Standard materials used in NMR probe construction, as well as normal NMR tubes, inevitably contain silicon which is visible as abroad peak in the spectrum. As this is due to a Q4unit, it will overlap at similar chemical shifts to Q3 and Q4 units in any sample being measured. The use of a silicon free probe and suitable tubes completely suppresses the background signal and even small signals can be clearly seen.
29Si spectra without sample
Actually measured data
Upper spectrum: Data from standard probe with heat-resistant glass tube
Lower spectrum: Data from Sillicon free probe with PTFE tube
This probe is particularly effective for broad peaks and dilute solutions!