Page 37 of NMR Sampling Tubes, Supplies & Accessories by Wilmad Labglass

dramatic improvement in linewidth result from using doty susceptibility plugs the plots are non-spinning 500mhz spectra of a water sample in d2o produced in a probe with a 9 mm long r coil the spectrum at left was produced from an 8mm high sample of 2 water taken without using susceptibility plugs linewidth 700 hz the spectrum shown below results from a 6mm high sample of 1 water confined between a set of doty susceptibility plugs made from aurum linewidth 4hz sucrose spectrum courtesy of helga cohen university of south carolina 130ul 5mm sucrose in 99.8 d2o sample mass 200 ug 32 scans run time 2 minutes water suppression 1 second presaturation bruker 500mhz 5mm 1h probe 9 mm sample height aurum plugs note water absorbed on plugs is not fully suppressed increasing sample height by 40 improves suppression dramatically steps to consider when selecting susceptibility plugs · determine the sample solvent note for easier bubble removal and for use with viscous samples/solvents plugs with vent grooves along the outer surface product numbers with a v should be used · select plug material-closest match of magnetic susceptibility constants note density of plugs must be greater than density of sample-solvent · check chemical resistance compatibility with sample/solvent · make sure unwanted background effects of nuclei in plug material do not interfere with the analysis · check water absorption factor · determine plug length which depends on r coil position sample height and distance from coil bottom to probe head bottom susceptibility constants of rod/collar are inconsequential rod/collar material selection is based on chemical resistance g-10 rods are more rigid and easier to use kel-f rods are recommended for use with organic solvents properties of solvents solvent glycerol chloroform water deuterium oxide carbon tetrachloride dimethylsulfoxide toluene benzene ethanol diethyl ether methanol acetone -xcgs 0.78 0.74 0.72 0.70 0.69 0.68 0.62 0.61 0.58 0.53 0.53 0.46 density glcc 1.26 1.48 1.00 1.10 1.58 1.10 0.86 0.87 0.79 0.71 0.79 0.78 inserts note deuterated solvents have susceptibilities close to their protonated equivalents 1-800-220-5171 31

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