My bio-inert HPLC system for carbohydrates show a rapid decrease in peak heights

Applies to

Agilent 1260II bio-inert HPLC system with PAD of carbohydrates at high pH.

Summary

The peak heights of carbohydrate standards decrease, and are not reproducible.

Cause

Certain pieces of bio-inert tubing need to be replaced with PEEK tubing (see picture blue and red indications). The tubing material is not pH resistant.

Remedy

There are a few ways to circumvent this issue, depending on the requirements.

1. Order the MP35N replacement tubings from Agilent, pn 5005-6800 Pump capillary kit for ECD. This is the best option.
2. Replace the 2 pieces of tubing by PEEK tubing of 500 um ID. There is a pressure rating though, which is 200 bar. In case the HPLC system pressure is higher than 200 bar use option 1 or 3.
3. Replace the 2 pieces of tubing by stainless steel tubing of 600 um ID, and passivate the stainless steel with 15% nitric acid prior to use. This is best done by connecting the tubings to a syringe with some silicone tubing adapter and rinse the nitric acid through for 20 min. Wash out the nitric acid prior to putting the tubings in place.