Kjeldahl method bug
Ok currently writing a lab report on protein determination using Kjeldalh method. The standard that I used was lysine with a calculated value of
19.15% (found in theory and calculated using 28g (2x14g since 2xN)/146.188g * 100). But my problem is that all my data obtained are more or less
consitent with a factor of 2 time less. Using a standard Se catalysed digestion with 300min of reflux heating I get yield of 8.91, 9.39 and 9.02. I
calculated using the following formula:
(5.56-x*0.09718) (this is my reverse titration molar calculation) *(14g/mole of N / (1000 (to convert mg->g) * initial mass))*100%
I used the 1 mole NH3 for 1 mole of HCl, the 1 mole of N for one mole of NH3. Can anybody see how come i come with this consistent factor of 2.
This website: http://www.njfl.com/protein_method.htm seem to indicate that lysine TKN is around 9.39, that would fit with my data but they got no source
whatsoever. I'm pretty puzzled by that, so if anybody could lead me anywhere that'd be helpful...
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