NMR / EPR Tube Information

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Economy or Precision NMR Tubes

 

Economy NMR tubes are recommended only for 1D NMR with small organic molecules (mw<1500) at ambient temperature.Class B (economy) tubes have less thermal shock resistance than Class A (precision) tubes and may contain Fe2O3 which may have an impact on shimming quality.For NMR experiments that involve cooling / heating, biological sample, multi-dimensional, multi-nuclei or DNP techniques, please use Precision tubes (Class A). 

 

Quartz EPR Sample Tubes

 

Product numbers that include "PQ" are Precision Tubes."SQ" are Non- Precision.For EPR experiments that must estimate electron spin density and/or produce highly repeatable signal amplitude between different runs we strongly recommend the Precision EPR Tube.

 

Suprasil EPR Sample Tubes

 

Product numbers that include "PQ" are Precision Tubes."SQ" are Non- Precision.For EPR experiments that must estimate electron spin density and/or produce highly repeatable signal amplitude between different runs we strongly recommend the Precision EPR Tube.

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Tube Selection Guide - CFQ or Suprasil

 

Two types of quartz are used for EPR sample tubes:

1) Clear Fused Quartz (CFQ), a naturally occurring material

2) Suprasil, the trade name of Heraeus-Amersil synthetic quartz

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Unique Properties of Quartz for EPR

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· Quartz is pure silicon dioxide

· Quartz has a high dielectric constant

· Quartz has a low level of paramagnetic impurities

 

Materials of high dielectric constant alter the microwave field and concentrate the field on the sample. The low level of paramagnetic impurity in quartz prevents interferences with the samples EPR lines.

 

Over long periods, CFQ irradiated with UV will discolour. Synthetic quartz transmits electromagnetic radiation through the UV spectrum. Synthetic Quartz EPR tubes (Suprasil) should be used when applying ionising radiation to generate radical species and for a sample of very low signal. In most other cases, Clear Fused Quartz will provide the same results as Suprasil.

 

Due to technological advancements the sensitivity of EPR has increased, the direct result is that certain high Q cavities will pick up the signal from these impurities especially in tubes over 4mm OD.

Clear Fused Quartz (CFQ) is purified from naturally occurring quartz so the existence of certain material radicals from mining is inevitable.

In this instance we recommend switching to Suprasil EPR products which are made of synthetic material and suppress major impurity contents by an average of 2 orders of magnitude.