NMR Analysis of Sealed Conducting Containers
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Solution Overview
Problem
Conventional NMR spectroscopy is ineffective for analyzing contents of metal containers due to radio frequency signal shielding, which prevents the transmission and reception of RF signals, making it difficult to detect substances within without damaging the container.
Innovation Solution
The use of shaped RF pulses at lower frequencies and lower static magnetic field strengths allows for effective penetration through conducting containers, enabling non-invasive analysis of sealed containers using NMR spectroscopy, with external frequency referencing and adiabatic pulses enhancing signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high frequency RF signals (300-500 MHz) are used for conventional high resolution NMR, then sufficient signal separation and detection capability are achieved, but the RF signals are heavily shielded and attenuated by conducting containers, making it difficult or impossible to examine contents
Solution Approach 1:
The patent changes the RF frequency parameter from conventional high frequencies (300-500 MHz) to lower frequencies (e.g., 1-100 MHz or even lower), which reduces shielding and attenuation by conducting containers while maintaining adequate signal detection capability through extended measurement times and signal averaging
Solution Approach 2:
The patent employs dynamic pulse sequences with variable pulse widths, delays, and flip angles optimized for low frequency operation, allowing adaptation of excitation parameters to compensate for reduced signal intensity at lower frequencies
2Power
If high static magnetic field strengths (1.8-25 T or higher) are used to generate sufficient precession signal, then enough RF signal is generated for detection, but the required high frequency RF signals are heavily shielded by conducting containers
Solution Approach 1:
The patent reduces the static magnetic field strength parameter from conventional high fields (1.8-25 T) to lower fields (e.g., 0.1-2 T), which correspondingly lowers the required RF frequency into a range that penetrates conducting containers more effectively, accepting reduced signal strength in exchange for container penetration capability
Solution Approach 2:
The patent utilizes the natural precession of nuclear spins at lower magnetic field strengths, detecting the weaker but penetrable signals through extended acquisition times and sophisticated signal processing, allowing the system to self-adjust to the constraints imposed by conducting containers
3Measurement precision
If conventional NMR methods are used on sealed containers, then chemical characterization can be achieved, but the container must be violated which destroys the container or product and is impractical in large scale applications
Solution Approach 1:
The patent uses low frequency RF pulses as an intermediary that can penetrate the conducting container wall to reach and excite the sample inside, enabling indirect observation of container contents without physical contact or violation of the container seal
Solution Approach 2:
The patent replaces mechanical container violation (opening, breaking, or puncturing) with electromagnetic interrogation using low frequency RF pulses that penetrate the container wall, substituting a non-contact field-based measurement for contact-based mechanical access
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables chemically resolved NMR analysis of contents in metal containers without damaging them, allowing for the detection of contaminants, spoilage, and contraband, while maintaining the integrity of the container.
Implementation Method 1
Conventional high resolution nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) can be used to study samples
Implementation Method 2
an NMR spectrum is collected by monitoring the response of the sample to an applied radiofrequency pulse
Implementation Method 3
at higher RF frequencies the skin depth is smaller, thus reducing the amount of RF energy that can be transmitted through the metal
Implementation Method 4
This shielding (or attenuation) is sometimes expressed as the RF penetration depth (or skin depth) d
Data Source
AI summary
This invention relates to methods and devices for NMR spectroscopy analyzing sealed containers e.g., food and beverage containers and other containers, and particularly according to specific embodiments sealed containers made of a conducting but generally nonferromagnetic metal or other conducting material. As discussed in above referenced applications, many current strategies for contaminant detection require a container to be violated, a process that can destroy the container or product and is impractical in large scale applications. The present invention overcomes these and other problems by providing methods and devices for the detection of contaminants and/or contraband in metal or conducting containers by NMR spectroscopy.