Appendix D: Analytical Methods 



The actual elution volumes have to be determined for any individual set-up. It is essential 

 that the suite of standards are available to verify the actual fractions and elution volumes. For the 

 purpose of the Mussel Watch Programme, fractions 2 and 4 are to be analyzed by GC-ECD 

 according to the ensuing methods, and fraction 3 may be used for the screening for toxaphene. 



Sources of Contamination 



Frequent sources of CHC's are solvents and adsorbents used for column chromatographic 

 clean-up. Even nanograde solvents occasionally contain surprising concentrations of PCB's. It is 

 not sufficient to test the untreated solvent for purity, because in the analytical procedure it will be 

 concentrated by a factor of approximately 500. Thus, for testing the purity of solvents, they must 

 be concentrated at least by the same factor before injection into the gas chromatograph. 



Alumina is often contaminated, not infrequently with PCB's. It should be noted that 

 alumina, when activated in a drying cabinet, becomes a very efficient sorbant for all vapors in the 

 oven atmosphere. Thus, Soxhlet extraction and subsequent reactivation in a less than perfectly 

 clean oven may result in a silica gel that is even more contaminated than prior to the intended 

 purification. Drying and reactivation under vacuum are recommended. Store in sealed glass 

 ampoules 2-3 g AI2O3. 



4.5 E.O.M. determination 



Solvent extractable organic matter (E.O.M.) is determined in the following manner. On the 

 weighing pan of an electro-balance evaporate a known amount of the extract prior to clean-up (5 to 

 10 \xl) and weigh the residue to ±1 jig. 



The quantity of E. O. M. is: 



E.O.M. = mg = weight of residue (mg x volume of extract (ml) x 10 ^ 



g amount evaporated (fil) x quantity of sample extracted (g) 



Note that extreme care must be taken to ensure balance and pans are clean, dry and stable to 

 obtain accurate readings of +1 jig. A small hot plate is used to warm pans and forceps and thus 

 keep these instruments dry after solvent cleaning. If no electro-balance is available, a known 

 volume of the extract can be transferred into a clean preweighed vial. The solvent is evaporated 

 with dry nitrogen gas until a constant weight of ±5mg is reached. Calculate the amount of "lipids" 

 in the sample taking into account the volume of the lipid extract which was dried. 



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