Abstract:The performance of rectangular radio frequency (RF) coils
capable
of being used to detect nuclear quadrupole resonance (NQR) signals
from blister packs of medicines has been compared. The performance
of a fixed-pitch RF coil was compared with that from two variable-pitch
coils, one based on a design in the literature and the other optimized
to obtain the most homogeneous RF field over the whole volume of the
coil. It has been shown from 14N NQR measurements with
two medicines, the antibiotic ampicillin (as tri… Show more
“…In addition, the probe sensitivity decreases when the signal frequency moves away from the tuning frequency ν 0 as 1 – 2 Q Δ ν /ν 0 , where Δ ν is the frequency offset while Q is the probe quality factor. Special attention was also taken to position all the samples exactly in the middle of the coil, as the coil itself is also less sensitive toward the edges . Both factors were estimated to comprise up to 5% in our previous measurements, where we did not pay attention to these details.…”
Hydration is a quite common process in pharmaceutical solids. Sometimes it is desirable, as it stabilizes the crystal structure; in other cases it is unwanted, as it changes the physical and chemical properties of drugs. We here use (14)N NQR spectroscopy to quantitatively analyze hydration of a model compound, 5-aminotetrazole. (14)N NQR has some great advantages compared to other routinely used techniques to study hydration, like a very simple spectrum, single point calibration, and no need for special sample preparation, but the method's great disadvantage is a rather small sensitivity. Nevertheless, here we demonstrate that (14)N NQR, although being significantly less sensitive than XRD, NIR, and also (35)Cl NQR, is still capable of providing excellent quantitative accuracies. We can achieve errors <1% of the total amount, provided good temperature stabilization is implemented, which then allows long experimental times. We also present results obtained with a SLSE pulse sequence, which is a less robust approach but allows the use of much shorter measuring times (∼200×) and could be used for quantitative real time monitoring of hydration or dehydration.
“…In addition, the probe sensitivity decreases when the signal frequency moves away from the tuning frequency ν 0 as 1 – 2 Q Δ ν /ν 0 , where Δ ν is the frequency offset while Q is the probe quality factor. Special attention was also taken to position all the samples exactly in the middle of the coil, as the coil itself is also less sensitive toward the edges . Both factors were estimated to comprise up to 5% in our previous measurements, where we did not pay attention to these details.…”
Hydration is a quite common process in pharmaceutical solids. Sometimes it is desirable, as it stabilizes the crystal structure; in other cases it is unwanted, as it changes the physical and chemical properties of drugs. We here use (14)N NQR spectroscopy to quantitatively analyze hydration of a model compound, 5-aminotetrazole. (14)N NQR has some great advantages compared to other routinely used techniques to study hydration, like a very simple spectrum, single point calibration, and no need for special sample preparation, but the method's great disadvantage is a rather small sensitivity. Nevertheless, here we demonstrate that (14)N NQR, although being significantly less sensitive than XRD, NIR, and also (35)Cl NQR, is still capable of providing excellent quantitative accuracies. We can achieve errors <1% of the total amount, provided good temperature stabilization is implemented, which then allows long experimental times. We also present results obtained with a SLSE pulse sequence, which is a less robust approach but allows the use of much shorter measuring times (∼200×) and could be used for quantitative real time monitoring of hydration or dehydration.
“…As most common consumer products contain plastic parts, we implemented the proposed material biometrics approach by tagging plastic filaments with an NQR-active compound, namely sodium chlorate ( ). Note that the tagged product need not contain only plastic parts; the inclusion of metal parts does not significantly affect the amplitude, other features, or signal-to-noise ratio (SNR) of the measured NQR signatures 13 , 14 . Figure 2 Spin echoes from pulsed NQR measurements using the spin-locked spin echo (SLSE) sequence 15 are collected, filtered, and fitted to exponential decay curves.…”
Section: Resultsmentioning
confidence: 99%
“…Thus, higher NQR frequencies allow the use of smaller amounts of tagging compound. For example, detecting a common quadrupolar nucleus such as 14 N, which has I = 1 and resonance frequencies in the 2-5 MHz range, is significantly more difficult than detecting 35 Cl, which has I = 3/2 and resonance frequencies in the 25-35 MHz range. Moreover, while compounds containing other quadrupolar nuclei, such as 27 Al, 79 Br, 81 Br, and 127 I, can have very high resonant frequencies, they are generally not suitable for tagging because they (1) have very short signal decays and broad linewidths, which decreases sensitivity; and/or (2) are poisonous, explosive, or otherwise hard to handle.…”
Automatic recognition of unique characteristics of an object can provide a powerful solution to verify its authenticity and safety. It can mitigate the growth of one of the largest underground industries—that of counterfeit goods–flowing through the global supply chain. In this article, we propose the novel concept of material biometrics, in which the intrinsic chemical properties of structural materials are used to generate unique identifiers for authenticating individual products. For this purpose, the objects to be protected are modified via programmable additive manufacturing of built-in chemical “tags” that generate signatures depending on their chemical composition, quantity, and location. We report a material biometrics-enabled manufacturing flow in which plastic objects are protected using spatially-distributed tags that are optically invisible and difficult to clone. The resulting multi-bit signatures have high entropy and can be non-invasively detected for product authentication using $$^{35}$$
35
Cl nuclear quadrupole resonance (NQR) spectroscopy.
“…This field gradient is highly specific to substances. One of the promising applications using nitrogen-14 nuclear quadrupole resonance (NQR) is non-invasive detection such as illicit drugs [1][2][3][4][5], counterfeit medicines [6,7], explosive substances and landmines [8][9][10][11][12], since the NQR frequency and the spectrum obtained from each substance is unique, and the detection is highly specific and has low susceptibility to false alarms [13].…”
This paper shows the advances in the development of a portable system for remote detection of ammonium nitrate by nuclear quadrupole resonance. Three different probe coils were constructed and compared in terms of the signal intensity and the noise rejection under different environments, using the developed system. For the gradiometer probe coil, which showed the best performance in terms of noise rejection, the '90°' equivalent pulse was determined for different distances between the sample and the probe, and the remote detection of ammonium nitrate was achieved not only in a shielded room inside the laboratory, but also in the outdoors. The system was capable of detecting 200 g ammonium nitrate at 3 cm apart from the probe within 12 s with a steady-state free precession pulse sequence. The comparable results were obtained with a free induction decay sequence in 25 min for the total acquisition time. The compact size of the system will allow the applications for the substance detection in the outdoors especially for landmines made from ammonium nitrate and fuel oil mixtures instead of military explosives.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
