Appendix D: Analytical Methods 



Reference solutions of individual chlorobiphenyl congeners and the necessary pesticides 

 will be distributed to participating laboratories. Follow the enclosed instructions in diluting them 

 with isooctane up to working solutions. 



5.3 Apparatus 



5.3.1 Narrow-bore (0.25 mm internal diameter), 25 m fused-silica open tubular column, 

 coated with SE-54 (0.15 um film thickness, preferably chemically bonded) with sufficient 

 resolution to separate the relevant peaks in the standards provided for PCB analysis. 



5.3.2 Gas chromatography with a split/splitless or on-column injection system, multiramp 

 temperature programming facilities (preferably microprocessor controlled), electron capture 

 detector interfaced with the column with electronic control unit and pulsed mode facilities. An 

 integrator with a short response time (less than 0.25) is essential. 



5.3.3 Carrier gas should be high purity H2. If this is not available, high purity He may be 

 used. Gas purification traps should be used with molecular sieves to remove oxygen, moisture 

 and other interfering substances. 



5.3.4 Ar/5%CH4 high purity gas as ECD make up gas is preferable, however, high purity 

 N2 (99.99+%) may also be used but will result in a loss of sensitivity. 



5.4 Gas Chromatography and Electron Capture Detection 

 5.4.1 GC Column 



5.4.1.1 Column characteristics: Fused-silica columns are the columns of choice for their 

 inertness and durability (they are extremely flexible). They are made of material that is stable up to 

 360°C. The 1% vinyl 5% phenyl methylsilicone gum (SE-54) liquid phase, is present as a thin 

 (o.l5 um) uniform film which can tolerate temperature up to 300°C. SE-54 is relatively resistant 

 to detrimental effects of solvents, oxygen and water at least at low temperatures. These columns 

 are even more resistant and durable if the liquid phase is chemically bonded by the manufacturer. 

 This column was chosen because at present it is the only column which allows unambiguous 

 identification of the most CB congeners. 



5.4.1.2 Column installation: The flexible fused-silica columns can be conveniently 

 connected directly to the inlet and outlet systems without the transfer lines used in conventional 



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