Abstract: An apparatus and a method for analyzing particles suspended in a liquid are described, which particles are of a type or are prepared so as to emit radiation characteristic of the particles when exposed to radiation. Particular fluorescence-photometrical flow cytometry is described in connection with biological cell populations.The apparatus comprises an elongated flow area in the shape of a channel provided in a cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface. The first and the second body members are adapted to be moved relative to one another between a first position, in which the planar facial surfaces are in fluid-tight contact with one another, and a second position, in which the planar facial surfaces are spaced apart. At least one of the planar facial surfaces of one of the body members is provided with an elongated groove.

Abstract: In a method of separating bacteria from a bacteria containing liquid sample by means of a dish-like centrifuge container (21) having an upper opening (25) defined by a radially inwardly extending rim portion (24), the following sequential steps are carried out. The centrifuge container is rotated at a high rotational speed. A volume of a high density component of a density higher than the density of the bacteria is introduced into the centrifuge container, whereupon a volume of a low density component having a density lower than the density of the bacteria is introduced into the container so that a two component gradient separation layer (60) comprising a high density layer (61) and a low density layer (62) is formed within the centrifuge container (21).