Metal ion-ligand coordination complexes, antibodies directed thereto, and assays using such antibodies

A method for removing a metal ion from a sample comprising the steps of:

• (a) contacting the sample with a ligand in order for the ligand to bind to the metal ion to form a metal-ligand complex (MLC), wherein said ligand has a structure selected from the group consisting of:
• ##STR1## Where r is selected from the group consisting of ##STR2## Y and Z can be the same or different and are selected from the group consisting of ##STR3## X is selected from the group consisting of ##STR4## R.sub.1 is C.sub.1 -C.sub.4 alkyl or ##STR5## R.sub.2 is C.sub.1 -C.sub.4 alkyl R.sub.3 is C.sub.1 -C.sub.10 alkyl contributed by a conjugate molecule;
• and
• (b) removing the MLC from the sample.