Comprehensive Guide to Ion Chromatography (IC) Systems: Selection, Operation & Maintenance

Ion chromatography (IC), as an essential analytical tool for detecting anions, cations, and organic acids, requires meticulous attention to instrument selection, operation protocols, and maintenance practices to ensure data accuracy and extended equipment lifespan. This guide provides a systematic approach—from initial setup to routine care—beneficial for both new users and experienced operators seeking optimized workflows.

1. Scientific Instrument Selection: Matching Needs with Specifications

Key Considerations:

• Analytical Targets:
  • Ion types (e.g., Cl⁻, SO₄²⁻, Na⁺, Ca²⁺)
  • Concentration range (trace μg/L vs. bulk analysis)
  • Sample matrix (aqueous, soil extracts, biological samples)
• System Configuration:
  • Pump system (HPLC-grade for high pressure)
  • Suppressor (chemical/electrolytic)
  • Detector (conductivity, amperometric, or UV-Vis)
  • Optional: Autosampler (high throughput), column oven (temperature-sensitive analyses), online sample prep (complex matrices)
• Detector Selection:
  • Conductivity (LOD 1–10 μg/L, general-purpose)
  • Amperometric (LOD 0.1 μg/L, for I⁻, CN⁻, sulfides)
  • UV-Vis (LOD 10 μg/L, selective for NO₂⁻, BrO₃⁻)
• Domestic vs. Imported Systems:
  • Imported (￥800K–3M): Lower noise (<1 nS), RSD <0.5%, suppressor lifespan 3–5 years (ideal for research/labs).
  • Domestic (￥200K–800K): Cost-effective, noise <5 nS, RSD <1.5% (sufficient for environmental/QC labs).

2. Precision Operation: Method Development to Sample Handling

Method Optimization:

• Eluent Selection:
  • Anions: KOH (gradient) or Na₂CO₃/NaHCO₃ (isocratic)
  • Cations: Methanesulfonic acid (20 mM)
• Flow Rate: 1.0 mL/min (standard), up to 1.5 mL/min (fast analysis).
• Column Choice:
  • Anions: AS11-HC (high capacity) or AS18 (fast separation).
  • Cations: CS12A (general) or CS16 (Li⁺-specific).

Sample Preparation:

• Aqueous samples: Filter through 0.22 μm nylon membrane.
• Solid samples: Ultrasonic extraction (DI water, 60°C).
• Complex matrices: Use OnGuard RP cartridges for organic interference.

Critical Steps:

• Prime system to remove bubbles after eluent changes.
• Flush columns (>10 min) before connecting detectors.
• Monitor pressure, baseline noise, and peak shape for anomalies (e.g., drift, broadening, retention shifts).

3. Proactive Maintenance: Daily Care to Long-Term Storage

Routine Practices:

• Daily: Check system pressure/baseline noise.
• Weekly: Flush suppressor, replace inline filters, refresh DI water in reservoirs.
• Pump Care:
  • Avoid dry runs; flush with ultrapure water post-use.
  • For long idle periods (>15 days), purge with 20% methanol.

Component Replacement Schedule:

Column Preservation:

• Store in eluent (never pure water).
• For long storage:
  • Anion columns: 10 mM Na₂CO₃.
  • Cation columns: 20 mM methanesulfonic acid.

Detector Maintenance:

• Conductivity: Rinse cell with DI water to prevent salt buildup.
• UV-Vis: Turn off lamp when idle.
• Amperometric: Neutralize with DI water before shutdown.

Troubleshooting Common Issues:

• Baseline drift: Contaminated eluent or suppressor failure.
• Peak broadening: Column degradation or void volume.
• Sensitivity loss: Dirty detector or electrode aging.

4. Documentation & Best Practices

• Maintain a logbook for all maintenance, calibrations, and repairs.
• Regular training for operators on updated protocols.

By adhering to these guidelines, IC systems can deliver high-precision data while maximizing operational longevity.

(Compliant with ISO 17025 and EPA Method 300.0.)

Note: For model-specific protocols (e.g., Thermo Scientific™ Dionex™, Metrohm), always consult OEM manuals.