Tetramethylsilane diffusion reference

Figure 8 Rate constants for electron attachment to solutes in tetramethylsilane at 295 K. For solutes numbered 1-28, see legends to Figs. 6 and 7. Other solutes 29—duroquinone, 30—CFI3I, 31—cycloC4F4, 32—C2HCI3, 33—phenanthrene. Dotted line is calculated diffusion rate. References for rate data [18,19,58,90,93,122,123,125,126] references for electron affinities [112-115].

Both tetramethylsilane (TMS) and terakis(trimethylsilyl)silane (TMSS) have been suggested as internal calibrants no doubt owing to their being chemically inert and in approximating well to the desired spherical shape. The use of an internal reference such as this can also be useful in indicating viscosity changes on a sample to sample basis even if itself is not required and may also act as an indicator of convective flow if their diffusion coefficients differ greatly. 

For self-diffusion NMR measnrements, ME samples are filled into standard NMR tubes. Tetramethylsilane dissolved in D2O and sealed into a capillary is commonly used as reference. H-NMR spectra of the pure components and the MEs are acquired and Fourier transformed. For analysis, peaks of the ME formulation can be assigned to the individnal components by comparison to spectra obtained from the pnre ME components. To obtain the data for exponential modelling using the Stejskal-Tanner equation (Equation 9.4), one or more peaks of the component are either integrated or analysis is performed on the peak height. Selfdiffusion coefficients ranging from about 10 to 10 m s" are typically observed in solutions at ambient temperature [73]. 

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