COMMUNICATION pubs.acs.org/jchemeduc
A Durable and Economical NMR Tube Cleaner Chad L. Landrie* and Richard Marszalek Chemistry Department, University of Illinois at Chicago, Chicago, Illinois 60607, United States ABSTRACT: An NMR tube cleaner that can be constructed in less than 15 minutes from common, inexpensive materials is described. This apparatus is significantly cheaper than glass versions available from commercial vendors and has proven to be durable and efficient. KEYWORDS: Second-Year Undergraduate, Upper-Division Undergraduate, Laboratory Instruction, Organic Chemistry, Laboratory Equipment/Apparatus, NMR Spectroscopy
Table 1. Materials To Construct the NMR Tube Cleaner
A
n NMR tube cleaner can be an invaluable timesaving tool in the laboratory. Designs vary from simple pipe cleaners1 to glass apparatuses that draw solvent into the NMR tube through a thin glass capillary. Unfortunately, glass models sold by commercial vendors are expensive and fragile; even construction by an experienced scientific glassblower can be a labor-intensive project. Surprisingly, then, there are few alternatives described in the literature for this costly equipment. Two notable exceptions are the apparatuses described by Eisenbraun and Denton2 and Karimian.3 Although both designs are equally economical, each requires a modicum of skill to construct because precise channels must be drilled through stoppers hardened in dry ice/acetone solutions. In both designs, the NMR tube is inserted into the stopper and the vacuum seal formed by either a rubber O-ring or by contact between the stopper and the NMR tube. A glass reservoir is fitted to the stopper in Eisenbraun’s apparatus, whereas Karimian’s employs no solvent reservoir, but rather a polypropylene tube that is immersed into a separate container of solvent. We wanted an apparatus that could be easily constructed by undergraduate students and teaching assistants; that had no glass components; that had no separate, small parts; that precluded the need to insert the NMR tube into the stopper to avoid cross contamination; and yet provided the functionality required by even the most demanding researchers. Here, a durable, economical NMR tube cleaner is described that can be constructed in less than 15 min from common, inexpensive materials (Table 1) and that can be modified to quickly clean many NMR tubes when a large volume of solvent will be consumed (Figure 1). The NMR tube cleaner is constructed by drilling two holes in a neoprene stopper 1 in. apart, with a 1/16 in. and 3/16 in. drill bit. Care should be taken not to widen the holes with excessive drilling to ensure the needle and syringe fit snugly. Next, the end of a 1 mL syringe is cut so the total length is 2 in. and inserted into the largest hole until the flange is seated on the stopper. The stainless steel needle is threaded through the smallest hole in the stopper and then through the barrel of the 1 mL syringe until the Leur lock hub is seated on the stopper and so that the needle extends 6.5 in. above the stopper. The needle is shaped by hand or with small pliers so that it is vertical above the stopper, taking care not to form any kinks at the bend. Needles with sharp tips should be filed or cut for safety. Finally, for the solvent reservoir, Copyright r 2011 American Chemical Society and Division of Chemical Education, Inc.
Materials 500 mL B€uchner flask No. 7 neoprene stopper (top o.d.: 37 mm; bottom o.d.: 30 mm) 1 mL polypropylene syringe 5 mL polypropylene syringe Septum penetration needle (18 gauge; 12 in.) Drill with 1/16 in. and 3/16 in. bits
Figure 1. NMR tube cleaner; a modified neoprene stopped for use in a B€uchner flask. Parts listed in Table 1.
the barrel of a 5 mL syringe is inserted into the needle’s Leur lock hub. Published: October 04, 2011 1734
dx.doi.org/10.1021/ed200104v | J. Chem. Educ. 2011, 88, 1734–1735
Journal of Chemical Education
COMMUNICATION
To operate the NMR tube cleaner, the modified stopper is inserted into a 500 mL B€uchner flask attached to a vacuum source. An NMR tube is inverted over the exposed needle and lowered until it makes contact with the plastic flange of the syringe, after which an appropriate solvent is added to the reservoir. After cleaning, residual volatile solvents can be quickly evaporated from the NMR tube by aspirating with air for an additional 5 10 s. When cleaning a large number of NMR tubes, solvent can be transferred directly from a larger source through tubing attached to the Leur hub. Because the vacuum is broken when the NMR tube is unseated from the plastic flange, these modifications allow for continual operation without the need to continually refill a smaller reservoir. Finally, an advantage of using the 1 mL syringe to form the channel in the stopper, as well as the seat for the NMR tube, is that the flange is easily cleaned and the syringe barrel can be replaced with little effort. This setup also supports NMR tubes of varying width provided that the flange is larger than the diameter of the NMR tube. In our experience, the seal formed at the glass plastic interface has been more than sufficient to hold a vacuum capable of washing NMR tubes thoroughly and quickly.
’ AUTHOR INFORMATION Corresponding Author
*E-mail:
[email protected].
’ ACKNOWLEDGMENT We would like to thank Brian Schwandt for his patience in repairing and willingness to construct the many glass NMR tube cleaners we have used over the years as well as his encouragement to find an alternative. ’ REFERENCES (1) Ladner, K. H.; Hinton, J. F. J. Chem. Educ. 1970, 47, 704. (2) Denton, T. T.; Eisenbraun, E. J. Chem. Educ. 1992, 69, 1036. (3) Karimian, K. J. Chem. Educ. 1986, 63, 914.
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dx.doi.org/10.1021/ed200104v |J. Chem. Educ. 2011, 88, 1734–1735
