science training program far high ability secondery schwl students sponsored by the National Science Foundation. At Rice the selection of Participants has been from grades 9 through 12. 21njectionof 0.j-1.0 ml of the mixture into s a/-in. X S f t Cerbow.~column has been successful. A Cole-Palmer heating gun set to emit a cold air stfeam is satisfactory. E. S. LEWIS M. M. BUTLER W. E. BILLUPS
Volume 48, Number 6, June 1971
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