| abstract |
The invention provides a method for identifying algae in a water sample and to apparatus which may be used in the method. More particularly, an aqueous fluid containing the algae is passed through an adapted flow cytometer which is operated with a high intensity light source, e.g. a laser, operating at at least one excitation wavelength. At least three parameters are determined from the output of the flow cytometer, one of these parameters being chlorophyll fluorescence. The other parameters may be forward light scattering, perpendicular light scattering, backward light scattering, pulse length and/or shape of the scattered signals, fluorescence, and pulse length and/or shape of the fluorescence signals. The apparatus of this invention comprises at least one high intensity light source, means for providing a liquid jet, and a system of detectors arranged to measure chlorophyll fluorescence and at least two other of the parameters identified above. In order to separate the light output from the flow cytometer into components which can yield useful measurements, a system of partially reflecting mirrors and dichroic mirrors is used. The invention can be used to monitor water purity. |