Benzenesulfonic acid bonded silica
40-75 μm
70 Å
480-530 m²/g
9% carbon
Permanently charged sulfonic acid group (pKa < 1)
For basic drugs, metabolites, and alkaline compounds in urine, plasma, and water
Availability: In Stock
SCX SPE Cartridge
Description
SCX SPE cartridge definition: SCX SPE cartridges are strong cation exchange sorbents based on benzenesulfonic acid bonded silica. The permanently charged sulfonic acid group (pKa < 1) provides consistent, high-capacity cation exchange to selectively retain protonated basic compounds from biological and environmental samples.
SCX is widely used for extracting basic drugs, metabolites, alkaloids, and other alkaline analytes from urine, plasma, serum, and water – where reversed-phase sorbents like C18 often fail due to poor retention or ion suppression.
When to use SCX:
- Your target analytes are basic (amines, quaternary ammonium compounds)
- You need high and reproducible recovery from biological fluids
- C18 gives poor retention or matrix interference
SCX SPE Retention Mechanism
The primary retention mechanism of SCX is electrostatic (ionic) interaction. The negatively charged sulfonic acid group binds to positively charged analytes (protonated amines, quaternary ammonium compounds). Under typical loading conditions (acidic pH 2-6), basic drugs are fully protonated and strongly retained.
SCX may also show secondary hydrophobic retention under high-organic wash or elution conditions due to the aromatic benzene ring. This can be exploited for mixed-mode selectivity but should be considered when designing methods.
Key point: To ensure retention, the sample pH must be at least 2 units below the pKa of your basic analyte. For drugs with pKa 8-10, load at pH 5-6.
SCX vs PRS vs C18 – Which One Fits Your Application?
SCX is preferred for general basic drugs with aromatic structures, while PRS is better for weak bases with minimal secondary interactions.
| Sorbent | Well–suited for | Primary Interaction | Limitation |
| SCX (benzenesulfonic) | General basic drugs, aromatic amines, drug metabolites | Ionic + mild hydrophobic (π-π) | Slight non-specific retention |
| PRS (propylsulfonic) | Weak bases, pyridines, malachite green, crystal violet | Pure ionic (no π-π) | Lower retention for hydrophobic basic analytes |
| C18 (reversed-phase) | Neutral and non-polar compounds | Hydrophobic only | Poor retention for charged basic drugs |
Selection guide:
– Choose SCX for routine basic drug extraction from urine, plasma, and water.
– Choose PRS for weak bases where non-specific binding is problematic.
– Choose C18 for neutral compounds or when your basic analytes are not the primary target.
SCX SPE Cartridge Applications by Industry
SCX SPE cartridges are used across multiple analytical sectors where basic compound extraction is required.
| Industry / Segment | Typical Matrices | Target Analytes |
| Pharmaceutical bioanalysis | Plasma, serum, whole blood | Basic APIs, drug metabolites, anti-arrhythmics, beta-blockers, antidepressants |
| Clinical toxicology | Urine, oral fluid, hair, blood | Drugs of abuse (amphetamines, opioids, benzodiazepines, cocaine metabolites), therapeutic drug monitoring |
| Environmental water testing | Groundwater, surface water, wastewater | Alkaline pesticides, quaternary ammonium compounds, basic dyes, personal care products |
| Food safety residue analysis | Meat, milk, eggs, honey, seafood | Veterinary drug residues (aminoglycosides, sulfonamides, tetracyclines, β-agonists) |
| Forensic & law enforcement | Post-mortem blood, urine, tissue homogenates | Basic toxicants, alkaloids, synthetic cathinones, fentanyl analogs |
Each application benefits from SCX’s ability to selectively retain positively charged analytes while allowing neutral and acidic interferences to wash through, reducing matrix effects in LC-MS/MS and GC-MS.
Typical Analytical Workflows
- Clinical & forensic toxicology– Drugs of abuse (amphetamines, opioids, benzodiazepines) in urine, plasma, whole blood
- Pharmaceutical bioanalysis– Basic API extraction from plasma for PK/PD studies
- Environmental monitoring– Alkaline pesticides, quaternary ammonium compounds, basic dyes in water
- Food safety– Veterinary drug residues (e.g., aminoglycosides, sulfonamides)
- Impurity profiling– Basic degradants and by-products in drug substance
SCX SPE Workflow (Step-by-Step)
Goal: Retain basic drugs, remove neutrals, elute with basic organic solvent.
| Step | Solvent | Purpose | Critical tip |
| Condition | Methanol → water or acid buffer (0.1% formic acid) | Activate sorbent | Do not let cartridge dry after conditioning |
| Load | Acidified sample (pH 2-6) | Retain positively charged analytes | pH must be ≤ pKa of analyte – 2 |
| Wash | Water or dilute acid buffer (same pH) | Remove neutral interferences | Avoid high organic content |
| Elute | 5% ammonium hydroxide in methanol (or 2% NH₄OH in 95% methanol/5% water) | Displace cations, recover analytes | Collect eluate in low-retention tubes |
Troubleshooting SCX SPE Problems
Even with a robust method, occasional issues arise. The table below lists common problems and recommended fixes.
| Problem | Likely Cause | Solution |
| Low recovery | Loading pH too high (analyte not charged) ; insufficient sorbent mass ; elution solvent too weak | Lower sample pH to ≤ pKa – 2 ; increase sorbent mass or load slower ; use 5% NH₄OH in methanol or 0.5 M ammonium acetate in 95% methanol/5% water |
| Breakthrough during load | Insufficient conditioning or equilibration ; sample flow rate too high ; sorbent overloaded | Re-condition with methanol and re-equilibrate ; reduce flow rate (≤5 mL/min) ; use larger sorbent mass or dilute sample |
| Dirty extracts / high background | Wash step too weak (interferences not removed) | Increase wash strength (e.g., add 5-10% methanol to wash) ; add an additional wash with 2% formic acid in water for highly dirty matrices |
| Ion suppression in LC–MS/MS | Matrix overload ; co-elution of neutral or acidic interferences | Reduce sample equivalent load ; add a mixed-mode wash (e.g., 2% formic acid in 20% methanol) before elution ; consider using PRS for weak bases |
| Poor reproducibility between batches | Inconsistent conditioning or elution ; pH variation in loading | Standardize conditioning steps (same volume, same solvent) ; verify sample pH with meter ; use certified SCX cartridges with batch-specific COA |
SCX vs PRS SPE Cartridge – Key Differences
| Feature | SCX (Benzenesulfonic) | PRS (Propylsulfonic) |
| Functional group | Aromatic (phenyl) | Aliphatic (propyl) |
| π-π / hydrophobic interaction | Yes (moderate) | Minimal |
| Well-suited for | General bases, aromatic basic drugs, drug metabolites | Weak bases (pyridines, malachite green, crystal violet) |
| Typical matrices | Urine, plasma, serum, wastewater | Water, aquaculture, food samples |
| Elution solvent | 5% NH₄OH in methanol | Same, but often cleaner for weak bases |
Ordering Guide – Choose the Right SCX Cartridge Format
Select sorbent mass based on your sample volume and matrix complexity.
| Sorbent mass | Reservoir | Best for | Cat# |
| 30 mg | 1 mL | Method development, trace bioanalysis (low sample load) | 15011079 |
| 100 mg | 1 mL | Routine urine/plasma screening (1-2 mL sample) | 15011080 |
| 200 mg | 3 mL | Standard bioanalysis, moderate matrix load | 15011082 |
| 500 mg | 3 mL | Higher loading, dirty matrices (e.g., plasma) | 15011083 |
| 200 mg | 6 mL | Low loading but larger reservoir (automation) | 15011084 |
| 500 mg | 6 mL | General purpose, environmental water (100-500 mL) | 15011085 |
| 1 g | 6 mL | High loading, large-volume water (>500 mL), dirty samples | 15011086 |
| 1 g | 12 mL | Large-volume biological fluids, preparative cleanup | 15011087 |
| 2 g | 12 mL | Very high loading, industrial scale | 15011088 |
All formats compatible with standard SPE manifolds, vacuum systems, and automated SPE workstations (Thermo, Horizon, Biotage, etc.).
Download PDF Datasheet
Technical Specifications
| Parameter | Value |
| Sorbent | Benzenesulfonic acid bonded silica |
| Functional group | -C₆H₄-SO₃H (permanently charged, pKa < 1) |
| Particle size | 40-75 μm |
| Pore size | 70 Å |
| Surface area | 480-530 m²/g |
| Carbon content | 9% |
| Retention mechanism | Strong cation exchange (primary) + mild hydrophobic under high organic |
| pH stability | 1-12 |
| Max temperature | ≤60°C |
Frequently Asked Questions
Can SCX SPE retain weak bases?
Yes, but weak bases (pKa 5-7) require careful pH control. For loading, the pH must be at least 2 units below the analyte pKa to ensure full protonation. If weak bases are poorly retained, consider using PRS (propylsulfonic acid), which eliminates non-specific π-π interaction and often gives cleaner recovery.
What pH should be used for SCX SPE?
Load and wash at pH 2-6. This ensures basic drugs (pKa typically 8-10) are positively charged. The sorbent remains ionized across the entire pH range. Elute with basic organic solvent (e.g., 5% NH₄OH in methanol) to neutralize the analytes and break the ionic bond.
SCX vs C18 SPE – which is better for drugs of abuse?
For basic drugs of abuse (amphetamines, opioids, benzodiazepines), SCX is superior. It retains protonated amines via strong ionic interaction, while C18 provides only weak hydrophobic retention at low pH. SCX gives higher and more reproducible recoveries, especially from urine. For neutral or weakly basic drugs, C18 may be sufficient, but SCX remains the preferred choice for regulated forensic and clinical methods.
Do you provide batch – specific COA?
Yes. COA including particle size, surface area, and cation exchange capacity verification is available for each production lot.
Are free samples available?
Yes. Qualified labs can request free SCX cartridges. Email sales@hawach.com with your application and target analytes.
Can SCX be used with automated SPE systems?
Yes. All our SCX cartridges (1 mL, 3 mL, 6 mL, 12 mL) are compatible with major automated SPE platforms (Thermo, Horizon, Biotage, etc.).
Why Procurement Teams Choose Hawach SCX SPE Cartridges
- Direct replacement for Waters Sep-Pak SCX, Agilent Bond Elut SCX – same protocols, no method revalidation
- Cost-effective– 30-40% lower price than leading brands with equivalent performance
- High surface area (480-530 m²/g) – better loading capacity than many standard SCX products
- In-stock– standard formats ship within 3-5 business days
- OEM & private label– custom cartons, pouches, bulk sorbent, and private labeling
- Full documentation– COA and lot traceability for GMP/GLP compliance
- Free samples for qualified labs – test before you buy
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