STUDY OF SOME ANALYTICAL-METHODOLOGICAL ASPECTS IN NUCLEAR MICROPROBEANALYSIS OF SOFT BIOLOGICAL TISSUES

Two methods for preparing cryosections from soft biological tissues we re compared. It was found that cryofixation in liquid N-2 cooled isope ntane resulted in much better sections than freezing in liquid Nz itse lf. Specimen mass loss, major element loss and alterations in minor an d trace elements were studied, and results from experiments on bovine liver sections of various thicknesses are presented. After a 90 min bo mbardment with a stationary 4 x 20 mu m(2) beam of 250 pA, the specime n mass thickness was on the average 85% of its initial value. No loss was found for C, but there was significant loss for O and some loss fo r N. The elemental mass thicknesses of P, S, Cl and K generally increa sed with bombardment (up to 110-120% of the initial values), most like ly as a consequence of shrinkage of the examined area. There was some evidence of loss for S, relative to the other minor elements, but it w as less than 10% ater 90 min. The Cl loss, if any, was smaller than 5% , and there was no significant loss for the trace elements Fe and Zn.