The stability of calcium oxalate during electron irradiation in an AEM

Abstract

Calcium Oxalate is a major constituent of most kidney stone material. Electron microscope studies of materials containing calcium oxalate are complicated by decomposition during observation. This structural instability not only limits the observation time but also precludes the use of focussed probe techniques such as microdiffraction.Two factors under the control of the experimenter which could help increase observation time are accelerating voltage and specimen temperature Available at the Center is a JEOL 200CX TEM capable of 200kV equipped with a Gatan 636 cold stage which can cool a specimen to -180C in-situ. Calcium Oxalate was deposited on carbon support films from an aqueous solution. The resulting specimens were then examined at 200kV at OC, -50C, -100C, -180C, and room temperature (RT) and at 100kV at 0 and -100C. Selected area diffraction patterns were taken at specific time intervals in order to follow the decomposition. This was done at least three times at each condition in order to insure reproducibility. Care was taken that the beam current (~ 20 microamps) and illumination were the same at 100 and 200kV.