Cover the sample with a ribbed watch glass or vapor recovery device and continue heating the acid-peroxide digestate until the volume has been reduced to approximately 5 mL or heat at 95EC ± 5EC without boiling for two hours. Maintain a covering of solution over the bottom of the vessel at all times
Alternatively, for direct energy coupled devices: Heat the acid-peroxide digestate to 95EC ± 5EC in 6 minutes and remain at 95EC ± 5EC without boiling for 10 minutes.