Welcome to the New Restek.com! Take a tour of the new site and feel free to send us your feedback.

Your web browser will no longer be supported by Restek.com as of 30 June 2021.
To avoid any interruption in access or functionality, install a current-generation web browser now. Learn more.

Chiral blog 3: Overloading and Tailing

By
  • Jana Hepner
Tags
  • #Chromatography Fundamentals
  • #Product Selection
  • #Troubleshooting
  • #Method Development
  • #Method Optimization
  • #Columns
  • #GC Columns
  • #Fused Silica Capillary Columns
  • #Blogs
  • Share:

Some chiral compounds show over- loading at lower concentrations than achiral compounds. One reason is the different amounts of cyclodextrin (5- 50%) dissolved in the stationary phase. Unlike the classical fronting peaks of normal stationary phases, the characteristic of an overloaded peak on cyclodextrin stationary phases is indicated by a tailing peak. Overloading chiral compounds results in loss of resolution, even when column capacity has not been exceeded. The first example is linalool separation on the Rt-βDEXsp (Figure 1). The amount is about 20 ng on-column (Figure 1A). Figure 1B shows the same components at a higher concentration of 200 ng on-column. Note that the linalool enantiomers are beginning to tail, and there is a small loss in chiral resolution. Even though the maximum sample capacity for 0.32mm ID capillary columns is normally 400- 500 ng per component, the peak shapes of chiral compounds indicate overload at one-third of the sample amount. Again, there is much less cyclodextrin for which a chiral compound can interact. Figure 1C shows pronounced overloading at 2 µg on-column. Extreme tailing and complete loss in resolution are the result.

blog-chiral-blog-3-overloading-and-tailing-01.png

Figure 1: Overloading of linalool on Rt-βDEXsp

The second example is 2,3-butanediol on Rt-βDEXsm (Figure 2). We see here a similar trend of overloading and tailing between 500 ng on-column (Fig 2A) and 25 ng on-column (Fig 2B). Due to a very good separation between the isomers, the loss of resolution isn’t as obvious as it was in the previous example, even though we can see more overloading.

 

blog-chiral-blog-3-overloading-and-tailing-02.png

Figure 2: Overloading of butanediol on Rt-βDEXsm

Related Articles

How do our GC chiral columns compare?

Read Article

Chiral Separation 2: Optimization of Chiral Separations

Read Article