Ultra-low level determination of phosphorus, sulfur, silicon and chlorine using the Agilent 8900 ICP-QQQ

Significance of the Topic

The quantification of phosphorus, sulfur, silicon and chlorine at ultra-trace levels is critical for semiconductor manufacturing, high-purity chemical production and stringent quality control. These non-metallic impurities exhibit high ionization potentials and are prone to polyatomic spectral interferences, challenging conventional ICP-MS techniques. The development of triple quadrupole ICP-MS (ICP-QQQ) with MS/MS capability offers enhanced interference removal and sensitivity to meet industry demands for reliable trace analysis.

Objectives and Study Overview

This application note evaluates the performance of the Agilent 8900 ICP-QQQ in MS/MS mode for measuring P, S, Si and Cl at ultra-low levels in ultrapure water (UPW) and high-purity hydrogen peroxide (H2O2). The goals are to demonstrate sub-ppb detection limits, low background equivalent concentrations (BECs) and robust interference elimination using optimized reaction cell conditions.

Methodology and Instrumentation

• Instrument: Agilent 8900 Triple Quadrupole ICP-MS (#200, semiconductor configuration) operated in MS/MS mode, employing Q1 and Q2 mass filters to control cell chemistry and reject unwanted ions prior to the collision/reaction cell.
• Sample introduction: PFA concentric nebulizer, quartz spray chamber, quartz torch, platinum interface cones. Overnight rinse with 1% HNO₃ and plasma warm-up ensured system cleanliness.
• Operating parameters: RF power 1500 W; sampling depth 8.0 mm; carrier gas 0.70 L/min; makeup gas 0.52 L/min; extraction lenses 4.0 V and –210 V; Omega lens bias –80 V; Omega lens 8.0 V.
• Reaction cell tuning: – O₂ mass-shift mode for P and S (mass pairs 31→47, 32→48), O₂ flow 0.41 mL/min, OctpBias –3 V, KED –8 V, axial acceleration 1 V, cell exit –90 V, deflect 8 V. – H₂ on-mass mode for Si (28→28), H₂ flow 5.0 mL/min, OctpBias –18 V, KED 0 V, cell exit –70 V, deflect –6 V, plate bias –60 V. – H₂ mass-shift mode for Cl (35→37), H₂ flow 5.0 mL/min, OctpBias –18 V, KED 0 V, cell exit –70 V, deflect –6 V.
• Reagents and calibration: Single-element standards (SPEX CertiPrep) diluted in UPW (ORGANO). High-purity HCl for Cl standards. Standard addition calibration with 1% TMAH rinse for Cl analyses. Integration time 1 s per isotope.

Key Results and Discussion

Good linearity was observed at sub-ppb levels for P, S, Si and Cl in UPW and for P, S and Si in H2O2 using standard addition. Detection limits (3σ of blank, 1 s integration) and BECs were as follows:

• UPW: P BEC 10.5 ppt (DL 3.3 ppt), S BEC 75.4 ppt (DL 5.5 ppt), Si BEC 259 ppt (DL 14.7 ppt), Cl BEC 1.83 ppb (DL 0.28 ppb).
• H2O2: P BEC 16.2 ppt (DL 2.3 ppt), S BEC 244 ppt (DL 12.5 ppt), Si BEC 492 ppt (DL 18.8 ppt).

The MS/MS configuration effectively eliminated major polyatomic overlaps (e.g., 16O2+ on S, 14N16O+ on P, 14N2+ on Si, 16O18O1H+ on Cl), yielding the lowest reported BECs for these elements in UPW.

Benefits and Practical Applications of the Method

• Reliable interference removal via dual mass filters and tailored reaction cell chemistry.
• Sub-ppt detection limits enabling trace impurity monitoring in semiconductor-grade chemicals.
• Simultaneous multi-element analysis of non-metallic contaminants in ultrapure matrices.
• Robust workflow suitable for QA/QC laboratories requiring high sensitivity and throughput.

Future Trends and Potential Applications

• Expansion of reaction gas chemistries to target additional challenging analytes (e.g., boron, fluorine).
• Integration with automated sample introduction and data processing for high-throughput screening.
• Standardization of ICP-QQQ protocols across industries to ensure method reproducibility and regulatory compliance.
• Coupling ICP-QQQ with separation techniques (e.g., LC, GC) for speciation and process monitoring.

Conclusion

The Agilent 8900 ICP-QQQ in MS/MS mode with O₂ and H₂ reaction gases achieved exceptional removal of spectral interferences and delivered ultra-low detection limits for phosphorus, sulfur, silicon and chlorine in UPW and for phosphorus, sulfur and silicon in high-purity H₂O₂. The second-generation triple quadrupole system offers a powerful solution for the trace analysis of non-metallic impurities in critical industry applications.

References

1. Agilent 8800 ICP-QQQ Application Handbook, 2015, 5991-2802EN
2. S. D. Fernández, N. Sugiyama, J. R. Encinar and A. Sanz-Medel, Triple Quad ICP-MS (ICP-QQQ) as a New Tool for Absolute Quantitative Proteomics and Phosphoproteomics, Anal. Chem., 2012, 84, 5851-5857
3. N. Sugiyama, Trace level analysis of sulfur, phosphorus, silicon and chlorine in NMP using the Agilent 8800 Triple Quadrupole ICP-MS, Agilent application note, 2013, 5991-2303EN