REVIEWS
-- The chemlst& content was accurate. Some variation, as expected, in terminology of oroblem tvoe caused students same diffi-
ty was fairly uniform, and the program gives students many opportunities t o select correct responses. The program takes a tutorial and problem-solvingapproaeh. Studentsmust determine oroblem tvoe before oroceedine. Some stwients felt that two or three attemots and
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the entire list of choices in cases where they did not know the answer. On the positive side, students said: 1. "The computer program was very informative because i t covered so many aspects of equilibrium problems. Further the program led the viewer through a methodical, step-by-step approach to salving these types of problems". 2. "I found the informationof the computer very helpful as a whole". 3. "The program helped me realize the different types of problems. It was explained very well why the category I chose was wrone". 4. "Owrall I thrnk the program was helpful ill being a ~ ~ I y d iItdw. i l ~r r ~ I I ygmd on showing you why something wns \\rung. 1 really liked it". On the other hand, some comments reflected the negative aspects of the program: 1. "I found the program to be very hard to follow andextremelv timecansumine .
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this program as a Learning aid".
2. "You don't get a lot of practice on your own calculator". 3. "The lettering is an eyesore to read . and this is compounded with the flashing of the cursor or the running of (messages) a t the bottom of the screen. I found these factors extremely hard an the eyes. Further drawbacks included having to refer constantly to charts within the disk". 4. "You can't edit your values typed in. You have to "not confirm" and start over . choosing the correct definition for pH in each pH problem seems very redundant". 5. There was "much trial and error" in input initially. The class used this as a review for the final. I t was very time consuming-anywhere from two t o six hours for a disk. However, far the most part students felt i t was time well spent. Results on the final in the equilibria sections, while not statistically treated, seemed to be better than in previous years. The program is academically rigorous and pedagogically very strong. The comprehensive nature makes i t suitable for review and practice. The major drawback is that students are not forced to solve the problem before it is worked out. Marilee Murrav Glendale Community College 6000 W.Olive Glendale. AZ 85302
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A116
Journal of Chemical Education
Thin-Layer Chromatography D. L. ZellrnerandB. H. Gurnp, McGraw-Hill Book Company, 1221 Avenue of the Americas. New York, NY 10020 Hardware: Apple II family Components: One disk. Instructor's Guide. and Students Guide Level and Subject: College students with some background in thin-layer chromatography cost: $59.95
Review I Thin-Layer Chromatography is a simulatian program aimed a t students who are "familiar with the basic theory of thin-layer chromatography". The user is presented with an unknown mixture of five amino acids whieh must be identified through TLC. To aid in this effort the user has 10 known amino acids which may be mixed together, an unlimited supply of silica gel thin-layer plates, and three solvent systems. Reward for success is given in the form of a point system, based on the least number of plates used and the number of successful identifications. On the surface the program appears to be well conceived and well written, an impression whieh eventually fades. After numerous title screens, the program explains the use of the "Command Bar", an interesting menu selecting device that turns a one key stroke operation (typing in a number) into a slow, multiple key stroke operation involving the horizontal arrows and the return key. This gives the program a Macintosh appearance which is lost without mouse compatibility. The user is then presented with a menu consisting of choices between an "Introduction", "Complete Instructions", "Basic Instructions", and "Begin the Lesson". T h e "Complete Instructions" choice slowly brings up 21 pages of instructions that are more detailed than the manual. Initially i t provides the names and the standard three-letter abbreviations for the 10 amino acids used in the simulation. Structures for only alanine and asparagine are given as examples. The user should write these down, or better yet, have a separate source of abbreviations and structures. Once in the simulation, there is no quick way back t o the instructions, and returning to the instructions results in the loss of all choices and data achieved up to that point. The stationary phase is identified as silica gel and the structure is given. The three developing solvent systems are identified as ' 3 1 phenol/water, 3:l:l butanol/acetic/acid water [sic], or 2 2 1 ehloroform/methanol/ ammonia". The rules and the scoring system are also explained. Neither 1 nor the two junior chemistry majors who examined this program totally understood the rules. We
recommend that the user read the instructions, try a simulation t o examine its appearance and operation, and then go back and reread the instructions. Basically the user may mix combinations of the 10 known amino acids and spot a plate with this mixture. Up to five spots of such mixtures and/ or the unknown mixture may be spotted on a plate and developed by one of the three solvent systems. The developing of a plate takes from 30 seconds to three minutes but is supposed to represent several hours as shown by a digital clack. Updates of the solvent front and the separating spots appear every three seconds in real time. Once the solvent has reached the top of the plate, a scale then appears so that the user may record the distances that the soots have m o w d The user may then spot other plates, choosenm,rher wlwnt using thesame spot. orntrempt tuidantiiy theccmponentsofthe unknown mixture. ~~~~
Instructions read: The instructions emphasize that the program is not a tutorial, but it is a simulation. Simulation programs present the greatest potential for misuse in computer-aided instruction. They are particularly dangerous when used as suggested by this program "in place of a conventional laboratory experiment". Appropriate substitution of simnlation programs for real laboratory experiments may include simulation of dangerous, expensive or time-consuming experiments, or experiments whieh involve equipment not available to the user. Simulations of handling toxic wastes or explosives, or the simulation of HPLC where such equipment is not available are examples of appropriate applications. Simulation programs also may be appropriately used to prepare students for the real experiments. A program which will allow a student t o become familiar with the tuning process of an NMR, can make the actual time on this expensive instrument much more efficient. Thin-Layer Chromatography appears to justify its existence in terms of the fact that real TLC can be very slaw. Reducing a three-hour TLC to three minutes allows the student t o try many more combinations of spots and developing solvents than could be done in a real fourhour laboratow session. This reviewer takes exception to this, t ~ c a u s there r nrr numeruua fast and inexpensive chromntqwiphy t.xprrimpnts including such commmly used experiments as the paper chromato~raphy ot thc ink in felt trpped prnsand theTLC'uf analgesic tnhlets. In fact, our h~olomdepartment performs a TLC experiment on amino acids in their freshman labaratow. Ditferent solvent systems may be trird by dffercnt students and the results combinrd in a post laborarory dwusaiun. ~~~
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Summary Ratings: Reviewer
Categov East of use' Subject Matter Content: Pedagogic Value: Student Reaction:
I
Average Below Average Below Average Below Average
Reviewer II
Excellent Good Gwd Good
Even given the appropriateness of a simulation program, i t is important that the program simulate the experiment as realistically aspossihle. Thin-Layer Chromatography again scores low marks. For example, real spotting of a plate does not consist of amenu choice but involves dipping a capillary into the solution and touching the plate. Mast chemists remember how long it took t o perfect this technique. A good program should a t least animate this operation. Such animation was not beyond the ability of the programmers and the equipment, as shown by the rather elaborate animation used when depicting the addition of the developing solvent to the developing chamber. Agood simulation program should also show goodtechnique. In Thin-Layer Chromatography the developing of the plate is terminated by the program with the solvent front just one pixel from the top of the plate. The user should have the responsibility of terminating the developing after having been warned to do so hefore the solvent front reaches the end of the plate. Anyone who has done the TLC of amino acids also knows that amino acids are colorless and are only observable after visualization using UV sensitive dyes in the plates or visualizing sprays. Such visualization is done only after the developing is complete and the plates dried. Such realism is lacking in this simulation and leaves the userwitha very artificial impressionof what the experiment is really like. Even correcting these faults would still make the program of little value because of the availahility of simple, real TLC experiments. If only this program had simulated HPLC, an instrument usually not available in high schools and in sufficient quantities in many undergraduate departments, it might have been worth the effort. Many instructors may feel that the use of an arcade game-type reward system may he inappropriate for college students. Science has to be its own reward for those who plan tomake ittheir career. If anaward systemis used, it should be based on goad science and alsogive the user a true measure of his or her accomplishments. One of my colleagues scored 3000 points by guessing without running a single plate. This may appear t o he a respectable score, but i t is obviously not a reliable evaluation of the user's mastery of the technique. When I was a student, I was told that if a substance was t o be solely identified by retention times in gas chromatography, a minimum of three coincidental retention times on three different columns of three different polarities must be obtained. there must be a similar rule for TLC. Obtaining an identification of an unknown with so few plates is mare luck than good chemistry. As suggested by the authors, the program may also be used "to supplement classroom instruction in chemical separation methods". Here there is some hope if the instructor gives the students: the structures of the amino acids, emphasizes the acidic and basic properties of the amino acid side groups and the effect of the neutral, acidic and hasic solvents on the charge of these side groups, and then explains the resulting interaction of the amino acids with the stationary phase. Converting the program into a tutorial with the snme instructions would make i t a much more useful product. As it stands now my reaction to this program is partially illustrated by the reaction of my
two students who tested it. They said that they had fun using the program, but when asked what they had learned from the experience, they responded with t h e word "Nothing". On closer reflection, I am afraid that they might have learned the wrong things ahout the TLC of amino acids. D. 6. Dahlberg Lebanon Valley College Annville. PA 17003
Some students will be confused by some nonstandard abbreviations for amino acids. For example, this program uses TRY as the abbreviation for Tryptophan; whereas, some teats use TRP. The chromatograms seem to be accurate with respect to Rrvalues obtained. The program could have been enhanced by allowing the student to recall chromatograms to the screen after reoortine the results. The soots on the olatec&d ha& been labelledsothat -~~~~~ the student could analyze his ur her method and discover any errors m logic. This could take considerable time if the chromatograms were t o he redrawn again, but perhaps the chromatograms could be stored in temporary files as graphics displays. This could also be utilized before the reporting of results so that the student could review the d a t e s in arrivine a t a conclusion. Most student? tended to adapt tu the software and drcw sketches of the plates on paper before spotting their next plate. Animation of the movement of the solvent and spots could have enhanced the realism of the software. The program would handle all possible inputs without "bombing". The user interface was one of the best that I heve seen in CAI packages. Most of the inputs were from menus or a command bar a t the bottom of the screen. The left and right cursor keys were used t o highlight the desired action. The only key which causes adverse results is the reset key which causes the program t o reboot. The program does not recognize the vertical cursor keys hut uses the left and right cursor keys t o highlight vertical menus. Apparently this was done t o preserve compatibility with the Apple It+. Allowing the use of the vertical cursor keys in addition to the left and right cursor keys wmld have lreen a nice feature. The softuare was pro\,ided on a i n g l e 5 ' , in. floppy disk. There was no hackup disk. and th&e were no instructions on how to acquire another copy if the original failed. The disk was copy protected. The instructor's guide did not mention anything about a warrany. I t was five pages in length, while the student's guide consisted of two pages. These guides and disk were supplied in a protective, padded booklet. The lack of printed instructions was more than made up for with instructions on the disk. The menu consisted of three screens of Instructions, 21 screens of Complete Instructions, and seven screens of Basic Instructions. The three screens of instructions dealt with how to use the disk. The Complete and Basic Instructions consisted of both a full and a n abbreviated version of instructions in the methods of TLC. This would help a student review the techniques, but it does not claim t o he a tutorial. The user interface was very well done. The top of the screen told which page of instructions was being viewed and how many pages were in that section. The student always bad the option of going back one or more screens or exiting to the main menu. The writen instructions on the screen were very easy t o read. Rather than the normal Apple text mode, the large lettering was done in the graphics mode. The display was well designed for either monochrome or color. A color monitor would not be a necessity. The software allowed for turning off the sound, which was
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Review I1 This software package is designed toMgive students practical experience in a thin-layer separation". The format is a simulation in which i t is assumed that the students have background in the principles of TLC. The student can practice the concepts of TLC usine the software with a minimum exoend l t u k of time and money. One 1'I.C plate can be spotted and dweloped in under three minutes. This prorers can he repeated as many times as necessary. The software eompresses time t o enable the student to do a thorough investigation and develop better competency in TLC procedures through repetition. The processing of a large number of TLC plates is often not feasible in academic lab settings because of the time and materials required. The student is assigned an unknown containingfive aminoaeids. Students are t o use TLC to identify these amino acids from a list of 10 amino acids. They can place up to 10 samples on a spot and up t o 20 samples total on the five spots allowed per plate. The three solvents nrovided are (A) ohenol and water, ~ B butanol I and acetw a c ~ dand , (C, rhlon,furm and methanol The computer draws the plate on thesueen and s h o w the spots. The time is compressed and shows "snapshots" of the plate a t what is reported as one-hour intervals for four hours. The rate of this time compression depends upon the number of spots. For most tests on a n Apple IIc, the total time for simulation of the development was less than twominutes. The student can switch plates, solvents, andlor amino acids in repeating the test as many times as desired. The student reports the amino acids that he or she thinks are present, and the computer identifies each of the 10 amino acids as either present or ahsent. Points are awarded on the basis of the number of amino acids correctly identified as well as the number of plates used. No provision is made for the recording of points for a grade either on disk or in printed form. The amino acids included in the samples are alanine, serine, asparagine, cystine, threonine, phenylalanine, glycine, tryptophan, glutamic acid, and leucine. The selected amino acids are well chosen in that they are representative of the different typesof aminoacids. The program would he more useful if more of the amino acids had been included as possibilities in the unknown. I t would have been more representative of the normal academic laboratory if there had not always been five amino acids in the unknown. Differing points could have been awarded as levels of difficultv varied depending on the number of amino.acids in the .... unknown. . . The reporting of the results ra done by using the cumor to highlight threr-letterabbre\,inticrnsfor the vnriuusaminoncids The program allows the student t o change selections until the word DONE is selected. ~~
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Volume 65
(Continued on page A118 Number 4
April 1986
A117
