The Analytical-Environmental Interface A Relevant Concept at the Community College Paul R. Loconto' Dutchess Community College, Poughkeepsie, NY 12601 The need for students in our National Resources Conservation Program (now called Environmental Conservation Science) toreceive an early introduction to analytical methodology as applied to environmental samples was realized with the development of a tape-based laboratory minicourse in thelate '70's (I).The course fulfilled this need at that time and vrovided hands-on techniaue unavailable in other c h e m k r y courses taught at t h e college. The course title "Environmental Chemistrv Laboratorv" underwent two major revisions since its inception in 1975. The technological exvlosion that has occurred in environmental analvsis. coupled with a clearer understanding of the relatio&hip hetween instrumentation and environmental analysis, necessitated that the second revision prepare students to meet the challenges of the future. For example, impending superfund legislation fuels the need for environmental analysts (2). Recently, a 1-hlweek lecture has been added to the course to provide a framework for introducing environmental chemistry. I t was quickly discovered that fifteen 3-h lab veriods in the semester orovide students an excellent oooortunity to develop their manipulative and observational$kills if the laboratorv - -oroeram oroceeds from earlv"emohasis . on technique to a later emphasis on the application of technique to environmental samoles. This concept was used sucressfully in the early version of the course. The added lecture hour also allows the inatrucur valuable time to discuss and even perform dernonsrrations that clarify the underlying unalytical chemistry. responsible . for the outcome of each laboratory exercise. Now the course is considered essential to entry-level jobs for our students in local environmentaliaboratories (3). , . The course can be described as consisting of classical quantitative analysis sprinkled with spectrophotometric and potentiometric methods applied to water quality evaluation. Students enjoy bringing samples of their drinking water for trace iron analyses or hardness values. They are surprised to learn the wide range of values. The table lists the laboratory
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' Present address: Nanco Laboratories, Inc., Wappingers Falls, NY 12590.
Outline for Laboratory Course Unit 1
Activity
(a) Orientation
(b) "Introduction to Precision Weighing" 2 3 4 5
6 7 8
9 10 11 12
13
%traducllon to Volumetric Measuremem" "Introduction to Sample Preparation and Gravlmetrlc Methods% Recovery of Oil-Spiked Water" (a) TECH-057: Absorption Measurements (b) "Introduction to Spectrophotometric Methods" '7ntrod~ctionto Titrimetric Methods" TECH-029: Standardization of a Solution "Anal-234: Standardization of a Sodium Hydroxide Solution with a Known Solution of Hydrochloric Acid'' "Determination of Total Dissolved Salts in an Unknown Water Sample by Ian Exchange" "Determination of Hardness in Groundwater by Titration Using EDTA" "Determination of the % Iron in an Ore by Spectrophmometri~ Tihation with EDTA "Spectrophotometric Determination of Trace Levels of Iron in Groundwater" (a) TECH-059: The pH Meter (b) "Determination of Acidity Levels In Rainwater via Potenti* metric and Spectrometric Methads" (c) "REAC-321: Estimating the Effects of Acid Rain" (a) "Anal-052: Gas Chromatographic Separation and Analysis of Hydrocarbon Mixtures" (b) Check Out
program as taught in the fall semester 1985. Experiment titles set off in auotes are written bv the author while the abbreviation, foiexample, TECH-o&, refers to a particular published modular experiment (4). Increased coherence between weekly lab periods is accomplished by carefully selectine analvtical determinations that are then used in a subsequent exercise. This concept has sewed to unify a seemingly incoherent set of experiments. For example, Unit 5 introduces the acid-base titrimetric technique followed by a standardization of a dilute hydrochloric acid solution against primary standard sodium
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carbonate in Unit 6. The standardized hydrochloric acid solution is used in Unit 7 to standardize a dilute sodium hydroxide solution. The standardized sodium hydroxide solution becomes the titrant in Unit 8 in which sodium chloride is converted to hydrochloric acid when passed through a column containing cation exchange resin (5).This sequence of four 3-h lab periods lends great continuity when students are struggling to improve their skills in volumetric analysis. The importance of percent recovery studies in methods development for environmental analysis cannot be overlooked (6). The validity of any trace analytical method deoends not onlv on the analvtical nrecision but also on the ability of the method to rec&er mbst of the substance being analvred from environmental matrices (7). The conceot of recovery is introduced in a simple but elegant manner early in the course with an exercise title "Percent Recovew of OilSpiked Water". To about 500 mL of water is added i mL or less of oil. A liquid-liquid extraction using Freon is performed and theaolvent is removed by simple distillation. The oil that remains is weighed carefully on the analytical balance. The percent recovery is based on the original weight of oil. Students seem gratified to learn that the exercise of careful manipulative technique assures recovery that exceeds 90%. Units 1through 7 comprise the techniques portion of the course. The emphasis is placed on learning to weigh, t o pipet, to read a buret, and t o prepare solutions whose concentration units are expressed in molarity or parts per million. The remaining units provide experience in applvinn basic analvtical techniques ;o environmental anal;dis:~Ke use of p"blished modules enhances this author's limited presentation in the handouts by showing diagrams and providing clearly written procedures. The acid rain project that encompasses both the handout and published modules clearly defines for the student the analytical-environmental interface. An analog pH meter is correctly used with student-prepared buffer solutions over the oH ranee " from 3 to 5. The same buffers are used to calibrate a spectrophotometer for colorimetric analysis using Bromcresol Green indicator. The recent literature (8) has focused on guidelines to achieve accurate pH values. The two-point calibration method is used. and a strong emphasis is-placed on the importance of acc&ate pH measurement. Rainwater is sampled using a standard collector located on top of one of the buildingam campus. The various samples are labeled, dated, and frozen until the pH measurements are scheduled. Acid rain continues t o be an environmental issue of utmost importance (9) and much discussion with the student ensues when the rainwater pH value dips below 4.0. The last laboratory period is devoted to a brief introduction to trace organic analysis. A separation of common aromatic compounds is achieved on a Varian 202 Gas Chro-
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Journal of Chemical Education
matograph modified to accept a 12-ft X 'I8-in. column with 10% dinonyl phthalate on Chromosorh. This column shows exceptional selectivity for various substituted aromatic hydrocarbons. Each student gets to make a t least one injection into the gas chromatograph. A published module introduces the basics of this extremely important and versatile technique. Students are introduced to the principles of gas chromatography by a slide-tape presentation (10) and leave the period with an appreciation of how gas chromatography is serving the environmental lahoratory. The l-hlweek lecture, which was initiated for the first time in fall 1985. orovided for a dialomre with the student concerning this a&lytical-environmental interface. No text has been found to he appropriate both to the level presented .. . and to the range of topics covered. The design of laboratory experimentsis flexible enough to allow an instructor to add new exercises and to delete old ones. This should be done after the core techniques have been introduced. As new techniques enter the environmental fields, the core exercises could also be modified. Texts by Manahan (11). Sniro (12). and Cresser (13) have nrovided this instrukor with tipiis that were fo"nd pertinent to a discussion of the analvtical-environmental interface. The initial inspirati"0n to explore the relationship between environmental contaminants and quantitative analysis came from the course work first presented by Stepenuck (14).
Acknowledgment This author wishes to acknowledee the late Richard Uf. Barnett, Professor of Biological ~ciences,Dutchess Community College, for his early role in the development of an environmental chemistry course a t the college in 1974. Unfortunatelv. .. he did not live to see the course evolve t o its present state. Llterature Cited 1. L m n t o . P. J. Cham. Edw. 1977.54.507. 2. O m d , R. Enuiron. Sci. Tech 1984.18.123A. 3. Gaind. Connie. President, Naneo Environmental Senices, hc..Hopewell Junction, NY, private communicafion. 4. Chemical Education Resources, Inc.. P.O. Box 357. 701 Colony Drive, Palmyra, PA >",,"S
5.
Harris.W.; Kratochuil.B. An hfmducIiii To Chemicol Anolvaia: S i i d d d : Philadel-
phia, 1981: pp 528530. 6. Lwonto, P. "Hydrophobic Intersetlone on Solid Surfaces As s Meena To Iaolste Environmentally Significant Analytes at Trace Concentrations in Water", PhD Thesis. University of Lowell. 1985. 7. Pmv08t.L.; Elder,R.Am.Lob. l983,15(121,57. 8. Fisher. J. Am Lob. 1984.16 I61 and 1985,17 (91,124. 9.Zajirek,O.J . Chrm.Edue. 1985,62,15S. 10. Communication Skills Corporation.Basic Gos Chmmologrophy,audio.visual. 11. Manshan, S. Environmental Chemialry, 3rd ed.: Willard Grant: Boston. 1979. 12. Spira,T.; Stiglini. W. Enuironmcnfollasues in Chemieol Porspecfiue: StateUniwrrity of New York: Albany, 1930. 13. Marr, I.; C~es*er.M.Enuironmanto1 Chemical Anolyaia: Int'l. Textbwk Co: London, 1983. 14. Stepenuek, S.J. Cham. Edue. 1975.52.795.
