27AI and 29Si MAS and CP MAS NMR have been used to monitor structural modifications of mordenite subjected to hydrothermal dealumination, acid leaching and calcination. Six, four-and possibly five-coordinate extraframework aluminium species are formed upon expulsion of aluminium from the framework. 'H-29Si CP MAS NMR monitors the creation of Si-OH defect sites. Calcination of dealuminated mordenite greatly reduces the number of such defects, indicating that they are substantially 'healed' by silicon atoms from other parts of the crystal, and also via dehydration of hydroxy groups to form bridging oxygen sites. The occupancies of crystallographically inequivalent Si(0AI) sites calculated from 29Si MAS NMR spectra of dealuminated mordenite show that aluminium atoms occupy some of the T2 tetrahedral sites in the parent material.

Stable van der Waals-bonded C 60 /benzene solvates were prepared using a novel crystallization technique. Solid-state NMR measurements on highly crystalline solvate under liquid benzene show that there is very little interaction between benzene and the C 60 molecules and that the rotation of C 60 at room temperature is not hindered. The magnetization transfer between benzene protons and local C 60 molecules is highly inefficient. Three benzene species have been found in the solvate: two, nearly freely mobile, in wide and narrow porous structures, and the third constrained by C 60 molecules in lattice defects. Premelting of deuterated benzene within the C 60 solvate has been observed at T m -10.5 K.

We report the detection and analysis of a suspected counterfeit sample of the antimalarial medicine Metakelfin through developing nitrogen-14 nuclear quadrupole resonance ((14)N NQR) spectroscopy at a quantitative level. The sensitivity of quadrupolar parameters to the solid-state chemical environment of the molecule enables development of a technique capable of discrimination between the same pharmaceutical preparations made by different manufacturers. The (14)N NQR signal returned by a tablet (or tablets) from a Metakelfin batch suspected to be counterfeit was compared with that acquired from a tablet(s) from a known-to-be-genuine batch from the same named manufacturer. Metakelfin contains two active pharmaceutical ingredients, sulfalene and pyrimethamine, and NQR analysis revealed spectral differences for the sulfalene component indicative of differences in the processing history of the two batches. Furthermore, the NQR analysis provided quantitative information that the suspected counterfeit tablets contained only 43 ± 3%, as much sulfalene as the genuine Metakelfin tablets. Conversely, conventional nondestructive analysis by Fourier transform (FT)-Raman and FT-near infrared (NIR) spectroscopies only achieved differentiation between batches but no ascription. High performance liquid chromatography (HPLC)-UV analysis of the suspect tablets revealed a sulfalene content of 42 ± 2% of the labeled claim. The degree of agreement shows the promise of NQR as a means of the nondestructive identification and content-indicating first-stage analysis of counterfeit pharmaceuticals.

HIGHLIGHTS• The proposed method effectively cancels complicated interference which can be strong, nonstationary, and have frequencies close to that of signal of interest.• The proposed method facilitates a valid detection of the NQR signal severely polluted by interference.• The proposed method performs better than general frequency selective methods of interference cancellation. AbstractNuclear Quadrupole Resonance (NQR) signal detection can be severely obstructed by interference in real life settings, especially when the interference is strong, nonstationary, and its frequencies are close to that of the NQR signal. A novel algorithm is proposed to effectively remove (or reduce) interference components in the data and facilitate a valid detection of the NQR signal. The proposed method exhibits better performance compared to the previously proposed ETAML and FETAML algorithms, when applied to both simulated and measured data. Importantly, the present algorithm directly operates on the original primary data, without requiring any secondary data (NQR signal-free data) for acquiring prior knowledge of the interference.

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