1. Empirical Isomers

• Definition: Compounds with the same empirical formula but potentially different atomic arrangements.
• Analytical Note: In LC-MS, these isomers may produce identical m/z values, making structural identification difficult without chromatographic separation.
• Recommended Column: Cogent Diamond Hydride™ – Ideal for polar compounds and often effective for separating empirical isomers.

2. Positional Isomers

• Definition: Compounds that differ in the position of a functional group on the molecular structure (e.g., ortho, meta, para substitutions on aromatic rings).
• Recommended Column: Cogent Phenyl Hydride™ – Offers selectivity for aromatic compounds and is well-suited for resolving positional isomers.

3. E/Z or Cis/Trans Isomers

• Definition: Isomers that differ in the spatial arrangement of substituents around a double bond.
  • Cis/Trans: Used when hydrogen atoms are present on both sides of the double bond.
  • E/Z: A more general system using Cahn-Ingold-Prelog priority rules for substituent ranking.
• Recommended Column: Cogent UDC-Cholesterol™ – Provides shape-based selectivity, making it effective for separating geometric isomers.

4. Stereoisomers

• Definition: Compounds with the same molecular formula and connectivity but different spatial arrangements at chiral centers.
  • Enantiomers: Mirror images; require chiral stationary phases (not currently offered by MicroSolv).
  • Diastereomers: Differ at one or more (but not all) chiral centers.
  • Epimers: A subtype of diastereomers differing at only one chiral center.
  • Meso Compounds: Contain chiral centers but are achiral due to internal symmetry.
• Note: Conventional HPLC columns can separate diastereomers and epimers, but not enantiomers. You should find a column designed specifically for Stereoisomers.

Tip: Always consider the isomer type and molecular characteristics when selecting an HPLC column. The right choice can dramatically improve resolution and analytical confidence.