A flow cell apparatus is provided comprising a body having a first surface, an inlet port and an outlet port. A channel is provided in the body having a first end and a second end. In one embodiment, the channel is sized so as to have a depth that allows for sufficient excitation and illumination of solutions or particles contained in a liquid to be analyzed. The inlet port is coupled to the first end of said channel and the outlet port is coupled to the second end of said channel. A window of optically transparent material overlies at least a portion of the channel to provide optical access to the liquid in the channel.