NMR Tube Cleaner The NMR-tube cleaner, shown in the drawing, was developed to provide a n inexpensive, rugged, and easily constructed alternative to allglass, NMR-tube cleaners. The latter are very fragile, labor intensive during construction, and hence expensive. The suggested construction procedure is to cut a piece of 12- x U8-in. 0.d. stainless-steel tubing and determine that the ends are open and that the tube is not otherwise obstructed. The tube is marked a t 2 in. from one end, inserted into a V8-in. tubing bender with the mark placed a t the center of the dial, and bent into a J shape. The bent tube is then used to mark positions on a No 8 Neoprene stopper corresponding with the two vertical holes a t the bottom of the stopper. The Neoprene stopper, frozen i n Dry Ice and acetone for 15 min, is drilled a t one mark with a 7164-in. bit. During construction, the Neoprene stopper will require refreezing several times. A second vertical hole, centered a t 22 nun,is drilled with the same bit. These holes are centered ahout 10 mm from either edge of the top face of the Neoprene stopper. One vertical hole is enlarged to a depth of 10 mm with a 318-in. bit. This hole will receive the solvent reservoir. The second hole also is enlarged by drilling to a depth of 8 mm with a 5116-in. bit. This hole receives the inverted N M R tube (5-mm x 7-in.) a s shown. Ta conserve space, the NMR tube and reservoir are not shown full length. The diagonal hole is drilled into the slanted face a t the bottom of the 5116-in. hale using a 5164-in. bit. This hole emerges a t the center of the bottom face of the stomer. The &tical holes are Lubricated with water and the J-shaped, U8-in. stainless-steel tube is inserted into the bottom of the Neoprene stopper toconnect the two vertical holes as shown. Any tubingprojectingmore than 163 mm above the top surface of the stopper is trimmed o E This tubing length allows about 5 mm head space between the end of the stainless-steel tube and the closed end of the N M R tube. The stainless-steel tube is V-notched with a fde a t the tip of the long end, to facilitate flow of solvent during the washing operation, and chamfered. The body of the 7-in. Pyrex reservoir is constructed of 13-mm o.d. tubing with the constriction made from 10-mm, medium-wall tubing. The Pyrex reservoir is added to the stopper and the assembled apparatus is inserted into the neck of a 500-mL suction flask The diagonal hole should be directed away from the side arm of the suction flask. Alternatively, a short length of 118-in. tubing may be inserted into the bottom opening of the diagonal drain hole to direct solvent past the opening of the side arm.An FETFE O-ring (3.7-mm i.d. x 7.5-mm 0.d. x 1.78-mm thick-Ace Glass Co., Vineland, NJ 08360. D a r t no. 7855-702) is added to the NMR tube. a t about 3-4 mm from the onen end.,before the tube is inverted. and fiikd over the vertical, stamless-steel ruhe projcking above the ~ e o p r e n ampper e Thin 0-nng provides an important .iucuon seal and a l w serves to prevent hlockage of the d~agonaldrain hole by the NMR tube. Aspirator suction is used to flush acetoneor other sulvent, from the reservoir, thorough the stainless-steel tube, and into the mverted ?JMR tube. This design is easily modified for use with larger NMR tubes ~~
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'Conesponding author.
T. T. Denton and E. Eisenbraun' Oklahoma State University Stillwater, OK 74078
1036
Journal of Chemical Education
