of the fluorescence peaks are proportional to concentration if the solute concentrations are determined in this way. This method should be useful in the identification and analysis of mixtures of polycyclic hydrocarbons. ACKNOWLEDGMENT
The authors are grateful to F. A. Vingiello, Virginia Polytechnic Institute, for supplying samples of 7-phenylbenz[alanthracene, 12-phenylbenz [alanthracene, and 12-(1 - naphthyl)benz[a]anthracene.
LITERATURE CITED
(1) Berenblum, J., Schoental, R., Biochem. J. 36,86 (1942). (2) . , Berenblum. J.. Schoental. R., J . Chem. SOC.1946, 1017.’ (3) Bowen, E. J., Wokes, F., “Fluorescence of Solutions,” 1945, Longmans, Green Co., NeZGork, 1953. (4) Hollaender, A., Cole, P. A., Brackett, F. S., Am. J . Cancer 37, 265 (1939). (5) Kaye, W. I., Devaney, R. G., J . Opt. SOC.Am. 42,567 (1952). (6) Miller, J. A., Baumann, C. A,, Cancer Research 3, 217 (1943). (7) Miller, J. A., Baumann, C. A., J . Am. Chem. SOC.65, 1540 (1943). (8) Priestley, W., Jr., ANAL. CHEM.22, 509 (1950) (abstract). ,
I
(9) Sangster, R. C., Irvine, J. W., J . Chem. Phys. 24, 670 (1956). (10) Schoental, R., Scott, E. J. Y., J . Chem. SOC.1949, 1683. (11) Thomas, J. F., Tebbens, B. D., Mukai, bfitsuyi, Sanborn, E. N., ANAL.CHEM.29, 1838 (1957). (12) Vingiello, F. A,, Boikovec, Alexej, J . Am. Chem. SOC. 7 7 , 3413, 4823 (1955). (13) Vingiello, F. A., Bofikovec, -4lexej, Shulman, Joseph, Ibid., 77, 2320 (1955).
RECEIVEDfor review April 18, 1960. Accepted August 30, 1960. Division of Petroleum Chemistry, 130th Meeting, ACS, Atlantic City, N. J., September 1956.
Colorimetric Method for Continuous Recording Analysis of Atmospheric Fluoride Test Chamber and Interference Studies with the Mini-Adak Analyzer DONALD F. ADAMS, ROBERT K. KOPPE, and NORMAN E. MATZEK Division of Industrial Research, Washington State University, Pullman, Wash.
b Automatic continuous measurement and recording of the variations in concentration of fluorides in the ambient air has been reported recently using the Mini-Adak atmospheric pollutant analyzer. A low fluoride reagent, micrograms per cubic meter or parts per billion atmospheric Concentration range, consisting of a zirconium-Eriochrome Cyanine R complex, is incorporated in the method. This paper delimits the tolerance of this reagent to a number of common gaseous and particulate atmospheric pollutants which might b e concomitantly present with fluoride in an air sample. Los Angeles smog-type gases appear to b e compatible with the reagent. The reagent may b e subject to interference from phosphate, sulfate, and aluminum. However, phosphate appears to offer the only significant source of error under typical field sampling conditions. The Mini-Adak analyzer with the low fluoride reagent has an approximate 18% analysis efficiency for submicron cryolite.
E
STABLISHMENT of the actual range
and fluctuation of atmospheric fluoride pollutants in the concentration range of micrograms per cubic meter is essential to the study of the response of certain species of vegetation and livestock to fluoride (6). The determination of instantaneous concentration levels is significant since controlled studies indicate that varying vegetation response is obtained from fluoride fumigations having equivalent
exposure factors, but with various combinations of exposure concentrations and durations (2, 4, 8). Extremely sensitive methods are required to detect microgram (part per billion) or lower Concentrations of fluorides. In addition, specific methods are necessary because other pollutants are frequently present in concentrations of 1 to 1000 times greater than the accompanying fluorides. The literature describes two automatic fluoride analyzers meeting the sensitivity requirement: the Adak, employing a liquid, colorimetric procedure ($), and the Stanford Research Institute fluoride recorder, utilizing a dry, impregnated tape fluorescencequenching method (18). No information has been reported concerning the possible response of either analyzer to the many potential interfering compounds frequently coexisting with fluorides in complex urban atmospheres. This paper presents data pertaining to the tolerance and response of the modified zirconium-Eriochrome Cyanine R fluoride reagent (6, 14) toward many commonly encountered atmospheric pollutants. EXPERIMENTAL
Mini-Adak Fluoride Analyzer. The Mini-Adak is a miniaturized version of the prototype Adak analyzer (S), which has been described in detail previously ( 6 ) . Production of Controlled Atmospheres. Test atmospheres of known concentrations were produced in a plastic chamber ( I ) , 11 X 21 X 24
inches, having an air-mixing plenum and a 30-cubic feet per minute (c.f.m.) squirrel cage blower. For most atmospheres studied, SOZ, HzS, CHBH, KO,and NOz, compressed or liquefied gases were weighed into evacuated stainless steel tanks, diluted to approximately 2% with compressed nitrogen, and injected under constant pressure through a 0.005-inch capillary into the test chamber plenum. Ozone was prepared by passing air through an electric arc generator (Aranair Corp., Wooster, Ohio). Submicron cryolite fume was thermally generated from a molten bath of alumina in cryolite a t 950” C. (Figure 1). Gaseous and supermicron-sized components of the bath effluent were removed by passing the mixture through a 6-inch X 4-foot Plexiglas countercurrent water spray tower, having a water flow rate of 500 ml. per minute. The submicron particulates issuing from the spray tower were introduced into the test chamber plenum. Analysis of Test Chamber Atmospheres. The concentrations of sulfur dioxide, hydrogen sulfide, and methyl mercaptan were determined continuously with a Titrilog (9). The Titrilog was standardized by simultaneous comparison with absorption solutions subsequently analyzed for sulfur by gravimetric and titrimetric methods. NITRICOXIDE. The nitric oxide in known volumes of air was first oxidized to nitrogen dioxide by passage through 20 ml. of an acid-potassium permanganate solution. The nitrogen dioxide concentration was then determined by reaction with Saltzman reagent (16) in a series of six impingers. Analysis was completed by spectrophotometric VOL. 33, NO. 1, JANUARY 1961
117
measurement a t 550 mp. Because of the relatively slow reaction rate, the sampling train consisted of six midget impingem connected in series, each containing 10 ml. of the Saltzman reagent. No color developed in the final impinger. NITROQEN DIOXIDE. Known volumes of test gas were drawn through Saltzman's reagent (16). The nitrogen dioxide concentration was determined by spectrophotometric measurement a t 550 mp. OZONE. Known volumes of test air were drawn through a 1% K I solution. The ozone concentration was determined by spectrophotometrically measuring the resultant iodine a t 352 mp
I
(is,i n . SUBMICRON CRYOLITE. Known vol-
Figure 2. Atmospheric fluoride concentration in phytotron by continuous and twice-daily chemical analysis
umes of air were isokinetically drawn through 46mm. diameter Millipore
Constant fluoride Input and diurnal temperoture change
Table II. Interference Limits of Common Gaseous Pollutants Limiting Concn., Compound P.P.M.0 Sulfur dioxide 0.8 Hydrogen sulfide 0.9 Methyl mercaptan 0.8 Nitric oxide 1.5 Nitrogen dioxide 0.23 Ozone >1.7 a That eoncn. which will Droduce response equivalent t o 1 &of fluoride (0.2 pg. F-/en. meter), in 15 ml. of zirconium-Erioehrame Cvanine R reaeent within 3 hours~ata 1-c.f.m. sampling &e. I
~
Figure 1.
Submicron cryolite f u m e generator
filters. The filter papers were ashed with CaO, the fluoride was then distilled from perchloric acid, and titrated photometrically with thorium nitrate
(6,W.
Fluoride Sensitivity of Mini-Adak. The Mini-Adak operates as a modified dosimeter to concentrate sufficient fluoride to permit detection. The analyzer is usually adjusted to a 3hour reagent cycle and an air sampling rate of approximately 1 c.f.m. Under these conditions the minimum detectable quantity of fluoride is in the order of 1 pg. To obtain a similar reading in 30 minutes would require 8 concentration of approximately 1 pg. of F- per cubic meter. Any other combination of minutes and concentration yielding a product of 30 will also permit detection. (Recent improvements in the photosystem now permit detection of 0.25 pg. of F- per cubic meter, a fourfold sensitivity increase.) Monitoring Fumigation Chamber Atmospheres. Statistical comparison was made between the continuous Mini-Adak record and manual air sampling and analysis data, obtained as a by-product of plant fumigation studies conducted in this laboratory.
1 18
ANALYTICAL CHEMISTRY
Air in a plant growth chamber was continuously sampled through a gasscrubbing tower (7) containing a dilute solution of sodium hydroxide. Samples were taken twice daily a t approximate!y 8:OO A.M. and 5:OO P.M. for photometric titration with thorium nitrate (6). Simultaneously, the chamber air was sampled with a Mini-Adak. The continuous record obtained with the automatic instrument was converted to an average atmospheric concentration for each period repreTable I. Statistical Comparison of Mini-Adak and Manually Obtained Data Av. Concn., pg. F-/Cu. Meter MiniStd. Adak Manual Dev., % Atmosphere collection, N = 228 5.1 5.2 +20.9 Cryolite collection. 7 9 . 8 467 10.8 hslysis effioiency = 17.9%.
~
~
~
~~~~
sented by an air scrubber sample. These Comparative data are presented in Table I. Figure 2 displays 6 days' comparative data, the continuous instrumental record superimposed on the twice-daily manual data obtained from the analysis of the absorption solutions. This figure vividly contrasts the continuing variations in chamber air concentrations revealed by the automatic instrument and concealed by the averaging process of long term sampling. Although fluoride is introduced into the incoming chamber air at a constant rate, these fluctuations in atmospheric concentration are primarily attributable to diurnal differences in incoming chamber air temperatures. Lower night time chamber air temperatures are associated with greater surface adsorption, whereas the warmer daytime air minimizes wall adsorption. Interference Studies with Controlled Atmospheres. Successful application of automatic fluoride recorders in a variety of industrial and urban situations depends primarily upon the freedom of the method of detection from interference by other pollutants frequently present in the atmosphere. A series of atmospheres containing a range of concentrations of each of a variety of common atmospheric pollutants was prepared. The concentration of each pollutant was increased in a stepwise manner until a
definite reagent response u as measured. The tolerance limit for each pollutant was selected to be that concentration producing a recorder response equivalent to 0.2 pg. of F- per cubic meter when sampled continuously for 3 hours. Table I1 presents the results of these studies. SGLFKR DIOXIDE. Sulfur dioxide atmospheres in the conc,entration range of 0.3 to 5.9 p.p.m. were prepared. Initial reagent response was observed at 0.8 p.p.m., although a concentration of 5.6 p.p.m. of SOs produced a response equivalent to only 0.7 pg. of F- per cubic meter. Sensitive species of vegetation will not show foliar markings when e x p o d to less than 0.5 p.p.m. of
so2 (11).
HYDROGEN SULFIDE. Hydrogen sulfide atmospheres mere developed in the range of 0.3 to 1.5 p.p.m. A concentration of 0.9 p.p.ni. of H2S produced the initial reagent response equivalent to 0.2 pg. of F- per cubic meter when continuously sampled for 3 hours. The threshold of odor detection is reported t o be in the range of 0.1 to 0.8 p.p.m. (10, 1 2 ) . METHYLMERCAPTAX. Atmospheres containing CHISH in the concentration range of 0.5 to 6.9 p.p.m. were prepared. Initial reagent response mas observed a t 0.8 p.p.ni. when continuously present at that concentration for 3 hours. The threshold for odor detection is reported to be approximately 0.4 p.p.m. (10, 12). YITRIC OXIDE. No change in the color of the fluoride reagent was obtained n i t h NO atmospheres up to 1.52-p.p.ni. concentration. This is in excess of the 0.6-p.p.m. maximum values reported in Los Angeles (15). NITROGENDIOXIDE. Six different NOz atmospheres were prepared in the concentration range of 0.13 to 1.5 p.p.m. The first noticeable effect upon the reagent was produced by a 3-hour sampling a t a concentration of 0.23 p.p.m. The short-term maximum concentrations observed in the Los Angeles atmosphere are reported t o be in the order of 0.4 p.p.m. Hourly average concentrations range upward to 0.15 p.p.m. (15). OZONE. No reagent response was obtained from ozone up to concentrations as high as 1.71 p.p.m. Further increase in concentration Bas not tested, since the maximum concentrations recorded in the Los Angeles area have been in the order of 0.6 to 0.8 p.p.m. (13).
Efficiency of Cryolite Aerosol Analysis. Submicron cryolite fume was generated a t a concentration up t o 30 pg. of cryolite per cubic meter. Experience has shown that hydrofluoric acid will also be present in the smelt effluent. Although the effluent was passed through a spray tower to remove acidic gases and larger particulates prior to introduction into the test chamber, an additional gaseous removal step was used during this study to ensure complete elimination of HF from the test atmosphere. Each test atmosphere was drawn isokinetically through a glass tube, 5mm. inner diameter and 40 inches long,
coated internally with sodium carbonate. Excellent fluoride removal is possible when fluoride-containing air is passed through these tubes within the range of turbulent flow. The sodium carbonate will remove as much as 180 pg. of F- per cubic meter for 3 hours before losing effectiveness. The Mini-Adak submicron cryolite analysis efficiency was determined by simultaneous sampling a t identical flow rates using Millipore filters. The Millipore filter was followed by an absorption tower containing a dilute solution of sodium hydroxide. Assuming the latter is 100% efficient, the solution was photometrically titrated with standard thorium nitrate solution at the conclusion of each test run to confirin the absence of gaseous fluorides in the test atmosphere ( 5 ) . Table I also compares the analysis ability of the strongly acid Mini-Adak reagent with the cryolite collected on the Millipore Filter. These data indicate that the Mini-iidak has an analysis efficiency of approximately 18% for submicron cyrolite fumes. Interference Studies with Added Cations and Anions. The response of the zirconium-Eriochrome Cyanine R complex t o additional compounds possibly present as dusts or aerosols in a complex atmosphere was determined by the stepwise addition of various ionic species in aqueous solution. The definition of t h e limiting concentration of added diverse ions mas identical with that used in the previous gaseous studies. The limiting concentration data are presented in Table 111. Aluminum, phosphate, and sulfate appear t o present the greatest source of potential interference.
Ion Alfa Mg+:’ Ca Na + POa-’ sod-2
c1NO3NOza
111.
See Table 11.
The tolerance limits for many common air pollutants with the MiniAdak zirconium-Eriochrome Cyanine R fluoride reagent have been established. Of the pollutants studied, only aluminum, phosphate, and sulfate are considered to be possible sources of interference, with phosphate being the most significant interfering substance. The fluoride reagent appears to be free from interference from the major Los Angeles smog gases. The analysis efficiency for submicron cryolite is approximately 18%, ACKNOWLEDGMENT
Alumina cryolite bath material was furnished by Kaiser Aluminum & Chemical Corp. The analytical assistance of Sharon Grimes and Judith Mowery is gratefully acknoiyleclged. LITERATURE CITED
(1) Adams, D. F., AXAL.CHEM.32, 1312 (1960). (2) Adams, D. F., Applegate, H. W.,
Hendrix, J. W., J . Agr. Food Chem.
5 , 108 (1957). (3) Adam$< D. F., Dana, H. J., Koppe,
!F
R. K., Report on Universal Air U. S. Dept. Pollutant Analyzer, Health, Education, and Welfare, Sept.
4, 1957. (4) Adams, D. F., Emerson,
M. T., Washington State University, Pullman, Wash., unpublished data, 1954. (5) Adams, D. F., Koppe, R. K., ANAL. CHEM.28,116 (1956).
(6) Ibid., 31, 1249 (1959). (7) Adams, D. F., Mayhew, D. J., Gnagy,
R. M , Richey, E. P., Koppe, R. K., Allan, I. W., Ind. Eng. Chem. 44, 1356 \ - -
Interference Limits Common ions
Added As AlC1, MgCh CaClz NaClz NaHzP04 Na2S04 NaCl NaNOs NaN02
7.5.
(19.52’). --*
CONCLUSIONS
Instrumental analysis of chamber atmospheres revealed a ‘[fine structure” of changing diurnal concentrations not previously possible with the long-term averaging-type sampling. The minimum sensitivity of the fluoride reagent is stated as any combination of micrograms of F- per cubic meter and minutes of exposure time,
Table
yielding a value of 30. Recent improvements in the photometric circuitry have reduced the sensitivity factor t o
Limiting Concn., rg./Cu. Metera 50 >1777 >6777 >6777 13 67 >6777 >6777 >6777
of
(8) Adams, D. F., Shaw, C. G., Yerkes, W.D., Jr., Phytopathol. 46, 587 (1956). (9) Austin, R. R., Am. Gas. Assoc. Proc. 31, 505 (1949).
(10) Della Valle, J. M., Dudley, E. H., Public Health Repts. (U.8.) 54, 35
(1939’). (11) Katz, M., “Proc. of the U. S. Tech. Conf. on Air Pollution,” p. 84, McGrawHill, New York, 1952. (12) Katz, S. H., Talbert, E. J., U. S. Bur. Mines Tech. Papers 480 (1930). (13) Littman, F. E., Benoliel, R. W., ANAL.CHEM.25,1480 (1953). (14) Megregian, S., Ibid., 26, 1161 (1954). (15) Rogers, L. H., J . Air Pollution Control Assoc. 8 , 124 (1958). (16) Saltzman. B. E., ANAL.CHEM.32. 135 (1960). ’ (17) Saltzman, B. E., Gilbert, X., Ibid., 31.1914 (19.59’). \ - - - - ,
ENG.CHEM.,ANAL. ED.5 , i (1933j.
RECEIVEDfor review August 13, 1960. Accepted October 24, 1960. Division of Water and Waste Chemistry, 138th Meeting, ACS, New York, N. Y., September 1960. This investigation was primarily supported by PHS Research Grant S-120 from the Division of General Medical Sciences, Public Health Service. VOL. 33, NO. 1, JANUARY 1961
119
