Unmatched Removal of Spectral Interferences in ICP-MS Using the Agilent Octopole Reaction System with Helium Collision Mode

Importance of the Topic

The accurate quantification of trace metals by inductively coupled plasma mass spectrometry is fundamental to environmental, clinical, industrial and quality control laboratories. Spectral interferences arising from plasma-derived and sample matrix–derived polyatomic ions can severely compromise data quality, especially in complex or variable matrices. The ability to remove these interferences efficiently under a single set of operating conditions greatly simplifies method development and enhances the reliability of multi-element screening workflows.

Objectives and Study Overview

This study investigates the multi-element interference-removal capability of the Agilent 7500ce ICP-MS equipped with an octopole reaction system operated in helium collision mode. A highly complex synthetic matrix was used to generate a wide range of polyatomic overlaps across the mid-mass region. The primary goal was to demonstrate that a single helium cell gas flow rate and voltage configuration can attenuate both plasma-based and matrix-based interferences for numerous analytes without individual method optimization.

Methodology and Instrumentation

A synthetic matrix containing 1 % HNO3, 1 % HCl, 1 % H2SO4, 1 % butan-1-ol and 100 mg/L each of Na and Ca was prepared to simulate worst-case interferences. Spectra were acquired in no-gas mode and with 5.5 mL/min helium added to the octopole cell. No targeted tuning was performed for specific analytes. A multi-element spike (5 ppb of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, As and Se) was introduced to assess analyte recovery.

Used Instrumentation

• Agilent 7500ce ICP-MS
• Octopole Reaction System (ORS) with helium collision mode
• ShieldTorch grounded interface

Main Results and Discussion

In no-gas mode, strong background peaks from ArO+, Ar2+, ClO+, S2+ and other matrix-derived polyatomics obscured key analyte isotopes between m/z 50 and 84. Introducing helium collision gas removed all high-intensity plasma- and matrix-based interferences via kinetic energy discrimination. Expanded-scale spectra confirmed suppression of low-level interferences. The 5-ppb spike recoveries for all targeted elements showed clear isotopic patterns free from overlap, with only minor residual ArOH+ and Ar2+ signals at m/z 57 and 80.

Benefits and Practical Applications of the Method

• Universal interference removal under one set of conditions for all analytes and matrices
• Access to major isotopes previously unusable due to overlaps (for example 52Cr, 56Fe, 63Cu, 64Zn)
• Simultaneous multi-element screening without per-element method development
• Flexibility in sample preparation chemistry, including HCl and H₂SO₄ digestions
• Compatibility with transient signals from chromatography or laser ablation
• Enables dual-isotope confirmation of results without additional tuning

Future Trends and Potential Applications

Advances may include integration of helium collision mode with laser ablation systems, enhanced data-processing algorithms for real-time interference monitoring, and automated cell-gas control for dynamic method adaptation. Further exploration of alternative inert gases, cell geometries or combined collision/reaction strategies could extend applicability to ultra-trace isotope ratio measurements and emerging sample matrices.

Conclusion

The Agilent 7500ce ICP-MS operated in helium collision mode provides a robust, universal approach to remove all polyatomic interferences across a broad mass range using a single cell gas flow and voltage setting. This eliminates the need for reactive gases, extensive method development, and sample-specific tuning, streamlining multi-element trace analysis in complex and unknown matrices.

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