Hi everyone!
I need some help with Kjeldal method validation (specificity, linearity, repeatability, intermediate precision and accuracy). Sample - amino acid complex (API).

Specificity: I will use API with addiction of non-nitrogen containing compound to show that there is no effect on the result (triplicate).

Linearity: I will use different amounts of API (80-100-120% range). Then plot linear regression; if correlation coefficient is ≥ 0.99 - it's OK.

Repeatability: 6 samples, then calculate %RSD. Acceptance criterion is ≤ 5%.

Intermediate precision: same as repeatability, but will be done by another analyst. I will calculate %RSD between two analysts.

Accuracy: I will use same volumes of API with addiction of nitrogen containing compound (acetanilide).

What did I miss?
What solvent do I need to use to dissolve acetanilide (it soluble in water, but very poorly).
What concentrations and volumes of acetanilide solution do I need to add to sample solution?

Thanks for your replies and have a good day!