Abstract: Species-linked diamine triacetic acids of the formula ##STR1## wherein T is an organic species containing at least one amine, hydroxyl, or thiol functional group, L is the residue of at least one of those functional groups and R is a two or more atom long covalent bridge, are disclosed. Methods for their preparation, for the preparation of metal chelates from them and for the use of the chelates are also disclosed. In a preferred embodiment, the metal ions employed in the formation of the chelates are rare earth metal ions capable of forming fluorescent chelates which can in turn be employed in fluoroassay techniques.

Abstract: A system for heat sealing in conjunction a pair of plastic strips each of having a series of regularly spaced transverse pockets so that the pockets together form chambers separated by webs. The two pocketed strips to be joined are brought together and the strips heat sealed around the pockets to seal the chambers from one another while passing cooling fluid over the pockets so as to avoid distortion or collapse of the pockets.

Abstract: A method for conducting a ligand assay in an inert porous medium wherein a binding material is immunologically immobilized within the medium, which includes the steps of immunologically immobilizing a binding material within a finite zone of the medium, applying an analyte to the zone containing the immobilized binding material, applying a labeled indicator to the zone which becomes immobilized within the zone in an amount which can be correlated to the amount of analyte in the zone, applying a solvent to substantially the center of the zone to chromatographically separate the unbound labeled indicator from the zone, and measuring the amount of labeled indicator remaining in the zone.

Abstract: A method for conducting a ligand assay in an inert porous medium wherein a binding material is immunologically immobilized within the medium, which includes the steps of immunologically immobilizing a binding material within a finite zone of the medium, applying an analyte to the zone containing the immobilized binding material, applying a labeled indicator to the zone which becomes immobilized within the zone in an amount which can be correlated to the amount of analyte in the zone, applying a solvent to substantially the center of the zone to chromatographically separate the unbound labeled indicator from the zone, and measuring the amount of labeled indicator remaining in the zone.

Abstract: It is disclosed that aryl-substituted 2,6-bis[N,N-di(carboxyalkyl)aminoalkyl] pyridines in which the aryl groups are substituted with one or more electron-releasing groups are an advantageous ligand for forming fluorescent chelates with rare earth metals. The pyridine moieties can be linked to target molecules, especially biologically active target molecules to provide fluorescent tagging for use in fluoroassay techniques. The pyridine moieties are disclosed as tetraacids, as salts and as esters. Preparation processes and precursors including the corresponding aryl-substituted 2,6-dicarboxypyridines as acids, salts and esters, are disclosed as well.