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Fast LC-MS on Astec CHIROBIOTIC CSPs

By: Craig Aurand, Reporter US Volume 27.2

Improve throughput, sensitivity and solvent savings by leveraging column dimensions and flow rate.

Astec CHIROBIOTIC® chiral stationary phases (CSPs) offer several different types of molecular interactions, and separate enantiomers of many analyte classes. Of particular interest are ionic interactions. These permit operation in the polar ionic mode, which is preferred for LC-MS because its mobile phases typically comprise high percentages of methanol or acetonitrile containing low concentrations (1 to 15 mM) of volatile acids, bases or salts, such as ammonium acetate or ammonium formate. Additionally, the polar ionic mode often yields more efficient analyte ionization and correspondingly improved LC-MS sensitivity compared to reversed-phase systems.

To maximize laboratory throughput, HPLC analyses should provide the needed resolution and sensitivity in the shortest amount of time. Column configuration can be leveraged to achieve this objective. The separation of fluoxetine enantiomers on Astec CHIROBIOTIC V2 in Figure 1 demonstrates the improvement in speed and sensitivity gained by using short columns with narrow internal diameter (I.D.). At constant linear velocity, retention and sensitivity achieved by a traditional 25 cm x 4.6 mm I.D. column (Figure 1A) was dramatically improved by reducing the column length and I.D. (Figure 1B). Because column efficiency is directly proportional to column length, the shorter column provided fewer theoretical plates, which resulted in lower resolution. However, Figure 1C shows that by decreasing the flow rate on the short column, resolution was maintained with increased sensitivity compared to the 4.6 mm I.D. column. The lower flow rates also permit direct connection to the MS without flow splitting.

Figure 1. LC-MS of Fluoxetine Enantiomers on Astec CHIROBIOTIC V2

 

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  • CHIROBIOTIC is a registered trademark of Sigma-Aldrich Co. LLC.

 

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