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in HCl solution should be a general radiochemical separation procedure for oxygen determination by other charged-particle-activation processes in samples with relatively low fluorine contents. ACKNOWLEDGMENT We thank Milan C. Oselka for performing sample irradiations a t the Argonne cyclotron facilities, Robert R. Heinrich for the use of counting equipment, and Milton Blander for his support of this project and many helpful discussions. Marilou Dysart wishes to thank the Chemical Technology Division, ANL, for a summer student fellowship which allowed her to perform the proton activation experiments. Registry No. 02, 7782-44-7;LiC1,7447-41-8;KC1,7447-40-7; LiF, 7789-24-4;KF, 7789-23-3;NaF, 7681-49-4;ISF, 13981-56-1; LiCl,, 10099-58-8. LITERATURE C I T E D (1) Thompson, B. A. Anal. Chem. 1981, 33, 583. (2) Markowitz, S. S.; Mahony, J. D.'Anal. Chem. 1982, 3 4 , 329.
Rook, H. L.; Schweikert, E. A. Anal. Chem. 1989, 4 1 , 958. Ricci, E.; Hahn, R. L. A n d . Chem. 1988, 4 0 , 54. Blaser, J. P.; Boehm, F.; Marmier, P.; Scherrer, P. Heiv. Phys. Acta 1951, 2 4 , 465. Blosser, H. G.; Handley, T. H. Phys. Rev. 1955, 100, 1340. Tanaka, S.; Furukawa, M. J . Phys. SOC. Jpn. 1959, 14, 1269. Lee, D. M.; Stauffacher, C. V.; Markowitz, S. S. Anal. Chem. 1970, 4 2 , 994. Handbook of Chernisfry and Physics. 64th ed.; CRC: Boca Raton, FL, 1983. Burgess, J.; Kljowske, J. Adv. Inorg. Radiochem. 1981, 2 4 , 5 7 . Mok, W. M.; Shah, N. K.; Wai, C. M. Anal. Chem. 1988, 5 8 , 110. Haupin, W. E. Light Met.; New York, 1979; p 475. Lauff, J. J.; Champlin, E. R.: Przybylowicz, E. P. Anal. Chem. 1973, 4 5 , 52.
RECEIVED for review May 12,1986. Accepted September 4, 1986. This work was performed a t Argonne National Laboratory (ANL) with the support of ANL and a grant from the Aluminum Company of America (Alcoa).
Syringe Pycnometer for Use with Electronic Microbalance Hugh A. Wyllie
Australian Atomic Energy Commission, Research Establishment, Lucas Heights Research Laboratories, Private Bag, Sutherland, New South Wales 2232, Australia A syringe pycnometer that is light enough to be weighed on an electronic microbalance has been developed from the apparatus first described by Lowenthal and Page (1). A silicone-treated glass needle of simpler design is fused directly to a disposable syringe t o form the pycnometer. The new pycnometer holder, which is employed during the dispensing of solutions, allows weighing to be carried out on a Mettler M3 electronic microbalance, whose pan can bear loads of up t o 3.05 g. The apparatus is used for dispensing radioactive solutions when preparing counting sources for the standardization of radioactivity.
A
EXPERIMENTAL SECTION Pycnometer Construction. The pycnometer is made from a 2-mL polypropylene syringe (supplied by Pharma-Plast (Australia) Pty Ltd.). Nonsterile syringes are used because sterilization with ethylene oxide reduces the tightness of fit between plunger and barrel. Glass needles are prepared from 2 mm i.d. by 7 mm 0.d. tubing. A 30-cm length is heated in the middle by an oxy-gas flame, drawn out, cooled, and bisected. Half (see left-hand side of Figure 1) is inserted into the Luer fitting of a syringe from which the plunger has been removed, withdrawn with thumb nail marking point A, and cut into two at that point. A needle of the required length is made from the piece shown above point A in Figure 1,by cutting off the excess at the narrow end. To render the needles water repellent, the following silicone surface treatment is carried out. The needles are dipped in a solution of Dow Corning 1107 Fluid, allowed to stand upright on a pad of cellulose tissue to drain, and then centrifuged with a similar pad at the bottom of the centrifuge tube. The coating is heat-cured at 175 "C for 15 min. To make the pycnometer, the plunger of a syringe is retracted 2 cm from the Luer fitting; with the syringe held horizontally, the wide end of a needle is inserted through the fitting to point B (see Figure 1). The syringe is slowly rotated with the tip of
Flgure 1. Construction of pycnometer. A glass needle (cut off at point A) is inserted into a syringe as far as point B and sealed in piace by heating at point C.
the fitting (point C) above a small Bunsen burner flame which melts and ignites the plastic. The syringe is moved away from the burner, and as the molten zone approaches the wide end of the Luer fitting the flame from the ignited plastic is blown out. Rotation is continued as the plastic cools; when the plastic has become sufficiently viscous, the seal is drawn out slightly by holding the pycnometer vertically by the tip of the needle until the plastic is hard. Sometimes, when the plastic is burning, the needle moves into the barrel of the syringe. This is rectified by
0003-2700/86/0358-3269$01.50/0 0 1986 American Chemical Society
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14, DECEMBER 1986 two strips of 16-gawe stainless steel. B and C, which are brazed to the tips of a pair of pliers, D. Behind the washer, E. there is a short vertical slot in the front strip, R. The bolt. F.which is screwed inw the rear strip, C, ensures that the strips move parallel to one another as the clamp is tightened. After its initial weighing. the pycnometer is removed from the stirrup by gripping the plunger with a 21-cm pair of forceps. the tips of which have k e n hent through nearly a right angle. With the pycnometer holder in the other hand, the pycnometer is held horizontally and lowered inw the clamp, G . A drop of solution of 1 mp or more is dispensed by rotating the screw, A. The screw is then wound hack a few millimeters. and the plunger pulled hack with thumb and finger SO as w move the meniscus back to point H in Figure 1. The pycnometer is replaced in the weighing chamber by means of the forceps.
DISCUSSION The mass of a typical finished pycnometer is 2.9 g. The mann of the stainless steel wire stirrup is 0.4 g less than the mass of the pan that it replaces. Thus the maximum mass of solution that can he weighed on a halance of capacity 3.05
g is 0.55 p. Flpna 2. Pycmmetef hdder: (AI Saew; (E) front stainless steel sbip: (CI rear stainless steel Sbip: (DI pliers: (E) washer; (F) bok (G)clamp; (H) pycnometer
holding the pycnometer vertically by the tip of the needle while the plastic is still sufficiently fluid for the syringe w move down to the required position. Electronic Microbalance. To weigh the pycnometer, the balance pan is replaced by a lighter stainless steel wire Stirrup. When the zero adjustment is made the stirrup is loaded with a piece of wire whme mass equals the difference ktween the m&p9e8 of pan and stirrup. Recause the pycnometer is tou long to fit into the balance, the weighing chamber in extended 4 cm by leaving the left-hand door open and placing across the opening a double-walled glass box. whirh IS open on the right-hand side. The gap between box and balance is sealed with adhesive tape. Pycnometer Holder. The pycnometer holder is used when dispensing solution (Figure 2). The clamp, C, is m n s t r u d from
The pycnometer of Lowenthal and Page (11, which was designed for use with a mechanical microbalance, has a mass of 13 g. It is thus too heavy to be used on the more accurate Mettler M3 electronic microbalance. The use of a nonsterile syringe with a tighter fitting plunger. as described above, ensures a reduction in evaporation loss. The pycnometer desrribed is simpler to make than is the detachable needle used by Imwenthal and Page but retains the advantages that their pycnometer has over the polyethylene ampule pycnometer, namely, being easier to manipulate and giving hetter control over drop sizes from 1 mg upward.
LITERATURE CJTED (1) LowemhBI. 0. C.; Pa@. V. AMI.
Uam.1970. 42, 815-816.
RFCEIVEDfor review May 30,1986. Accepted July 15,1986.
