A method for determining B1 field inhomogeneity.: Are the biases assumed in heteronuclear relaxation experiments usually underestimated?

We describe a method allowing the determination of the effective B-1 field amplitude distribution in a high-resolution NMR spectrometer. This method which can be adapted to almost any sequence, essentially consists of a nutation followed by a purging B-0 gradient pulse. Experimental results obtained with this approach are described in homonuclear and heteronuclear cases. The experimental distributions are used to estimate the biases induced by B-1 inhomogeneity, as well as the loss of RF power on heteronuclear transverse self-relaxation rate determination. In this type of measurement, the experimental biases induced on the intensities can be as large as 5% for long mixing times. (C) 1999 Academic Press.