A nuclear magnetic resonance (NMR) spectrometer for investigating a liquid sample in a sample tube, in particular a glass sample tube (12), has a sample bushing (1) surrounding the sample tube having a bore into which one end of the sample tube is inserted with tight fit. The sample bushing (1) is preferably substantially cylindrical and the bore extends along the cylindrical axis. The NMR spectrometer has a gripping device (13) for handling the sample bushing (1), the gripping device (13) having at least three gripping fingers (14a-14d), and the outer periphery of the sample bushing (1) has at least one groove (2) into which the gripping fingers (14a-14d) can engage to press onto the two outer edges of the groove (2) when the gripping device (13) is closed. The cooperation between the groove and the gripping device permits fully automated, precise handling of the samples.