For the estimation of the limits of detection, identification and determination, considerations from analytical practice were applied to the statistics of the calibration line and its prediction interval. The detection limit was the concentration calculated from the maximum height of the prediction interval at zero spiking concentration. The identification limit was twice the detection limit and was the lowest concentration that could safely be detected. The determination limit was the lowest concentration fulfilling three criteria: 1. None of the signals resulting from determination limit concentration should interfere with any signal from detection limit concentration, thus providing an unambiguous separation between the two limits. 2. Recovery should be between 70% and 120%. 3. Lowest and highest predictable signal at determination limit concentration should not deviate more than B 30% from the average. Practical analytical guidance and the necessary mathematical formulae are presented.

Summary Organochlorine residues in German Osprey (Pandion haliaetus) eggs Residues of organochlorine pesticides and polychlorinated biphenyls (PCB) were investigated in 17 unhatched eggs of German Ospreys. The samples had been collected in the federal states of Brandenburg and Mecklenburg‐West Pomerania in north‐eastern Germany in 1992 and 1995. Further, size and shell thickness were measured and shell index calculated for 338 osprey eggs collected in Germany between 1853 and 1997. In all 17 samples, residues of p,p'‐DDE and PCBs were found with a mean of 8.7 ppm (mg/kg dry weight) and 14.8 ppm respectively. In the eggs collected from 1959 to 1983, the shell index was found to be reduced by 9 % in comparison with those from 1853 to 1933 (n = 24). Four clutches collected from 1959 to 1964 showed an average reduction of the shell index of 14 %. Egg size (length, width, volume) however, remained unchanged. At present, the effect of organochlorine residues on the reproduction of Ospreys breeding in Germany is estimated to be low. Today, shell thickness and shell index values almost equal those of the pre‐DDT‐era.

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