Question: why tmz is used as internal standard in nmr?
Answer: Uses in NMR spectroscopy Tetramethylsilane is the accepted internal standard for calibrating chemical shift for 1H, 13C and 29Si NMR spectroscopy in organic solvents (where TMS is soluble). ... Because all twelve hydrogen atoms in a tetramethylsilane molecule are equivalent, its 1H NMR spectrum consists of a singlet.