Hi all,
I am currently using micro-Kjeldahl method for determination of total protein. Sometimes I get inconsistent result or the result doesn't make any sense. For example i got ~48% of protein (with conversion factor of 5.75) for flour sample.
I am trying to find a protocol that I can use to determine whether the instrument that I used are in good shape, but at the moment I couldn't find any.
Thank you.
You could buy a standard protein solution for Kjeldahl calibration and check that one.
BTW, how are your system suitability tests? Perhaps you would need to revalidate your method.
Hi Tilen,
Thank you very much for your reply.
As my sample is solid samples, I actually want to have a standard solid with known N or protein content.
I am using this method for fluor protein determination. It should be working just fine. Therefore I want to check whether something wrong in the apparatus or maybe the reagent that I use by using sample with known protein content.
You could use a solid, purified protein, such as bovine serum albumin or casein, which have known amino acid sequence, so you should be able to calculate the nitrogen content.
Hi Adam,
Thank you very much for your answer.
That also occurred on my mind. But, is that mean that the protein content is 100%? since if I use BSA or casein it only composed of protein. So by using casein, we just need to calculate the percentage of nitrogen in the protein, and confirm it with the Kjeldahl method?
Hi,
I assume that from Dr.Adam), by having a weighed pure protein with known sequence, one can estimate theoretically the nitrogen content of the protein. The method to estimate the nitrogen content in kjeldahl can be calibrated against achieving the closer values of nitrogen content which was calculated for the same pure protein.
In this context the only aim is to estimate the nitrogen content (by a % value) of the taken pure protein, the known sequence of this protein will help you to rightly calculate the nitrogen content (presumed value for calibration).
Thanks.
If you are going to try the method I suggested, make sure you use a dry protein that is free of excipients, like salts and buffers. That way, you can be sure that all the nitrogen is from the protein. This is not the case with all products.
- Badges
- Science topic
- Similar topics
- Biological Science
- Molecular Biology
- Biomolecules
- Proteins