Analyzing and correcting spectrometer temperature sensitivity

Stability and reproducibility of the spectrometer are fundamental to the su ccess of many modern NMR experiments. Variation in room temperature is a pa rticularly important source of instability, in part because it can cause co herent artifacts in NMR spectra. Small changes in room temperature lead to corresponding changes in the phases, amplitudes, and frequencies of NMR sig nals. These can lead in turn to apparently random spectral artifacts such a s t(1)-noise in two-dimensional (2D) NMR and to the incomplete cancelation of signals in difference spectra, but also, importantly, to F-1 satellite s ignals in 2D spectra. These "parallel diagonals" arise from the use of air conditioning, which typically forces room temperature to oscillate within a fixed band. Work to identify, quantify, and suppress sources of temperatur e sensitivity in a modern 300-MHz spectrometer has led to a greater than 10 -fold improvement in the signal-to-artifact ratio. (C) 2001 Academic Press.