Proton Fourier Transform NMR as a Trace Analysis Tool; Optimization of Signal-To-Noise

Abstract

An experimental study has been made of all the factors which influence the Signal-to-Noise ratio in FT NMR. In particular the achievable Signal-to-Noise per time unit is discussed. A detection limi t of 1 ppm (1 ug) or a reasonable spectrum at 10 ppm (10 ug) is achievable in 1 hour of experimentation time. A further improvement by a factor of 10 in detection limit appears feasible, at the sacrifice of very long experimentation time but the major obstacle is provided by proton-carrying solvent impurities. In practical applications the same problem gives rise to the need for highly specific extraction and clean-up procedures. A general description of the Puls Fourier Transform technique is given and a general method for optimizing towards maximum Signal-to-Noise per-time-unit is evolved.