  We demonstrate the possibility to use UDEFT (Uniform Driven Equilibrium
Fourier Transform) technique in order to improve the sensitivity and the
quantification of one-dimensional ${}^{29}$Si NMR experiments under Magic-Angle
Spinning (MAS). We derive an analytical expression of the signal-to-noise
ratios of UDEFT and single-pulse (SP) experiments subsuming the contributions
of transient and steady-state regimes. Using numerical spin dynamics
simulations and experiments on ${}^{29}$Si-enriched amorphous silica and
borosilicate glass, we show that 59${}_{180}$298${}_{0}$59${}_{180}$ refocusing
composite $\pi$-pulse and the adiabatic inversion using tanh/tan modulation
improve the robustness of UDEFT technique to rf-inhomogeneity, offset, and
chemical shift anisotropy. These pulses combined with a two-step phase cycling
limit the pulse imperfections and the artifacts produced by stimulated echoes.
The sensitivity of SP, UDEFT and CPMG (Carr-Purcell Meiboom-Gill) techniques
are compared experimentally on functionalized and non-functionalized mesoporous
silica. Furthermore, experiments on a flame retardant material prove that UDEFT
technique provides a better quantification of ${}^{29}$Si sites with higher
sensitivity than SP method.
