65 
Table 12: Comparison of quantification of s- and mPCAs in spiked fish (mackerel) and naturally exposed 
fish livers using four different mass spectrometric methods (single measurements). Spikes 1 and 2 
contained 1500 ng in total (150 ng/g assuming a sample weight of 10 g) of sPCA with 55.5 % Cl content 
and spike 3 contained 1500 ng each of sPCAs and mPCAs with Cl contents of 55.5 % and 52 %, 
respectively. The relative deviations from the spiked amount are given in parenthesis. 
Compound 
Expected 
total (ng) 
ECNI-HRMS 
(ng) 
ECNI-LRMS 
(ng) 
CH 4 /CH 2 C1 2 - 
NICI-LRMS 
(ng) 
EI-MS/MS 
(ng) 
Spike 1 
sPCAs 
1500 
1720(14%) 
1560 (5.7 %) 
1810(20 %) 
1610(7 %) 
Spike 2 
sPCAs 
1500 
1190 (21 %) 
1610(7.2 %) 
1300(13 %) 
1580 (5 %) 
Spike 3 
sPCAs 
1500 
1730(15 %) 
1750(17 %) 
1290(14 %) 
np 
mPCAs 
1500 
1360 (9 %) 
1510(1 %) 
1450(3 %) 
np 
s+mPCAs 
3000 
3090 (3 %) 
3260(9 %) 
2740 (9 %) 
2950 (2 %) 
Mean (ng/g) 
Liver 1 
sPCAs 
40 
57 
43 
21 
np 
mPCAs 
56 
52 
75 
40 
np 
s+mPCAs 
93 
109 
118 
61 
84 
Liver 2 
sPCAs 
21 
30 
19 
23 
np 
mPCAs 
24 
21 
25 
25 
np 
s+mPCAs 
48 
51 
44 
48 
59 
Liver 3 
sPCAs 
16 
13 
na 
20 
np 
mPCAs 
82 
77 
76 
37 
np 
s+mPCAs 
94 
90 
np 
57 
66 
na: not analysed 
np: instrumentally not possible 
5.3.3.4 PCA result comparability, former studies 
In 1999, an intercalibration was carried out between seven laboratories using different 
methods (Tomy et al., 1999b). Deviations between laboratories were minimum a factor 
of two, and no significant difference between low and high resolution MS methods was 
observed. This means that the differences between the tested techniques were caused by 
problems with the applied sample clean-up and quantification procedure and not by 
mass spectrometric disturbances of LRMS. 
Moreover, PCA concentrations should be evaluated with caution, if determined before 
the 1990ies. No quality assurance or proper method validation data are normally presen 
ted. Most of them are indicative at the best.