Bio-Rad Chelex® 100 Resin - Manual (Page 9)

80 °C in 3 N ammonium hydroxide for 2 hours. The
resin is autoclavable in the sodium form.
Applications of Chelex Resins
Chelex 100 resin has found many uses. These
include analysis of trace metals in natural waters,
reagents, biochemical, and physiological fluids;
removal of trace metals from reagents, biochemicals,
physiological fluids, culture media, soils, and enzyme
systems; recovery of metals from process streams; and
chromatography of closely related metals.
Trace Metal Removal
Chelex resin offers a rapid and thorough method
for removing trace metal contaminants that could have
an effect on biological fluids or biological systems
under study. A unique ion exchange resin that is more
selective for multivalent metals than the standard
cation exchange resins, Chelex resin will scavenge
multivalent metal ion contaminants without altering
the concentration of nonmetallic ions. In most cases,
15
Buffering
Chelex resin in the hydrogen form has a pH of
2–3. The pH in the sodium form is about 11 and may
be slowly lowered by extended water washing.
However, a more satisfactory procedure for adjusting
the pH is to use a buffer. Thus, a sodium form at
pH 6.3 can be prepared by rinsing with 4 bed volumes
of 0.5 M sodium acetate buffer, followed by 5 bed
volumes of water.
Storage
Chelex resin is stable for at least 2 years when
stored sealed in the original container at 22 °C. It should
be stored in a salt form such as sodium or ammonium. If
left in the hydrogen form for more than a few hours, the
resin has a tendency to lose chelating capacity. Should
such a loss occur, the resin can be regenerated by heat-
ing it at 60 °C in 30-50% alkali for 24 hours. Free imin-
odiacetic acid produced upon long standing (detected by
its odor) may be extracted by methanol or by heating to
14
LIT200B 6/17/98 11:50 AM Page 14