Radio Frequency Oxygen Excitation Apparatus for Low-Temperature Ashing

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Abstract
Recent publications have indicated the usefulness of a radio frequency oxygen excitation apparatus which can be used for low temperature macro- and microashing of biological specimens which require removal of organic constituents before chemical analyses and physical studies are performed. To determine the possible usefulness of this technique, a low-temperature ashing apparatus was assembled from commercially available radio frequency transmitting equipment. Ashing rate experiments on bone indicate that the initial rate was greater for the smallest sieve fraction but decreased for all samples to 1/4 that of the initial rate after 2 hr. exposure to excited O2. Total weight loss obtained for bone samples was about 18-26% (i.e., just below 50% of that obtained at 550[degree]C) when ashed in the cold trap (-75[degree]C) for 24 hr. Further ashing for 100 hr. did not produce a significant increase in weight loss. X-ray diffraction analyses of bone and non-crystalline calcium phosphate showed no detectable phase changes or change in crystallinity when the operating temperature was maintained between -75 and 140[degree]C. Octacalcium phosphate increased in crystallinity, but phase changes associated with elevated temperature were not detected in the infrared absorption patterns.