A LOW-COST, PORTABLE FLOW CYTOMETER SPECIFICALLY DESIGNED FOR PHYTOPLANKTON ANALYSIS

This paper describes the construction and testing of a flow cytometer illuminated by a low-power (40 mW), air-cooled argon laser and incorporating a novel flow cell with a wide (0.3 mm) nozzle for hydrodynamic focusing. The resolution of the instrument is comparable to that of commercial equipment operating at much higher laser powers, and it is sensitive enough to detect autofluorescence from single picoplankton cells. By using recent innovations in laser technology and electronics, the design allows a research-quality flow cytometer to be constructed at relatively low cost (̃£15 000 at current prices). The instrument does not require cooling water, three-phase power or compressed gas supplies, and is easily portable from one operating site to another. The large focusing nozzle is very resistant to clogging by detritus, cell clumps or filaments, but is still capable of producing cores down to 5 μm diameter. These characteristics are particularly suitable for the analysis of microalgal cultures and phytoplankton samples. The discriminatory power of the instrument has been tested using a range of marine and freshwater algae. © 1990 Oxford University Press.