The invention concerns a method for detecting the amounts of substances that may disturb chemical analysis performed by an analyzer for clinical chemistry. The presence and concentration of hemoglobin, bilirubin and lipemia are detected by measuring the absorbance or reflectance on at least two, preferably six, different wavelengths over the measured spectrum. The measurements are performed at two wavelengths for each substance, preferably on the absorbance peaks of the specific substance and on the root of the specific peaks. Since the three substances mentioned above each have at least one peak in the spectrum, the measurement is done on three peaks and three root positions respectively when three substances have to be measured.