Research Projects for Undergraduate Students A More Rewarding Approach to Analytical Chemistry Courses Victor Demczylo, Jorge Marllnez, Arlene Rivero, Eleonora Scoseria, and Jose Luis Serra Facultad d e Quirnica. University de la Rephblica. C.C. 20061, Montevideo-Uruguay Students who take analvtical chemistry courses, especially a t the beginning of their training, tend to accept the analytical techniques that are handed to them, without trying to find out whether they are working in optimum conditions or whether they are using the best possible analytical procedure. Formal teaching methods, such as lectures, demonstrations, and laboratory experiments have (in general) proved inadequate, both in solving this problem and in obtaining from students the desired degree of motivation. As an alternative, a group of analytical chemistry, statistics, and computing professors formed a team in order to test a different methodology to be tried out on an experimental basis, followed by the evaluation of its results. This new methodology intended t o cover both the theoretical and practical aspects of the subjects under consideration, introducing a t the same time the principles and concepts that support scientific research and integrating those subjects that constitute useful analytical tools. These subjects had heen in nrevious courses that isolated them from a . - -studied practical application to chemistry; this approach had not nrovided sufficient motivation, and therefore learning ahout ;hem became simply a curricular obligation to the students. General Aims of the Project A group of students was given a research project covering one of the areas developed during "formal" quantitative analytical chemistry laboratory courses. The project was chosen so as to become important enough to insure the students' full commitment. The first group was asked to optimize an analytical procedure in everyday use in pharmaceutical and industrial areas that had heen found to present several nrohlems if not carried out under very controlled conditidns. I n a meeting with the teachers in charge of the .oroiect. " . students were told the difficulties generally found in the application of the technique without any recommendation as to bibliography or practical approach. This insures that students will be faced with the need to carry out a thorough bibliographic search with the following advantages. ~
(1) They willlearn to handle specialized literature and the mechanics of research and communiration. 12) While scannrng all the avarlable information in order to select the useful items, they willolrtain a wider throret~calknowledge of the subject. (3) They will have to choose the most adequate procedure, hearing in mind: availahle time, available materials, costs, and operational difficulties. Once they have chosen a certain technique, the group will start a pilot test a t the laboratory, thus coming face to face with the difficulties of putting into practice a procedure that has been described in the literature. This will bring them to the optimization stage, doubtless the most fruitful, where in order t o achieve the right planning of experiments, they will have to make use of statistics and computing as invaluable auxiliaries to their work.
' Box, G.: Hunter. S. SraNstlcs for Experlmenfers: An lntrodudlon to Design Data Analysis and Model Building. Wiley: New York. 1978. 048
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Statistics as a Tool of Analytical Chemists The need to choose an adequate design for the collecting of experimental data has been emphasized especially in the last 10 vears.' This need becomes even more pressing when the maximum information must he obtained &om a reduced set of data (costs and time factors must be taken into account) and the information must be significant. I n order to allow a correct incorporation of statistics as a tool of the analyst, this project must enable students to realize the following. (1) Every process is affected by a certain variability; the sources of
the data dispersion must be identified and the dispersion estimated in order to establish the significance of results as compared to this variahility. (2) Variability can be estimated only by means of repetitions of measurements, provided the latter are genuine. For instance, students must take into account that the experimenter's influence must be controlled, in order to prevent the overestimation of variability (especially when several experimenters are involved). (3) A correct estimation of variability implies keeping controlled conditions. Nonrandom variations, if correctly controlled will contribute to increase (erroneously) the estimated variahility. This must he prevented by means of an adequate experimental design. (4) Any statistical procedure is based on certain hypothesis on which the validity of the procedure will rest. Analysts must realize fully that statistical methods cannot he applied indiscriminately to any given set of data. Besides, any method implies a correct randomization of measurements. For instance, if repetitions of a given measurement are carried out consecutiveIv. . ~,.the exoerimenter mieht become biased. In eeneral.. analvsts tend to expect measurementr to agree, u,hich could result in too low an esumatron of variability. ( 5 ) Preliminary exyerimenrs are necessary t u study the significance of different factors on the process of measurement. (6) Analysts cannot expect statistical methods to validate badly collected data or to create information that experimental results do not contain. ~~~~
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Computing as an Auxiliary to Analytical Chemists Nowadays, computers allow calculations to he carried out in a matter of seconds. However, their use can result in several bad habits. (1) Design might he overlooked and reality hecome oversimplified
and sacrificed to the ease with which calculations are carried out. (2) Students might come to regard computers as a "black box" without devoting attention to its functioning, constituting parts, and the way a program works. (3) The great computational ease might lead to incorrect handling of data. In order to ensure a fruitful use of computers in this kind of project, the following aspects must be taken into account. (1) The understanding of the basic aspects and the theoretical basis
of the method in use, together with its risks and limitations, must he of paramount importance. (2) During preliminary operations, the performance of manual calculations should be encouraaed so that students will value the importance of computers and reinforce their knowledge of the operations implied hy the utilization of the method.
(3) Users should he encouraged to build their own programs, with
indirect support from their teachers, in those areas which might "rove too difficult for them. This will enable knowledee - from computing courses to be incorporated into the project and will guarantee the flexibility and usrfulneas of the program. 7~
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Punlng the Idea Inlo Practlce Three students from a group of 20, were chosen for a test of the idea. These students were allowed to work without direct supervision; therefore, a condition for their eligibility was a minimum practical ability. The group was informed of the problems observed in the complexometric titration of calcium: endpoint visualization and problems of pH adjustment. We shall outline this first project. Bibliography The group consulted approximately 20 different sources, investing about 25 h and concentrating on Kolthoff and Elving's Treatise on Analytical Chemistry, Schwarzenbach's Complexometric Titrations, Box's Statistics for Experimenters, and Chemical Abstracts, Analytical Abstracts, Analytical Chemistry, The Analyst, and Anal. Chim. Acta. This represents an increase of more than 100% over the number of sources resorted to by average students in quantitative analytical chemistry courses. In general, Chemical Abstracts and iournals are not consulted systematically during basic couries. The teaching staff considered the choice of papers and specialized literature to he more than adequate. This shows that the group developed their own selection criteria fan infreauent outcome durine "formal" courses where students --~-confine themselves to recommended bibliography). I t mieht be areued that the moup might become specialized in-a restricted area whi6 missing the more general asoects of the subiect. However, this is highly improbable since their development of the right criteriafor approaching anv. problem while a t the same time applying a basic proce. dure (i.e., titration), will enable them &analyze more elaborate problems from the same scientific point of view. ~
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tionable value in a scientific training are generally difficult to achieve through traditional courses. Optimization For a preliminary screening, students chose as their experimental design a complete factorial, since i t is useful to obtain all the oossible combinations of treatment together with repetitions. Besides, this design provides an estimation of exoerimental error and the significance of interactions. oper&ors, indicators, and concentrations were the factors included. Number of levels: three for each factor. Number of repetitions: three. Flrst Experiment Statistical analysis of the data obtained in a first experiment showed a high significance for every factor and their interactions, except operator, which was significant a t 5% hut not a t 1%.Since sienificance from this latter factor could he explained due to dzferences in the interpretation of some stens of the techniaue under studv, the different stwes of thLprocedure were discussed. ope&rs were found todiffer in color change visualization, amount of indicator used, and titration rate. However, the significance of concentrationoperator and concentration-indicator-concentration interactions were totally unexpected, since they would lead to the conclusion that results are influenced by the calcium concentration in the sample. As a result, the group decided to repeat the experiment, correcting the differences in the application of the analytical technique and stressing the importance of a complete randomization of the samples, a factor that had been somewhat overlooked in the first experiment.
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Test Experiment According to bibliography and reagents availability, the group selected three indicators-Murexide Calcon, and Calcein. Taking into account the fact that natural as well as industrial products normally contain magnesium ions, calcium titrations using EDTA were carried out a t pH = 12, thus insurine the complete precipitation of magnesium as
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The application of techniques described in the literature to calcium solutions showed that (1) the use of KOH or NaOH in order to adjust pH values was not indistinct; and (2), since solutions were not buffered, there were considerable pH variations during the addition of the titrating agent. This led to oremature endooints. Once these problems had been realized, the group followed pH variations during titrations potentiometrically and solved the problem by adding to the sample an experimentally estimated amount of alkali so as to compensate for the acidity introduced during titration. ~ h u s , - t o w a r dthe titration endpoint, the sample reached pH = 12, and premature endpoints were effectively eliminated. This staee allowed students to see for themselves that those techniques, which seem so straightforward and easy to carry out when read in bibliography, frequently present various problems and require optimization. The group of students was followed periodically by means of discussion .~~-~~~~~~ sessions. Their attitudes chanaed visiblv during the project and specially after the test experiment: hey became more motivated and more critical. They no longer accepted the literature a t face value. These traitsof unques~
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Second Experiment
This trial showed significance for the factors of indicator and calcium concentration, with only small indicator-operator interactions, which might be interpreted as a preference on the part of operators for certain indicators, probably due to better endpoint visualization. Finished Procedure Once the different factors affecting the analytical technique had been evaluated, and the pH adjustment problems solved, the group presented a successfully used optimized technique. Dlrcusslon The project we have proposed proved highly satisfactory. The group of students who undertook the first trial are now finishine their studies a t this universitv and have more than once stkssed the importance of this project in handling of literature sources.. exoeriment olannine. . -. and reoort writine. " But above all, it is important to point out their dedication, since thev soent about 90 h. without curricular obliaations. Besides, thLy learned the importance of real team aork, a fundamental aspect of serious research. This does not imply that individual laboratory experiments should be eliminated; indeed, they should be a part of the basic training. We suggest team work on a project as the culmination of formal courses. Thus, students will learn to interact and to work together toward a common goal. This aspect will be of paramount importance during their professional activities since interdiscinlinarv team work is nowadavs considered vital. A formal ex& of the subject revealeb. their solid theoretical knowledge, and their performance at the laboratory reflected their gain from the project. Data processing improved the knowledge acquired in formal computing and statistics courses. Doubts that arose during the project led the group to further bibliographic search and to consultation with their professors. Evidently, in order to participate in this kind of project, Volume 67 Number 11 November 1990
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students must have a minimum general knowledge on which
to build. As a result, far from eliminating formal teaching methods, projects should become complementary. In this specific case, the project was proposed to second-year students who had completed qualitative and quantitative analytical chemistry as well as statistics and computing courses. However. we do not dismiss the annlicabilitv of this kind of approach a t higher levels and f o i k y Experience bas shown that a oroiect can be advantaeeouslv substituted for the majority oifoimal tests. In thelast decades, education has tended to become polar-
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ized, toward either the excessively practical or theoretical. None of the polea seems to be the answer and education is apparently failing to stimulate the student's curiosity and to help them shape their own criterion. These two factors will no doubt become fundamental in their professional performance. Every great scientific achievement has implied a large amount of dedication, creativity, curiosity, and self-criticism. Our educational process should aim a t producing scientists with those main characteristics. We believe projects might be one of the means to achieve this.
