[en] In this paper there are described three different algorithms of Minimum Detectable Activity (MDA) calculus, and its use in high resolution gamma spectrometry. In the first part, few introductive theoretical aspects related to the MDA are presented. Further, the theory was applied to real gamma rays spectrometry measurements and the results were compared with the activities reference values. Two different gamma spectrometry systems, both of them using High Purity Germanium (HPGe) detectors, but having different efficiencies, were used. Samples having different geometries and radionuclides content were measured. The measured samples were made by dissolving of some acids containing anthropogenic radionuclides in water, obtaining a density of 1 g/cm"3. Choosing this type of matrix was done because of its high homogeneity. - Highlights: • Three different MDA algorithms were applied to gamma spectrometry measurements. • The measurements were performed using two HPGe detectors. • MDA performances of the two spectrometric systems were compared. • The measured samples had different geometries and contained a mixture of radionuclides. • MDA was studied also as a function of measuring time.