Sample spinners design

Several methods may be used to attach an NMR tube to a vacuum system. The O-ring union, illustrated in Fig. 8.5, permits attachment of standard NMR tubes to a vacuum outlet. Once the NMR tube has been filled with an air-sensitive sample on the vacuum system, it is necessary to bring the tube up to atmospheric pressure with inert gas, remove the tube, and quickly stopper it. Recently, a small in-line valve has been introduced which has a provision for an O-ring seal with a specially constructed NMR tube.22 This valve allows the NMR tube to be sealed before it is disconnected from the vacuum line, and the valve s left on the tube during data collection. Owing to its symmetric design, the valve does not interfere with the spinner. 

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