Wavne F. McDiffett. Hans Veening, Bucknell University Lewisburg, Pennsylvania 17837 and Roberl F. Comte
Technicon lnstrurnents Cor~oration Tarrytown, New York 10591
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Automated Continuous FIOWAnalvsis in the Study of Aquatic Systems ' NITRATE . NITRITE IN WATER A N D WASTE WATER
In January 1970 Bucknell University and Technicon Corporation co-sponsored the first undergraduate short course in Continuous Flow Analysis. The results of this program were reported previously in THIS JOURNAL.' - A number of colleges and universities have adopted this mode of instruction for teaching the concepts of automated analysis in connection with their chemistry and biology courses. We would now like to report the extended use of this technique in undergraduate courses and research projects in the chemistry and biology departments a t Buclmell UNversity. An experiment utilizing the Technicon AutoAnalyzer has been introduced into the elementary analytical
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ICOMTE,R. F., NORREGAARD, A. M.,
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J. CHEM.EDUC., 48, 110 (1971). SKOOG, D. A,, AND WEST, D. M.,"Fnndarnentalsof Analytical Chemistrv." .. Holt. Rinehart and Winston. Inc.. New York.
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a KAMPHA L.I J., ~ , HANNAH, S. A,, AND COHEN, J. M., Watw Re*., 1, 206 (1967).
Technicon AutoAndyzer Methodology, Method 33-69W.
510
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Journal of Chemical Education
Figure 1.
The AutoAnolyrer flow diogrom for total nitrate m d nitrite.
Figwe 2.
Nitrate concentrations Ippml in Buffalo Creek rnoinstreorn and
tributarier.
chemistry course this year. This course usually has an enrollment of seventy-five to one hundred students and is taught in the sophomore year for chemistry, biology, chemical engineering majors and pre-medical students. The text by Skoog and Westz is used. The laboratory work includes the standard pH, reductionoxidation, complexometric titrations as well as elementary instrumental experiments covering spectrophotometry, potentiometry, and gas chromatography. We have now added an optional experiment involving the oontinuous flow determination of nitrate and nitrite in aqueous Sixteen students in the class chose this experiment. The method for total nitrate and nitrite utilizes the reduction of nitrate to nitrite by alkaline hydrazine containing copper sulfate catalyst. The stream is then treated with sulfanilamide under acidic conditions to yield a diazo compound which couples with N-1-naphthylethylenediaminedihydrochloride to form a soluble dye which is measured colorimetrically at 520 nm in a 15 mm flowcell. The AutoAnalyzer flow diagram for total nitrate and nitrite is shown in Figure 1. I n order to determine nitrite alone, the nitrate reduction step is omitted by substituting distilled water in place of the copper, sodium hydroxide, and hydrazine sulfate reagent lines. Two lecture-demonstration periods are devoted to the principles of automated continuous flow analysis with particular reference to the method for nitrate and nitrite. Examination questions are included covering the development of flow diagrams by the student for the analysis of new systems after being given a set of chemical data and facts normally used in a manual analysis for that system.
The biology department has also used the Auto-" Analyzer for an undergraduate research project, involving several students, in connection with the study of the eutrophication of aquatic systems in the Susquehanna Valley area. Eutrophication of aquatic systems refers to the natural or artificial introduction of nutrients into bodies of water and the consequences of such addition on productivity. A few nutrient materials such as nitrate, p%phate, and some organic substances seem to be primarily responsible for the process. An initial study of the nitrate content of one of the main streams (Buffalo Creek) and its tributaries has already been completed. Five sampling stations have been established, covering a distance of about 20 mi. The first station was set up at an elevation of approximately 1100 f t where the stream is a small spring-fed brook. Subsequent stations were approximately four miles apart with the last station near the confluence of Buffalo Creek and the Susquehanna River. A number of tributary streams were sampled as well, to determine the effect of these on the overall nitrate content of the main stream. Figure 2 illustrates the relationship of the Buffalo Creek sampling stations (vertical line) to the tributaries (horizontal lines) examined thus far. The concentrations shown in Figure 2 are mean values of eight nitrate determinations carried out with the AutoAnalyzer during the summer of 1970. It has been possible to make some initial observations from these data. (1) There is a general trend of increasing nitrate concentration downstream. (2) Tributaries B,E,F, and I all drain cultivated fields and/or dairy farm pasture land. (3) Tributary C is associated (4) Tributaries with a sewage treatment plant. A,D,G, and H drain basically wooded areas. These are "clean-looking" streams with relatively little algal growth. (5) G and H, in particular, have much larger rates of discharge than the other tributaries, and the dilution effect of these two probably accounts for the decrease in nitrate conceutratiou observed between stations 3 and 4. A similar study of phosphate content in these same streams is planned. Conclusion
The introduction of automated continuous flow analysis into the chemistry curriculum and the rrsearch carried out in the ,biology department have been enthusiastically received by students. It is felt that this program has been very successful, in that students are exposed to the everyday practical utility which is inherent although not always obvious in many manual analytical procedures. The use of the AutoAnalyzer for research involving a study of streams also appears to he very promising and will make students more aware of the relevance of chemistry and biology to environmental and ecological problems. Acknowledgment
The authors wish to thank Mr. Harry D. Wilson for technical assistance rendered in connection with this work. Volume 49, Number 7, July 1972
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