Empore™ SPE Extraction Disks, Chelating

• Empore Chelating Disks provide a way to selectively remove multivalent metal cations from solutions
• This selectivity can be used to concentrate metals from a sample for analysis or to isolate and remove metal interferences from a complex organic or inorganic sample matrix. In the latter case, the purified filtrate is ready for use.
• The chelating disk has an affinity for multivalent (primarily 2+ and 3+) transition elements. The functional group exhibits differing ionic charges depending on the pH of the solution.
• At pH 2, the carboxylate groups are neutral and the nitrogen has a net positive charge. This allows the sorbent to function as a weak anion exchanger.
• Increasing the pH ionizes the carboxylate groups and at pH=5, both are negatively charged.
• As the pH approaches neutral, the sorbent functions as a cation exchanger or a chelating resin.
• Ultra-fast flow rate at 350mL/min– 2X faster than other leading brands
• Least elution volume– 1/3 of other leading brands and 1/10 of loose-packed SPE
• Highest consistency & reproducibility– 10-15% higher than Waters Oasis plates
• Least particle fines in eluates-1/10 of other leading brands to increase efficiency >25 (reducing tube clogging & system downtime

Product Usage
For many applications, the Empore™ Chelating Disk can be used directly by wetting with only water. For trace (ppb) metal analysis, the disk should be conditioned.

Note: Because of the adsorptive properties of the disk, handling with non-metallic instruments is recommended.

1. Wet the disk with 20mL of reagent water under vacuum.
2. Wash the disk with 20mL of 3.0M nitric acid or 3.0M hydrochloric acid followed by two 50mL water washes. Let the disk go dry between each wash.
3. To put the disk in the ammonium form (its most active form), wash with 50mL of 0.1M ammonium acetate buffer at pH 5.3 followed by several reagent water washes.

The disk is now conditioned and ready to extract the sample.

Extraction Considerations
Add the sample and apply vacuum (<20 in Hg, 0.68 bar). Flow rates will vary. Typically, using a 47mm disk, 1 Liter DI water at 25°C and 20 in Hg will extract in less than 10 minutes.

Flow rate is dependent on vacuum source and the particulate content of the sample. Empore Filter Aid 400 and/or other prefiltration may be helpful if the sample contains excessive amounts of particulates.

Remove as much of the residual water as possible from the disk, before the elution step, by applying the vacuum to dry the disk for 5 – 20 minutes.

Elution Requirements
Elution of metals from the chelating disk is achieved with strong acids such as 3.0M nitric acid or 3.0M hydrochloric acid. Most metals can be quantitatively recovered by eluting twice with 10mL (47mm disk) of 3.0M nitric acid or 3.0M hydrochloric acid and combining the eluates.

A few metals (e.g., chromium) may be difficult to elute, particularly if left on the membrane for several hours.