A robotic end effector for collecting frozen aliquots from an array of frozen samples in a plurality of containers has a coring bit for taking frozen sample cores from the frozen samples and a frozen sample core extraction system adapted to extract frozen sample cores from the frozen samples. A fill level detection system is adapted to detect the positions of the surfaces of the frozen samples. A processor is adapted to receive signals from the fill level detection system and use the signals and information concerning operation of the frozen sample core extraction system to determine at least one of the following: (a) the amount of material contained in a frozen sample core obtained by the coring bit; and (b) the number of frozen sample cores needed from a particular frozen sample to obtain a predetermined amount of material from that frozen sample.