Michael Dong 唐緯中

Subject matter expert in HPLC, CMC, and pharm analysis. Author of bestseller HPLC book and 130 articles.

Published Sep 21, 2021

https://www.linkedin.com/pulse/what-best-hplc-column-id-analytical-analysis-michael-dong-%E5%94%90%E7%BA%AC%E4%B8%AD?trk=articles_directory

What is the best HPLC column i.d. for analytical analysis, and why is everyone still using the 4.6 mm id column?

The answer is likely historical as ?” o.d. and 4.6-mm i.d. were common standard dimensions for precision-bore SS 316 stock tubing. It also happened to be a good fit for performing analytical HPLC since the 1960s with columns packed 5 – 10 mm particles.

Today, this dimension is no longer optimum for modern columns packed with sub-3 mm particles in many laboratories equipped with UHPLC-like equipment with small UV flow cells. The main reason is that most labs use ~1.0 mL/min, which is the optimum flow rate for 4.6-mm columns packed with 5-mm or 10-mm particles.? Nevertheless, the optimum flow rate for 4.6-mm columns packed with sub-3-mm particles would be ~2 mL/min, which would be too high to support a 24-hour use with one liter of mobile phases.? ?

The rational choice is to standardize on the 3.0 mm i.d. columns for most analytical HPLC, where 1 mL/min is the optimum flow rate. The exception is for high-throughput screening applications where the use of 2.1 mm i.d. columns packed with sub-2 mm superficially porous particles (SPP) would be more appropriate.

References:

1. M.W. Dong, HPLC and UHPLC for Practicing Scientists, 2nd Ed.,. Wiley, 2019, Chapters 3.

2. R. Majors, Historical Developments in HPLC and UHPLC Column Technology: The Past 25 Years, LCGC North Am, 33(11), November 2015.