Less is better: Uncorrected versus pheopigment-corrected photometric chlorophyll-a estimation

Photometric determinations of uncorrected and pheophytin-corrected chlorophyll-a concentrations were compared with HPLC-determinations. All determinations were based on the same water samples, which were taken during a two-year survey of seven lakes with varying trophy and morphology. Uncorrected and pheophytin-corrected chlorophyll-a concentrations determined from the same samples differed significantly. Furthermore, pheophytin-coffected chlorophyll-a concentrations differed significantly from the HPLC-determinations, whereas the uncorrected photometric measurements did not differ. In addition, measurements of the same samples with different photometers, showed a significantly increased variation for the pheophytin-corrected chlorophyll-a concentrations. The presented data suggest the abandonment of the acidification of sample extracts resp. the determination of pheophytin-corrected chlorophyll-a concentrations, because i) the methodological procedure for the photometric determination of uncorrected chlorophylla concentrations is less time-consuming, ii) the accuracy of the resulting data is better and iii) measurements obtained with different photometers are better comparable.