2.8. Method validation
For all nine standard compounds (see Fig. 2 for structures) calibration
curves were established. By accurately weighing and dissolving
them in water a single stock solution with a
concentration of 100 lg/ml each was obtained. This solution was
stable at least for 7 days if stored at 4 C. Eleven calibration levels
were prepared from the stock solution, and each of them analyzed
under optimum HPLC conditions in triplicate. Limit of detection
(LOD) and limit of quantification (LOQ) were visually evaluated
corresponding to concentrations equivalent to S/N ratios of 3
(LOD) and 10 (LOQ). Accuracy was determined by spiking
non-irradiated L. foveolarum samples with known amounts of the
reference compounds at three concentration levels. The methods