a45
Anal. Chem. 1984, 56,845-847
(3) Harker, A. B.; Richards, L. W.; Clarke, W. E. Afmos. Environ. 1977, 11, 87-91. (4) Durham, J. L.; Wilson, W. E. Atmos. Environ. 1978, 12, 883-886. (5) Ferm, M. Atmos. Envlron. 1979, 13, 1385-1393. (6) Lewin, E. E.; Klockow, D. I n "Physlco-chemical Behaviour of Atmob pherlc Pollutants"; Proceedings of the Second European Symposium, Varese, Italy, Sept 29-0ct 1, 1981; pp 54-61. (7) Forrest, J.; Spandau, D. J.; Tanner, R. L.; Newman, L. Afmos. Environ. 1982, 16, 1473-1485. (8) Keiding, K.; Hansen, A.-M. Report MST LUFT-A66: SOp-analyser i det landsdaekkende luftkvalitetsmaaleprogram. (9) Gormley, P.; Kennedy, M. Proc. R . I f . Acad. S e d . A 1949, 52A. 133-169.
capacity corresponds to about 100 m3 of air. At present the system is undergoing field trials with respect to its performance under different ambient conditions. Also, it is planned to investigate the applicability of the acid-DDA for collection of SOz and HC1 gas. Registry No. NH3, 7664-41-7; Sod2-,14808-79-8; NO3-, 14797-55-8; C1-, 16887-00-6.
LITERATURE CITED (1) Stevens, R. K.; Dzubay, T. 0.; Russwurm, G. M.; Rickel, D. Afmos. Environ. 1978, 12, 55-68. (2) Brosset, C. Paper presented at the Division of Environmental Chemistry, 177th National Meeting of American Chemical Society, Honolulu, HI, April 1-6, 1979.
RECEIVED for review September 6,1983.
Accepted December
8, 1983.
Condenser for Reclamation and Reuse of Organic Solvents John J. Blaha* and DuWayne E. Ready Food and Drug Administration, 1009 Cherry Street, Kansas City, Missouri 64106 Clifton E. Meloan and Mitsugi Ohno Department of Chemistry, Kansas State University, Manhattan, Kansas 66506 The Total Diet Study of the FDA is a surveillance program which monitors the levels of chemical residues in foods as they would be eaten by the American consumer. Details of the program are discussed elsewhere (1-3). The methodology used for the determination of organic chemical residues, such as herbicides and pesticides, requires the use of large volumes of organic solvents. These are used as pure solvents or as solvent mixtures depending on the application. The sheer volumes of solvents required for the study and the ever increasing cost of these solvents have caused us to investigate procedures for cutting expenses without sacrificing the quality of the study. One procedure investigated was the possible reuse of selected solvents.
EXPERIMENTAL SECTION The solvents are of pesticide quality and have been distilled in glass prior to initial use. During the analyses for chemical residues, the solvents are collected in Kuderna-Danish (K/D) flasks fitted with graduated tips. A Snyder column is attached and the solvent removed by heating over a steam bath. We designed a simple glass condenser to collect the solvent vapors and pass the condensed liquid to a storage bottle. The assembled solvent collection system is shown in Figure 1. The condenser (labeled A) is a 50 mm i.d. tube fitted with an 18 mm i.d. tube mounted in the center and traversing the length of the larger tube. The overall length of the condenser is 75 cm. A schematic of the condenser is shown in Figure 2. Cold water is passed through the smaller tube which then acts as a condensation site for the solvent vapors. There are four ports for connection to the K/D glassware (labeled B). Flexible Teflon tubing (1 cm i.d.) is used for all connections between the condenser and the K/D glassware. A stoppered still head (labeled C) is used to add additional reagents if necessary. The condenser has also been fitted with a vacuum line attachment (labeled D)to aid in the collection of solvent vapors. For the applications discussed here, the vacuum port was not used. Condensed solvents are collected in a bottle or flask (labeled E) and stored in brown bottles.
RESULTS AND DISCUSSION All analytical procedures for the determination of organic chemical residues in the Total Diet Program are described in the Pesticide Analytical Manual (4). The foods analyzed
~~
~
Table I. Relative Percent Composition of the Used Solvent after the First Collection Compared to the Original Solvent
solvent 1
2 3 4 5
6 7 8
component methylene chloride hexane acetonitrile methylene chloride hexane ethyl ether petroleum ether ethyl ether petroleum ether ethyl ether petroleum ether methylene chloride methylene chloride hexane methylene chloride hexane
orig composn composn, after 1st % collctn, % 25 75
40 60
0.5 49.5 50
0.4 43.6 56
6 94
5 95
15
12 88 40 60
85 50 50
100 10 90
50 50
100 13 81 70 30
are representative of the full range of raw and cooked food items commonly eaten by the American consumer. These include fruits, vegetables, meats, fatty foods such as peanut butter, grains, recipe items such as lasagna, dairy products, baby foods, and alcoholic beverages. The extraction procedures which remove the organic chemical residues from these foods also remove a large number of indigenous sample compounds. These compounds complicate the determination of organic chemical residues. Therefore a number of cleanup procedures are used. These include the use of gel permeation chromatography and Florisil column chromatography for the cleanup of food eluates. Each cleanup step requires a different solvent or solvent mixture. For this work, we focused our attentions on eight solvents/solvent mixtures. These are itemized in Table I. Solvents 1through 5 are used for Florisil column cleanup. Solvents 1 and 2 are used in series to
0003-2700/84/0356-0845$01.50/00 1984 American Chemical Society
846
ANALYTICAL CHEMISTRY, VOL. 56, NO. 4, APRIL 1984
Table 11. Percent Recovery of Organophosphorus Pesticide Spike to Foods for 10%Methylene Chloride in Hexane and Methylene Chloride Solvents Used in Seriesa solvent reconstitution (SR) number and food spiked compound diazinon monitor acephate malathion malaoxon phenthoate azodrin supracide dimethoxon dimethoa te a
spike level, PPm 0.3 0.4 0.5 0.5 0.2 0.2 0.4 0.6 0.4
original, peppers 94 90 90 89 89 97 94 94 108 97
0.3
1 s t SR, onions
2nd SR, whiskey
3rd SR, grapes
99 (97) 92 (90)
89 (91) 8 1 (82) 9 1 (96) 108 (99) 88 (93) 98 (94) 96 (94) 100 (96) 98 (92) 101 (95)
97 (95) 95 (95) 99 (94) 106 (100) 93 (92) 96 (94) 92 (97) 100 (97) 93 (92) 105 (98)
113 (103) 110 (101) 92 (94) 97 (93) 89 (93) 94 (94) 92 (92) 104 (96)
Recoveries from fresh solvent are listed in parentheses.
Table 111. Percent Recovery of Organophosphorus Pesticide Spike to Foods for 50%Methylene Chloride in Hexane Solventa solvent reconstitution (SR) number and food spiked
a
compounds
spike level, PPm
original, lasagna
1st SR, coleslaw
2nd SR, cornbread
diazinon parathion ethion
0.4 0.8 1.2
92 102 112
87 (89) 95 (94) 100 (93)
90 (94) 102 (97) 107 (103)
3rd SR, pork chow mein 84 (85) 9 1 (93) 108 (101)
Recoveries from fresh solvent are listed in parentheses.
Table IV. Percent Recovery of Organohalide Compound Spike to Foods for (1:3 Methylene Ch1oride:Hexane) and (0.5% Acetonitrile + 49.5%Methylene Chloride + 50% Hexane) Solvents Used in Seriesa
compounds lindane heptachlor a-BHC aldrin hept, epoxide p-chlordane
spike level, PPm 0.2 0.2
0.3 0.5 0.6 1.0
solvent reconstitution (SR) number and food spiked original, milk 1st SR, oranges 2nd SR, spinach 3rd SR, grapes 88 89 88 89 91 85
83 88 86 88 90 88
(88) (90) (89) (93) (85) (83)
87 (86) 84 (85) 108 (92) 8 1 (83) 82 ( 8 3 ) 84 (86)
88 97 110 95 95 90
Recoveries from fresh solvent are listed in Darentheses. quantitatively elute residues from the Florisil column. Solvents 3 , 4 , and 5 are also used in series as a separate elution system. Solvents 6 and 7 are used in sequence for the quantitative extraction of organic chemical residues from food samples, and solvent 8 is used as the elution solvent in the gel permeation chromatographic cleanup procedure. The collection of solvents is not a new idea. In practice, however, all spent solvents, regardless of original composition, are usually collected together and then individual components are separated by fractionation. We found this approach to be impractical as many of the solvents form azeotropes and we would not easily recover individual solvents from the distillation. Instead, we grouped all like solvents and collected each independently. These were subsequently analyzed for any residues that may have contaminated them and the solvent mixtures were tested for relative composition to determine the feasibility of reconstitution and reuse of those solvents. For our tests, 20 samples (18 foods 1 food and spike + 1blank) were analyzed through the use of the original solvent. The solvents from all 20 samples were combined. We found that all solvents recovered were free of chemical residues. Each solvent was analyzed by taking 400% of the volume normally used for residue determinations (e.g., 800 mL for a normal volume of 200 mL) and concentrating to 2 mL. Thus
+
each solvent was concentrated at least 200-fold prior to being tested. This concentrated sample was then examined by gas chromatography with electron capture, electrolytic conductivity and thermionic detectors on a variety of columns. We then examined the solvent collection by gas chromatography on a Chromasorb 102 column with a flame ionization detector to determine the relative composition of the solvent. These had modified slightly but could be easily reconstituted by adding fresh solvent to bring the composition of the collected solvents back to that of the original solvent/solvent mixture (see Table I). Appropriate fresh solvent was added to make the collected mixture equivalent to the original solvent mixture. These solvents were used shortly after being reconstituted and were not stored for long periods of time before being used. This reconstituted solvent was then used in the analysis for residues from 20 additional food samples. The entire process was repeated three times. A total of 80 samples of the various types enumerated above were analyzed. The 60 food items analyzed with reconstituted solvents were also examined in parallel with fresh solvent. No differences in analytical capability between the fresh and reconstituted solvents were observed. Tables 11-V show the percent recovery of standards added to the foods for the tests. Each solvent was collected separately. Total recoveries are reported. Recoveries are comparable. We did not further repeat the
Anal. Chem. 1984. 56. 847-849
047
Table V. Pereent Recovery of Organohalide Compound Spike to Foods for Mixed Ether Solvents (Number 3.4, and 5 of Table I ) Used in Series” spike level, ppm
compounds
solvent reconstitution (SR)number and food spiked original, mayonnaise 1st SR, tomatoes 2nd SR, syrup 3rd SR, apple juice
dieldrin
0.5
85 100
methoxychlor
0.8 2.0
p,p ‘-DDT
92
85 (93) 91 (89) 83 (86)
89 (86) 87 (89) 88 (92)
93 (81) 81 (86) 89 (87)
Recoveries from fresh solvent are listed in parentheses
Figure 1. The assembled solvent collection system wiih condenser (A). KID glassware attached to polls (E), stoppered stillhead (C), vacuum line port (D). and collection flask (E).
75cm len th 18 mm i.d.
5Omm i d .
ported are averages as there were variances in the actual percentages of each individual component. As the greatest variant in the mixed ether solvents (listed as 3, 4,and 5 in Table I) was ethyl ether, we did not attempt to exactly reproduce the original composition of the petroleum ether. Instead. fresh ethyl ether was added to the mixture. Our subsequent tests in parallel to fresh petroleum etherfethyl ether solvent mixtures showed no difference in total analytical capability. Preservatives, which might have been lost during the concentration proma, are replenished with the added fresh ethyl ether. We estimate that the collection and reconstitution of these selected solvents in the manner stated above will reduce the volume of fresh solvents required by approximately 80% and will reduce the overall volume of solvents used in our operations by about 40%. This translates to a cost savings of approximately $15000 per year. This figure may be increased by judicious collection and reconstitution of all solvents used. Registry No. Diazinon, 333-41-5;monitor, 10265-92-6;acephate, 30560-19-1;malathion, 121-75-5;malaoxon, 1634-78-2; phenthoate, 2597-03-7;azodrin. 6923-22-4;supracide, 950-37-8; dimethoxon, 1113-02-6; dimethoate, 60-51-5;parathion, 56-382; ethion, 563-12-2;lindane, 58-89-9;heptachlor, 76-44-8;a-BHC, 319-84-6;aldrin, 309-00-2;heptachlor epoxide, 1024-57-3:@chlordane, 5103-74-2;dieldrin, 60-57-1; p,p’-DDT, 50-29-3;methoxychlor, 72-43-5;methylene chloride, 7509-2: hexane. 110-54-3: acetonitrile, 75-05-8;ethyl ether, 60-29-7
LITERATURE CITED in
lOmm 0.d.
In
Figum 2. Schematic of condenser showing the dimensions of the component parts. The vacuum etlachment is not shown.
process to asnure that interferences did not overwhelm our analytical capabilities. The collection/reconstitutionprocedure could be repeated but further tests would be necesaary to validate the procedure. All possible solvents used in the Total Diet Program were not tested. Note that petroleum ether is a mixture of several solvents with a boiling range from 30 to 60 “C. The percentages re-
Pennhgton. J. A. T. J . Am. mi.A m . 1989. 82. 10B-173. Johnson. R. D.: Msnske. D. 0.;New. D. H.: Pcdmbarac. D. S. pssllc.
mn.J. 1981. i5.39-so. Johnson. R. D.: Manske. D. D.: New. D. H.: Pr&ebamc. D. S. Pes*. m n . J . 1081. 15.54-09. Food and h u g Admlniabalh “Peslicld. Anawical Manual“: Natlarsl Technkd I n l m l h %cs: washingon. Dc. revised 1983; Vol. 1. Sectms 211. 212. 220. 231. and 232. R E ~ E N Efor D review August 16,1983. Accepted January 4, 1983. Reference to any commercial materials, equipment, or proeess does not in any way constitute approval, endorsement, or recommendation by the Food and Drug Administration.
Perchloric Acid-Celite Chromatographic Technique for Volatile N-Nitrosamines Harry
M.Pylypiw, Jr., and George W . Harrington’
Department of Chemistry, Temple Uniuersity. Philadelphia, Pennsylvania 19122 N-Nitrosamines (NAB)have been the subject of many articles dealing with sample preparation, detection, quantitation, and confirmation, ever since the carcinogenic activity of dimethylnitrosamine (DMN) was first documented (I). Analytical methodology for volatile NAs was recently reviewed (2). The current trend for confirmation by m&98 spectrometry (3)and the development of capillary gas chromatographic 0003-2700/84/03566847501.50/0
metbods (4) require sample cleanup techniques that produce final extracts that are far superior to those presently used. The most common sample preparation method in use today for volatile NAs is a mineral oil distillation (5) followed by detection and quantiation by gas chromatography interfaced with the thermal energy analyzer (GC-TEA) (6). T o further purify the extract produced by this method, the technique 8 1984 Ammican Chemical Socbly
