I am trying to digest Enteric coated tablet using microwave assisted acid digestion. But i am not getting clear solution after digestion. I dont want to use HF.
Please advice.
Microwave assisted digestion with nitric acid (several doses if needed) should do it. You can try it directly with heat in a hood. Wait until you see heavy brown smoke. This indicates the oxidation is really happening. After some minutes you should have a clear solution.
You can try to use a mix HNO3 (70 %) : H2O2 (>30%) as 4 : 1 (vol.), and apply a MW digestion with temperature not less then 220 C.
If the mixture HNO3 : H2O2 is not suitable, you can try to use aqua reggia ( HNO3 : HCl -> 1:3)
Aqua Regia ( HNO3 : HCl -> 1:3) is not giving clear solution for enteric coated tablets.
In the Cookbook of TopWave (Analytik Jena) microwave digestor is recommended: one tablet (350-1000 mg) +15 ml nitric acid and 3 ml hydrogen peroxide and 25 ml water.
Digestion program in 3 steps:
Temperature (Celsius degree): 170 210 210
Pressure (bar) 80 80 80
Power (%) 80 100 100
Ramp (min) 2 10 1
Time (min) 5 30 15
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