Choosing the apt vessel for the sample

For the measurement of samples in the EPR/ESR Spectrometer one has the choice between the following sample vessels:

• Capillary

• Sample Tube

• Flat Cell

• Tissue Cell

• Special Cuvette

• Fixed Temperature dewar

 

Capillaries are standardized calibrated sample vessels. They are cheap one way items and allow an easy sample exchange. Usually capillaries are used together with a matching guidance tube. For aqueous solutions the maximum volume of capillaries is 50 µl. In the case you use organic solvents with a lower dielectric constant, you can use capillaries with a higher volume or sample tubes.

Sample Tubes are used for liquid and solid samples. We offer sample tubes of different diameters and lengths. The dielectric constant of the solvent of your liquid sample lays down the diameter of the sample tube. For example radicals in hydrocarbons can be measures using a 4 mm or 5 mm sample tube. Concerning the solid samples the humidity of the sample restricts the diameter of the sample tube. The length 135 mm is used in general. The length 240 mm is adapted to the finger dewars, we offer. In the case a sample is not tuneable you can either choose a sample tube with a smaller diameter or you reduce the amount of sample inserted into the resonator.

Flat Cells are used for liquid samples in solvents with a high dielectric constant. The ideal sample distribution in the resonator leads to a 2 – 2.5 fold higher intensity compared to 50 µl capillaries. The crucial point, when using a flat cell is the orientation of the flat section, the vertical position and the filled volume of the flat cell.
Therefore we recommend using the special holder SH-P as the system to achieve always the same sample positioning.

Tissue Cells can be used to measure skin sections, paste and emulsions. The same requirements have to be fulfilled that are valid for flat cells.

A Special Cuvette we offer for alanine dosimetry of thin film test strips. This cuvette has a flat section too. Furthermore we offer special tubes for alanine tablet dosimeters.

Fixed Temperature Dewars are used to measure samples at liquid nitrogen temperature of 77K. You can either drop the sample into the liquid nitrogen and the frozen drops are collected in the finger for measurement. A further possibility is to freeze a cylinder of 4 mm diameter matching to the size of the inner finger of the dewar. In the case you like to measure solid samples you can use sample tubes of 3 or 4 mm outer diameter and 240 mm length.

Glassware

For measurements of samples in the ESR spectrometer one has the choice between Capillaries, Sample tubes, Flat cells, Tissue cells, Special cuvette and/or Fixed temperature dewars.