A search for losses of chemical elements during freeze-drying of biological materials

Possible losses of seven chemical elements were investigated in biological tissues during freeze-drying in vacuum. Thyroid glands were taken during post-mortem examination of 23 people died of different diseases. Instrumental neutron activation analysis (INAA) was used to estimate contents of Br, Ca, Cl, I, K, Mg, and Na. The nuclear reactor vertical channel with flux density of 1.2 x 1013 n x cm-2 x s-1 was used for neutron irradiation. The analysis was carried out using short-lived radionuclides induced in samples after neutron irradiation. Then thyroids were freeze-dried at below 0 deg C in vacuum up to the constant mass (lyophilisation) and then homogenized. Samples of lyophilised and homogenized tissues were again studied by INAA. The lack of difference between the results of the analysis before and after lyophilisation is an evidence of no loss of Br, Ca, Cl, I, K, Mg, and Na during freeze-drying of biotissues in vacuum. (author)