Our Kjedahl heating flask suddenly erupts into the condensing tube from a small simmer. This has just begun happening after running TKN succesfully. Anyone else had this experience?
In digestion, we are decomposing nitrogen in organic samples utilizing a concentrated acid solution. In Kjeldahl heating we are boiling a homogenous sample in concentrated sulphuric acid with rolling boil between 370 and 400 degree Celsues. The end result is ammonium sulphate solution. Your sudden boil over may be the following reasons:
1. You have very little organic matter/organic nitrogen in your sample
2. CHECK YOUR HEATING ELEMENT SETTING: Heating elements used for Kjehldahl digestion has variable setting. Most specified used setting of heating input is which brings 250mL of water at 25 degree Celsues to a rolling boil in 5 minutes.
Initially an organic sample usually chars and blackens. The reaction may be first be very vigorous depending on the matrix and the heat input. With organic decomposition the digestion mixture gradually clears as CO2 evolves. Metallic ions might tint the clear digestion mixture.
Iʻve only ever had that problem after adding hydrogen peroxide. Counteract it by adding flask rack to the heating element until it just begins to boil, then removing. Do this several times until the boiling doesnʻt occur then can leave on heating element for reaming digest time.
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