Chelex^® 100 Chelating Resin

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Overview

Analytical Grade Resin Wet Mesh and Equivalent Diameters



Wet mesh (U.S. Standards)	16	20	40	50	80	100	140	200	270	325	400
Diameter, µm	1,180	850	425	300	180	150	106	75	53	45	38

Selection Guide

Analytical Grade Resin Selection Guide

Relative Sensitivity

Relative Selectivity of Various Counterions

AG^® MP-1 neutral species and cations do not interact with the resin. In the chloride form of AG1, AG MP-1, and AG2 resin, the counterion on the resin is C1. A resin can be converted from one ionic form to another. Ususally the resin is used in an ionic form with a lower selectivity for the functional group than the sample ions to be exchanged. The sample ions are then exchanged onto the resin when introduced, and can be eluted by introducing an ion with higher affinity for resin or a high concentration of an ion with equivalent or lower affinity. The table below shows the relative selectivity of various counterions. In general, the lower the selectivity of the counterion, the more readily it exchanges for another ion of like charge. The order of selectivity can also be used to estimate the effectiveness for different ions as eulants, with the most highly selective being the most efficient. Finally, the order of selectivity can be used to estimate the difficulty of converting the resin from one form to another. Conversion from a highly selected to a less highly selected form requires an excess of the new ion.

Relative Selectivity of Various Counterions
Counterion	Relative Selectivity for AG^® 1 and AG MP-1 Resins	Relative Selectivity for AG 2 Resin
OH^-	1.0	1.0
Benzene sulfonate	500	75
Salicylate	450	65
Citrate	220	23
I^-	175	17
Phenate	110	27
HSO₄^-	85	15
CIO₃^-	74	12
NO₃^-	65	8
Br^-	50	6
CN^-	28	3
HSO₃^-	27	3
BrO₃^-	27	3
NO₂^-	24	3
Cl^-	22	2.3
HCO₃^-	6.0	1.2
IO₃^-	5.5	0.5
HPO₄^-	5.0	0.5
Formate	4.6	0.5
Acetate	3.2	0.5
Propionate	2.6	0.3
F-	1.6	0.3

Chelex 100 resin is a styrene divinylbenzene copolymer containing paired iminodiacetate ions, which act as chelating groups in binding polyvalent metal ions. The carboxylic acid groups of Chelex 100 resin classify it as a weak cation exchange resin, but it differs from other exchangers in this class by featuring uniquely high selectivities for metal ions and much higher bond strengths.

Chelex 100 chelating ion exchange resin has a stronger selectivity for copper, iron, and other heavy metal ions over monovalent cations such as sodium and potassium. Its selectivity for divalent over monovalent ions is approximately 5,000 to 1, and it has a strong affinity for transition metals, even in highly concentrated salt solutions.

The following forms of Chelex 100 resin are available:

Analytical grade Chelex 100 resin — exhaustively sized, purified, and converted to make it suitable for accurate, reproducible analytical techniques
Biotechnology grade Chelex 100 resin — the analytical grade form certified to contain fewer than 100 microorganisms per gram of resin