Multi-Band Automatically Tunable High- Sensitive Nuclear Quadrupole Resonance Spectrometer

CERIONI LUCAS, PUSIOL, DANIEL

Conferencia; 18th ISMAR 2013/14th NMR Users Meeting; 2013

ISMAR

MO148: Multi-Band Automatically Tunable High- Sensitive Nuclear Quadrupole Resonance Spectrometer 1;2_Lucas Matías Cerioni, 1;2;3Daniel José Pusiol 1SPINLOCK SRL, Córdoba, Argentina, 2Argentinian National Research Council, 3Instituto de Física Enrique Gaviola, CONICET, Ciudad Universitaria, Córdoba, Argentina Nuclear quadrupole resonance (NQR) is a nondestructive, highly specific, noninvasive spectroscopic technique. NQR can be used to detect signals from solids and its parameters are highly sensitive to local environment changes. These features make NQR a powerful technique for identifying and study the properties of different polymorphs as well different hydrates forms in pharmaceutical agents, providing effective assistance at the main steps of drug development, manufacturing process and quality control. In this work we present the development and implementation of a high sensitive pulse NQR spectrometer, capable of measuring in different frequency bands, allowing the scan of new NQR signals in a fast, automatic and unattended way. The spectrometer was developed for measuring in two different ranges: 1.9-4.1 MHz (14N) and 34-36 MHz (35Cl). In order to make the spectrometer capable of measuring in both bands, a two capacitively coupled high-Q coils probe-head was built. To cover the whole bandwidth, the high-Q tuning and matching capacitors are mechanically adjustable. The spectrometer also includes a full bandwidth Q-damper system; a switchable transmitter filters; and a sample temperature control. The performance of the two-coil circuit was evaluated and compared with the standard single coil configuration. The tuning and matching capacitors are adjusted by a fast auto-tuning algorithm, feedbacked by reflected power. Qdamper frequency band and power amplifier filters are also fast and automatically adjusted. This allows making a full frequency sweep, performing measurements on the whole range of interest in a complete automatic way. The spectrometer sensibility was tested using the standard samples hexamethylenetetramine (hmt) for 14N, and p-diclorobenzene (pdb) for 35Cl. The spectrometer allows detecting 19 mg of hmt in 30 minutes and 7 mg of pdb in 1 minute. The spectrometer was tested reconstructing the previously reported spectra of pharmaceutical samples including carbamazepine, furosemide and hydrochloro-thyazide. Unreported lines were found in diclofenac sodium, aripiprazole and clopidigrel bisulfate. No NQR signal of these last two samples had been reported before. ACKNOLEDGEMENTS: CONICET, FONTAR, SPINLOCK