Your IC results are only as good as your sample vials

Importance of the Topic

In ion chromatography (IC), the choice of sample vials critically influences analytical accuracy. Polymeric vials may release trace organic and inorganic ions into samples. These leachables can obscure genuine analyte signals, especially at low microgram-per-liter levels, making vial quality a pivotal factor in trace IC workflows.

Objectives and Study Overview

• Compare leaching behavior of various polymeric vials from different suppliers.
• Assess initial and 12-hour leaching of key anions (F⁻, Cl⁻, NO₂⁻, Br⁻, NO₃⁻, HPO₄²⁻, SO₄²⁻), cations (Li⁺, Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺), and common organic acids.
• Develop recommendations to minimize vial-derived contamination for ultratrace IC applications.

Methodology and Instrumentation

• Vials produced from healthcare-grade polypropylene under cleanroom (ISO 14644 class 7) conditions.
• Leaching tests: fill vials with ultrapure water (≥18.2 MΩ·cm, TOC <5 µg/L), analyze immediately and after 12 hours.
• Anion analysis via Metrohm ProfIC Vario 9.1 with inline eluent production (941 module), MiPCT-ME preconcentration, Metrosep A Supp 7 column, conductivity detection.
• Cation analysis via ProfIC Vario 15 with partial-loop injection (MiPT), Metrosep C Supp 2 column, sequential suppression.
• Ultrapure water supplied by ELGA Purelab® flex 6 for both eluent preparation and sample handling.

Main Results and Discussion

• Metrohm vials met stringent criteria (<1 µg/L for inorganic ions, <5 µg/L for organic acids) both at initial fill and after 12 hours.
• Third-party vials exhibited elevated levels of acetate, formate, chloride, sodium, and ammonium, often exceeding 1 µg/L thresholds.
• Prerinsing protocol (three 10 mL rinses) further reduced blank signals, enabling direct detection below 0.6 µg/L for critical analytes.
• Testing of different geometries (11 mL tubes, 125 mL bottles, 50 mL tubes, culture flasks) showed compliance with cation limits when rigorous prerinsing is applied, though atmospheric ammonium remains a variable.

Benefits and Practical Applications

• Ensures accurate trace-level quantification in environmental, pharmaceutical, and quality-control laboratories.
• Reduces background noise and column maintenance via inline eluent production and clean handling.
• Offers a simple prerinsing procedure to achieve ultratrace detection limits without extensive downtime.

Future Trends and Applications

• Design of new polymeric materials with inherently lower extractables.
• Automation of vial cleaning within sample processors.
• Advancements in suppression and detection to extend IC sensitivity.
• Establishment of universal vial-quality standards for trace analysis.

Conclusion

Vial purity is a fundamental determinant of reliable trace IC outcomes. Metrohm’s controlled production and rigorous leaching validation guarantee minimal background contamination. Combined with ultrapure water use, inline eluent generation, and a formal prerinsing routine, these practices support robust ultratrace analyses below the microgram-per-liter level.

Reference

• Metrohm White Paper WP-049EN, August 2019.