This symptom may be due to incomplete desalting or failure of the Dionex ERD 500 component membranes.

Eluent salts result from incomplete desalting, and regenerant salts result from leakage of regenerant through the cation exchange membranes separating the regenerant and eluent chamber.

See the following table for causes of eluent salts in the purified sample.

Causes of eluent salts in the purified sample

Issue

Solution

Excessive eluent concentration (i.e., > 0.35 M Na+)

Procedure

  1. Reduce the eluent concentration or flow-rate, so that no more than 350 µeq / minute of Na+ pass through the Dionex ERD 500 4mm or 87.5 µeq / minute for 2 mm.
  2. 4 mm: 1 mL/min * 350 mM = 350 µeq of Na+/min.
  3. 2 mm: 0.25 mL/min * 350 mM = 87.5 µeq of Na+/min

Excessive flow (i.e., > 1.0 mL/min for 4 mm or > 0.25 mL/min for 2 mm)

Inadequate recovery time after exposure to a high concentration of eluent cations

Procedure

  1. Increase the time between exposure to the high cation concentration eluent and the subsequent injection.

Inadequate regeneration capacity

This might result from low regenerant flow, low current supply to the Dionex ERD 500, or failure of the Dionex RFC-10 controller or Dionex ERD 500.

Procedure

  1. Do one of the following:
  2. Low regenerant flow: Increase pressure on the regenerant reservoir to provide at least 7 mL / minute of 150 mM TFA regenerant for 4 mm or at least 2 mL/min for 2 mm.
  3. Low current supply: Set the Dionex RFC-10 controller to the recommended current.

If the Dionex RFC-10 controller or ERD 500 fail, they will need to be replaced.