For the determination of methadone, gas chromatography was preferred to the oxidation procedures of Wallace et al. (12, 13).The latter methods involve the conversion of methadone to benzophenone, which is estimated spectrophotometrically, and suffer from a loss of specificity as several other drugs will produce benzophenone under the same conditions. A very minor peak (peak height less than 2% that of methadone) was detected in the gas chromatograms of both the acid and alkaline digest extracts at about R methadone of 1.50 on 3% OV-17 and 1.48 on 2.5%OV-1. This peak was tentatively identified as the primary methadone metabolite 1,5-dimethyl-3,3-diphenyl-2-ethylidenepyrrolidine which has been detected in biological specimens (13, 14). The low level present did not permit positive identification of the compound.
CONCLUSIONS Of the three isolation procedures studied, only the acid and alkaline extraction procedures were satisfactory for the determination of methadone in liver at the low levels frequently encountered in post-mortem investigations. If methadone is the only basic drug for which the tissue samples are being examined, then the isolation procedure of Wallace et al. ( 1 2 ) yields a cleaner extract and would be the method of choice. If other basic drugs are suspected, an acid digestion, as generally used in routine post-mortem analyses is quite satisfactory, but the detection of methadone by gas chromatography is limited by the choice of column. In the present study 3% OV-17 and 2.5% OV-1 columns were found to be more suitable than a 3% XE-60 column for acid digestion extracts.
LITERATURE CITED V. P. Dole and M. Nyswander. J. Am. Med. Assoc., 193, 646 (1965). A. Goldstein and B. W. Brown Jr., J. Am. Med. Assoc., 214, 31 1 (1970). L. Lasagna, Pharm. Rev., 16, 47 (1964). R. Gardner, Lancet, 2, 650 (1970). (5) M. M. Baden, "Committee on Problems of Drug Dependence", National Academy of Sciences-National Research Council, Division of Medical Sciences, Washington, D.C.. 1970, pp 6767-9. (6) C. E. lnturrisi and K. Verebely, J. Chromatogr., 65, 361 (1972). (7) I. K. Ho, H. H. Loh, and E. L. Way, J. Chromatogr., 65, 577 (1972). (8) H. R. Sullivan and D. A. Blake, Res. Commun. Chem. fathol. Pharmacob, 3, 467 (1972). (9) J. Ramsey and D. B. Campbell, J. Chromatogr., 63, 303 (1971). (10) L. B. Hetland, D. A. Knowlton, and D. Couri, Clin. Chim. Acta, 36, 473 (1) (2) (3) (4)
119721. - -, \
(11) P. E. Nelson and R . C. Selkirk, Chemistry Division, D.S.I.R., Auckland, N.Z., October 1974. unpublished results. (12) J. E. Wallace, H. E. Hamilton, J. T. Payte, and K. Blum, J. Pharm. Scb, 61, 1397 (1972). (13) H. E. Hamilton, J. E. Wallace, and K. Blum, J. Pharm. Sci., 63, 741 (1974). (14) A. E. Robinson and F. M. Williams, J. Pharm. Pharmacal., 23, 353 (1971). (15) J. V. Jackson, in "lsolatlon and Identification of Drugs,'' E. G. C. Clark, Ed., The Pharmaceutical Press, London, 1969. (16) A. E. Robinson in "Forensic Toxicology," Proceedings of a Symposium heid at the Chemical Defence Establishment Porton Down, 29-30 June 1972, B. Ballantyne, Ed., John Wright & Sons Ltd., Bristol, 1974.
Stuart J. Dickson Philippa A. Palmer Chemistry Division Department of Scientific and Industrial Research Private Bag Petone, New Zealand
RECEIVEDfor review December 5 , 1974. Accepted May 23, 1975.
I AIDS FOR ANALYTICAL CHEMISTS Break-Bulb Technique for Sample Introduction Frederick J. Tehan and James L. Dye' Department of Chemistry, Michigan State University, East Lansing, Mich. 48824
Handling of isolated amounts of materials, especially for use in vacuum systems has been a serious problem over the years ( I ) . In 1947, Coops et al. (2) introduced the use of fragile glass ampoules sealed to a ground-glass joint. Disadvantages included a total mass of approximately 2.5 grams, which prevented the use of very small samples, and the necessity to remove all grease from the ground glass joint. The general method was revised for the isolation of alkali metals in small quantities (approximately 50-100 mg) by Watt and Sowards ( 3 ) , and also by Shriver (1). These authors were able to eliminate the ground-glass joint and therefore reduce the bulb weight to 100-400 mg. However, the method could not be used for sealing-off small amounts of salts or liquids in the bulb without introducing air into the ampoules. Jones and Dewald ( 4 ) recently described a convenient technique for the preparation of sodium samples. I t is often desirable to obtain small quantities of materials that can be easily introduced into a vessel without the loss of vacuum or inert atmosphere. In this regard, the isoAuthor to whom correspondence should be addressed. 1876
lation of alkali metals in small quantities has posed especially serious problems. For example, if a 1 X 10-3M solution of sodium in 20 ml of ammonia is desired, less than 1 mg of alkali metal must be isolated. The accurate isolation of such a small mass of metal without oxide or other impurity is not trivial. An ideal sample-handling system should meet the following objectives: 1) Complete isolation of the sample from air and moisture. Both vacuum and inert atmosphere capabilities are desirable. 2) The ability to handle a wide range of sample weights. The method should be capable of delivering small as well as large amounts of material. 3) The ability to introduce samples in the form of liquids, solids, or solutions. 4) The preparation technique should be relatively rapid and simple to perform. 5 ) The method should allow quick handling and easy manipulation 'of the samples during an experiment. We have extended the general bulb technique to permit the isolation of very small known amounts of salts, solvents, and solutions. Premeasured milligram and sub-milligram quantities of alkali metals were also isolated in small, fragile, easily breakable glass ampoules. This method dif-
ANALYTICAL CHEMISTRY, VOL. 47, NO. 11, SEPTEMBER 1975
======a C
Flgure 1. Steps used
in fabricating break-bulbs
( A ) Capillary left on both sides of thick center section. (B)Bead or hollow section left on end of capillary. (C)Bulb blown on end. A plastic "blow-bag"
in a fllter flask between the glassblower and the capillary prevents contamination of bulb
fers slightly from that for non-reactive substances and is outlined i n a separate section.
EXPERIMENTAL T o meet these objectives, the general bulb technique was extended by the utilization of heat-shrink tubing. Heat-shrinkable Teflon tubing is commercially available in a variety of sizes (Pope Scientific, Inc., 13600 West Reichert Ave., Menomonee Falls, Wis. 53032). A very common use for such tubing is in vacuum systems Torr can readily be obtained. where pressures as low as 2 X For example, in this laboratory, a sealed tube containing cesium metal is scratched with a glass cutter and is placed inside of a larger glass tube which is sealed to the apparatus with heat-shrink tubing. After evacuation of the vessel, the Teflon tubing can be bent to break the inner tube, which can then be allowed to slide into the main vessel. The outer tube can then be sealed off. Heat-shrinkable tubing can be easily removed by cutting it with a razor blade and it leaves no residue. Therefore, it is an excellent way to attach ampoules of known mass to a vacuum system since all glass parts can be easily weighed before and after filling. Preparation of Ampoules. Since the bulbs are rather difficult to clean, the 10-mm borosilicate tubing should be cleaned before blowing the ampoules. An area of approximately 2 cm long is heated uniformly and then pulled to a length of 25 to 40 cm. It is very important to pull the tubing only a few centimeters a t first, allow it to cool slightly, and then slowly pull the capillary. If the capillary is pulled too rapidly, it will be non-uniform and the diameter will be too small. As shown in Figure 1,the capillary is cut between the heavy sections such that each piece has capillary a t either end and a thick portion in the center. A portion of the center (approximately % cm) is then heated uniformly and pulled away from the capillary such that the diameter of the closed end is approximately 1-2 mm. The amount of glass left a t the end of the tube is critical. It determines the size and strength of the ampoule. For bulbs 10-13 mm in diameter, the length of solid glass should be approximately 2-3 mm. (Alternatively a hollow, relatively thick end may be used.) The tube is then rotated with the solid glass in the flame until it emits a soft red color. T o keep impurities to a minimum, a blowbag should be used to blow the bulb. If the bulb is too small or too large, it may sometimes be melted again down to solid glass and reblown. The bulbs can easily be tested. First, for a bulb 10-13 mm in diameter with a 5- to 8-cm stem, the mass should be between 100 and 400 mg. Second, typical sample bulbs can be tested to see if they will break under appropriate conditions. The test bulbs are sealed with air inside and placed in a test tube approximately 15 cm high. One should be able to shake the bulb without damage and yet it should easily break when a 2-4 cm stir bar (Teflon covered magnet) is dropped from a height of approximately 4 inches. Each of the various stages of the preparation should be stockpiled before procecding to the next stage. The success ratio will be greater by blowing 100 bulbs in succession than by performing all of the steps over the same number of times. Filling the Bulb. The bulbs can be easily filled. Different methods are available depending upon the type of material to be isolated. In all cases, the empty bulbs are first weighed on an analytical balance. Solids. For solids that are unreactive to air and moisture, the bulbs can be filled by simply funneling the powder down the stem
Figure 2. Glass manifold used to evacuate and seal-offbulbs. Capillary stems are inserted into tips and Teflon shrinkable tubing pro-
vides a vacuum-tight seal and gently shaking the ampoule. The only requirement is that the substance be dry. The bulbs can then be attached with heat-shrink tubing to the manifold shown in Figure 2. A heat gun is used to shrink the Teflon (or irradiated poly-olefin) tubing around the glass. If the solid is reactive to the atmosphere, the entire process may be performed in an inert atmosphere box. Electrical outlets are usually available in the box so that not only can the material be weighed but also the heat gun may be used. A Teflon needle valve stopcock which is closed immediately prior to the removal of the manifold from the box keeps the compounds under the inert glove box gas. The entire manifold is placed on a vacuum line and evacuated. In this way, the material never contacts the atmosphere. The bulbs can easily be sealed by bringing a hot flame near the stem until it just starts to collapse. Then, this procedure is followed on another side of the tube. By rotating around the stem in this manner, the glass collapses nearly uniformly. This prevents the formation of weak spots which are prone to form since the glass wall of the stem is fairly thin. After sealing, the stem (which is easily removed by cutting away the Teflon tubing with a razor blade) and the bulb are weighed on an analytical balance. A buoyancy correction can be performed by measuring the diameter of the bulb and calculating the volume of the sphere. Liquids. Liquids can be introduced into the bulbs by two general procedures. First, liquids can be injected with a hypodermic syringe and needle. The needle should be long enough to allow the tip to enter the bulb area. Otherwise, the surface tension of the liquid may cause filling of the stem only. The bulbs can then be placed on the manifold and the same method is followed as for solids, except that the bulbs must be kept cold to prevent evaporation in the case of volatile liquids. This is done by placing a large Dewar flask containing liquid nitrogen around the bulbs. It is often necessary to de-gas the liquid by repeated freeze-pump-thaw cycles. Second, it may be desirable to distill the liquids directly into the bulbs under vacuum. This can be done by attaching the empty bulb to the manifold and cooling all the bulbs with a Dewar flask. Again, the bulbs can be sealed as described earlier and weighed together with the stems. Solutions. A hypodermic syringe may also be used to inject a solution by using the same technique as for liquids. By appropriate dilution and evaporation of the solvent after solution introduction, very small amounts of non-volatile solutes can be isolated in the bulb. This method is extremely valuable when one wishes to prepare small volumes of dilute solutions in a closed system. Isolation of Alkali Metals. The isolation of small amounts of alkali metals presents special problems which are not overcome by
ANALYTICAL CHEMISTRY, VOL. 47, NO. 11, SEPTEMBER 1975
a
1877
A
B
Figure 3. Steps used in making break-Dulbs on capillary tubing ( A ) Capillary tUDe inside diameter is measured at 00th ends with a microscope. (8)End is sealed-off leavlng a bead. ( C ) Thln-walled oulo is blown on end of tuoe
Figure 4. Steps used to isolate alkali metal in capillary
~
~~
Table I. Comparison of Observed and Calculated Weights of Potassium Metal Isolated by the Bulb Technique
( A ) Metal distilled into manifold and onto capillary. (Band C)Desired amount
of metal driven into capillary tube and allowed to cool. (D)Excess metal distilled out Df tube. ( E ) Capillary sealed off and metal moved to the next sample tube
Weight, mg Calcd from Sample
length of
No.
Observed
m e t a l cylinder
Diff., mg
Diff., %
1
2.443 1.287 2.017 2.385 2.589
2.472 1.293 1.998 2.408 2.643
-0.029 -0.006 0.019 0.023 -0.054
-1.17 -0.49 0.92 -0.98 -2.08
2 3 4 5
the method of Watt and Sowards (3). First, the buoyancy correction (-1 mg) will sometimes be greater than the mass of metal desired. Second, the bulbs are normally filled ( 5 ) by forcing molten alkali metal through the stem and into the bulb. After filling the bulbs, it is possible to introduce more metal in the stem to isolate the metal in the bulb from the atmosphere. This additional metal can be removed after sealing the stem. However, it is almost impossible to obtain small quantities of the metal in this fashion since the metal in the stem near the seal will often weigh more than 1 mg. However the method is very satisfactory for metal samples in the mass range of 10-400 mg. For these reasons, a new procedure was developed to isolate the small quantities of alkali metal needed for our metal-amine studies. ( 6 ) Preparation of Bulb. Capillary tubing approximately 0.25-mm i.d. and 4-6 mm 0.d. was cut into 10-cm lengths and cleaned. The internal diameter a t both ends was measured with a microscope whose scale had been calibrated. After appropriate tubes had been found, one end was sealed as shown in Figure 3. With a length of approximately 3-4 mm of sealed glass a t the end, a bulb was blown. In this way, bulbs of approximately 10 to 13 mm in diameter were constructed. Sample Filling. The bulbs were sealed onto a manifold. The alkali metal was distilled through the manifold and seals were made a t various constrictions behind the metal to prevent back distillation. After heating, a pool of alkali metal was formed on top of the capillary tube (Figure 4A). Upon continued heating, the metal began to move down into the capillary. When the capillary was gently warmed, the metal continued to move down the capillary tubing (Figure 4B). After the approximate desired length had been obtained, the capillary tubing was allowed to cool and the remainder of the metal pool was heated to force the metal back into the manifold (Figure 4C). The capillary was again gently heated and the metal cylinder moved down (Figure 4 0 ) . The tubing was then sealed (Figure 4E). Care should be taken not to heat the capillary too strongly or else metal will distill from the metal cylinder onto the walls of the capillary. The film can be easily distinguished from the metal cylinder by shining light through the capillary tube. The metals, sodium, potassium, rubidium, and cesium, can be easily isolated in this manner. In the case of sodium, a slight pressure of helium gas was used to force the metal pool down into the capillary tubing. Since the diameter of the metal cylinder was known, only the length needed to be determined in order to calculate the volume of 1878
metal and hence its mass. The length can be found in a variety of ways: First, the length of the metal cylinder can be directly measured with the aid of a magnifier and a vernier caliper. Second, photographic slides may be taken of the metal cylinder with a scale placed next to the metal cylinder. The slide can then be projected and magnified so that the length of metal can be easily determined. After its length had been measured, the cylinder was heated so that it moved down into the bulb. After collecting all the metal in the bulb, the capillary stem was sealed.
CALIBRATION RESULTS To check the accuracy of the technique, the mass of alkali metal inside several ampoules was determined by Atomic Absorption. A Jarrell-Ash AA unit, equipped with a tencentimeter path length burner was used. The potassium blue line (A = 4042.8 A) was studied. Standard solutions of potassium thiocyanate in a water-isopropanol mixture were used for calibration of the instrument. The bulbs were broken inside a vessel containing a known volume of solvent. All solutions were prepared to contain 1000 ppm sodium from the salt sodium thiocyanate, in order to reduce ionization in the flame. The calibration results are listed in Table I. Not only can accurately known milligram quantities of metal be isolated in this way, but also larger or smaller amounts may be prepared dependent only upon the diameter of the capillary tube chosen. Although the samples used for calibration contained several milligrams of metal, the lengths of samples as small as 0.5 mg can easily be measured. Use of Bulbs. The bulbs can be piled into a side arm attached to the measurement vessel and held in place by a Teflon-coated bar magnet. (See Figure 2 of reference 7 for a typical piece of apparatus). The magnet can be moved by means of a horseshoe magnet outside of the vessel. The bulbs can be shaken one at a time, into arm A and the magnet can then be dropped. If desired, the bulbs may be rearranged by manipulation into arms A and B. A coarse frit may also be introduced between the bulb-breaking section and the main body of the apparatus t o prevent the passage of glass fragments into the system. This technique is not only rapid and efficient but also can be adapted to many different problems. For example, this method was used by us to study the effects of pulse radiolysis on different solutions (7). As many bulbs as required may be stacked into a reaction vessel for use one a t a time. The technique allows the introduction of materials during an experiment without a large time loss and without opening the system. Another advantage is that solvent
ANALYTICAL CHEMISTRY, VOL. 47, NO. 11, SEPTEMBER 1975
"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
