Symposium: Present Status of the Teaching of Analytical Chemistry Analytical Chemistry in an Integrated Laboratory Sequence Kyle E. Dolhow College of William and Mary Williamsburg, Virginia 23185 Within the last decade there has been considerable interest within undergraduate chemistry departments in changing from the traditional course-associated laboratories to a separate and integrated lahoratory program, representing all areas of chemistry. The integrated laboratory cuts across the traditional boundaries of the classical subdivisions of chemistry to allow for experimentation which more closely reflects the interdisciplinary nature of current chemical research. Such a program could also eliminate the sometimes trite and selfcontained exneriments often found in the traditional course-associated laboratory, and students could build a more flexible laboratow bv choosing among- advanced . exnerience . experiments in several areas. The role of analvtical chemistrv in a totallv integrated lahoratory is illustrated-by the weli-established proeram at the Massachusetts Institute of Technology. chemistry majors complete four semesters of the integrated laboratorv course which begins the first semester of the second year andconsists of five hours a week in the lahoratory. The following three semesters each require ten hours a week. Associated lectures for two hours a week with each lahoratory course cover discussions of general information and explantions of specific points on each experiment. Although a given group of experiments performed in a prescribed order by every student is required in each course, a variety of experiments is offered from which the student can choose several to comnlete the course. Durlng thr four semesters of lahoratory the students perform 3 w~deselection of both class~calwet anslgirnl methods and modern instrumental methods. In the first semester, for examole. the following experiments are performed: the equivalent weight of an unknown carhoxylic acid is determined by acid-base titration with a visual indicator and its pK, determined by potentiometric titration; the amount of cholesterol in a crude solid is determined by derivatization and quantitative visible spectroscopy; the yields of various products produced during the acetylation of ferrocene under different conditions are analyzed by quantitative high pressure liquid chromatography; and the analysis of student-prepared tris(ethylenediamine)cobalt(III) chloride is made for both cobalt, by cation exchange and subsequent acid-base titration, and chloride. hv the Faians ~recipitation titration method. . . . In the succeed& semesters orher annlvtical techniques i n tnxlwed include both qualitative and quantirari\.e uses of ir, nmr, uv and mass spe&oscopy, esr, gas chromatography, thin-layer chromatography, liquid-liquid extraction, spinning band distillation, polarography, cyclic voltammetry, and basic electronics.
From the above listing i t is apparent that there need be no lack of analytical methodology in an integrated lahoratory sequence. The question, then, concerns the exact nature of the way analytical chemistry is presented within such a framework. Mere use of a wide selection of analytical techniques is not trainine for a orosoective analvtical chemist nor does it . . accurately represent what practicing analytical chemists do. Analvtical chemistrv is a orohlem solvine". nrocess which has a definite pattern involving much more than simply pushing a series of buttons in the correct order and copying a number from a digital readout. Important steps along the way in an analysis include, for example, such questions as whether a representative sample has been obtained, and how the sample can he converted to a form susceotible to measurement hv a given technique. I t is probably safe to say that when an analytical chemist is responsihle for the course and associated lecture, the analytical methodology involved in the experiments is emphasized more than when an organic chemist is responsihle. Thus, depending on the individual instructor's emphasis, the integrated lahoratory format could sidestep parts of the analytical procedure or of the analytical prohlem solving approach with cookbook-type directions. On the other hand. the inteerated format does provide an efficient frameworkfor cove;ng a wide variety of analytical techniques in the laboratorv. A wealth of current interdisciplinary analytical problems, including environmental and clinical, can he drawn upon for experiments which exhibit the complete analytical problem solving Whether such experiments are done in a .approach. ~course-associated analytical laboratory or in an integrated lahoratory sequence is not nearly as important in analytical chemical education as the proper treatment of the analytical method.
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Analytical Chemistry at a Community College: A Balance of Wet Chemical Methods and Instrumental Analysis Janan M. Hayes American Riuer College Sacramento, California 95841
Most community colleges offer at most one analytical chemistry course, quantitative analysis, which must he directed toward students w ~ t ha of prof~ssional Although American River Cdlege is rather large, we still have many of the advantages associated with comkmity college Prngrams. Analytical chemistry classes are small (a maximum of 24 in lecture and 12 in lahoratory sections), lab sections are taught by the lecture professor, and instrumentation is totally devoted to instruction. Because students normally will not have an additional inThese papers were at the Division of Chemical Education, Symanalysis course, we must also provide a firm i ~ t i ~ ~strumental l posium on the Present Status of the Teaching o f ~ ~ ~ chernistry, American Chemical Society ~ n n u aMeeting, l Chicago, ~~linois, hackground of instrumental techniques. Two major themes August 28-September 2,1977. have seemed to develop throughout the course. First, the
96 1 Journal of Chemical Education
general theory of each type of analysis must be understood before actual procedures are perfected to avoid student cook book readers and button pushers. Second, all analytical procedures discussed and practiced should he related to actual situations and should use known samples for standardization and verification. The course is roughly two-thirds "wet" chemical methods of both gravimetric and volumetric analysis and one-third instrumental methods with an emphasi; on visible spectral techniques. The f i s t unit introduces elementary quantitative skills with mavimetric analvsis and statistics as the foundation. Lecture on theory of baiance operation and calibration is complementrd by a laboratory exrrcise in popping popcorn utilizing 1~3thh u h l e pan and electronic analytical balances.' Studentn make the statistical study by hand calculation and verify it with a previously prepared statistical prngram on our a ~ l l r g e computer. Because the second semester ireshman course at ARC has a strone on eauilibrium theorv. - emphasis . .. we can concentrate on techniques for maximization of accuracy and orecision in eravimetric analvsis. In the laboratory the traniition from gra\,imetric to volumetric analysis is made by 11 rhluride determination both on a standard chloride sample and on wiener seasonings frum a local seasoning producer. The additional use of a gravimetric buret2 here demonstrates the relation of precision and ease of operation to equipmrnt (~osts. Calil~rationof all vdumctric equipment is also emphasized. Because students commonly believe that every number displayed by any instrument is valid., thev.are ureed to evaluate consrsntlv the realistic orecision of the equipment or instrumentation they are using. Volumetric analvsis lectures azain build upon student knowledge of acid-base equilibria but emphasLe use of the titration and aloha curves for end ooint determination and selection of experimental conditions. In the laboratory the students try a variety of indicators for a titration of carbonate in soda ash and water hardness with EDTA. In addition to unknown hardness samples, the students, using previously discussed EPA sampling techniques,3 bring in water samples to analyze. In the area of electrochemistry, the phosphate content of baking powder is determined using a potentiometric end-point determination.4 The use of pH meters and ion-selective electrodes introduce the instrumental portion of the course. Instrumental theorv is develooed with emohasis on ouestioning usages and liktations oi the technique, dependagility of the results, and calibration of the instrumentation. Centering upon the Nernst equation, we discuss the techniques of ootentiometric titration, electrodeposition,. . polaromaphv. - . .. and voltammetry. Spectroscopic methods taught, including fluorometry and atomic absorption spectroscopy, involve consideration of the four basic components of light source, wavelength selection, sample containment, and light detection. We start with a Klett colorimeter and work up through Spectronic-20 to an automated Beckman-25 spectrophotometer. Infrared and nuclear magnetic resonance spectroscopy are covered lightly since they are used in organic classes a t ARC. The last two experiments, which tie the course together, demonstrate the total analytical procedure of sampling, separation, technique selection, calibration, actual analysis, and result interpretation. In one experiment, the students are
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Macomber,R. S., J. CHEM. EDUC., 49,714 (1972). 2Butler, E. A,, and Swift, E. H., J. CHEM. EDUC., 49, 425 114771 LA".",.
"Manual of Methods for Chemical Analysis of Water and Wastes," U.S.E.P.A. Methods Development and Quality Assurance Research Laboratory, National Environmental Research Center, Cincinnati, OH 45268.1974. ' Walton. H. V.md Reyeq..J. "Modern Chemical Analy-isand I n strumentar~nn."Marcel IJrkkrr. Inc.. New Yurk. 1973, p. 1 1 . ;'A mure derailed wume outline and lahnrotmy Pxpmment hsr with references may be obtained upon request.
eiven a brass sample from which they are to separate and analyze tin as tin oxide, analyze copper by electrodeposition, photometric t ~ t r a t i mwith EUI'A, and atomlc absorption: and analyze lead by electrodeposition, atomic absorption, and ion-selective electrode analysis. The final experiment of the semester directs simulv: "auantitativelv measure somethine." Experiments p e r f o k d hive ranged fiom the determinatLn of the copper in crayfish blood to the amount of calcium in egg shells. Students also report the toxicity of any chemicals used and the approximate costs of the chemicals involved. Concluding with a visit to a local independent analytical lahoratorv. we feel that the student has a mod start on being able to lolk'at an analytical problem and deal with it, whether i t be in chemistry, biology, or g e ~ l o g y . ~
The Sophomore Level Analytical Laboratory Richard A. P a c e r Indiana Uniuersity-Purdue Uniuersity a t Fort Wayne Fort Wayne, 46805 What obiectives should euide an instructor in shaoine an analytical faboratory course? In selecting a balanced set of experiments, it is helpful to implement a variety of learning objectives and to consider the objectives met in other courses (e.g., ir work in organic lab). First and foremost, there should be a balance between the classical (gravimetric and volumetric) methods and the instrumental methods. Some of the laboratory work should involve analytical separations. Statistical treatment of data should be presented early in the course. The burden of reporting a single "best value" for each determination should he placed on the student, so that these statistical concepts are put into practice quite early. Rigorous standards for accuracy must be reinforced by the grading svstem. The following set of laboratory experiments has been used by the author in such a course: (1) gravimetric sulfate; (2) sodium carbonate in soda ash (volumetric acid-base); (3) phosphate in a rock sample; (4) Mohr chloride; (5)calcium1 EDTA (water hardness); (6) iron by redox titration with dichromate; (7) mixture of aromatic species by gas chromatography; (8) copper by electrodeposition; (9) colorimetric manganese in steel; (10) calcium by atomic absorption; (11) APC tablets by ultraviolet spectrophotometry; (12) nickel by polarography. Illustration of the incorporation of a variety of learning objectives in four of these specific determinations follows. 3) Phomhate rock-use
of ion exhanee resins. DH curves of
7) Aromatic species by gas chromatography-selection of analytical response (peak heights or areas?) and compensation for differences in extent of response (use of relative response factors). 10) Calcium by atomic absorption-the role of EDTA in preventing formation of refractow oxides. com~ensationfor drift of instrument resoonse with time. a d orohleks at ihe trace level (suchas adsorotion
separation by solvent extraction, simultaneous speetrophatometrie determination and technique for selection of optimum wavelengths, and solvent cutoff. In order to reflect some of the trends in the development of analytical chemistry, analytical courses in the future will need to devote meater attention to problems of analvsis a t the trace level; the many applications td clinical chemist&; greater emphasis on samolinz, particularlv with respect to environarea OF chemical sepamehtal samples; ihe rapidly rations; combinations of established techniques, such as gclmass spec.; newly emerging techniques related to surface Volume 56, Number 2, Februav 1979 / 97
