Wash all glassware (and spatulas) in the hottest 

 water practical and rinse thoroughly also with 

 very hot tapwater. (Unless an all-glass still and 

 piping system is available, tapwater is preferable 

 to distilled water because stills often contain plas- 

 tic tubing and sealing compounds containing 

 PCB.) Bake glassware overnight at 225°-250°C to 

 reduce residual contamination. Cover glassware 

 with aluminum foil. Rinse 3-5 times with petro- 

 leum ether or hexane immediately before use. 

 Keep containers covered with foil or stoppers ex- 

 cept during evaporation or chromatography to 

 exclude dust, etc. 



Procedure For DDT and PCB 



The details in time and quantity of chemicals 

 are given only as general guidelines. The exact 

 parameters of these procedures vary with ambient 

 temperature, humidity, altitude, etc. They must 

 be adjusted in each laboratory to optimize recov- 

 ery, cleanup, and separation of desired compo- 

 nents. 



Caution 



All procedures involving benzene must be per- 

 formed in a well-functioning hood. 



Blank 



Carry out the complete procedure as described 

 below without any test sample (omit step 1 under 

 Extraction) to assure that the blank is substan- 

 tially below the level to be determined. Evaporate 

 the final solutions to 2 ml and quantitate the res- 

 idues, typically <0.001 ng/)Lil DDT, TDE, and DDE 

 and <0.01 ng/>l PCB. (Incompletely washed 

 glassware and new batches of reagents are com- 

 mon sources of high blanks.) 



Recovery 



Carry out the complete procedure with solutions 

 of standards of known concentration in the range 

 anticipated for the samples to assure quantitative 

 recovery. (Some loss of chlorinated hydrocarbons 

 always occurs in the absence of proteins and lipids, 

 which act as keepers. A minimum recovery of 80^f 

 is essential. Doping samples originally containing 

 very low levels of chlorinated hydrocarbons gives 

 results which better reflect the accuracy of the 

 method: 859'f or higher recovery of DDE, TDE, 



DDT, and PCB, and 80-85'7r recovery of dieldrin 

 and endrin.) 



Extraction 



1) Weigh approximately 10 g of the material 

 (see Procedure Variations for exceptions), to be 

 analyzed into a Virtis flask and record exact 

 weight to the desired degree of accuracy. 



2) Add 20 ml of a 1:1 IPA/benzene mixture to 



the flask. 



3) Homogenize at about 23,000 rpm for 5 min. 



4 ) Rinse homogenizer blade and Teflon cap with 

 hexane so that the hexane drips into the Virtis 

 flask. Fill the flask with hexane nearly to the bot- 

 tom of the flask neck. 



5) Place the Virtis flask in a hot-water bath (ca. 

 85°C) or sand bath. (An electric fry pan with a 

 layer of sand covered with water provides an 

 economical heating bath.) Boil moderately for at 

 least 45 min, adding hexane whenever the level 

 falls to about one-third of the flask capacity. (If the 

 solution boils too rapidly, material will be lost in 

 the spray. The rate of boiling must be adequate to 

 distill all the H^O, IPA, and benzene from the 

 flask, because they interfere with the cleanup.) 

 When adding hexane, do it so as to rinse down the 

 sides of the flask as well. Keep the water level in 

 the bath and the hexane level in the flask adjusted 

 so that the flask does not become buoyant and tip 

 over. After 45 min of boildown, reduce the vol- 

 ume of the solution to about 20 ml (ca. 1 cm from 

 the bottom of the flask). Cool. If a layer of water 

 separates, add Na.^ SO^ and allow to stand 1-3 min. 



6) Filter through a funnel plugged with glass 

 wool into a 50-ml graduated centrifuge tube. Rinse 

 the flask with three or four 5-ml portions of hexane 

 and pour the rinse solutions through the filter into 

 the centrifuge tube. 



7) Concentrate the extract in a hot- water bath 

 to desired volume (20-25 ml), record volume, and 

 pour most of extract into a 23-ml borosilicate 

 screw-cap bottle (with Teflon-lined cap) contain- 

 ing 1 g Na^SOj. (The extract can be stored in this 

 condition for extended periods.) (If the extract, 

 prior to concentration, still contains traces of H2O 

 or IPA, as indicated by cloudiness, add hexane 

 while concentrating in order to remove the H2O or 

 IPA.) 



Oil Determination 



8) Pipette exactly 1 ml of the extract into a 

 tared aluminum weighing dish and allow it to 



882 



