An analytical apparatus (130) is proposed for detecting at least one analyte in a sample (126), in particular for detecting blood glucose, wherein the analytical apparatus (130) is designed to perform at least one analyte measurement, during which analyte measurement at least one changeable property of at least one test chemical (119) of a test element (110) is detected, in particular an electrical and/or optical property, and the analytical apparatus (130) is furthermore designed to conduct at least one quality measurement on the test chemical (119), at least one characteristic luminescence of the test chemical (119) being detected in the quality measurement, and a conclusion being drawn from the characteristic luminescence about the quality of the test chemical (119), especially a degradation.