Patent ID: 7276351

Claim:
A method of determining a cell constituent extracted from or secreted into a volume of medium ( 130 ) in a vessel ( 100 ) by a sample comprising cells ( 120 ), the method comprising: (a) placing said sample in a vessel in an apparatus comprising: the vessel, including a chamber containing an original volume of medium and, within the chamber, a surface to hold or contain the sample; a moveable barrier ( 140 ) which alters the volume of the medium in contact with the sample; and a sensor in sensing contact with the medium; (b) moving the barrier to reduce the volume of the chamber and thereby the medium, forming a reduced-volume measuring chamber ( 150 ) in contact with the sample; (c) determining a cell constituent in the medium in the reduced volume measuring chamber with the sensor; and (d) moving the barrier to increase the reduced volume of medium about the cells to substantially the original volume.