FEATURED LABORATORY
Chemical Experimentation Principles and Practice at Northwestern University CLAUDE A. LUCCHESI, Department of Chemistry, Northwestern University, Evanston, Ill. 60201
Northwestern University’s cen t ralized analytical s e rvices-ad vanced practices laboratory introduces students to a wide variety of modern research methods and allows them ready access to high quality analytical instrumentation a unified, practical approach to broad-based chemical experimentation has been a continuing goal a t Northwestern University for many years. I n line with this philosophy, a laboratory course on “advanced practices” was introduced into the undergraduate curriculum about five years ago, and more recently, centralized analytical services were made available for both graduate and undergraduate research students. With last year’s completion of a 7000ft2 Chemistry Department addition to house an analytical services laboratory and an adjoining advanced practices teaching laboratory, Northwestern students are now getting a unique introduction to chemical measurement techniques. The new laboratory arrangement gives every student ready access to quality research apparatus and provides a common ground for all research groups-organic, inorganic, biochemical, physical, and analytical-to see the wide array of methods and equipment used in each of the various fields. The new laboratory unit was established to consolidate the Chemistry Department’s analytical instrumentation under a Director of .4nalytical Spryices who would manage the services lab and teach in the advanced practices course. The unit is staffed with three technicians and T H E PRESENTATION O f
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Figure 1.
N e w laboratory unit
four professionals, including the laboratory director, Dr. Claude A. Lucchesi, who joined the chemistry faculty two years ago after 14 years of industrial experience in the practice and management of chemical analysis. The layout of the Chemistry Department addition is shown in Figure 1.
Advanced Practices Laboratory
The advanced laboratory course evolved as a way to lend coherence t o the undergraduate curriculum ( 1 ) . The course objective is to provide broad-based experiments that more closely resemble the kind of work a
ANALYTICAL CHEMISTRY, VOL. 43, NO. 1, JANUARY 1971
professional chemist actually does rather than just to give the student an exercise illustrating only a single principle. To achieve this scope, the methods and techniques traditionally learned in courses labeled inorganic, physical, and analytical chemistry have been combined to give the student an opportunity to integrate his earlier chemical experience. Topics covered in the course are listed in Table I. Experimental techniques, including the techniques used in synthesis, are stressed. Most evperiments make use of conventional solution preparation methods, hut high-temperature syntheqes and vacuum-line preparation of air-qensitire compounds also are in-
Instruments in the analytical laboratory have been arranged so that those which are primarily student-operated are most accessible. The area shown above includes most of the spectrometers available t o students on a 24 hr/day basis Included in the analytical services-advanced laboratory area is a conference room which may be used by the graduate teaching assistants who give many of the oral exams required in the chemical experimentation course. It is also used for formal discussions of current research problems. Here, Dr. Lucchesi is discussing a problem with students and a staff member
Table I. Advanced Practices Course Synthesis Coordination compounds High temperature preps Vacuum line preps
Chemical kinetics Cis-trans isomerization Gas phase cyclization Rapid proton exchange
Separations Fractional crystallization Ion exchange Gas chromatography Paper chromatography
Ca I ibration principles Reference standards Internal standards Standard addition technique Criteria of purity
Determinations Titrimetry Spectrophotometry Gas c h romatogra phy Optical rotation
Basic electronics Operational amplifiers Common circuits Readout devices
Structure-identification Line spectra (sodium) Band spectra (iodine) Vib-rotational spectral (DCI) Optical activity (ord-cd) Magnetic susceptibility Nuclear magnetic resonance X-Ray diffraction Gas chromatography Electrochemistry Current-voltage curves Polarography Cyclic voltammetry Electrolytic conductance
Instrumentation principles AC vs. DC systems Double/single beaim Signal averaging Data treatment Statistical evaluation Computer programs Presentation practice Formal written reports Oral exams
cluded. Methods for performing determinations are utilized in the experiments as are the methods and techniques of structure determination and identification. The determination of the concentration of various species also is used t.0 illustrate the kinetics of the three types of transformations listed in Table I. Before the institution of the laboratory practices course, there was some question as to where in the undergraduate curriculum certain topics belonged. For example, there had been a question about, where to put basic electronics and electrochemistry. A chemical experimentation course turns out t o be an ideal place for these topics. Other areas, such as calibration and instrumentation principles as well as data treatment also are readily covered-explicitly or implicitly-in the course. I n addition, an especially difficult aspect of an undergraduate’s training, oral presentation of his experimental findings, is given special attention. The experimental units developed to date are listed in Table 11. The hope is that with these experiments, the techniques and principles of the
ANALYTICAL CHEMISTRY, VOL. 43, NO. 1, JANUARY 1971
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Featured Laboratory
Table II. Experimental Units Atomic spectra Operational amplifiers Current-voltage curves Preparation of inorganic complexes Kinetics of cis-trans isomerization Preparation and analysis of CoFe,On X-Ray powder patterns Polyphosphates Formation constants of a complex Polarography and cyclic voltammetry
Table 111. Analytical Laboratory ITstruments Baird 4-55 infrared spectrophotometer Beckman ir.5 infrared spectrophotometer Beckman ir.9 infrared spectrophotometer Beckman ir-IO infrared spectrophotometer Beckman ir-11 infrared spectrophotometer Cary Model 11 uv:visible recording spectrophotometer Cary Model 14 uv-visible-near ir recording spectrophotometer Beckman Model DK-2 uv-visiblenear i r recording spectrophotometer Perkin.Elmer-Hitachi MPF.2A fluorescence spectrophotometer MPF.2A with phosphorescence attach. ment Cary Model 60 optical rotatory dispersion-circular dichroism spectropolarimeter Hewlett-Packard automatic carbon, hydrogen, nitrogen analyzer Mechrolab Model 302 osmometer Barber Coleman programmed temperature gas chromatograph CEC Model 21-104 analytical mass spectrometer Two Spinco Model E analytical ultracentrifuges, one with’ photoelectric scanning system Two Beckman amino acid analyzers Packard Tri-Carb scintillation counter, Model 314E Varian Model T-60 nmr spectrometer Varian Model A-60 nmr spectrometer Bruker Model HFX-10 nmr spectrometer with conventional and high-speed signa’l averaging capability Spex Industries laser-Raman spectrometer Two Picker X-ray generators with associated accessories, including an integrating precession camera and a Weissen berg camera
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ANALYTICAL CHEMISTRY
Gas chromatography Ion exchange Synthesis of NDa or DCI lr spectral study of DCI or ND1 Synthesis of chromous acetate Magnetic susceptibility Band Spectrum of iodine Fluorescenceof europium(ll1) Gas-phase kinetics Chemical dynamics by nmr
three traditional fields are so well mingled that the student uses many of them without consciously thinking he is doing inorganic, or analytical, or physical chemistry. Rather, he is doing chemistry to solve a problem. One example of “doing chemistry” involves the preparation of an inorganic complex. The student is given the problem of preparing tris(ethy1enediamine) cobalt(II1) chloride and resolving the opdical isomers produced. In carrying out the work, he learns the principles involved in separating a racemic mixture-ie., conversion to diastereoisomers which may be separated by fractional crystallization. He learns to use optical rotation as a measure of concentration and as a means for calculating yields. Hopefully, he sees the arbitrariness of the term “pure” because a rather unfamiliar quantity, optical rotation, is used as a measure of purity. He also learns about optical rotatory dispersion and circular dichroism. Oral Examinations
The laboratory practices course covers two quarters and is taken by chemistry majors in their junior or senior
year and by graduate students from other departments. The course meets three days a week, four hours per day, and typically, eight or nine experiments per quarter are required. The student chooses one experiment each quarter for a “long” report which he prepares as a journal-type review or research article, depending on the nature of the experiment. H e is expected to do a fair amount of library work for this report. The other experiments are done as “short” reports which means that the student hands the instructor assigned to that particular experiment a carbon copy of the data he obtained and takes an oral exam on the work he did. The oral exams are a very significant aspect of the advanced practices course because they serve to inject reality into the student’s training. Certainly, in most real-life work situations likely t o be encountered-in later graduate work as well as in industrythe student will have to present his work verbally. The oral exams provide the student with practice in thinking on his feet, and give the instructor ample opportunity t o find out bhe extent of his understanding. The disadvantage of the oral exam is that it is very time consuming. This is one reason for a high iustructor-tostudent ratio for the course. Last year for the 12 students, there were two faculty members and five graduate teaching assistants. Analytical Services Laboratory
Adjacent to the chemical experiment.ation teaching laboratory is the analytical services laboratory. The layout of the analytical lab is shown in Figure 2, and the instruments now in use in the lab are listed in Table 111. The instruments can he classified broadly as spectrometric or bioaualyti-
The mass spectrometer is one of the instruments operated only by the analytical laboratory staff. The instrument shown here is a medium resolution spectrometer capable of handling gas, liquid, or solid samples. Adjusting the ion accelerating voltage before commencing a, run is staff member, Roger Crain
The 90 MHz multinuclide nmr spectrometer is used to study 'H, "F, " 6 , 'IP, T, "0 resonances. It is equipped with conventional and high-speed Fourier transform signal averaging and is primarily staff-operated. Only specially designated students doing n m r research are trained to operate the instrument in a limited range. The laboratory s u pervisor, Dan Netzel, is shown making the spectrometer ready for student use.
One of the advantages of having the advanced practices laboratory adjacent to the analytical laboratory is more efficient utilization of equipment. For exammple, the gas chromatograph was used exclusively in the chemical experimentation course only one quarter a year prior to the present arrangement. It is now located in the analytical lab where it !nay be used a s needed. Adjusting the instrument is Lily Kao who works full-time i? the advanced practices lab but is available for special analytical projects.
cal, and they are arranged for the user's convenience. I n general, an instrument is operated primarily by one of three groups: students in the chemical experimentation course, research students (graduate and undergraduate), and the analytical laboratory staff. Because of the complexity of the mass spectrometer and the 90MHz nmr spectrometer, for example, it is impractical to train student operators, and these instruments are used only by analytical staff members. Most of the apparatus in the lab, however, is available to students on a 24 hr/day basis after suitable instruction by the staff. I n addition to providing special instruction on request, the staff is charged with keeping the equipment in operating condition and with enforcing good practices on the part of the student users. Instrument maintenance and repairs are done by the Chemistry Department's electronics shop. The work is supervised hy an instrument engineer who also is available for consultation regarding inst.rument design and construction. Another function of the analytical laboratory staff is to keep abreast of the latest developments in analytical met.hods and instrumentation, and each staff member is available to students and faculty for consultation relative to chemical malysis. The laboratory director makes recommendations regarding acquisition of equipment and prepares the NSF Research Equipment Grant Request.
Featured Laboratory
Each incoming graduate student, learns about the analytical services as part of his orientation program. The incoming graduate class spends a n afternoon in the analytical laboratory learning about the scope and limitations of each instrument and service available. They are instructed in the businesslike operation of the laboratory as well as in the technical factors to be considered in the selection of a particular piece of equipment for a specific measurement problem. For example, if it is decided that an nmr measurement is required, they learn they must choose one of three units which vary in resolution, temperature range, decoupling capability, cost to the user, and in other respects as well. During the orientation session, the student also is reminded of some of the essential factors in considering a particular analytical met'hod, such as reliability, detection limit., sensitivity, and minimum sample size. Separation of esterified catecholamine metabolites by partition chromatograDhv in 1,2-dichloroethane: mdhanol ( 7 3 ) .
(linggird, E., et al.,Reproduced Submitted to Chromatog, J,
by kind permission of the ALthors and the Publisher.)
Gel filtration of triglycerides and fatty acids in chloroform.
Separation of oestrogens by adsorption chromatography in distilled water.
(AdaDted from Downev. W.K., et al.; J. Chromatog. 46 (1970) 120 124. Reproduced by kind permission of the Authors and the Publisher')
(Van Baelen. H.. et al.. J. Chromatog. 30 (1967) 226227. Reproduced by kind permission of the Authors and the Publisher.)
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ANALYTICAL CHEMISTRY, VOL. 43, NO. 1, JANUARY 1971
New Lab Advantages
The combination of a chemical experimentation teaching laboratory with an analytical services laboratory has advantages for both graduate and undergraduate instruction. For research students, t,here is the obvious advantage of equal opportunity to use whatever equipment is necessary t o solve their particular current problems, including apparatus normally used for the laboratory practices course. Students as well as faculty members and postdoctoral fellows also may use the consulting services of the analytical staff. -4 number of departments in the University, including astronomy, chemical engineering, civil engineering (environmental sciences), geology, and the medical school, have made use of these services. The undergraduate has the advantages of ready access to qunlit'y research apparatus and exposure to a wide array of methods and equipment. Because about half of the advanced lab experiments are carried out in t'he analytical lab, the student has almost daily contact with the analytical staff for two quarters and gets a first-hand view of a professionally run analytical laboratory. H e also has the opportunity to hear the attitudes of industrially experienced chemists. I n short, the analytical lab provides a link with the real world, and the student can see both the preaching and practice of analytical chemistry, side by side. Reference
(1) F. E. Stafford, D. E. Smith, U. Hofacker, and D. D. DeFord, J . Chem. Ed. 44, 162 (1967).
