Device to Overcome Spinning Difficulties with Nuclear Magnetic Resonance Sample Tubes at Variable Temperature John Barzilayl Unileuer Research Laboratories, Vlaardingen/Duiuen, The Netherlamis THE SAMPLE tube during spinning is a common difficulty with the variable temperature probe in high resolution NMR spectrometers employing cylindrical turbine rotors. This is caused by the nitrogen flow that is used to control the temperature. Van Geet ( I ) has recently put forward a method of controlling this by using a cylindrical Teflon (Du Pont) weight sliding over the sample tube. However, for application to spectrometers with narrow pole gaps
LIFTINGOF
(e.g., Varian HA-loo), sufficient weight can be achieved only with an inordinately long and cumbersome cylinder. We have overcome the problem by developing a small aluminum attachment (Dutch patent applied for.) (see Figure 1) which locks into the spinner housing of the Varian Probe V 4333 by means of a bayonet plug. From the four boles in the bottom of the attachment (see Figure Z), a gas stream gives a downward pressure on the top of the turbine rotor to overcome vertical movement of the sample tube. The air or nitrogen supply to this attachment is tapped by a T-piece junction from that used to control the spinning. No separate control of the gas supply to the attachment is necessary, since varying the gas pressure to alter the spinning speed of the sample tube apparently automatically com.
14iair w t l ~ tQ,3# l
13.0 6
17.5#
wnn rnis syarern, wc nave LUULN LLUUUIILULLIC~ U L u u m u u ~ smooth and controllable spinning over the whole temperature range (-100 to +180 "C)and we now routinely operate the spectrometer at room temperature with the attachment in place. This has the further advantage that sample tubes are introduced into the probe without first attaching a turbine rotor, since this is already locked within the spinner housing.
Figure 1. Aluminum attachment to spinner housing to pre vent sample tube from lifting (sizes are in mm)
Author's address, Olivier van Noortlaan 120, Vlaardingen, The Netherlands. 1
(1) A. L. van Geet, AN&. CHEM., 40,1914 (1968).
160
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ACKNOWLEDGMENT
"banks are due to L. de Snayer and P. Oostveen for valuable discussions and technical assistance.
RECEIVEDfor review Julv 27. 1970. Acceuted October 19, I
ANALYTICAL CHEMISTRY, VOL. 43, NO. 1, JANUARY 1971
