A method for improved quantification of 1H NMR signals under low-resolution conditions for solids

Accurate determination of 1H NMR signal intensities is useful for quantitative analysis of the hydrogen content and also to determine the relative peak intensity ratios in different application scenarios. To this end we have investigated the reliability and sources of intensity errors in 1H solid-state MAS NMR. If sufficient resolution can be achieved by very high spinning speeds and high magnetic fields, quantification is straight forward. However, for poorly resolved spectra we show that small phase errors add a considerable amount of uncertainty. An analytical expression for the phase induced intensity-errors allowed us to suggest a robust and reliable recipe which is based on a combination of the spin-echo experiment, an extrapolation technique and a deconvolution algorithm which includes fitting of the signal phase. It significantly reduces errors caused by phase distortions, homonuclear dipolar dephasing, the receiver dead time delay and baseline rolling. The method was validated experimentally on samples with strong homonuclear dipolar interactions.