Determination of selectivity differences for basic compounds in gradient reverse phase high performance liquid...

Area of Science:

• Analytical Chemistry
• Chromatography
• Chemometrics

Background:

• Compound retention in chromatography is influenced by multiple physico-chemical properties.
• Multivariate analysis techniques like Principal Component Analysis (PCA) and Partial Least Squares (PLS) are valuable for exploring complex solute-phase interactions.
• Understanding these interactions is crucial for optimizing separation and selectivity in High-Performance Liquid Chromatography (HPLC).

Purpose of the Study:

• To investigate the chromatographic behavior of basic compounds using optimized gradient conditions.
• To explore and model the selectivity differences among various octadecyl (C18) HPLC columns under high pH separation conditions.
• To establish quantitative structure-retention relationships (QSRRs) using multivariate modeling.

Main Methods:

• Analysis of three pharmaceutical mixtures using linear gradient reverse-phase HPLC (RP-HPLC) at high pH.
• Utilized ammonia as a pH modifier and methanol/acetonitrile as organic modifiers.
• Employed multivariate PCA and PLS modeling to analyze retention data and molecular descriptors across three different C18 columns (Waters XTerra MS C18, Agilent Zorbax Extend C18, Thermo Hypersil-Keystone BetaBasic-18).

Main Results:

• PCA and PLS successfully visualized and modeled the complex relationships between basic compounds and chromatographic system variables.
• Significant selectivity differences were identified among the tested octadecyl columns under high pH conditions.
• The study related compound molecular descriptors to the observed selectivity, explaining the interactions with mobile and stationary phases.

Conclusions:

• Multivariate PCA and PLS are powerful tools for understanding and explaining selectivity variations in HPLC systems, particularly for basic compounds at high pH.
• The choice of octadecyl column significantly impacts the separation selectivity of basic analytes under high pH conditions.
• Relating molecular descriptors to chromatographic selectivity provides insights into the fundamental interactions governing retention.