"blanks" can be run on the same sample of solvent which is later used to prepare the solutions.
ACKNOWLEDGMENT We are grateful to Andrew Seer of the University Glassblowing Shop for his help in fabricating some of the apparatus used.
LITERATURE CITED (1) D. F. Shriver, "The Manipulation of Air-Sensitive Compounds," McGrawHill Book Company, New York, 1969.
(2) J. Coops, D. Mulder, J. W. Dienske, and J. Smittenberg, Rec. Trav. Cbim. Pays-Bas, 66, 153 (1947). (3) G. W. Watt and D. M. Sowards, J. Am. Cbem. Soc., 76,4742 (1954). (4) R. L. Jones and R . R . Dewald, Anal. Cbem., 46, 1623 (1974). (5)J. L. Dye, R. F. Sankuer, and G. E. Smith, J. Am. Chem. Soc., 82, 4797 ( 1960). (6)M. T. Lok, F. J. Tehan, and J. L. Dye, J. Pbys. Cbem., 76,2975 (1972). (7) J. L. Dye, M. G. DeBacker, and L. M. Dorfman, J. Cbem. Pbys., 52, 6251 ( 1970).
RECEIVEDfor review February 7, 1975. Accepted May 12, 1975. This work was supported by the U S . Atomic Energy Commission under Contract AT(ll-1)-958.
Solvent Recovery and Reuse with the Kuderna-Danish Evaporator I?.Don Wauchope
'
Southern Weed Science Laboratory, Agricultural Research Service, USDA, P. 0. Box 225, Stoneville, Miss. 38776
The Kuderna-Danish evaporator ( I ) has found wide application in pesticide analysis, providing rapid and efficient concentration of pesticides in low-boiling solvents. However, these evaporators are typically operated in a hood with venting of the stripped solvent to the outside air. With increasing solvent costs and shortages and air pollution a concern, recovery and reuse of this solvent is desirable. In cooperation with the Kontes Glass Company (Vineland, N.J.), an in-line lightweight condenser was designed S that retains the convenience and small space requirements 01 of the Kuderna-Danish evaporator, requires no additional clamp support, and may be quickly disconnnected when the evaporator is to be removed from its steam bath (Figure 1). Condensed solvent from several evaporators may be collected in a single flask, as shown. The 6-mm tubing is extended to the bottom of the flask and immersed, so that vapor losses are minimized. The glass wool/ball joint combination allows flexibility and quick disconnection at the condenser. Early vapor from the evaporator is usually moist; when the condenser is placed atop the column after a few milliliters of evaporation, the collected solvent is dry. Flgure 1. Kuderna-Danish evaporator with condenser and recovery The efficiency of recovery and quality of recovered solflask vent were tested with 250-ml evaporators. Solutions of 1 pg trifluralin (a,a,a-trifluro-2,6-dinitro-N,N-dipropyl-p-tolupears that solvents may be recovered from Kuderna-Danidine), an herbicide with a relatively high vapor pressure of ish evaporators and reused without further purification, 2X Torr at 30 "C ( 2 ) , in 200 ml of n-hexane or methtaking advantage of the high efficiency of the Snyder colylene chloride, were evaporated to 5 ml in the evaporaumn. Even a t bulk prices, this recovery represents pertor/condenser. Typical evaporation times were 15 min. The sample savings of about $0.50 for 200 ml of "glass-distilled" collected solvents were then reevaporated in a second evapcommon solvents. Pollution and fire/explosion potentials orator. The concentrates of the trifluralin solutions and of are lowered also, but the evaporators should still be operthe recovered solvents were analyzed by electron-capture ated in a hood. gas chromatography; the methylene chloride solutions were evaporated to dryness in air and the trifluralin residues LITERATURE CITED taken up in benzene ( 3 ) .Trifluralin recoveries were 90% or (1) F. A. Gunther, R . C. Blinn, M. J. Kolbezen, and J. H. Barkley, Anal. better with both solvents, whereas the concentrated recovChem., 23, 1835 (1951). ered solvents contained no detectable herbicide (detection (2) Weed Science Society of America, "Herbicide Handbook". 3rd ed, Champaign, 111. 1974. limit 1 pg). (3) W. L. Payne, Jr., J. D. Pope, Jr., and J. E. Benner, J. Agr Food Chem., With a single (three-ball) Snyder column, hexane recov22, 79 (1974). eries were complete. A double (six-ball) column was reRECEIVEDfor review April 7,1975. Accepted May 14,1975. quired for good recoveries with methylene chloride, with an average of 160 ml of solvent recovered. Mention of a trademark or proprietary product does not When relatively nclnvolatile solutes are involved, it apconstitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be Mississippi Agricultural and Forestry Experiment Station cooperating. suitable.
-
-
ANALYTICAL CHEMISTRY, VOL. 47, NO. 11, SEPTEMBER 1975
1879
