Liquid Phase NMR

Liquid phase Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful analytical technique used to investigate the molecular structure, dynamics, and interactions of compounds dissolved in liquid solvents. It works by exploiting the magnetic properties of certain nuclei—most commonly hydrogen (¹H) and carbon-13 (¹³C)—which behave like “tiny magnets” when placed in a strong external magnetic field.

Outer Diameter & Inner Diameter
Outer Diameter (O.D.) – A measure of the distance across the
center of the tube from the outermost surfaces.
Inner Diameter (I.D.) – A measure of the distance across the
center of the tube from the innermost surfaces.

Concentricity
A measurement of variation in the radial centers, measured at
the inner and outer walls.
Concentricity can be thought of as the degree to which the
cylinders defined by the inner and outer surfaces of the tube
are parallel. If the inner surface deviates and becomes closer
to the outer surface that will cause one portion of the tube to
have a smaller wall thickness than the other.

Camber
The lack of straightness of an NMR tube.
The camber of an NMR tube is measured by holding the tube
on both ends and rotating it. During rotation, gauges measure
the deflection in the middle of the tube giving a (+/-) deviation
reading. All Wilmad Labglass Precision & Economy Thin-Walled
tubes are guaranteed to have deviations less than 53.34 μm
and can be expected to spin reliably.

Why it’s Important
An NMR tube with poor O.D. & I.D. tolerances, concentricity, or
camber can produce undesirable experimental outcomes
such as…

• Tube rupture when the I.D. is too small and inserts are
  used
• Modulation sidebands and decreased spectral quality
  when the concentricity or camber is large
• Tube slipping or wobbling when the O.D. is too small
  which can cause major probe damage
• NMR tube breakage due to probe contact when the O.D.
  or Camber is too large causing instrument downtime &
  contamination

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