Abstract
A pulse sequence and sample geometry which allows the measurement of 13C chemical shifts of solid materials relative to liquid tetramethylsilane (TMS) are described. Using this technique, the chemical shifts of a series of common engineering plastics were measured and reported. A small number of candidate secondary shift reference materials were considered and their chemical shifts measured. Most of these materials proved to be unsuitable for general 13C shift references for differing reasons. The most promising standard investigated was polydimethylsilane. The measurement of chemical shifts in solid materials is slightly complicated by anisotropic magnetic properties and sensitivity to magic-angle missetting when the material exhibits macroscopic orientation. These complications are discussed in detail and examples of misleading spectra are shown.
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