Development of a microalgal PAM test method for Cu(II) in waters: comparison of using spectrofluorometry

Test methods are needed to monitor Cu concentrations in reservoirs and water supplies. Dictyosphaerium chlorelloides (Chlorophyta) cells were immobilized in a silicate sol–gel and the toxic effects of Cu(II) were examined using different techniques: fluorescence measurements (using a spectrofluorometer with an optic fiber coupled to a flow cell or a 96-well-plate reader) or by Pulse Amplitude Modulation (PAM) parameters using a portable instrument and the pulse saturation method. Fm′ and qN were the most sensitive indicator parameters when performing Cu analysis in water. D. chlorelloides PAM biosensor presented a detection limit of 0.6 mg l−1 for Cu(II), within the limits to establish if Cu concentrations exceeded regulatory levels. Moreover, a 1.9 mg Cu l−1 (30 μM) resistant strain of the D. chlorelloides microalgae was produced in order to obtain more selectivity on the metal determination.