System and method for nuclear quadrupole resonance spectroscopy in tandem

Abstract

An apparatus for characterizing a sample using nuclear quadrupole resonance (NQR) spectroscopy is described whereby a plurality of NQR detectors operate in tandem, whereby each NQR detector is optimized to operate within a designed frequency range, having the means to shuffle the sample from one NQR detector to the next such as an automatic sample changer, having the means of controlling the frequency and amplitude of the radiofrequency field generated by the NQR detector through motors controlling variable capacitors or through the use of varactor diodes, digital capacitors, or digital potentiometers, having a plurality of Zeeman modulation coils to create a magnetic field surrounding the sample which may be arranged to minimize stray fields, such as a toroid, having the means of operating the spectrometer in frequency modulation mode, and having the capability of configuring the device for either continuous-wave NQR or pulsed NQR.

Description

[0001] SYSTEM AND METHOD FOR NUCLEAR QUADRUPOLE RESONANCE

[0002] SPECTROSCOPY IN TANDEM

[0003] CROSS REFERENCE TO RELATED APPLICATION

[0004] The present application claims priority to U.S. Provisional Application No. 63 / 657,054, entitled “METHOD AND SYSTEM FOR NUCLEAR QUADRUPOLE RESONANCE SPECTROSCOPY IN TANDEM” filed on June 6, 2024, the contents of which are incorporated herein by reference in their entirety.

[0005] FIELD

[0006] The present disclosure relates to nuclear quadrupole resonance spectroscopy, in particular, methods of arranging an apparatus capable of characterizing samples under test using continuous- wave excitation or pulsed excitation detection.

[0007] BACKGROUND

[0008] Nuclear quadrupole resonance (NQR) spectroscopy is a form of radiofrequency (RF) spectroscopy that analyzes samples in their solid form. NQR spectroscopy is applied to quadrupolar nuclei (spin angular momentum I > U) and provides direct information on the quadrupolar interaction between the nuclear quadrupole moment of a nucleus (Q) and its electric field gradient (EFG). Transitions between nuclear spin states of the quadrupolar nucleus can be excited by placing the sample in an oscillating magnetic field, i.e. a radiofrequency (RF) field, typically within an inductor generating the oscillating magnetic field and detecting the magnetic resonance response. NQR experiments can be performed in the absence of a magnetic field, i.e. pure quadrupole resonance, or in the presence of a small external magnetic field, i.e. Zeeman perturbed NQR spectroscopy. An NQR spectrum may feature one or multiple signals, with the spectrum reflecting a combination of the crystallography, the chemical bonding environment, and the spin angular momentum, I, of the nucleus. Every isotope has a defined nuclear quadrupole moment, whereas the EFG is determined by the chemical structure, chemical bonds, and to a smaller extent, the structure of the solid form of the substance under test (e.g. the crystallographic environment). As a result, NQR spectroscopy can be used to infer information concerning the chemical structure, the nature of the chemical bonds, and the structure of the solid form (e.g. the crystal structure).

[0009] Due to the variance in the characteristics of quadrupolar nuclei across the periodic table, notably the quadrupole moment (Q), the gyromagnetic ratio (y), the spin angular momentum (I), the isotopic natural abundance, and the chemical structures and bonding the elements may participate in, there is a large spread in the frequencies and amplitudes of the NQR signals. NQR frequencies can range over several orders of magnitude, from kHz frequencies, such as for2H, to GHz frequencies in the case of large quadrupoles in asymmetric environments (e.g.127I). NQR signals in crystalline materials are typically narrow relative to the overall spectral width, and, consequently, there is a need to search across large spectral ranges to find NQR resonances of previously uncharacterized compounds. In addition, NQR spectroscopy suffers from a relatively low mass sensitivity in part due to the small population difference between nuclear spin states, especially at low frequencies (e.g. <10 MHz). As a result, the search for unknown NQR resonances is a lengthy process and typically requires the attention of a specialist to operate the instrumentation. Overall, in part due to these challenges, NQR spectroscopy has been kept as an auxiliary method reserved for the specialist.

[0010] NQR spectroscopy can be performed by pulsed excitation (i.e. pulsed NQR) or by using continuous-wave excitation (i.e. continuous-wave NQR). In the case of pulsed NQR, the sample is subjected to a carefully calibrated RF pulse or series of RF pulses, and the sample’s response in the form of a free induction decay (FID) is recorded after the RF pulse, akin to NMR spectroscopy. In the case of continuous-wave NQR, the sample is subjected to continuous RF irradiation while monitoring for absorption or dispersion from the nucleus. The intensity of the RF field needed in pulsed NQR is orders of magnitude larger than that of continuous-wave NQR. Continuous-wave NQR can use non-linear devices, such as a super regenerative oscillator (SRO), or by using a linear oscillator. In the case of continuous-wave NQR, modulation is typically employed to improve the detection of NQR signals using lock-in detection.

[0011] One type of modulation used in continuous-wave NQR spectroscopy is Zeeman modulation, whereby a weak magnetic field is applied to the sample to perturb the nuclear spin system by means of the Zeeman interaction. A second type of modulation is frequency modulation, whereby the frequency of the oscillator is modulated at a modulation frequency or modulation waveform, and the modulation frequency is detected from the output of the NQR detector upon nuclear resonance.

[0012] As the NQR spectral range spans seven orders of magnitude, from kHz to GHz, NQR instruments can be designed to have broadband capabilities. In pulsed NQR, the resonant frequency and impedance of the NQR probe circuit can be tuned and matched using automated systems, allowing for the search of unknown resonances to be performed nearly autonomously. However, a compromise is typically made in terms of sensitivity when designing broadband NQR probes, both in terms of the inductance of the RF inductor and the Q-factor of the detector circuit. As a result, NQR probes may be designed to have the inductor replaced by the operator throughout the search for unknown resonances in order to access the full spectral range while improving the sensitivity of the NQR experiment. As a consequence, a fully autonomous search across large frequency ranges using a single pulsed NQR spectrometer without the intervention of an operator is not currently available.

[0013] A further drawback of employing pulsed methods in the search for unknown resonances is the requirements for precisely setting RF pulse lengths and intensities across the entire operational range of the device. As the gyromagnetic ratios of the nuclei on the periodic table vary quite considerably, and the EFG can affect pulse lengths, pulses are best calibrated to the sample under observation. For instance, a pulse optimized to observe35C1 NQR signals (y(35Cl) = 4.2 MHz T'1) would give suboptimal results for127I (y(127I) = 8.6 MHz T'1). In the search for unknown resonances, having to vary pulse lengths substantially increases the experimental times. Further, relaxation times in NQR vary considerably across the spectral range. Without prior information on the spin system, unsuitable relaxation delays between pulses may be chosen in pulsed NQR experiments, resulting in suboptimal operations either by compromising sensitivity (i.e. the spin system has not fully relaxed between transients) or unnecessarily increasing experimental times.

[0014] In contrast to pulsed NQR systems, continuous-wave NQR circuits tend to have narrower operational frequency ranges. Consequently, numerous continuous-wave NQR detection circuits have been proposed, with their topology and components designed to operate within a designated spectral range. As a result, a fully autonomous search across large frequency ranges using a single continuous-wave NQR spectrometer without the intervention of an operator is also not currently available. The RF field intensity in continuous-wave NQR generally has a weaker dependence on the gyromagnetic ratio of the nucleus and the relaxation times as compared to pulsed NQR experiments. While maximizing the signal intensity of a continuous-wave NQR signal still requires an optimal RF field intensity, the tolerances are less stringent than in pulsed NQR. As a result, continuous-wave NQR offers benefits over pulsed NQR in searching for unknown resonances.

[0015] Continuous-wave excitation with Zeeman modulation offers several advantages, such as high fidelity of NQR line shapes. In this case, the sample is typically surrounded by an electromagnetic coil, i.e. a Zeeman modulation coil, and a bisymmetric square waveform is applied to the coil in order to generate alternating magnetic fields of 0.5 mT - 30 mT at frequencies of 50 Hz and higher. The NQR signal is modulated by the Zeeman effect, with the magnetic field causing broadening of the NQR signal. The bisymmetric waveform allows for second harmonic detection using a lock-in amplifier, thereby allowing for narrowband detection. If the Zeeman modulation field is sufficiently homogeneous, the magnetic field waveform is not distorted, and the Zeeman effect is small relative to the quadrupolar coupling interaction (i.e. the magnetic field is not excessively strong), Zeeman modulation can provide both the NQR signal and the Zeeman perturbed NQR spectrum. The latter is especially helpful in measuring the full quadrupolar coupling tensor, with notable applications for spin I = 3 / 2 nuclei, such as35C1,37C1,79Br, and81Br. The challenges of using Zeeman modulation include interference in the NQR detector from stray fields arising from the Zeeman modulation coils, and the sensitivity of the apparatus to ferromagnetic contamination.

[0016] Alternative signal detection methods have been described since the first experimentally observed NQR signal. Firstly, novel signal detection methods based on superconducting quantum interference devices (SQUID) or atomic magnetometry have been proposed, but insofar have been limited to low NQR frequencies. Secondly, superconducting resonators such as those described in US Patent No. 4,511,496 (Matsumoto) have been proposed both in pulsed and continuous wave NQR to improve the signal -to-noise ratio but does not directly address the challenge of searching for unknown resonances. Thirdly, detector arrays such as those in US Patent Nos. 7,248,046 (Alvarez), 7,279,896 (Alvarez2), 7,279,897 (Alvarez3), 7,355,401 (Laubacher), 7,521,932 (Carter), 5,457,385 (Sydney), 8,901,926 (Apostolos), US Patent Publication No. 2023 / 0375487 (Huber) and United Kingdom Patent Application No. 2,289,344 (Smith) have been proposed whereby a sample is placed within an array of NQR detectors, but such detection systems are suboptimal due in part to the couplings between the detectors. Overall, while NQR spectroscopy can offer substantial information on the nature of the sample under test (crystallography, chemical structure & bonding, nuclei, ...), a major limitation to the application of NQR spectroscopy continues to be in the labor requirements in operating NQR devices and the time needed to perform a search for unknown resonances. Therefore, there is a need for an autonomous system for acquiring NQR spectra exists which makes use of multiple detection systems operating in tandem to scan the full NQR spectral range.

[0017] SUMMARY

[0018] In an aspect, the present disclosure provides a spectrometer to analyze a sample, the spectrometer comprising: a plurality of resonating cells, each one of the plurality of resonating cells further comprising: a detector operating in tandem with each other detector of each other plurality of resonating cells, the detector further comprised of and electrically connected to a resonator configured to resonate within a specific frequency range; and, a processor electrically connected to the plurality of resonating cells to actuate each resonator and the plurality of modulators.

[0019] In another aspect, the present disclosure provides a spectroscopy system to analyze a sample, the spectroscopy system comprising: a plurality of resonating cells to contain and affect the sample, each one of the plurality of resonating cells further comprised of a detector; a processor coupled to the plurality of resonating cells to actuate the detector; and, an automatic sample changer to mechanically move the sample between the plurality of resonating cells, wherein the plurality of resonating cells is configured to operate in tandem with one another within a specific frequency range.

[0020] In yet another aspect, the present disclosure provides a method for analyzing the spectrum of a sample, the steps comprising: inserting the sample into a first bay of a first resonating cell of a spectrometer for analysis, the spectrometer comprising a plurality of resonating cells; using a processor to actuate a detector of the first resonating cell; moving the sample from the first resonating cell to an adjacent resonating cell, each resonating cell configured to operate in tandem with one another within a specific frequency range; using the processor to actuate an adjacent detector of the adjacent resonating cell; repeating the steps for each resonating cell of the plurality of resonating cells; and, determining the spectrum of the sample.

[0021] An improved NQR spectrometer for analyzing samples in their solid form, such as the oral dosage forms of pharmaceutical products, is described. Embodiments of the present disclosure feature multiple NQR detectors operating in tandem, for example, using linear or non-linear oscillators, or pulsed NQR detectors. An embodiment of a tandem NQR spectrometer also features an automatic sample changer to move the sample under test (SUT) between NQR detectors, a digitizer to record the data, a means of recording and controlling the RF frequency and amplitude, a modulator to modulate the output of the NQR detector, and a central computing system to process the digitized data and coordinate the operations of the NQR spectrometer. The use of multiple NQR detectors operating in tandem allows for each NQR detector to be optimized to a specific NQR spectral region, allowing for improved sensitivity of the detector and therefore improved performance. For the first time, the tandem NQR spectrometer would allow for the full NQR spectral range to be scanned under optimal conditions. With the implementation of autonomous operations in each NQR detector by means of computer control, a skilled operator is no longer needed to scan large spectral ranges, thereby directly addressing the primary challenge of NQR spectroscopy. Further, as multiple NQR detectors are operated simultaneously by means of computer control, the sample throughput capability is multiplied, thereby directly addressing another major challenge of NQR spectroscopy.

[0022] A tandem NQR spectrometer is an assembly which may include multiple continuous-wave NQR oscillators or pulsed NQR detectors. In this way, multiple NQR detectors can operate simultaneously, allowing for a higher sample throughput capability as compared to a single device. A tandem NQR spectrometer can be designed to be modular, such as having the capabilities to search large NQR spectral range, or it can be designed to an intended application. For example, a tandem NQR spectrometer may be assembled to cover large spectral ranges to maximize the number of isotopes to be observed (e.g. 100 kHz - 2 GHz), therefore maximizing the breadth of applications. In a separate embodiment, a tandem NQR spectrometer can be configured to have multiple NQR detectors operating within the same spectral range (e.g. 30 MHz - 40 MHz), thereby limiting the device to a specialized application but increasing the sample throughput capabilities.

[0023] In a tandem NQR spectrometer, the SUT can be moved from one NQR detector to the next by means of an automatic sample changer or by external forces, such as gravity, compressed gas, or manually by the operator. The automatic sample changer, which is controlled by software and a computer, effectively allows the samples to be analyzed by the selected NQR detectors in the tandem NQR spectrometer without the need of external intervention from an operator. An embodiment of a tandem NQR spectrometer operates the NQR detectors in parallel rather than in series, so as to reduce potential bottlenecks and allow all NQR detectors to operate simultaneously. When combined with computer control of the tandem NQR spectrometer, a highly autonomous device can be constructed which can operate over nights and weekends while removing the need for any external intervention from an operator.

[0024] An example tandem NQR spectrometer using continuous-wave detection, as shown in Fig 5., is comprised of an automatic sample changer, a plurality of NQR probes, a plurality of continuous-wave NQR detectors equipped with the means of controlling and reading the RF frequency and amplitude, a modulator or a plurality of modulators (such as a Zeeman modulator or frequency modulator), a plurality of digitizers (such as an analog-to-digital converter), a central computer system to process the data by means of digital signal processing and control the experiments, and an appropriate enclosure to reduce the occurrence of electromagnetic interference. The frequency and amplitude for each continuous-wave NQR detector’s RF fields can be controlled either mechanically by means of a stepper motor controlling a capacitor, or electrically, by means of a varactor diode, by means of a digital capacitor, or by means of a digital potentiometer. The NQR probe consists of an RF inductor surrounding the sample, allows for the sample to be ejected and inserted into the probe, and allows for the temperature of the sample to be controlled by means of compressed gas or by other means.

[0025] In a separate embodiment of a tandem NQR spectrometer, as shown in Fig 4, a local processing unit is included with every NQR detector in order to perform the tasks of acquiring the digitized data from the analog-to-digital converter, reading the frequency from the continuous- wave NQR detector, controlling the frequency and amplitude of the continuous-wave NQR detector by mechanical or electrical means, and sending the data to the central processing unit for digital signal processing.

[0026] In the case where Zeeman modulation is used to modulate the output of a continuous-wave NQR detector, the region of the NQR probe containing the inductor and sample is subjected to a bisymmetric square wave magnetic field generated by means of an H-bridge or by a waveform generator and amplifier. A bisymmetric square wave consists of a square wave whereby each period reverses in polarity. The bisymmetric magnetic field modulates the output of the NQR detector by means of broadening the NQR signal. Zeeman modulation is also advantageous for studying the influence of Zeeman perturbation on the NQR signals, allowing for the assignment of NQR signals to the NQR transition, measuring the gyromagnetic ratio of the nucleus, and measuring the entire quadrupolar coupling tensor of a spin I = 3 / 2 nucleus.

[0027] In the case where Zeeman modulation is used to modulate the output of a continuous-wave NQR detector in a tandem NQR spectrometer, interference from stray fields may compromise adjacent NQR detectors through inhomogeneous broadening of NQR lines. Consequently, in an example embodiment of a tandem NQR spectrometer, the Zeeman coils in the form of Helmholtz coils surrounding the NQR inductor can be arranged circularly as to generate a toroidal magnetic field as a means to confine the magnetic field and thus reduce interference caused by stray fields, as shown in Fig 10. Due to the confinement of the Zeeman magnetic field, the device can also be miniaturized in order to shorten the transmission line between the NQR inductor and the oscillator, thereby improving the Q-factor of the circuit and improving the sensitivity of the experiment. The miniaturization of the apparatus would allow for the apparatus to fit on a benchtop, thereby reducing space requirements. A further benefit of generating the Zeeman modulation field as a toroidal field in a tandem NQR spectrometer is the possibility of synchronizing all Zeeman modulators to one modulation waveform reference frequency and therefore having the ability of using one modulation reference for all detectors operating in tandem. As a result, significant simplifications of the apparatus can be achieved by means of synchronizing the NQR detectors. For example, while a continuous-wave NQR detector using lock-in amplification requires a reference signal and an output signal, a tandem NQR spectrometer can have multiple NQR detectors operating with the same reference signal. In a separate embodiment, the NQR detectors are not arranged circularly, may be operating in series or in parallel, and the magnetic fields generated from the Zeeman modulation coils may or may not conduct through other Zeeman modulation coils. For instance, a long tube with multiple NQR detectors can be constructed, whereby the sample simply moves across detectors by means of gravity or other external forces. In a separate embodiment, as shown in Fig 9, the NQR detectors are arranged linearly in a way that would allow the SUT to be moved across sample bays by means of a force acted upon the sample, such as manually moving the sample, or by means of an automatic sample changer, gravity, a flow of gas, an actuator, or series of actuators (e.g. a robotic arm), an electric field, or a magnetic field.

[0028] In a separate embodiment, the NQR detector may feature an additional Zeeman perturbation coil and be controlled by the Zeeman modulator unit, as shown in Fig 2. The magnetic field from the Zeeman perturbation coil may be oriented parallel or perpendicular to the RF field and surrounded by the Zeeman modulation coils. In this case, a Zeeman perturbation NQR spectrum may be obtained with the field at 0° or 90° relative to the RF field. The Zeeman perturbation field can be kept powered continuously, with the Zeeman modulation field still modulating the output of the NQR detector by means of inhomogeneous broadening of the NQR resonance lines. In a separate embodiment, a pulsed NQR system may feature the Zeeman modulation coils, at angles to the RF field of 0° or 90°, for instance, in order to allow for the collection of Zeeman perturbed NQR spectra.

[0029] In a separate embodiment, and as shown in Fig 3, the sample inside the NQR probe may be surrounded by a second RF inductor oriented at 90° of the NQR inductor as a means of decoupling the two coils and reduce spoiling the Q-factor of the NQR oscillator through coupling. The second RF inductor can be powered by external means, such as a signal generator and an amplifier, in order to irradiate the sample at a second RF frequency. The second RF frequency may be frequency modulated, amplitude modulated, phase modulated or not modulated at all. In the case where multiple NQR transitions are expected, such as the case in higher spin angular momentums (spin I = 1, 3, 5 / 2, 7 / 2, 9 / 2, ...), the oscillator can be centered on an observed NQR frequency, and the second RF field can be used to excite the other NQR frequencies on the spectrum while observing the response on the first NQR frequency. Using this approach, the NQR spectrum can potentially be assigned, and NQR signals can be correlated. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The following figures serve to illustrate various embodiments of features of the disclosure. These figures are illustrative and are not intended to be limiting.

[0031] Fig 1. shows a block diagram of a single NQR cell of a tandem NQR spectrometer, according to an embodiment of the present disclosure;

[0032] Fig 2. shows a block diagram of a single NQR cell of a tandem NQR spectrometer equipped with a Zeeman perturbation coil in addition to a Zeeman modulation coil, according to an embodiment of the present disclosure;

[0033] Fig 3. shows a block diagram of a single NQR cell of a tandem NQR spectrometer and an additional RF generator, according to an embodiment of the present disclosure;

[0034] Fig 4. shows a block diagram of a single NQR cell of a tandem NQR spectrometer equipped with a local processing & control unit and a central processing & control unit, according to an embodiment of the present disclosure;

[0035] Fig 5. shows a block diagram of a tandem NQR spectrometer with a plurality (n) of NQR cells, according to an embodiment of the present disclosure;

[0036] Fig 6. shows a block diagram of a tandem NQR spectrometer with a plurality (n) of NQR cells, with each cell equipped with a local processing & control unit, according to an embodiment of the present disclosure;

[0037] Fig 7. shows the assembly of an NQR probe and a continuous-wave NQR detector, showing the RF inductor, the NQR probe, and the NQR detector, according to an embodiment of the present disclosure;

[0038] Fig 8. shows the assembly of an NQR probe, continuous-wave NQR detector, and the Zeeman modulation coils, according to an embodiment of the present disclosure;

[0039] Fig 9. shows a plurality of NQR probes and Zeeman modulation coils arranged linearly in tandem, according to an embodiment of the present disclosure;

[0040] Fig 10. shows a plurality of NQR probes and Zeeman modulation coils arranged circularly to form a toroidal field, according to an embodiment of the present disclosure; Fig 11. shows the assembly of the NQR probes and Zeeman modulation coils arranged circularly in tandem to form a toroidal field and equipped with an autosampler, according to an embodiment of the present disclosure;

[0041] Fig. 12a shows a sample holder in a diagonal view, according to an embodiment of the present disclosure;

[0042] Fig. 12b shows a sample holder in a front view, according to an embodiment of the present disclosure; and,

[0043] Fig. 12c shows a sample holder in a cross-sectional view, according to an embodiment of the present disclosure.

[0044] DETAILED DESCRTIPTION

[0045] The following embodiments are merely illustrative and are not intended to be limiting. It will be appreciated that various modifications and / or alterations to the embodiments described herein may be made without departing from the disclosure and any modifications and / or alterations are within the scope of the contemplated disclosure.

[0046] A tandem NQR spectrometer makes use of multiple NQR detectors (30) operating in parallel, with each detector capable of analyzing the SUT. The SUT is moved from one NQR detector to the next by means of an automatic sample changer (80) or manually. An embodiment of a tandem NQR spectrometer makes use of Zeeman modulation and continuous-wave detection as a means of obtaining high fidelity line shapes, simplifying the hardware and reducing the overall cost of the apparatus. As shown in Fig 1, the sample is placed in a sample bay (1) within an NQR probe (20) which is connected to an NQR detector (30). The output of the NQR detector (30) is digitized by means of an analog-to-digital converter (40) and sent to a central processing & control unit (50), which may be an external server computer or a small internal computer, for digital signal processing. The frequency of the NQR detector is adjusted and read by the frequency control unit (60), which is controlled by the central processing & control unit (50). The central processing & control unit (50) is used to control the Zeeman control unit (12), which powers the Zeeman modulation coils (10). Lock-in detection is generally required to measure the NQR signal using the output of a Zeeman-modulated oscillator circuit. In an alternate embodiment, frequency modulation is used instead of Zeeman modulation. A tandem NQR spectrometer can be designed to contain as many sample bays (1) and NQR detectors (30) as needed for a specialized application, with possible arrangements being, but not limited to, linearly or circularly arranged. The modulated output signal from the oscillator can be digitized by an analog-to-digital converter (40), and digitally processed on a central processing unit (50) by means of digital signal processing. The use of digital signal processing is convenient as it allows the data to be processed with various processing parameters and allows for the same data to be re-processed afterwards if needed. An embodiment of a tandem NQR spectrometer should be fully automated in effort to eliminate the need for any user intervention, allowing the apparatus to operate over nights and weekends. Such automation includes a means of adjusting the frequency and amplitude of the oscillator, such as using electromechanical (e.g. variable capacitor with a motor) means and / or electrical means (e.g. varactor diode, digital capacitor, digital potentiometer). Each component of the apparatus will be described in greater detail.

[0047] To facilitate the construction and description of a tandem NQR spectrometer, the sample bay, NQR probe, Zeeman modulator, and NQR detector form a resonating cell, also termed an NQR cell. The NQR cell serves the purpose of interacting with the sample and detecting the NQR signal. The NQR cell may include the analog-to-digital converter, a local processing & control unit, and a frequency control unit. A tandem NQR spectrometer operates multiple NQR cells in parallel.

[0048] NQR Probe

[0049] As shown in Fig 7, the NQR probe (20) houses the RF inductor (24), the sample bay (1), and must allow the sample to enter and exit the sample bay (1). A model has been designed to allow for this, whereby the sample is inserted above and enters the sample bay (1) and is surrounded by the RF inductor (24). The 3D model of the probe insert (22) includes a former for the RF inductor (24) to be wound and be kept in place. The RF inductor (24) may be constructed from copper but would be preferably constructed from silver due to its higher conductivity and to prevent interference from the quadrupolar nuclei of copper (63Cu and65Cu). The entire NQR probe assembly, apart from the RF inductor (24), can be made of various plastics, such as polyethylene, noting that special care must be used to exclude ferromagnetic contamination from the assembly and the material must not contain quadrupolar nuclei that could interfere with the NQR experiment. The NQR probe (20) should have RF shielding, such as a layer of aluminum, and may include a grounded RF connector (26) of various types, such as a BNC connector, to allow the rapid exchange of the NQR probe should the NQR probe need to be replaced, or for the purposes of configurability. Alternatively, instead of a BNC connector, the NQR probe may feature edge connectors to interface to a motherboard, thereby allowing the NQR spectrometer to be easily configured to an intended application. In one example, as shown in Fig 7, a bulbous frame was designed for the NQR probe to increase the distance between the RF inductor (24) and the RF shielding as a means of minimizing losses between the RF inductor (24) and the shielding and thereby maximize the Q-factor of the NQR oscillator, though this feature is not critical.

[0050] The sample can be ejected and inserted using compressed gas or by mechanical means. In addition, gas of a controlled temperature can be flowed through the NQR probe (20) and onto the sample in order to regulate the temperature of the sample, as NQR signals are highly dependent on the experimental temperature. The NQR probe (20) may be designed to accommodate samples of various geometries, such as a rectangular package commonly used in pharmaceuticals or for transportation. The NQR probe may also be adapted to allow a specialized sample holder (110) to fit inside, thus placing the sample cavity (124) within the core of the RF inductor (24).

[0051] In one embodiment, the NQR probe (20) may be equipped with a means of measuring the strength of the magnetic field, such as a Hall effect sensor. A magnetic field sensor adjacent to the sample would allow the current in the Zeeman modulation coils (16) or Zeeman perturbation coil (90) to be adjusted to generate the desired Zeeman modulation strength, or Zeeman perturbation field strength. Further, by monitoring the magnetic field sensor’s output over time, a waveform showing the strength of the magnetic field as a function of time can be generated to be used as a diagnostic tool to improve the performance of the Zeeman modulator (10).

[0052] Zeeman modulation coils & Zeeman control unit

[0053] Zeeman modulation is a convenient method of modulating NQR signals to improve detection, yielding the difference between the Zeeman perturbed and unperturbed spectrum rather than a derivative spectrum, as would be obtained when using frequency modulation. Second harmonic detection using a bisymmetric waveform is used to reduce spurious signals, reduce interference, and improve the signal-to-noise ratio. This can be achieved using an H-bridge circuit controlled digitally, such as those based on the L298n motor drive controller boards and wiring the Zeeman coils (16) to the output of the H-bridge. The H-bridge is advantageous to use as it allows electric current to flow in both directions of the Zeeman coil (16) to generate a magnetic field in either direction and can easily be controlled by a Zeeman control unit (10), such as an Arduino Uno. The Zeeman control unit can be controlled through the central processing & control unit (50), thereby allowing the modulation frequency and waveform to be controlled digitally.

[0054] The advantage of Zeeman modulation is the possibility of simultaneously obtaining the Zeeman perturbed NQR spectrum and pure NQR spectrum, which provides an opportunity to measure the full quadrupolar tensor, even for spin I = 3 / 2 nuclei. Additionally, Zeeman perturbation allows for assigning the NQR signals to their spin transitions in bosons (spin 1 = 1, 3, 7). In order to obtain the Zeeman perturbed NQR spectrum, magnetic field homogeneity is required to resolve fine spectral features. One method of obtaining adequate magnetic field homogeneity is by using Helmholtz coils, as shown in Fig 8, but may also be constructed as a solenoid. In addition to homogeneity, the Zeeman coils (16) need to be engineered to yield a time constant that is short relative to the modulation frequency. This can be accomplished by increasing the resistance of the filament used in the Zeeman coil (16) either by choosing finer filament or more resistive metals, thereby decreasing the inductor’s time constant at the cost of higher power requirements and heat generation. Another factor to consider is the effect of shielding and Eddy currents, with thicker shielding generally causing inductor time constants to be longer. Consequently, thin shielding is preferrable, such as metallic foil. The Zeeman modulation coils (16) can be built using a plastic frame, such as polyethylene, while considering that heat management using air cooling or water cooling may be necessary to prevent the plastic frame from deforming upon heating. Special attention is needed to exclude magnetic parts and ferromagnetic contamination from nearing the Zeeman field in order to reduce interference, e.g. due to vibrations.

[0055] In Zeeman perturbed NQR, the angle between the Zeeman modulation field and the RF field is important to consider. In order to maximize the significance of the spectral features in Zeeman perturbed NQR, it is beneficial to have the Zeeman perturbation field be aligned parallel to the RF field. However, in this geometry, significant voltage may be induced in the RF inductor if the magnetic field strength varies with time, which may lead to suboptimal results due to Faradaic pickup. Alternatively, the Zeeman magnetic field may be at an angle (e.g. orthogonal) to the RF field, which may still lead, in some circumstances, to the full quadrupolar coupling tensor. As shown in Fig 2, another alternative is to include a second Zeeman perturbation coil (90) around the sample, with the magnetic field from the Zeeman perturbation coil aligned to be parallel to the RF field. A continuous current can be passed through the Zeeman perturbation coil in order to generate the desired Zeeman perturbation field, thus causing the Zeeman perturbation. The same Zeeman modulation scheme remains applicable, as the Zeeman modulation field would cause broadening of the NQR signal by means of inhomogeneous broadening. Another alternative is to include an additional Zeeman perturbation coil (90) around the sample, with the magnetic field from the Zeeman perturbation coil aligned to be perpendicular to the RF field.

[0056] In the case where the SUT contains materials that vibrate due to the Zeeman modulation field, for instance, due to being magnetic or paramagnetic, it may be necessary to forego Zeeman modulation in favor of frequency modulation (see the discussion below in the Frequency control & frequency control unit section). In this case, the Zeeman modulator coils would either be energized continuously so as to generate a non-varying magnetic field for use in Zeeman perturbed NQR, or it can be kept off altogether. Consequently, an embodiment of a tandem NQR spectrometer may feature both Zeeman modulation capabilities and frequency modulation capabilities. The inclusion of frequency modulation may also extend the application of the spectrometer for the analysis of internal-field nuclear magnetic resonance (ifNMR), such as for57Fe ifNMR of metallic iron.

[0057] NQR Detector

[0058] As the name suggests, the NQR detector (30) performs the function of detecting the NQR signal. The two categories of detection schemes are pulsed NQR and continuous-wave NQR. While pulsed magnetic resonance offers several advantages, such as the application of pulse sequences, the construction tolerances are tighter in pulsed NQR than in continuous-wave NQR. For instance, high power amplifiers are needed to generate RF pulses of sufficient intensity to excite the NQR transitions. While constructing a tandem NQR spectrometer with multiple pulsebased detectors is certainly possible, the simplicity of constructing and operating a continuous- wave NQR circuit is advantageous for a tandem NQR spectrometer which may operate multiple NQR detectors simultaneously. As a result, an embodiment of a tandem NQR spectrometer is based on continuous-wave circuits, such as an oscillator. However, an embodiment of a tandem NQR spectrometer based on pulsed techniques may include a single set of pulsed hardware (e.g. amplifier, waveform generator, detector) connected to multiple NQR probes, an NQR probe equipped with multiple channels, or a plurality of NQR probes and a plurality of pulsed hardware. In one of these embodiments, the RF pulses & NQR response measurement would alternate between probes so as to have one amplifier operating across multiple NQR probes. In another alternative embodiment of a tandem NQR spectrometer based on pulsed techniques, a plurality of NQR probes, amplifiers, and detectors are operated in parallel.

[0059] The continuous-wave NQR detectors should be optimized to operate within a designated frequency range. A resonator is provided, connected to the NQR detector. In the present embodiment, the resonator is an LC circuit, although other resonators may be suitable. The LC circuit connected to the NQR detector should be capable of resonating within the designated frequency range, noting that the capacitor in the LC tank circuit is typically a variable capacitor, a varactor diode, or a combination of both. In one embodiment, a standard variable capacitor is used across all circuits, and an optimal inductor is designed to allow the LC circuit to operate within the frequency region of interest. For example, in a tandem NQR spectrometer operating eight NQR detectors, a standard variable capacitor with a range of 5 - 25 pF capacitance can be used across all LC circuits. The inductor as part of the LC circuit can then be constructed to have an inductance of 120 nH, thereby allowing the LC circuit to operate from 206 MHz to 92 MHz. In the LC circuit of the second NQR detector, the same standard variable capacitor can be used, while the inductor can be constructed to have an inductance of 480 nH, thereby allowing the LC circuit to operate from 103 MHz to 46 MHz. In the LC circuit of the third NQR detector, the same variable capacitor can be used, while the inductor can be constructed with an inductance of 1900 nH thereby allowing the LC circuit to operate from 51 MHz to 23 MHz. In this example, the trend continues for the eight NQR detectors.

[0060] As the inductance becomes smaller and operating frequency increases, the spectral range of the NQR detector also increases. This is beneficial to the operation of a tandem NQR spectrometer as higher NQR frequencies are generally associated with higher sensitivity, and thus, detection times are generally shorter than NQR signals occurring at lower frequencies. In the time that it takes the NQR detector operating at higher frequencies to complete scanning its wider spectral window, the NQR detectors operating at lower frequencies can complete the scan of their narrower spectral window. Consequently, a tandem NQR spectrometer can be designed to reduce bottlenecks by equalizing the scan times across NQR detectors by means of engineering the operating frequencies of each NQR detector, while considering the sensitivity differences along the spectral range.

[0061] Frequency control & frequency control unit

[0062] In the case of continuous-wave NQR using an oscillator, and in the case of pulsed NQR, the resonant frequency of an LC circuit can be adjusted by means of a variable capacitor or an electronically controlled varactor diode. In the case where a variable capacitor is used, the capacitance can be adjusted by means of a stepper motor and a microcontroller. For instance, coupling a 5 - 25 pF precision variable capacitor to a 28BYJ-48 stepper motor, controlled by a frequency control unit (e.g. an Arduino Uno) and a central processing & control unit (50), allows for the frequency of the oscillator to be stepped at the desired intervals (e.g. 1 kHz steps across the NQR spectrum) by initiating the stepper motor with the desired step size. Rather than using a continuously turning motor with a step-down gearbox, which leads to instability of the oscillator’s frequency during lengthy lock-in time constants, the capacitor can be stepped at the desired intervals and the data can be acquired after the motion has completed. The use of stepwise acquisition using a stepper motor, in contrast to a continuously turning motor, allows for longer lock-in amplifier time constants to be used while allowing for improved line shape fidelity due to a higher stability in the oscillator’s frequency. The amplitude of the RF field within the NQR probe of a continuous-wave NQR detector can also be controlled, for instance, by the frequency control unit (60), by means of a stepper motor turning a variable capacitor which controls the amount of feedback in the oscillator and thereby controlling the voltage within the LC circuit, or by means of a varactor diode, a digital capacitor, or by means of a digital potentiometer. As shown in Fig 4 and Fig 6, the integration of a local processing & control unit within the NQR cell could be beneficial in providing further stability in the oscillator circuit by means of controlling a varactor diode. For instance, a microprocessor, such as a Raspberry Pi 4, can continuously monitor the RF frequency of the circuit, and control a varactor diode accordingly to adjust the RF frequency to compensate for drifts.

[0063] The frequency control unit may also include the means of frequency modulation. Frequency modulation is an alternative method to Zeeman modulation for detecting NQR signals. The advantage of frequency modulation is for the analysis bosons, such as14N, or the analysis of magnetic or paramagnetic materials which may vibrate due to the Zeeman modulation field, thus leading to suboptimal results. Frequency modulation can be accomplished by means of a varactor diode and applying a modulation frequency or modulation waveform (e.g. a bisymmetric square wave) of a specified amplitude to that varactor diode. In the embodiment featuring a local processing & control unit, such as a Raspberry Pi 4, the local processing & control unit can generate a voltage waveform onto the varactor diode by means of a digital-to-analog converter in order to generate the frequency modulation in the oscillator. The modulation frequency dictates the rate at which the frequency of the oscillator is modulated, whereas the amplitude of the modulation dictates the depth at which the frequency changes. As mentioned above, an embodiment of a tandem NQR spectrometer with a continuous-wave detector could feature both Zeeman modulation and frequency modulation in order to maximize the types of samples that can be analyzed and the modularity of the system. Digitizer, Central Processing & Control Unit, Digital Signal Processing

[0064] Significant simplifications can be made to the hardware by using digital signal processing. As shown in Fig 1, the output from a continuous-wave NQR detector (30) can be directly digitized using an analog-to-digital converter (40) for the duration of the lock-in time constant, and subsequently using digital signal processing by means of software within the central processing & control unit (50) to generate the NQR spectrum. The frequency control unit (60) records the frequency of the NQR detector (30) which is used to relate the results from the digital signal processing to the NQR frequency. Alternatively, as shown in Fig 4, the analog-to-digital converter (40) and the frequency control unit (60) can be integrated directly into a local processing & control unit within each NQR cell. In the case of using a local processing & control unit, all capabilities of the experiment can be integrated into the NQR cell, such as measuring the NQR detector’s (30) response, measuring the RF frequency by means of a frequency counter (60), measuring the amplitude of the RF voltage, controlling the frequency and amplitude of the NQR detector by means of stepper motors attached to variable capacitors or by electronic means, such as varactor diodes, digital capacitor, or digital potentiometer, and sending all the digitized data to a central processing & control unit for digital signal processing.

[0065] Operating commands may be sent from a user over the internet to the central processing & control unit in order to further simplify the user experience. In addition, the processed NQR data may be sent from the central processing & control unit to the cloud in order to allow the user to collect their data from one centralized location.

[0066] The coordination of the NQR experiments across all NQR detectors or NQR cells, including initiating the Zeeman modulator (10), initiating the frequency stepping by means of the frequency control unit (60), initiating the data collection by means of the analog-to-digital converter (30), and generating the output NQR spectrum can be performed by a central processing & control unit (50), which may be in the form of a server computer or small internal computer. Alternatively, a local processing unit can be used to initiate the frequency stepping by means of the frequency control unit (60), initiating the data collection by means of the analog-to-digital converter (30), and transferring the data to the central processing & control unit for digital signal processing. The use of digital hardware allows for reducing the cost of the apparatus, miniaturization of the system, and the ability of reprocessing the acquired data under different conditions, for instance, to improve the signal-to-noise ratio.

[0067] Tandem NQR spectrometer arrangements

[0068] As shown in Fig 5 and Fig 6, a tandem NQR spectrometer contains multiple NQR detectors operating in parallel. In order for a tandem NQR spectrometer to perform optimally, an automatic sample changer (80) can be used to move the samples between sample bays (1) of the NQR probes (20) connected to the NQR detectors (30). As shown in Fig 10, an embodiment of a tandem NQR spectrometer has the NQR detectors (30) and Zeeman modulation coils (16) arranged circularly, so as to generate a toroidal magnetic field. The toroidal magnetic field allows for the Zeeman field to be confined to the toroid, allowing for the miniaturization of the apparatus and for higher Q- factors of the NQR detector to be obtained due to the use of shorter transmission lines. In order to further confine the magnetic field from the Zeeman modulating coils, magnetic field shielding can be used, such as mu-metal, which serves two purposes. Firstly, magnetic field shielding serves the purpose of conducting the stray fields from the Zeeman modulating coil away from the NQR detection circuit, reducing potential interference. Secondly, magnetic field shielding allows stray fields from outside the apparatus, such as Earth’s stray magnetic field or nearby stray fields from magnets or electrical lines, to be conducted around the NQR probes. Shielding the sample from stray magnetic fields is an advantageous means of maximizing the reproducibility of NQR spectra between instruments. Given that a tandem NQR spectrometer may be found in a magnetic resonance laboratory, nearby stray fields from superconducting NMR magnets may be present. Magnetic field shielding can be placed above and below the Zeeman coils (12) to further contain the magnetic field.

[0069] Another important factor to consider in a tandem NQR spectrometer is temperature regulation of the samples. As NQR signals are sensitive to the experimental temperature, care must be taken to ensure that the temperature of the sample is regulated, and that the Zeeman modulation coils do not heat the sample. Numerous thermal management systems can be used to cool the Zeeman modulation coils, such as water-cooling systems. However, to ensure the temperature stability of the sample, a temperature-controlled stream of gas, such as nitrogen gas or compressed air, can be passed over the sample. While the Zeeman modulators do not necessarily have to be synchronized in a tandem NQR spectrometer, the synchrony of the NQR experiments allows for a single reference waveform to be used for multiple NQR detectors, and for the Zeeman modulation fields to be conducted across Zeeman modulation coils. Overall, synchronizing the Zeeman modulation across multiple NQR detectors allows for simplification and miniaturization of the apparatus.

[0070] In a separate embodiment, as shown in Fig 9, the NQR detectors are arranged linearly in a way that would allow the SUT to be moved across sample bays by means of a force acted upon the sample, such as manually moving the sample, or by means of an automatic sample changer, gravity, a flow of gas, an actuator, or series of actuators (e.g. robotic arm), an electric field, or a magnetic field.

[0071] A tandem NQR spectrometer can be designed to cover a large NQR spectral range, or it can be configured for a specific application, such as for the analysis of pharmaceuticals by exploiting the14N nucleus. In this example, the tandem NQR spectrometer would have multiple NQR detectors operating within the same frequency region, such as the 2 MHz - 6 MHz region in the case of14N NQR, allowing for a larger volume of samples to be analyzed by the same spectrometer. The NQR probe (20) can also be designed to the application, allowing for pharmaceuticals in their commercial packaging to be inserted into the sample bay of the NQR probe (20).

[0072] Automatic sample changer

[0073] An embodiment of a tandem NQR spectrometer includes an automatic sample changer (80) as a means of loading the samples into the NQR detectors without the need for manual intervention. The automatic sample changer (80) must be capable of inserting the SUT into the NQR detector, removing the sample from the NQR detector, and swapping the SUT for other samples to be tested. In one embodiment, an automatic sample changer (80) consisting of a circular device with multiple sample positions aligned above the NQR detectors, as shown in Fig 11. In this case, the automatic sample changer (80) was designed to automatically load samples into a tandem NQR spectrometer operating a toroidal field, allowing for the automatic sample changer (80) to be significantly simplified. In this example, a motor (88) controls the position of the automatic sample changer (80) by rotating the sample slot (84) to align the sample holder with the desired NQR detector. Samples are ejected from the NQR detector (30) by means of a strong flow of compressed gas to push the sample out of the sample bay (1), and samples are inserted into the NQR detector (30) by means of a gentler flow of compressed gas to slowly allow the sample to enter the sample bay (1). Alternatively, the sample can be inserted and ejected from the autosampler by mechanical means, such as a linear actuator. The autosampler therefore needs to be equipped with the means of holding the samples in the automatic sample changer’s sample slot (84) until the insert or eject process is initiated, which can be accomplished by means of an electronic solenoid actuator (82). The solenoid actuator can be controlled by means of a relay board connected to the central processing & control unit, which would also control the motor turning the automatic sample changer’s sample carousel (80).

[0074] An automatic sample changer (80) is not necessary for the operation of a tandem NQR spectrometer. For example, it may be more practical in some contexts for the user to load samples manually into the device. For instance, in handling packaging for manual inspection, it may be more convenient for a user to insert and withdraw the samples manually.

[0075] Sample holder

[0076] As shown in Figs 12a, 12b and 12c, the sample holder is fabricated from various non- conductive and non-magnetic materials, such as plastic, and serves the purpose of holding the sample in the sample cavity (124). The material of choice for the sample holder must be inert, such as polyethylene, so as to prevent chemical reactions between the SUT and the sample holder. Further, the sample holder must not be conductive or contain ferromagnetic impurities, as conductive materials (e.g. copper) will interfere with the NQR detection and ferromagnetic materials will interfere with the Zeeman modulation of the NQR experiment. An embodiment of a sample holder features the ability to seal the sample inside to avoid spills, such as threads (114, 120) on the sample holder’s body (110) and on the sample holder’s cap (112). An embodiment of the sample holder assembly features threads on the outside of the sample container in order to minimize interference of the threads when filling the sample holder. In addition, threads located on the outside of the sample container may allow for a more hermetic sealing without compromising the sample in the case where thread sealer was to be applied to the threads. In a separate embodiment, the threads may be on the inside of the sample holder, or a simple clipping mechanism may be used to seal the cap of the sample holder to its body. The inner walls of the sample holder’s body may be angled in a way to create a funnel (122) in order to facilitate adding samples to the sample container. The sample holder’s cap may also feature angles that match the funnel (122) of the sample holder’s body as a means to seal the sample inside the cavity (124) of the sample holder. The tip (118) of the sample holder’s cap may extend as needed as a means of applying slight pressure to the sample inside the sample holder’s cavity (124), as a means to position the sample into the sample cavity of the sample holder. The sample holder’s body (110) contains a lower edge (126) which serves the purpose of controlling how deep the sample cavity (124) holding the sample enters the NQR detector. The lower edge (126) may also serve the purpose of being held by the autosampler, as well as allowing the sample to be ejected from the sample cavity by means of compressed gas.

[0077] Operating a tandem NQR spectrometer

[0078] In operating a tandem NQR spectrometer, the user places their SUT into the sample positions on the automatic sample changer (80) and enters in the acquisition details through the central processing & control unit (50). In the case where a user designates the full scanning range of the NQR spectrum, and the tandem NQR spectrometer is equipped with multiple NQR detectors operating across multiple frequencies, the tandem NQR spectrometer will shuffle the sample across the NQR detectors (30) and search the entire RF region. In the case where the user wants to search pre-designated regions, the tandem NQR spectrometer will add the sample to the designated NQR detectors. In all cases, the acquisition data is automatically processed by software to provide the user with the final NQR spectrum. In the case where the spectrometer is operated through the cloud, the user would input the acquisition parameters on the web interface, with the experimental details transmitted to the central processing & control unit through the internet.

[0079] Applications for a tandem NQR spectrometer

[0080] Applications for a tandem NQR spectrometer includes investigating pharmaceutical products, authenticating medicine, research & development in materials sciences, minerology, and academia, to name a few. For instance, there has been an emphasis on investigating the polymorphic landscape of pharmaceutical products, in which case NQR spectroscopy would be well suited. Beyond pharmaceuticals, NQR spectroscopy can be used to investigate functional materials, such as monitoring gas absorbing materials. In the field of minerology, NQR spectroscopy has been proposed to identify minerals that are present in a SUT. While NQR spectroscopy was first observed in 1950, it has remained an auxiliary technique reserved for specialists. A tandem NQR spectrometer addresses multiple barriers to regular usage of NQR spectroscopy, which includes increasing sample throughput capability, offering broadband capabilities, and full autonomous operations. Due to the simplicity of operations, a tandem NQR spectrometer based on continuous-wave NQR detectors can be conceived which has very simplified operations relative to current pulsed NQR spectrometers, allowing for improved accessibility of the technique to non-specialists.

[0081] The term "coupled", along with its derivatives, may be used herein. In particular embodiments, "coupled" may be used to indicated that two or more elements are in either direct or indirect (with other intervening elements between them) physical or electrical contact with each other, or that the two or more elements co-operate or interact with each other (e.g. as in a cause- and-effect relationship).

[0082] Reference Numerals: 1 - Sample bay; 10 - Zeeman modulator; 12 - Zeeman control unit; 14 - Zeeman modulation coil mount; 16 - Zeeman modulation coil; 20 - NQR probe; 22 - NQR probe insert; 24 - RF Inductor; 26 - RF connector of NQR probe; 30 - NQR detector; 32 - Signal output of the NQR detector; 34 - RF output of the NQR detector; 36 - RF connector to the NQR probe; 40 - Analog-to-digital converter; 50 - Central processing & control unit; 60 - Frequency control unit; 70 - Local processing & control unit; 80 - The autosampler carousel holding the samples above the NQR detectors; 82 - Mechanism to holding and releasing the sample from the autosampler; 84 - Sample slot on the autosampler; 86 - Coupler used to attach the autosampler’s motor to the sampler holder of the autosampler; 88 - Motor to rotate the autosampler’s position; 90 - Zeeman perturbation coil; 100 - RF generator; 110 - Sample holder body; 112 - Cap of the sample holder; 114 - Threads on the cap of the sample holder; 116 - Cone on the cap of the sample holder; 118 - Sample positioner and sealer on the cap of the sample holder; 120 - Threads on the sample holder body; 122 - Funnel on the sample holder bottom; 124 - Sample cavity of the sample holder; 126 - Lower edge of the sample holder.

Claims

CLAIMS1. A spectrometer to analyze a sample, the spectrometer comprising: a plurality of resonating cells, each one of the plurality of resonating cells further comprising: a detector operating in tandem with each other detector of each other plurality of resonating cells, the detector further comprised of and electrically connected to a resonator configured to resonate within a specific frequency range; and, a processor electrically connected to the plurality of resonating cells to actuate each resonator and the plurality of modulators.

2. The spectrometer of Claim 1 wherein the sample is moveable between the plurality of detectors.

3. The spectrometer of Claim 2 further comprised of an automatic sample changer to mechanically move the samples between the plurality of detectors.

4. The spectrometer of Claim 1 wherein each one of the plurality of resonating cells is further comprised of a modulator electromagnetically coupled to the detector.

5. The spectrometer of Claim 1 wherein at least one of the plurality of resonators is an LC circuit.

6. The spectrometer of Claim 4 further comprised of an H-bridge circuit electrically coupled to the plurality of modulators to reduce spurious signals, reduce interference and improve a signal-to-noise ratio.

7. The spectrometer of Claim 1 further comprising an active electrical component electrically coupled to the plurality of resonators, and wherein the processor is configured to monitor a radiofrequency (RF) frequency of the plurality of resonators and adjust the RF frequency by controlling the active electrical component.

8. The spectrometer of Claim 4 wherein the plurality of resonating cells is arranged in a toroidal fashion to confine a magnetic field of the modulators.

9. The spectrometer of Claim 1 wherein the plurality of resonating cells is arranged in a linear fashion to facilitate a movement of the sample from one cell of the plurality of resonating cells to an adjacent resonating cell.

10. A spectroscopy system to analyze a sample, the spectroscopy system comprising: a plurality of resonating cells to contain and affect the sample, each one of the plurality of resonating cells further comprised of a detector; a processor coupled to the plurality of resonating cells to actuate the detector; and, an automatic sample changer to mechanically move the sample between the plurality of resonating cells, wherein the plurality of resonating cells is configured to operate in tandem with one another within a specific frequency range.

11. The spectrometer of Claim 10 wherein each one of the plurality of resonating cells is further comprised of a modulator and a resonator.

12. The spectrometer of Claim 11 wherein at least one of the resonators is an LC circuit.

13. The spectrometer of Claim 11 further comprised of an H-bridge circuit electrically coupled to the modulator to reduce spurious signals, reduce interference and improve a signal -to-noise ratio.

14. The spectrometer of Claim 11 further comprising an active electrical component electrically coupled to the resonators, and wherein the processor is configured to monitor a radiofrequency (RF) frequency of the resonators and adjust the RF frequency by controlling the active electrical component.

15. The spectrometer of Claim 11 wherein the plurality of resonating cells is arranged in a toroidal fashion to confine a magnetic field of the modulators.

16. The spectrometer of Claim 10 wherein the plurality of resonating cells is arranged in a linear fashion to facilitate a movement of the sample from one cell of the plurality of resonating cells to an adjacent resonating cell.

17. A method for analyzing the spectrum of a sample, the steps comprising: inserting the sample into a first bay of a first resonating cell of a spectrometer for analysis, the spectrometer comprising a plurality of resonating cells; using a processor to actuate a detector of the first resonating cell; moving the sample from the first resonating cell to an adjacent resonating cell, each resonating cell configured to operate in tandem with one another within a specific frequency range; using the processor to actuate an adjacent detector of the adjacent resonating cell; repeating the steps for each resonating cell of the plurality of resonating cells; and, determining the spectrum of the sample.

18. The method of Claim 17 further comprised of a remote control unit actuatable by a user to allow the user to collect data and control the spectrometer from a centralized location.

19. The method of Claim 17 wherein the processor is used to actuate a first modulator and a first resonator of the first resonating cell and an adjacent modulator and an adjacent resonator of the adjacent modulating cell to determine the spectrum of the sample.

20. The method of Claim 17 wherein the movement of the sample from the first resonating cell to an adjacent resonating cell is actuated by an automatic sample changer to mechanically move the samples.

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