gaseous impurities which do not affect the dew point of air but retard the dissolution rate and solubility of the hygroscopic materials in water existed in the atmosphere, the existing clouds and fogs should tend to disappear. Sodium chloride particles were recently used in tests to clear fog from airports. Relatively good results were reported for these tests in the 1969 Spring issue of Research Trends by Cornel1 Aeronautical Laboratory, Inc., Buffalo, New York. It would be interesting to determine the extent that polluted atmospheres affect the efficiency of this technique. Acknowledgment The author wishes to thank Dr. Clyde Orr, Jr., for valuable discussions and suggestions and Mrs. Clara Wellons for her contribution in the experimental phases of the study. Literature Cited Aitken, J., “Collected Scientific Papers,” C. G . Knott, Ed., Cambridge University Press, London (1923). Cadle, R. D., “Particles in Atmosphere and Space,” pp. 7-1 1, Reinhold Publishing Corp., New York (1966).
Goetz, A., Preining, O., Geophys. Monogruph, No. 5 , NASNRC No. 746, 164-82 (1960). Grafe, K., Gesundh-lngr. 81, 302-8 (1960). Hidalgo, A. F., Orr, C., Jr., Ind. Eng. Chem., Fundam. 7, 79-83 (1968). Hurd, F. K., Mullins, J. C., J. Colloid Sci. 17, 91-100 (1962). Lucas, D. H., Intern. J. Air Pollution 1, 71-86 (1958). Orr. C.. Jr.. Hurd. F. K.. Corbett. W. J.. J . Colloid Sci. 13. 4i2-82 (1958). ’ Parker, A,, Trans. 5th World Power Conf. Vienna, Div. 3, Sect. M. Paper 9 Mil. 23 (1956). Twomey, S., j . Meteoi. 11, 334-8’(1954). Woodstock, A. H., Sei. American 197, 42-7 (1957).
Received for review September 16, 1968. AcceptedSeptember 5 , 1969. Presented in part at Symposium on Colloid and Surface Chemistry in Air and Water Pollution, Dicision of Colloid and Surface Chemistry, 156th Meeting, A C S , Atlantic City, N . J . , September 1968. The work was supported by the Dicision of Air Pollution, US.Public Health Sercice, Grant No. AP-00345.
Collection and Determination of Trace Quantities of Pesticides in Air James W. Miles, Laurice E. Fetzer, and George W. Pearce Technical Development Laboratories, Laboratory Division, National Communicable Disease Center, Health Services and Mental Health Administration, Public Health Service, U.S. Department of Health, Education, and Welfare, Savannah, Ga. 31402
rn Techniques for sampling air for pesticides were studied. Pesticide dusts and vapors were trapped more efficiently from air by Greenburg-Smith type impingers than by filters. Ethylene glycol was superior to water and hydrocarbon solvents as a trapping medium. Membrane filters were more efficient than filter paper or glass fiber filters and showed unusual affinity for some organophosphorus vapors. An apparatus for continuous or intermittent air sampling is described along with methods for recovery and determination of the pesticide residues.
I
n order to study human and animal exposure to pesticides by the respiratory route, it is necessary to sample the ambient air and determine concentrations of the various compounds that may be present. Although most work of this type has been concerned with occupational exposure to specific pesticides (Batchelor and Walker, 1954; Culver, Caplan, et al., 1955; Culver, Caplan, et al., 1956; Durham and Wolfe, 1962; Jegier, 1964a and b; Simpson and Beck, 1965; Wolfe, Armstrong, et a/., 1966; Wolfe, Durham, et a/., 1967) or exposure of populations in treated areas (Caplan, Culver, et a/., 1956; Culver, Caplan, et a/., 1955; Culver, Caplan, et a/., 1956), some random sampling of the atmosphere (Abbott, Harrison, et a/., 1966; Tabor, 1966) has been reported. The sampling of air for pesticides is complicated by the fact that they may exist in aerosol, vapor, or particulate form. 420 Environmental Science & Technology
The most widely used techniques for air sampling include collection on packed columns which adsorb the pesticides (Hornstein and Sullivan, 1953; Mattson, Sedlak, et a/., 1960; Simpson and Beck, 1965) passing the air through scrubbers fitted with fritted disks or gas dispersion tubes that break up the air stream t o promote absorption of the pesticide by a liquid phase (Abbott, Harrison, et ul., 1966; Caplan, Culver, et a/., 1956; Culver, Caplan, et ul., 1955; Hirt and Gisclard, 1951; Jegier, 1964a and b ; Kay, Monkman, et a/., 1952); collection in freeze-out traps filled with glass helices and maintained at low temperatures (Shell Development Co., 1959); drawing large volumes of air through glass-fiber filters (Tabor, 1966) or cellulose filter pads (Batchelor and Walker, 1954; Durham and Wolfe, 1962; Jegier, 1964a and b ; Simpson and Beck, 1965; Wolfe, Armstrong, et al., 1966; Wolfe, Durham, et a/., 1967); or trapping in midget or Greenburg-Smith type impingers (Adams, Jackson, et a/., 1964; Batchelor and Walker, 1954; Caplan, Culver, et a/., 1956; Culver, Caplan, et a/., 1956; Durham and Wolfe, 1962; Hirt and Gisclard, 1951 ; Kay, Monkman, et a/., 1952; Roberts and McKee, 1959; Simpson and Beck, 1965; U.S. Public Health Service, 1961; Wolfe, Durham, et al., 1967). Although each of these methods has certain advantages, none is ideal. For example, packed columns are very efficient for trapping vapors, but recovery of the sample is frequently difficult; the filter systems permit the collection of large volumes of air in short periods of time, but their efficiency for vapors is low and unknown losses of particulate and aerosol samples occur during the sampling period; the scrubbers are good for aero-
sols and vapors, but the sampling rate is slow and the use of sintered glass precludes the collection of particles; and cold traps are of limited value in field work in view of the maintenance problem. Midget and Greenburg-Smith type impingers seem to offer a compromise in that they can be operated at a reasonably fast rate, they are very efficient for collection of particulate matter, and with proper selection of solvent they can collect aerosols and vapors efficiently. Midget bubblers, midget impingers, and Greenburg-Smith impingers were studied by Roberts and McKee (1959) as absorption devices for trapping ammonia, chlorine, and SOs. The midget bubblers and midget impingers were found t o trap the gases with high efficiency if the flow rates were closely controlled. The Greenburg-Smith impingers trapped the gases with better than 90% efficiency over a wide range of flow rates. Gage (1960) also studied liquid absorbers and concluded that design of the apparatus is important when trapping particulate matter but not vapors or gases. H e found the main factors to be the volatility of the substance from the absorbing solution and the volume of the sample taken. Culver, Caplan, et a/. (1956) sampled aerosols of malathion and chlorthion with midget impingers and claimed 90 % trapping efficiency. Caplan, Culver, er a/. (1956) sampled malathion aerosols after aerial spraying with a 7.5% solution of malathion in an oil base. H e used scrubbers and Greenburg-Smith impingers and found the scrubbers to be more efficient than the impingers. Mattson, Sedlak, et cil. (1960) reported o n a method for determination of DDVP (2,2-dichlorovinyl dimethyl phosphate), in air based on the quantitative removal of DDVP vapors by a n activated alumina column. Although the method proved to be useful, there were several disadvantages. First, there is considerable variation in commercially available alumina, which results in variable and sometimes high blank values; and second, while activated alumina is an efficient trapping medium, it catalyzes the decomposition of DDVP and makes it necessary to determine the pesticide by a nonspecific method, namely, by determination of phosphorus in the eluted sample. A search for an improved medium to trap DDVP vapors revealed that Greenburg-Smith type impingers charged with water can trap DDVP vapors with an efficiency of approximately 90% at flow rates of 10 liters per minute. The U.S. Public Health Service published a method (1961) for determination of DDVP in air in which two Greenburg-Smith type impingers charged with water were connected in tandem t o trap the vapors. The present work was undertaken to extend the impinger sampling technique to other insecticides and to develop a semiautomatic instrument for atmospheric sampling. In view of the success obtained with DDVP vapors, it was decided to test the efficiency of the Greenburg-Smith type impingers with other insecticides. In the work described here, the mediumsize Greenburg-Smith type impingers were charged with 25 ml. of solvent and connected in tandem. Various solvents were tested to determine which was most efficient. Consideration was also given to recovery of the samples from the solvent for quantitative determination.
pump (Gelman Instrument Co., Ann Arbor, Mich.). Each set of impingers was calibrated with a wet-test meter to determine the exact flow rate. At vacua greater than 15 inches Hg the impingers act as critical orifices, and once the flow rate was determined for a given set, the volume of air sampled was calculated from the flow rate and the length of time of sampling. The average flow rate of air through one, two, and three impingers in series was 12.6, 10.3, and 8.3 liters per minute, respectively. Gas chromatographic determinations of the pesticides were made on a MicroTek gas chromatograph Model 2500R using a Ni63 electron capture detector. In the case of DDVP, separations were made o n a 5-foot X '/(-inch glass column packed with 3 % SE-30 on 100/120 mesh Chromosorb W, AW, DMCS, at 160" C. with 50 ml. per minute N2flow. All other pesticides were separated on a 6-foot X %-inch aluminum column packed with 3 z OV-101 on Chromosorb W, AW, DMCS at 195 O C. with 60 ml. per minute Nz flow. Peak areas were compared with standards to determine the pesticide concentrations. Three organophosphorus compounds, DDVP, Diazinon, and parathion, and two halogenated hydrocarbon insecticides, DDT and dieldrin, were chosen t o determine the efficiency of the Greenburg-Smith type impingers for trapping insecticide dusts and vapors. The efficiency of the traps for organophosphorus vapors was determined by introducing small amounts of the insecticides into the air stream entering the impingers by means of a glass U-tube attached to the inlet of the first impinger. After introducing DDVP o r parathion into the U-tube, the impingers were charged with water and air was drawn through the train at 10.3 liters per minute. A cold trap packed with glass helices and immersed in a dry ice-acetone bath was connected to the trailing impinger in the tests with DDVP. At the end of each run, traps were analyzed for insecticide content. The DDVP was determined by the phosphomolybdate method for total phosphorus (U.S. Public Health Service, 1961). The parathion was determined by gas chromatography after extraction from the water with benzene. Data from these experiments are shown in Table I. The impingers charged with water proved to be efficient traps for DDVP vapors, with approximately 97% of the total sample in the first two traps after one hour of sampling. On the contrary, the parathion vapors were trapped efficiently only for short sampling periods with appreciable losses occurring after 30 minutes of sampling. A variety of solvents were substituted for water in the impingers in a n effort to improve the efficiency by taking advantage of greater pesticide solubilities. Isooctane, toluene,
Experimental All of the experiments were conducted with at least two Greenburg-Smith type impingers (Ace Glass Co., Model 7542) connected in tandem. The impingers were modified by the addition of 18/9 ball and socket joints so that connections could be made without the use of rubber or plastic tubing. The impingers were charged with 25 ml. of solvent and air was drawn by means of a Gelman Model 13152 vacuum
DDVP DDVP DDVP Parathion Parathion Parathion Parathion
Table I. Efficiency of Greenburg-Smith Impingers for Trapping DDVP and Parathion Vapors in Water Cornpound
Period 9f A u a n t i t y of insecticide found, mcgm. run, min. ( of total trapped given in parentheses) Cold Impinger I Impinger I1 trap 60 60 60 10 15 30 60
7 1 . 3 (82.6%) 1 2 . 3 ( 1 4 . 3 % ) 81.4 ( 8 3 . 6 z ) 13.2(13.6%) 77.0 ( 8 2 . 7 z ) 13.3(14.2%) 1 1 . 3 (100.0%) 0 . 0 19.1 (90.9z) 1 . 9 16.0 (76.2z) 5 . 0 1 0 . 0 (52.6%) 9 . 0
2.7 2.8 2.9
Volume 4, Number 5, May 1970 421
and ethyl benzene trapped parathion with high efficiency; however, solvent losses from the impinger train were high and long runs could not be made. Aliphatic hydrocarbons of higher molecular weight, including wnonane and ti-decane, tended to form aerosols when air was passed through the impingers, with a resulting loss of solvent. These solvents were also difficult to evaporate, and concentration of the trapped pesticide was a problem. Far better results were obtained with ethylene glycol. It was a good solvent for most insecticides; it had a low vapor pressure, and losses from the traps were very low even when sampling was conducted for long periods; and finally, it was easy to separate the sample from the solvent for cleanup and concentration for gas chromatographic analysis. After collection of the sample, the ethylene glycol solutions from the traps were transferred to I-liter separatory funnels containing 500 ml. of water. The pesticides were then extracted three times with 25-ml. portions of benzene and the extracts dried over sodium sulfate and concentrated to an appropriate volume for gas chromatographic analysis. The efficiency of the extraction step was determined by adding known quantities of pesticides to ethylene glycol and analyzing the samples by the above procedure. Satisfactory recoveries of both chlorinated hydrocarbon and organophosphorus compounds were obtained. The efficiency of Greenburg-Smith type impingers charged with ethylene glycol was determined for parathion and Diazinon vapors by the U-tube technique described above, as well as by sampling air from Peet-Grady chambers (1928). Vapors of parathion and Diazinon were produced in the chambers by placing a shallow dish of the technical grade pesticide on a hot plate and blowing a stream of air over the surface. Data from these tests are presented in Table 11. Excellent recoveries of both parathion and Diazinon were obtained, although some slippage was observed with increasing sampling periods, as indicated by the small quantities of material found in the dry ice traps. The efficiency of Greenburg-Smith impingers for trapping pesticidal dusts was also studied. A special chamber was constructed for dispersing and sampling dust particles. The chamber was made of galvanized sheet metal formed into a cylinder 6-feet tall and 1 foot in diameter, with a conical
bottom tapering to a diameter of 2 inches. Approximately 10 grams of the powder under test was placed in a 2-inch sintered glass funnel fitted to the bottom opening of the chamber and dust particles were dispersed by conducting compressed air upward through the stem of the funnel. Dust samples were taken through holes drilled in the chamber wall. To keep the sample quantities low, the dust particles were allowed to settle for 30 min. before the sampling. Assuming the particles had a density of 1.0 or greater, according to Stokes’ Law, the maximum diameter of the particles remaining suspended in the chamber would be less than 6 p. The materials used in the experiment were 90%p,p’-DDT, 75 % dieldrin, 15% parathion, and 40% Diazinon water-dispersible powders. Samples were collected with impingers charged with water o r ethylene glycol, and analyzed as described previously. Data from these tests are given in Table 111. All dusts tested were trapped with very high efficiency. In the case of parathion. the traps charged with water were significantly less efficient than those with ethylene glycol. Additional tests were conducted to determine impinger loss when large volumes of air were passed through the system. Small quantities of DDT, parathion, or Diazinon were introduced into the solvent in the first impinger and the second impinger was charged with solvent alone. Air was drawn through the system for 4 or 5 hours at 10.3 liters per minute and subsequently each impinger was analyzed. In all tests, more than 90% of the sample remained in the leading impinger. Tests were run to determine the efficiency of paper, glassfiber, and membrane filters for trapping dusts and vapors. Two-inch circles of the filter media were placed in open filter holders type 1200A (Gelman Instrument Co., Ann Arbor, Mich.) modified by the addition of l8/9 ball joints. The filter was connected t o the inlet of a train of three impingers charged with ethylene glycol. Sampling for DDT dust was done in a laboratory where routine tests were run on DDT water-dispersible powders. No dusts were introduced into the room for at least 24 hours prior to sampling and no dust was visible in the room during the sampling period. Under these conditions, according to Stokes’ Law, the maximum diameter of particles in the air would be less than 1.O p.
Table 11. Efficiency of Greenburg-Smith Impingers for Trapping Parathion and Diazinon Vapors in Ethylene Glycol Quantity of insecticide found, mcgm. of total trapped given in parentheses) Method of Period ,of introduction run, min. Impinger I Impinger I1 Cold trap
(x
Compound Parathion Parathion Parathion Parathion Parathion Parathion Diazinon Diazinon Diazinon Diazinon Diazinon Diazinon Diazinon Diazinon a
U-tube U-tube U-tube P-G Chamber P-G Chamber P-G Chamber U-tube U-tube U-tube U-tube P-G Chamber P-G Chamber P-G Chamber P-G Chamber
U-tube heated.
422 Environmental Science & Technology
30. 240 300 60 60 240 60 60 240 240 60 60 240 240
8 . 4 (77.8%) 23.7 (94.8%) 23.9 ( 9 0 . 2 z ) 174.0 (87.0%) 18.2 (87.0%) 19.8 (87.2%) 70.5 (85.8%) 8 2 . 8 (86.1%) 26.1 (79.3%) 25.5 (79.7%) 176.3 (97.6%) 215.6 (95.2%) 319.0 (83.0%) 812.0 (84.0%)
2.4 1.3 2.6 25.0 (12.5%) 2 . 5 (12.0%) 2.7 (11.9x) 10.6 (12.9%) 11,2(11.7%) 6 . 0 (18.2%) 5.8(18.1%) 4 . 3 (2.4%) 9 . 5 (4.2%) 60.0 (16.0%) 148.0 (15.0%)
1.o 0.2 0.2 1.1 2.1 0.8 0.7 0.01 1.4 4.0 9.0
Table 111. Efficiency of GreenburpSmith Impingers for Trapping Insecticide Dusts in Water and Ethylene Glycol
Dust DDT DDT DDT
DDT DDT Dieldrin Dieldrin Dieldrin Dieldrin Dieldrin Parathion Parathion Parathion Parathion Diazinon Diazinon Diazinon Diazinon Diazinon a
Solvent
of pesticide found, mcgm. (zQuantity of total trapped given in parentheses)
-
Period of run, min.
Impinger I
4 4 8
7500 (99.3%) 1220 (99.4%;) 3950 (99.8 %)
55.0 6.8 6.5
8
3717 (99.0%)
9.0
8
4050 (99.6%)
18.0
4 4 4
170 (97.6%;) 124 (98.5%) 440 (99.7 %)
3.5 (2.073 1 . 7 (1.4%) 1.1 (0.273
0.6 0.2 0.08
4
225 (99.8 %)
0 . 4 (0.2%;)
0.06
240.
30.8 (86.5%)
4 . 1 (11.5%)
0.7
4 4 4
1410 (94.1 %) 230 (88.475) 3000 (99.9 %)
85.0 30.0 2.3
4
1700 (99.8%)
3.0
4 4 4 4
2470 (99.1 %) 6100 (98.7 %) 9900 (99.7%) 2800 (99.3 %)
22 78 28 19.0
4
3200 (99.7%)
11.1
Water Water Ethylene Glycol Ethylene Glycol Ethylene Glycol Water Water Ethylene Glycol Ethylene Glycol Ethylene Glycol Water Water Ethylene Glycol Ethylene Glycol Water Water Water Ethylene Glycol Ethylene Glycol
Impinger I1
Impinger I11
Run made after allowing dust to settle in chamber for 24 hours
Table 1V. Efficiency of Various Filter Media for Trapping DDT Dust, Diazinon, and DDVP Vapors Pesticide found, mcgm. Filter Impinger holder I
Impinger
7.5 (88.2z)
0.42
0.36
0.14
0.08
1920
7 . 0 (89.6%)
0.45
0.30
0.03
0.03
996 1944
1 . 2 (93.0%) 71.3 (93.0%)
0.02 4.4
0.05 0.9
0.02 0.1
0.07
1920
41.3 (42.2%)
9.4
42.3
4.4
0.5
648 648 81
13.8 (97.9%) 9 3 . 8 (98.7%) 21.7(38.1%)
0.30 0.29 1.2
