18. What are the differences between standard and H-series columns?

The older CHIRALCEL and CHIRALPAK columns are based on 10-micron particles, whereas H-series CHIRALPAK and CHIRALCEL columns are based on 5-micron particles. The H-series columns have chiral stationary phases identical to their non-H counterparts (i.e., an AD and AD-H column have the same chiral stationary phase), which provide similar selectivity to the standard columns while providing much better chromatographic efficiency. The smaller 5-micron particles thus give better overall resolution. This means better performance for the most difficult separations, or for separations in which impurities would otherwise interfere with the main components. For those situations in which speed of analysis is most important, a 15 cm H-series column may give an equivalent separation with a shorter analysis time, than the same separation on a 25 cm non-H column. -RH series (reverse phase) columns are also based upon 5-micron particles.

In this context, it can be noted that the immobilised columns, CHIRALPAK IA, IB, IC, ID, IE and IF are available in  10-, 5- and 3-micron particle sizes for analytical separations.