ABSTRACT
T w o approaches have been u s e d for the p reconcen t ra t ion of cat ions o n act ive carbon . E i t h e r the metals are chela ted w i t h a n organ ic c o m p l e x i n g agent a n d pas sed d o w n a c o l u m n of act ive ca rbon w h i c h adsorbs the m e t a l complexes , o r act ive ca rbon is m o d i f i e d b y reac t ion w i t h a n organ ic che la t ing agent a n d then the s o l u t i o n of m e t a l ions is passed t h r o u g h the c o l u m n a n d thereby adsorbed . E x a m p l e s of the fo rmer a p p r o a c h are the p reconcent ra t ion of m o l y b d e n u m as its a m m o n i u m p y r r o l i d i n e d i t h i o ca rbamate c o m p l e x o n c h a r c o a l [1] a n d the p r e c o n c e n t r a t i o n of manganese , i r o n , cobalt , n i c k e l , c o p p e r a n d z i n c as their 8-quinol inates o n act ivated c a r b o n [2]. A n example of the latter a p p r o a c h is the separa t ion a n d p reconcen t ra t ion of traces of c o p p e r a n d l e ad f r o m m a c r o amoun t s of c a l c i u m m a g n e s i u m , s o d i u m a n d p o t a s s i u m b y a d s o r p t i o n f r o m the sample o n to ac t ive ca rbon m o d i f i e d w i t h 8 - h y d r o x y q u i n o l i n e , d i t h i z o n e or d i e thy ld i t h ioca rbama te [3].
