Handling of PWG-Gliadin

When you get a new batch of PWG-gliadin please note the protein content given in the accompanying information. This protein content should be used to calculate the protein concentration of PWG-gliadin solutions.

The PWG-gliadin stock material is stored at -80 °C until shipment. The material is shipped under ambient conditions. It should immediately be frozen after it has been received by the user. The storage temperature should be as low as possible depending on the equipment, but below -18 °C. Prior to use bring the material to ambient temperature in a desiccator before opening the cap. PWG-gliadin is hygroscopic. Therefore, minimize the time the vial is open. Once dissolved in 60% (v/v) ethanol the sample solution should be stored at room temperature (20 - 22 °C) and should be used within maximum four weeks after dissolution.

Handling procedure for weighing and preparation of sample solutions:

1. Equilibrate PWG-gliadin vial to room temperature
....in a desiccator for at least 1 h
2. Prepare glass funnel or aluminum foil device for weighing
.... and put it on a balance (precision of balance 0.01 mg)
3. Set balance to zero
4. Remove cap from vial
5. Weigh PWG-gliadin into weighing device
6. Close vial
7. Record mass of PWG-gliadin in the weighing device
8. Transfer PWG-gliadin into a sample dilution vessel
9. Weigh back weighing device on the balance, record mass
.... and calculate mass of PWG-gliadin transferred to the sample
.... dilution vessel
10. Dissolve PWG-gliadin in sample dilution vessel
...... in an appropriate amount of 60 % (v/v) ethanol
11. Calculate gliadin concentration on the basis of the protein
..... content of dry PWG-gliadin
12. Close sample dilution vessel tightly and seal e.g.
...... by Parafilm®
13. Store PWG-gliadin solution at 20 - 22 °C
14. Use PWG-gliadin solution within four weeks


General remarks:

Since the material is hygroscopic speedy handling and correct operation is of major importance. This is especially necessary during the weighing procedure, i.e. any kind of water uptake by the sample material must be minimized. Water uptake contributes to a mass change at a level above a relative humidity of 34 % with a maximum weight gain of 7.9 % at 75 % of relative humidity (Fig. 1).


Figure 1. Mass change of PWG-gliadin (stored under argon) against relative humidity. Graph from C. Klein, S. Yazgan, F. Franchini, The certified reference material for gliadin from European wheat: status quo. Proceedings of the 18th Meeting of Working Group on Prolamin Analysis and Toxicity (ed. M. Stern), 2-5 October 2003, Stockholm, Sweden, pp. 125-127


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