Frank A. Settle. Jr. Virginia Military Institute Lexington, Virginia 24450
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I
Project Select An assignment in instrument evaluation for undergraduate analytical students
The evrluation and s d e c t i w of instrumrntation has become an importnnt part of analytical chemistry. I'ROJECT SF:I.ECI' is an attempt I,, intwdure studrnts to this aspect ot instrumental analysis. The project requirrs students to ~ ~ t i l i zthe e manufacturws' 1irer:ltun~in selecting instrumentation npprnpriarr for a specified analytiod situation. t'HOJEC'I'SELE('T has been intr(,duced as an rxercise in the srnmii semester of a two-semester analytical chemistry rgnlrst! ieauence. This murse. titled '.Instrumental hlrthwli of Analysk," covers mostly spect~o~hotometric and electrochemical techniaues. Students have had hands-on experience earlier in the semester with the instrumentation which they are to evaluate in the project. Objectives The primary objectives of the project are (1)to stress the parameters important to the selection of a particular type of instrumentation, (2) to emphasize the relationship between instrumental parameters and the methods required for a specific analy&, and (3) to give students an introduction to evaluatina state-of-the art instrumentation through the use of basic concepts acquired in the course. The . project has been of value in aiding students in these. Iertim i ~ n dunderstanding of important instrumental pnramrtcrs. It has forrid t11t.m to utilize textual material more i d h and has stimulated meaninrful and livels discussions wit6 both peers and the instruct;. The analytical situation described in the assienment has reauired students toview the " instrument as an integral part of the overall analysis rather than as the separate entity. Students learn that factors such as sample preparation and handling, data retrieval, and operator training are important considerations in the selection process. The current vendors' publications, which introduce students to commercially available instrumentation, are beneficial supplements to textbooks, which are dated by several years a t the time of publication. The manufacturers' literature orovides a different point of view and is often a colorful supplement to conventional methods of presentation. The use of this literature to complement textual materials allows students to see the relationship among basic instrumental principles, real world analyses, and the vendors' salesmanship. Assignments Students were ueiven a hwothetical analvtical situation and .. manufacturers' literature describing four or five potentially suitable instruments. This material included current price lists for instruments and accessories. The analytical situations were selected from methods found in "Standard Methods of Chemical Analysis" (I). These situations involved routine analyses typically found in industrial or governmental lahoratories. Other sources for methods include periodicals, manufacturers' technical publications, and references containing standardized procedures (2-4). The three situations chosen for initial investigation in PROJECT SELECT included analyses which required instrumentation with either visible-ultraviolet, infrared, or atomic absorption systems. These particular.instruments were selected because of (1)the previous experience of students; (2) . . the wide rauae of applications: and (3) the variety of manufacturers' literature available. Students worked in pairs on the assignment for a period of one week. While discussions
between partners were encouraged, each student wrote his own evaluation and recommendations. Only one situation was evaluated by each student during the course. Students were asked to select the instrument best-suited to perform the desired analysis in the specified environment. The following factors were to he considered in making a selection: (1) Instrumental specifications (e.g., wavelength range, band-width,stray light, etc.). (2) Approximate time required for analysis of a single sample. (3) Training required for the analyst. (4) Type of sample (routine or non-routine). (5) Output formatof instrumental data (e.g., meter, digital display, computer interface connections, etc.). (6) Cost of instrument and necessary accessories. (7) Other factors the students might consider important. The reoort included a comnarison of all the instruments. ~tuden'tswere then asked to indicate their first and second choices. These decisions were to be supported with evidence from manufacturers' literature, the a & t i c a l methods (1), and other appropriate references, including the text ( 5 ) . .. . The Fullowing situntions and instruments turmt!d the basis of PROJECT SF:I.b:CT aisiynments: Ultraviolet-Visible 1. Situation Your laboratory has been assigned the task of determining mounts of preservatives in food products. The preservatives to he determined are benzoic acid, boric acid, sorbic acid, and sulfur dioxide. The methods to he used are described in "Standard Methods of Chemical Analysis" (I),pp. 1111-1113. You will he expected to do the following number of tests per day: test determinationdday benzaic acid 30 boric acid 10 sorbic acid 10 sulfur dioxide 20 You have two technicians available to perform the analysis. One has a degree in chemical technology from a two-year college, and the other has a high school diploma. 2. Instrumentation available: a. Bauseh and Lomb Spectronic 21 b. Zeiss PM 2 c. GCAIMcPherson 700 Series d. Beekman Model 34/35 e. Perkin-Elmer 200 Infrared 1. Situation Your polymer analysis laharatory has been assigned the following quantitative procedures: (1) Determination of resins, plasticizers, stabilizers, and fillers in polyvinylehloride (PVC). (2) Determination of methyl groups, carhonyl groups, and unsaturation in polyethylene. (3) Determination of mineral oil, 2,6-di-tert-hutyl-o-cresal, 9-octadeeenamide in polyethylene. (4) Comparison of your company's polymeric material with a competitor's material. The methods to be utilized are described in "Standard Methods of Chemical Analysis" (I), pp. 1606-1611. You are expected to analyze 10PVC samples and 20 polyethylene samples per day. You have available a technician with a degree in chemical technology from a two-year community college. Volume 56, Number 6, June 1979 1 41 1
Results of PROJECT SELECT
2. Instrumentation available: a. Reckman Model 4200 Series
.
h. Reekman Aeculah Series c. Perkin-Elmer X97 Series d. Perkin-Elmer Model 281 and Model 283 Atomic Absorption 1. Situation Your laboratory has been given the assignment of determiningwear metals in the lubricating oil of jet aircraft engines fnr the purpose of srhedulinu oreventive maintenance. The methods to be used aredescrihed in"~tomie Absorption Spectroscopy," by W. Slavin, pp. 2333-34, and "Standard Methods of Analysis," (I),pp. 1507-1517. You are required to run 60 samples per day determining the amounts of Pe, Cu,Ni, Cr, Mn, and Al in each sample. You have a technician with a high school education working under your supervision. 2. Instrumentation available: a. darrell-Ash Model 850 h. Varian Model AA-575 e. Perkin-Elmer Model 603 d. Jnrrell-Ash Dial-Atom I11 Results The students responded enthusiastically to the project. In general, their selections were well-conceived. The table shows the results of the class (nineteen students) to the various situations. In most cases the number of samples to he analyzed weighed the decisions in favor of instruments which were or could he automated easily. In several cases reports omitted necessary accessories which added considerable cost. Some reports tended to emphasize the time required for sample preparation, while others more correctly dealt with comparisons of instrument specifications. Cost effectiveness was difficult for students to measure, and therefore they tended to recommend the more expensive equipment. The extreme case of disregard for expense is represented by the student who wrote, "Assuming the project is funded by the government, cost versus practical factors are omitted." However, the results, for the most part, indicate that PROJECT SELECT accomplished the previously stated ohjectives. Discussion Students often asked for more detailed information concerning the methods of analysis and the desired accuracy of results. A more detailed description of the analytical procedures will he included in future assignments. The choice of analvtical situations was random. Other situations will he chmen h i e d on relewnr and intrrest~nganalyses. The selrcrion nf i~wiilat~lc inatrumentarion will he increased to give greater variety. Each assignment will include low, moderate, and high cost equipment. This will aid the instructor in evaluating student reports. The n u m h e ~of instruments to he evaluated for a given situation will be no greater than five. More emphasis will be placed on cost effectiveness by requiring students to estimate cost per sample, etc. Two items will he added to the list of evaluation factors; maintenance costs (estimated a t 10%of ourchase orice Der year) and estimated useful life time of the instrument. The' latter may he difficult to estimate hut should receive consideration in an environment of rapidly changing technology. For e x a m ~ l e ,"smart" instruments (those containinp built-in m i ~ r ~ c o m ~ u t epresented rs) a challenge to students with little computer background. Those students who had taken the course in laboratory automation offered in the VMI Chemistry Department experienced little difficulty in evaluating "smart" instruments. This type of instrumentation will
412 / Journal of Chemical Education
Number of StudentS with this Number of students assignment selecting instrument First Second Choice Choicea Ultraviolet~i~ible Bau~chand Lomb Spectronic 21 Zeiss PM 2 GCA/McPhersan 700 Beckman Model 34/35 Perkin-Elmer 200
(81
Infrared Beckman Model 4200 Series Beckman Acculab Series Perkin-Elmer X97 Series Perkin-Model 281. 263
(51
Atomic Absorption Jarrell-AshModel 850 ~arrell-AshDial Atom Ill Varlan Model AA-575 Perkin-Elmer Model 603
(6)
0% 0% 0% 62%% 37%%
0% 0% 0% 25% 62%%
40% 40% 20% 0%
20% 20% 20% 0%
50% 0% 50% 0%
33% 0% 16'12% 33%
N o t all students lndlcated a second cholce.
remain among the selections availahle for the analytical situation, hecause it represents the current trend in analytical chemistry. Extensions The ideas incorporated in this assignment may he expanded in several directions. A purely research situation might be described in which instrumental parameters would he more critical than in the industrial situations of the current project. The situations might he expanded to cover gas-liquid and liquid chromatograms, potentiometric instrumentation including electrodes, and polarographs. It was not possible for students to have hands-on experience with these methods in our current course prior to the assignment of PROJECT SELECT. A rearrangement of laboratory experiments would allow these instruments to be evaluated by students. Instruments not readily available to undergraduates might he investigated with the aid of a PROJECT SELECT assignment. These might include instruments for surface analysis (for example, X-ray energy spectrometry, electron spectroscopy (ESCA), and Auger spectroscopy), Raman spectrometers, gas chromatography-mass spectrometry systems, and Fourier infrared spectrometers. Acknowledgement The enthusiastic response to PROJECT SELECT by the members of the Instrumental Analysis class of the Spring of 1978 provided the motivation for this article.
,-..".".".i,n,=,,,,n 11)
welcher, F. J., IEdif~r!."Standard
12) ~
Methods of Chemical Analyris." 6th od.. D. Van Nufitrand Co.. Princotnn. Nd.. 1966,Vslume 3. Part R.
~ ~ ~ ~ ~ ~ t ~ ~ d ~ ~ d ~ : a ~ ~ ~ ~ ~ ~ ~ pa. la! Horwitr. W.. iMil,,r!.'~OfficialMethodod of Analysis" Asrocistion of Oflieis1Analytical chemists, washinpton. D.C. (41 ~ a u l k n e W. ~ . ~..snd~ i n g . w., ~ . i ~ d i t m ! ,"~anudorclinical ~ahorstoni~mcodurea," TheChemical Rubber Co..Cleveland,OhB 11970). R. L.. et , - ~ M ~~M Sdor ~~ ~ h Analynis;'2nd ~ ~ ed.. ~ JO~ Wilay i " ~ ~ ,,( s ~ ~ s . N ~ w Y 1976. ~ ~ L .
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