Importance of Vial Selection in LC and LC/ MS Analysis: Effects on Analysis of Alkaline Metals from Glass

Significance of the Topic

The choice of sample vials in liquid chromatography (LC) and LC/mass spectrometry (LC/MS) critically affects analytical sensitivity and reproducibility, especially for trace‐level compounds. Adsorption of analytes on vial surfaces and elution of metal ions from glass can reduce recovery and alter ionization behavior, leading to inaccurate quantitation and unexpected adduct formation.

Objectives and Study Overview

This study evaluated how sodium and other alkaline metals eluted from standard borosilicate glass vials influence adsorption of basic compounds and LC/MS adduct profiles. Two specially treated glass vials (Shim-vial S and Shim-vial H) were compared with conventional vials to assess their performance in minimizing metal elution and compound loss.

Methodology

Atomic absorption spectroscopy quantified sodium released into water from different vial types. Adsorption of the basic compound chlorhexidine (1 mg/L) was measured by HPLC-UV at 254 nm after storage at 40 °C for 24 and 72 hours. The recovery rate was benchmarked against polypropylene vials. For LC/MS evaluation, 5 mg/L meloxicam solutions were allowed to equilibrate for 48 hours before analysis. Adduct formation (H+, Na+, K+, NH4+, Fe+, Cu+) was quantified in ESI-positive SIM mode.

Used Instrumentation

• Atomic absorption spectrophotometer for sodium measurement
• HPLC system with Shim-pack XR-ODS (100 mm × 3.0 mm, 2.2 µm) column, mobile phase sodium perchlorate/phosphoric acid–acetonitrile (55:45), 0.5 mL/min, 5 µL injection, UV detection at 254 nm, column at 40 °C
• LC/MS with ESI-positive ionization, SIM monitoring of m/z 352, 359, 374, 391, 407, 414; flow rate 0.2 mL/min, 1 µL injection, sample at 15 °C

Main Results and Discussion

Shim-vial H exhibited the lowest sodium elution among all tested vials, followed by Shim-vial S and conventional glass. Chlorhexidine recovery in Shim-vial H remained above 95 % over 72 hours, while higher sodium levels in other vials correlated strongly with decreased recovery (correlation coefficient –0.77). In LC/MS analysis, Shim-vial H showed the highest protonated meloxicam adduct ratio and minimal sodium and other metal adduct formation, demonstrating that reduced metal elution preserves sensitivity at the target m/z.

Benefits and Practical Applications

Using low-elution, low-adsorption vials enhances trace‐level detection by preventing analyte loss and limiting formation of interfering adducts. This leads to more accurate quantitation, improved method robustness, and greater confidence in LC and LC/MS workflows across pharmaceutical, environmental, and food analysis laboratories.

Future Trends and Potential Applications

Advances may include new surface coatings or alternative vial materials that further suppress metal release and nonspecific binding. Integration of such vials into high-throughput and miniaturized LC/MS platforms will support ever-lower detection limits. Standardization of low-adsorption containers could become part of regulatory guidelines to ensure consistent trace analysis results.

Conclusion

Elution of alkaline metals from glass vials significantly impacts adsorption of basic analytes and adduct formation in LC/MS. Specialized treatments that remove or passivate metal ions, as in Shim-vial H and S, yield superior recovery and reproducibility. Selecting appropriate vials is essential for reliable trace‐level chromatography and mass spectrometry.

References

1. Fundamentals of Inorganic Glasses, 4 (1994)
2. U.S. Pharmacopeia 41-NF36, General Chapter <1660> (2017)
3. npj Materials Degradation, 5, 15 (2021)
4. Journal of Pharmaceutical and Biomedical Analysis, 213 (2022)