PURPOSE: To enable inspection of performance of an analyzer in a short time, by using only a specified single amino acid, introducing the second sample before the end of the first analysis, and repeating it likewise in many times in constant cycle after that.

CONSTITUTION: As an amino acid hardly affected by NH3 contained in a sample solvent, the sample solvent, fluctuation of a baseline at the time of feed of a sample, and pH of the sample, and elutable by a single solvent in a short time, only lysine is used to check sensitivity (height of peak) of an amino acid analyzer, baseline noise, an amt. of drift of the baseline, reproductivity of the peak position and the peak area, etc. A soln. of lysine is added before the end of the analysis of the preceding soln., and it is repeated at ≤10min intervals in 3W20 times, and stability of the baseline, and reproductivity of the position and the area of the peak are especially checked. Thus permitting checking at a speed as high as 6W20 times that of the conventional method.