Establishing time stability for multivariate qualitative methods. Case study: Sudan I and IV adulteration in food spices

In general, the main performance parameters were very satisfactory. As far as training samples is concerned, sensitivity was 100% for the three classes studied. And specificity was 100% for the unadulterated class and for the adulterated with Sudan IV class, and slightly lower (96%) for the adulterated with Sudan I class. Regarding samples from the additional set, excellent specificities were obtained because no samples were assigned to the unadulterated class. In addition, sensitivity was close to 100% for the Sudan IV class and around 75% for the Sudan I class. All the main performance parameters were maintained throughout the 6 months of the study.