Madmacstew: He's talking about NMR spectroscopy. Ppm and hz are two different scales for which NMR spectra can be given. They are related because if you divide Hz by MHz, you get parts per million. It's kind of like a way of normalizing NMR spectra of different size spectrometers.
Guest: Ppm = (shift of sample in Hz - shift of TMS in Hz)/(frequency of the spectrometer in MHz)
Guest: Ppm = (shift of sample in Hz - shift of TMS in Hz)/(frequency of the spectrometer in MHz)