Impurity proton NMR signals from common proton-free laboratory materials

For the study of small samples (tens of microns cubed) by NMR, impurities from the environment and construction materials (Teflon, Kel-F, glass NMR tubes, etc.) can dominate the signal, in particular for proton NMR. Using pulsed NMR with a resolution of several microseconds, we have studied a number of common construction materials considered to be proton-free and find considerable proton impurity. We present results in terms of impurity proton spins per milligram and discuss procedures to minimize the effects of impurity signal. (C) 2003 Elsevier Science (USA). All rights reserved.