I have to do some d13C and d18O measurements in the carbonate component of modern and fossil bioapatite (tooth enamel). Usually, each apatite sample is reacted separatly under vacuum for a long time (ie, 5 hours at 50 °C) in a few drops of 100% degased phosphoric acid to obtain CO2. Unfortunatly, the mass spectrometer I am working with is equiped with a common acid bath at 90°C. While there is virtually no memory effect for pure calcite after 5 minutes of reaction at 90°C, I am not sure that this is the same for apatite.
Has anyone any experience concerning this issue ? If so, how long would it take to achieve the reaction at 90°C under vacuum ?
Many thanks in advance,