Laboratory of NMR Spectroscopy, University of Warsaw, Pasteura 1, 02-093 Warszawa, Poland;
Modern NMR spectrometers allow the observation of weak signals, important for studies in the gas phase where compounds are monitored at very low concentration. Some nuclei have low natural abundance and their NMR signals are extremely weak. We have developed new unique experimental techniques, which permit us to monitor micrograms of chemical compounds in gaseous matrices. Gas samples are prepared condensing gases from the calibrated part of vacuum line to glass tubes and sealed. This method is good when the pressure of gases does not exceed 50 bar. For higher pressure we use the zirconia tube with a metal valve for gas filling delivered us by Daedalus Innovations (USA). Applying this approach we have studied numerous chemical compounds containing various magnetic nuclei, including 1H, 2H, 3He, 10B, 11B, 13C, 14N, 15N, 17O, 19F, 29Si, 31P, 73Ge, 77Se and 119Sn. It is shown that NMR gas-phase studies can easily be extended on molecules, which are liquid at room temperature as shown for sevoflurane (2,2,2-trifluoro-1-(trifluoromethyl) ethyl ether, an agent used for induction and maintenance of anesthesia.