Artificially introduced into the environment 90Sr is highly radiotoxic, so its content levels in foodstuff and biota require constant monitoring for radiological protection. Most analytical procedures used for 90Sr determination are time-consuming, and therefore, a faster approach is needed. Employing the Bateman equation enables more efficient exploitation of the secular equilibrium between 90Sr and its daughter radionuclide 90Y in the calculations. This article describes a method for computing the 90Sr activity concentration, while accounting for 90Y activity. The developed approach was tested and validated in terms of its applicability in everyday analysis.