Reaching sub-ppm limits of detection for carbon, nitrogen and oxygen with the Element GD Plus GD-MS

Importance of the topic

In industries producing semiconductor materials and high-purity metals, trace levels of gas-phase impurities such as carbon, nitrogen, and oxygen critically affect material performance and reliability. Achieving accurate sub-ppm detection of these elements ensures product quality, reduces rework, and fosters better process control.

Objectives and study overview

This technical note aims to demonstrate how the CNO option for the Thermo Scientific Element GD Plus glow discharge mass spectrometer enables simultaneous quantification of carbon, nitrogen, and oxygen at sub-ppm levels. The study evaluates the design of the CNO gas purification system, outlines calibration strategies, and assesses detection limits in a copper matrix.

Methodology and instrumentation

• Instrument: Thermo Scientific Element GD Plus GD-MS equipped with CNO option (moisture trap, heated gas purifier, high-purity valve, stainless steel capillaries).
• Sample preparation: High-purity copper standard with low baseline C, N, O content.
• Operating conditions: Fast-flow GD source at 1000 V discharge voltage, ≈13 mA current, pulsed DC (2 kHz, 75 µs), source vacuum 1.06 mbar, Ar flow ≈500 mL/min, resolution 4000.
• Pre-sputtering: 90 s at 60 mA DC for surface cleaning, followed by stabilization period of 40–60 min.

Main results and discussion

The purified argon gas stream achieved stable low backgrounds for carbon, nitrogen, and oxygen. Calibration in iron and copper matrices produced relative sensitivity factors (RSF) of 2.03 for C, 409 for N, and 102 for O in copper. Limits of detection (3σ) were determined by repeating analyses:

• Carbon: 0.05 ppm mass fraction
• Nitrogen: 0.12 ppm mass fraction
• Oxygen: 0.5 ppm mass fraction

These sub-ppm detection levels reflect high signal-to-noise ratios, minimal polyatomic interferences, and rapid sample exchange.

Benefits and practical applications

• Simultaneous multi-element analysis of metallic and non-metallic impurities.
• Fast sample turnaround: < 1 min pump-down, < 2 min exchange.
• Elimination of supplementary combustion analyzers for gas elements.
• Wide sample compatibility, including porous materials without liquid nitrogen.

Future trends and potential applications

Continued improvements in discharge gas purification and source design may push detection limits into the sub-ppb range. Integration with automation and advanced data processing could enable high-throughput screening in semiconductor fabs, battery material quality control, and research on ultra-high-purity alloys.

Conclusion

The CNO option for the Element GD Plus GD-MS significantly enhances trace analysis capabilities for carbon, nitrogen, and oxygen, achieving sub-ppm detection limits. Combined with a fast-flow source design and streamlined sample handling, this platform provides a robust solution for high-purity material characterization.

Reference

Thermo Fisher Scientific. Technical Note 001935: Reaching sub-ppm limits of detection for carbon, nitrogen and oxygen with the Element GD Plus GD-MS.