Adjust the sensitivity so that the height of the peak due to 2-methyl-5-nitroimidazole in the chromatogram obtained with solution (3) is about 50% of full-scale deflection. Measure the height (a) of the peak due to 2-methyl-5-nitroimidazole and the height ( b) of the lowest part of the curve separating this peak from the principal peak. The test is not valid unless ais greater than 10b.