34 May / June 2019 Oligonucleotide Separations with RP Phases
Therapeutic oligos represent an important area of research in the pharmaceutical industry today. These drug candidates are typically 8-50 nucleotides long and contain single-stranded DNA or RNA. Oligonucleotides are typically analysed using ion-pairing chromatography. Oligonucleotides are easily degraded via phosphodiester-cleaving enzymes. However, with a thiophosphate modified phosphate group, the stability significantly increases. Phosphorothioate modified oligos will have a stereocenter at
each modified phosphate group, leading to 2n-1 diastereomers, all with an individual retention time in the chromatography. For a 20-nucleotide long oligo, that’s 524 288 species present. The partial resolution of these species results in peak broadening, further complicating chromatographic separation. To resolve the problem, ion-pairing agents with longer alkyl chains can be used.
In a study of the influence of stationary phase and ion-pairing agent on the separation of oligos, Kromasil Phenyl showed to be a very good choice when separating oligonucleotides in general, exhibiting very sharp peaks, and good selectivity.
More information online:
ilmt.co/PL/XvKy
New PFAS Delay Column Eliminates the Impact of PFAS Instrument Contamination
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Per-and polyfluorinated alkyl substances (PFAS) are often used in tubing and other liquid-contacting parts of an HPLC system, where they can leach into the mobile phase and interfere with sample analysis. This contamination is particularly problematic when analysing at trace levels, such as at the ppt health advisory levels for drinking water. With many labs analysing at single-digit ppt levels and striving for sub-ppt level detection, PFAS contamination from HPLC components can prevent accurate identification and quantitation of PFAS in samples. To eliminate this issue, Restek’s new PFAS delay column traps and ‘delays’ system-related PFAS, preventing them from interfering with sample analysis. This delay column is a universal solution that can be used with any type of HPLC or UHPLC system up to 15,000 psi (1034 bar) and with any analytical column (fully porous or superficially porous).
More information online: ilmt. co/PL/DZ5m
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