title: A new type of sample tube for reducing convection effects in PGSE-NMR measurements of self-diffusion coefficients of liquid samples.
abstract: Pulsed gradient spin-echo (PGSE) NMR measurements of the self-diffusion coefficients of low viscosity liquids are greatly hampered by the effects of convection especially away from ambient temperature. Here we report on a new NMR tube designed to minimize the deleterious effects of convection. In this tube, which derives from a Shigemi symmetrical NMR tube, the sample is contained in an annulus formed from a concentric cylinder of susceptibility matched glass. The performance of this tube was demonstrated by conducting measurements on the electrochemically important LiN(SO3CF3)2 (LiTFSI)-diglyme (DG) system. Calibrations were first made using DG at column heights of 2, 3, and 4-mm in the temperature range between -40 and 100 degrees C. Measurements of the diffusion coefficients of the lithium, anion, and DG were then performed to probe the solvent-ion and ion-ion interactions in the DG doped with LiTFSI. Changes in the 1H, 7Li, and 19F PGSE-NMR attenuation curves at -40 degrees C provided clear evidence of interactions between the DG and lithium ion.
authors.affiliation: National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Center 5, Tsukuba 305-8565, Japan. hayamizu.k@aist.go.jp
authors.forename: Kikuko
authors.initials: K
authors.lastname: Hayamizu
authors.forename: William S
authors.initials: WS
authors.lastname: Price
mesh_terms: D018481:Convection; D004058:Diffusion; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005026:Ethylene Glycols / Q000032:analysis / Q000737:chemistry*; D008094:Lithium / Q000032:analysis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods*; D008738:Methyl Ethers / Q000032:analysis / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012996:Solutions / Q000032:analysis* / Q000737:chemistry*; D013048:Specimen Handling / Q000295:instrumentation* / Q000379:methods
chemical_list: D005026:Ethylene Glycols; D008738:Methyl Ethers; D012996:Solutions; D008094:Lithium; C007391:diglyme