Pulsed Amperometric detection cells are limited to 100 psi (ED) back pressure. Exceeding these pressures will cause leakage of eluent through the cell’s reference electrode chamber, causing an unstable detector baseline, and loss of collectable sample.

A confirming symptom for the ED detector is a pH reading shift to 15 (the normal reading should be pH 12-14). Pressure induced failure may also be evident as fluid leakage out of the shielded ED cells.

Excessive cell pressure may be caused by any of the following:

  • Excessive flow rate (>1.0 mL/min)
  • Restriction of post-detector tubing (e.g., use of .005" i.d. tubing with 4-mm i.d. columns and flow-rates)
  • Cold-flow of plastic fittings resulting in partial blockage of eluent flow at fittings

If removal of these restrictions does not correct the problem, ED reference electrode O-ring seal may be damaged and should be replaced. The Dionex ERD 500 is rated to 150 psi total post desalter back pressure.

WARNING

Interfacing the HPAEC/PAD system to any post-detection system that imposes a total of > 100 psi is not recommended. Exceeding 450 psi may cause irreversible damage to the Dionex ERD 500 and will void the warranty.