This symptom may result from two sources:

  • Inaccurate setting of the ‘delay’ parameter of the fraction collector (i.e., time or volume between detection at cell and collection after subsequent passage through the Dionex ERD 500, cell reference electrode chamber, and associated transfer tubing).
  • The effect of dispersion in the post-detection passages adversely effecting peak shape.

Accurate assignment of the delay parameter requires knowledge of the volume of the transfer tubing between the detector and the collection point, as well as the volume in the reference electrode chambers and Dionex ERD 500.

The delay volume in the Dionex ERD 500 is ~ 60 µL. The volume of interconnecting tubing is usually minor, and can be easily calculated to ~ 20% accuracy using the following formula:

volume (in milliliters) = π r² * length (units in cm)

where r is the inside radius of the tubing in cm.

The effect of dispersion in the post-detection, tubing, and Dionex ERD 500 is fairly minor. Another source of dispersion is the detector’s reference electrode chamber. The volume added by the reference electrode chamber in Dionex detectors in the ED is ~ 60 µL.

The following example shows the effect of passage through an ED reference electrode chamber and the Dionex ERD 500 on oligosaccharide peak shape.

Effect of Passage through Detector, Tubing, and Dionex ERD 500 on Retention and Resolution of PNGase-released Fetuin Oligosaccharides
Effect of Passage through Detector, Tubing, and Dionex ERD 500 on Retention and Resolution of PNGase-released Fetuin Oligosaccharides