OPTIMIZE - CHROMATOGRAPHY FOR THE WORLD SINCE 1985

Introduction

Packing materials on small packed beds ("trap cartridges") can selectively retain target analytes for sample cleanup, concentration or removal of unwanted components (salts, detergents) prior to analysis.

Trap cartridges are divided into three main pressure ranges:

• Medium pressure (OPTI-TRAP™ – manual and on-line trapping to ~1,500 psi).
• High pressure (OPTI-LYNX™ – quick‐connect system up to 6,000 psi).
• Ultra‐high pressure (EXP®/EXP®2 – hand‐tight & wrench‐tight use to 20,000+ psi).

Traps may be uni‐ or bi‐directional and used on‐line (in injection/switching valve) or off‐line (manual loading/flush), coupling to LC or LC‐MS.

Benefits of Trapping

• Pre‐concentration of dilute samples (“trap and elute” in smaller volume).
• Removal of matrix components (salts, detergents) that interfere with analysis.
• Sample cleanup for improved sensitivity and reproducibility.

Trap Cartridge Selection

Choose trap by:

• Bed volume (0.12 µL to 100 µL) and flow rate capacity.
• Stationary phase chemistry (reversed‐phase C18/C8/C4, HILIC, SCX/SAX, mixed‐mode, etc.).
• Pressure requirements (manual syringe loading to UHPLC pressures).

Use lower pressure OPTI‐TRAP/OPTI‐LYNX systems for routine HPLC. For UHPLC, select EXP®/EXP®2 traps.

Off‐Line Trapping Workflow

1) Load sample (with matched mobile phase) onto trap via syringe or auxiliary pump.
2) Analyte binds; matrix flows to waste.
3) Rinse trap to remove residual salts or detergents.
4) Elute analyte in small volume of stronger solvent to vial or loop.

On‐Line Trapping Workflow

• Install trap in injection or valve loop.
• Use auxiliary pump for sample loading; trap routing directs matrix to waste.
• Switch valve to inject: elute analyte to analytical column or directly to MS.
• Automates trapping cleanup & concentration.

Key Applications

• Small molecule concentration & desalting (reversed‐phase, C18‐AQ or similar).
• Peptide cleanup & concentration (polymeric C8‐like reversed‐phase).
• Protein cleanup & desalting (polymeric C4‐like reversed‐phase).
• SDS (ionic detergent) removal (polymeric SAX at low pH to bind SDS).
• Non‐ionic detergent (NID) removal (mixed‐mode SCX/SAX traps to exclude detergents).
• Strong cation exchange (SCX) trapping of peptides (pH ~3) with salt elution steps.
• Internal surface reversed‐phase (ISRP) to remove proteins while capturing small hydrophobic analytes.

Trap Operation Guidelines

• Clean and equilibrate trap: use high‐strength wash (e.g., 90/10 ACN/water) then equilibrate in loading buffer.
• Match sample solvent to loading conditions.
• Load at recommended flow rate to avoid bed overload.
• Wash to waste to remove matrix.
• Elute in small volume: gradient on‐line or manual flush.
• Regenerate trap: strong organic or salt solution depending on phase.

Conclusion

Trap cartridges streamline sample prep by integrating cleanup, concentration and matrix removal in both HPLC and UHPLC workflows. OPTI‐TRAP™, OPTI‐LYNX™ and EXP®/EXP®2 systems offer a range of pressure ratings, low swept volumes and versatile chemistries to maximize sensitivity, protect downstream columns and MS sources, and automate high‐throughput analysis.