respectively and each time a fraction having a measurable characteristic e g an optical density deviating from background optical density passes tube 26 intermediate light source 48 and optical detector 46 transducer 44 displaces pen 40 transversely to the normal spiral path referring to fig2 the normal position of the line inscribed by pen 40 is shown at 52 which line corresponds to the path traversed by nozzle 24 relative body 18 a portion of the inscribed line displaced from such normal position is shown at 54 and indicates that the fractions collected in the containers 18 that spatially correspond with the location of curve 54 contain fractions of more pertinence than fractions in other containers in body 14 that show no corresponding pen excursion as seen in fig2 sheet 36 can have preprinted thereon a plurality of circles 18 39 which are spatially arranged in correspondence with the spatial arrangement of containers 18 in body 14 accordingly when a sample has been fractionated and collected the lab technician has available to him a body 14 containing the various fractions in containers 18 and the sheet 36 which identifies by spatial correspondence with the arrangement of the containers the specific compartments that contain.