Flow-through nmr probe having a replaceable nmr flow tube

Abstract

A flow-through NMR probe having an NMR flow tube that is easily inserted or removed is provided together with a method for exchanging the flow tube assembly in the probe. The NMR flow tube is positioned through a lower and upper insulator in a flow-through NMR probe by the use of a guide tube. The upper and lower insulators preferably comprise a pulsed field gradient housing. The guide tube leads from the base of the probe to the lower insulator. The NMR flow tube with attached inlet tubing is inserted into the probe through the guide tube and aligned along the central axis of the probe through upper and lower insulators. The flow tube is aligned using upper and lower insulator rings positioned in the upper and lower insulators. The ease of insertion or exchange of the flow tube in the probe is further promoted by the guide tube having a smoothly tapered inner surface. Once the NMR flow tube is disposed through the lower and upper insulators and lower and upper insulator rings, the outlet end of the flow tube is connected to an outflow tubing with a detachable connector. The lower end of the connector is then seated in a key in the upper insulator ring to position the flow tube for spectral measurements. The flow-through NMR probes and flow tube assemblies in accordance with the invention are useful in continuous flow-through analysis or stop-flow analysis applications, particularly for applications that couple high performance liquid chromatography (HPLC) with nuclear magnetic resonance spectroscopy (NMR), including flow-based NMR sampling.