ABSTRACT
This technique differs f rom purge a n d trap techniques (see C h a p t e r 16) i n the f o l l o w i n g respect. In purge a n d trap, the water sample is p u r g e d w i t h a gas a n d the organics r e m o v e d a n d adsorbed o n to a s o l i d s u c h as Tenax or active ca rbon . The adsorbed organics are then desorbed i n a s m a l l v o l u m e of a n organic solvent, u s u a l l y ch lo ro fo rm or ca rbon d i s u l p h i d e w h i c h is subsequent ly analysed b y gas chromatography. A l t e r n a t i v e l y the organics are released the rma l ly f r o m the s o l i d adsorbent . A l t h o u g h capable of a c h i e v i n g v e r y h i g h concent ra t ion factors a d i sadvantage of this technique is that the organic so lvent a n d impur i t i e s therein can cause difficult ies at the gas chromatograph ic state of the analysis . Headspace analysis is solventless i n that the aqueous sample is heated say to 30°C i n the presence, usual ly , of inorganic salts w h i c h he lp to d r i v e the organics in to the inert gas f i l l ed headspace above the sample . Por t ions of the headspace gas are then w i t h d r a w n b y syr inge for gas chromatograph ic analysis . T h u s headspace analys is u n l i k e purge a n d trap, is a static me thod . B y at tention to deta i l i n the de s ign of the apparatus a n d opera t ing condi t ions , it is poss ib le b y this technique to obta in concentra t ion factors of u p to 100 for the organics i n the o r i g i n a l water sample .
