C18 SPE Cartridge (Reversed-Phase)

C18 solid phase extraction (SPE) cartridges are based on octadecyl-bonded silica and operate via reversed-phase retention. Non-polar and moderately polar analytes are retained from aqueous matrices through hydrophobic interactions and subsequently eluted using organic solvents such as methanol or acetonitrile.

The Hawach C18 SPE series includes two sorbent chemistries designed for different matrix conditions: Standard C18 (end-capped) and C18A hydrophilic-modified C18. Both are based on USP L1 classification materials for reversed-phase SPE.

Sorbent Chemistry Overview

Standard C18 (End-Capped)

• Octadecyl-bonded silica with double end-capping
• Carbon loading: 17%
• 120 Å pore size, high surface area silica
• Designed for hydrophobic retention of non-polar analytes
• Reduced silanol activity for improved peak shape and recovery

C18A (Hydrophilic-Modified C18)

• Hydrophilically modified octadecyl phase
• Carbon loading: 12%
• Optimized surface wettability for aqueous matrices
• Maintains retention performance under 100% aqueous loading
• Improved retention of polar and water-soluble compounds

Retention Mechanism

Both sorbents operate under reversed-phase mechanism:

• Retention driven by hydrophobic interactions between analytes and C18 ligands
• Elution achieved using increasing organic solvent strength
• Matrix effects reduced through selective partitioning of analytes from aqueous phase

Key Analytical Characteristics

Application Domains

• Environmental analysis: PAHs, PCBs, pesticides, herbicides, SVOCs in water and soil extracts
• Food safety: pesticide residues, additives, antioxidants
• Pharmaceutical analysis: APIs, metabolites, impurity profiling
• Clinical and toxicology: drugs of abuse, biological fluid screening
• Biological matrices: plasma, urine, serum sample cleanup

Matrix Compatibility Considerations

• Aqueous environmental samples (drinking water, wastewater, groundwater)
• Biological fluids with protein precipitation pre-treatment
• Food extracts with moderate organic content
• High-salinity or complex matrix samples requiring cleanup prior to LC-MS or GC-MS

SPE Procedure (General Workflow)

1. Conditioning: Methanol followed by water or buffer
2. Equilibration: Aqueous matrix-compatible solvent
3. Loading: Sample introduction under controlled flow
4. Washing: Water or low organic solvent to remove interferences
5. Elution: Organic solvent (methanol, acetonitrile, ethyl acetate)

C18A allows direct loading of fully aqueous samples without phase collapse, improving workflow robustness in water-only methods.

EPA Method Compatibility

C18 SPE cartridges are applicable to common environmental analytical methods including:

• EPA 525.2 / 525.3 – Semi-volatile organic compounds
• EPA 508.1 – Chlorinated pesticides
• EPA 506 – Phthalates
• EPA 550.1 – PAHs
• EPA 608 – Organochlorine pesticides and PCBs
• EPA 3535 – Solid phase extraction procedures

Sorbent Selection Guide

Quality Control & Manufacturing

• Manufactured under ISO 9001 quality system
• Controlled silica bonding chemistry
• Batch-to-batch consistency verification
• QC testing: particle size distribution, sorbent mass, recovery performance
• Full lot traceability and documentation (COA available)

Ordering Information

Standard C18 (End-Capped) | 40–60 µm, 120Å, 17% Carbon

C18A Hydrophilic Modified Type | 40–75 µm, 60Å, 12% Carbon

Download PDF Datasheet

• Formats: 1 mL – 12 mL cartridges
• Sorbent mass: 100 mg – 2 g
• Packaging: bulk and OEM configurations available
• Compatible with vacuum manifolds, positive pressure systems, and automated SPE platforms