Mitigating Metal Surface Interactions in HPLC Hardware: Past and Present

Stainless steel has long been used across many industries, including HPLC instruments and consumables, for tubing, valves, fittings, pumps, and filter elements due to its abundant availability, corrosion resistance, and mechanical robustness. Despite these benefits, stainless steel has many disadvantages. It is not universally corrosion resistant as high acid and/or salt concentrations can cause catastrophic corrosion. Even seemingly benign conditions such as UHPLC grade water, acetonitrile, and methanol can cause ppb to ppm levels of metal ions to leach from the steel. Additionally, the steel surface has been known to cause metal-analyte interactions that may lead to poor peak shapes, low recoveries, and overall poor performance for metal-sensitive analytes. This type of non-specific adsorption has been documented in the literature and many pharmaceutical separations from small molecule to protein analysis suffer from metal surfaces.

Here, we will review previous solutions to these metal-analyte interactions such as passivation, priming, and replacing steel with a different material. We will then discuss a relatively new innovation for the HPLC industry: chemical vapor deposited silica-like coatings that can be applied to all metallic components in the flow path. Advantages over past solutions as well as case studies showing the benefits of these coatings will be presented.