NMR Sample Tube Spacers for Stable High-Speed Rotation
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Solution Overview
Problem
High-speed spinning of NMR sample tubes in solid-state NMR spectroscopy is hindered by synchronous vibrations caused by imbalance, making it difficult to achieve the necessary rotational speeds for obtaining sharp spectra, as the natural vibration frequency often coincides with the spinning speed, leading to seizure or damage.
Innovation Solution
The design incorporates a tubular member with spacers that reduce sample imbalance, allowing the sample tube to be filled without bias or deformation, enabling stable high-speed spinning beyond the natural vibration frequency by using spacers made of engineering plastics or ceramics that are smooth and corrosion-resistant, positioned to minimize friction and deformation during spinning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sample tube is spun at high speed to obtain sharp solid-state NMR spectra, then the spectral resolution is improved, but synchronous vibrations occur due to imbalance, causing seizure or damage
Solution Approach 1:
The sample tube is segmented into multiple sections by inserting spacers at specific positions. These spacers divide the sample into separate regions, allowing independent adjustment of sample distribution. This segmentation enables balancing of the sample tube by concentrating sample in specific segments, thereby reducing imbalance and preventing synchronous vibrations during high-speed spinning while maintaining spectral resolution
Solution Approach 2:
Different regions of the sample tube are given different qualities by using spacers with specific positions and dimensions. The spacers create zones with varying sample density and distribution characteristics. By strategically placing spacers, the sample distribution is optimized locally to minimize imbalance without compromising the overall spectral quality, thus resolving the contradiction between high-speed spinning stability and spectral resolution
2Speed
If gas bearing is used to reduce friction and enable high-speed spinning, then the rotational speed is improved, but the natural vibration frequency coincides with spinning speed, causing resonance
Solution Approach 1:
The spacers are pre-positioned in the sample tube before filling with sample, and their positions are carefully calculated to create optimal sample distribution. This preliminary arrangement ensures that when the sample is filled, it naturally concentrates in regions that balance the tube's mass distribution. By performing this balancing action in advance, the system avoids resonance vibrations during high-speed spinning while maintaining the benefits of gas bearing support
Solution Approach 2:
The spacers serve as templates or copies of ideal mass distribution patterns. By replicating the spacer positions and dimensions according to calculated optimal configurations, the sample tube achieves consistent and reproducible balance. This copying approach ensures that the natural vibration frequency does not coincide with operating speeds, preventing resonance while enabling high-speed rotation with gas bearing
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 configuration allows for stable high-speed spinning of the sample tube, reducing displacement at resonant points and enhancing sensitivity of NMR signals, as demonstrated by reduced displacement measurements compared to conventional designs without spacers.
Implementation Method 1
spacers made of engineering plastics or ceramics that are smooth and corrosion-resistant, positioned to minimize friction and deformation during spinning
Implementation Method 2
an NMR spectrometer equipped with a sample spinner having a gas bearing that supplies gas into between a sample tube and a sample tube-holding mechanism to keep the sample tube afloat
Implementation Method 3
A turbine 16 is mounted in an upper part of the rotor 12 to impart a rotating force to the rotor 12 by gas jets ejected from turbine nozzles 15 formed in the stator 11
Implementation Method 4
MAS (magic angle spinning) has attracted attention as a method of overcoming this undesirable phenomenon and giving rise to sharp solid-state NMR spectra. In particular, anisotropic interactions are removed and chemical shift terms can be extracted by tilting the sample tube at the magic angle of 54.7° to the static magnetic field and spinning the tube at high speed
Data Source
AI summary
An NMR sample tube is offered which can be spun at high speed stably. The NMR sample tube is adapted for use in solid-state NMR spectroscopy and includes a tubular member, spacers, and cover bodies. The spacers are disposed inside the tubular member. Each spacer has first and second surfaces located on opposite sides. The first surfaces of the spacers define a space filled up with a sample. The tubular member has openings which are closed off by the cover bodies.