75 
5.3.7.3 Selectivity of clean-up 
Chloroparaffins 
The clean-up step on Florisil allowed separating nearly completely PCA from other 
interfering compound classes such as PCB or toxaphenes. Moreover, the internal 
standard 1 ’C io-/ra/7.s'-chlordane was also present in this fraction. Table 19 shows the 
fractionation behaviour for selected compounds. 
Table 19: Fractionation of the single PCA congeners CioHi 6 Cl6 and Q3H20CI8 from PCB 153, 
toxaphene #62 and rra/rv-chlordane by Florisil column clean-up. Relative distributions are given 
(prefraction: 60 ml of n-hexane followed by 5 ml of dichloromethane, PCA-fraction: 60 ml of dichloro- 
me thane). 
Compound 
Distribution [%] 
Prefraction PCA-fraction 
C10H ifF-lf, 
5 
95 
C13H20CI8 
<1 
100 
PCB 153, HCB, HCH 
100 
<1 
Toxaphene #62 
100 
<1 
frans-chlordane 
5 
95 
Chlordanes 
The separation behaviour of Florisil for chlordanes was more complex. Table 20 shows 
the variability between two different batches, which was considerable. Therefore, a 
large quantity from the same batch was purchased and its elution properties optimised to 
avoid such a variable elution range. This improved also the recovery of heptachlor to 
>80 %. Nevertheless, /ran.s-nonachlor eluted in about equal parts in the pre- and PCA- 
fraction and had to be quantified in both. 1 ’C1 o-zranv-ch lordanc was a suitable internal 
standard for the PCA-fraction and 4,5-dichlorochlordene (Karls son el al., 1997) for the 
pre-fraction. Due to the missing persistence to sulphuric acid, it had to be replaced by e- 
HCH for the analysis of biota.