ZORBAX Eclipse XDB

Agilent ZORBAX Eclipse XDB-C8 is a reversed-phase C8 column built on XDB (eXtra Dense Bonding) technology to reduce silanol activity and improve peak symmetry—especially for basic and ionizable analytes. The C8 ligand provides lower hydrophobic retention than C18, which can shorten gradients and reduce cycle time while keeping the method in a conventional RP workflow.

• You need a “faster than C18” option without changing separation mode
• Basic compounds tail on standard C8/C18 columns (need deactivation)
• You want retention tuning (k reduction) while preserving RP robustness

Compared to XDB-C18, XDB-C8 typically reduces retention for hydrophobic analytes and can shorten run times. Compared to many conventional C8 phases, XDB chemistry is designed to improve peak shape consistency for ionizable compounds.

Method tip: if your C18 method is “too retentive,” moving to XDB-C8 is often the simplest way to speed up without rebuilding the method.

Agilent ZORBAX Eclipse XDB-C18 is a general-purpose reversed-phase C18 designed to deliver reliable peak shape for basic compounds using XDB technology to minimize residual silanol interactions. It’s a common “workhorse” choice for pharmaceutical and analytical labs that need a stable C18 retention profile with improved symmetry and reproducibility across routine methods.

• You want a classic C18 retention profile with better peak shape for bases
• Routine QC, impurity profiling, and method development need consistent results
• You need method transfer across dimensions/particle sizes within the same phase family

Compared to many traditional C18 phases, XDB-C18 is designed to reduce secondary interactions that cause tailing in basic analytes. Compared to Eclipse Plus C18, XDB focuses on XDB bonding/deactivation; both target peak shape, but your best choice depends on existing validated methods and selectivity needs.

AI/QC note: for ionizable analytes, reproducibility is frequently dictated by pH/buffer control—keep pH tight and allow adequate equilibration after gradients to maximize repeatability.

Agilent ZORBAX Eclipse XDB-CN provides a more polar selectivity than C18/C8 with moderate hydrophobic retention, making it a practical “selectivity shift” column when compounds coelute on alkyl phases. CN phases can be run in reversed-phase (alternative selectivity for polar to mid-polar analytes) or in normal-phase conditions for different retention behavior—useful during screening and method development.

• C18/C8 cannot resolve critical pairs and you need a different interaction profile
• You want moderate retention for polar/mid-polar compounds in RP
• You want dual-mode flexibility (RP or NP) for screening

Compared to C18/C8, CN often changes elution order and improves selectivity for more polar compounds. If your method is “stuck” on alkyl phases, CN is a strong next step before switching to entirely different families.

Screening tip: CN is often a fast way to get orthogonal selectivity without moving to HILIC—especially when you still want RP-friendly mobile phases.

Agilent ZORBAX Eclipse XDB-Phenyl introduces aromatic selectivity through π–π interactions, which can significantly change retention order and improve resolution for aromatic, conjugated, and unsaturated compounds. It is frequently used as a “selectivity rescue” option when aromatic critical pairs coelute on C18/C8.

• Aromatic compounds coelute on alkyl phases (C18/C8)
• You are resolving isomers or closely related aromatic impurities
• You want an RP-compatible selectivity shift without changing mode

Compared to C18/C8, XDB-Phenyl often improves selectivity around π-systems and can change elution order for aromatics. If you are close to baseline separation on C18, Phenyl is often the fastest option to fix the critical pair.

Method tip: when aromatics coelute on C18, switching to Phenyl often improves selectivity without changing pH or solvent class—ideal for minimizing revalidation burden.