Comparison of Sensitivity for Sulfur Compound Species by Nexis™ SCD-2030: Equimolar Sensitivity Measurement

Importance of the Topic

Quantitative detection of sulfur compounds is essential across environmental monitoring, petrochemical quality control and flavour analysis. Precise measurement of total sulfur or specific sulfur‐containing species informs regulatory compliance, process optimization and product safety.

Study Objectives and Overview

This work evaluates the equimolar sensitivity of a Sulfur Chemiluminescence Detector (SCD) for various sulfur compounds using the Shimadzu Nexis SCD-2030. A comparative experiment with a Flame Photometric Detector (FPD(S)) assesses how each detector’s response scales with the number of sulfur atoms in the analyte.

Methodology and Instrumentation Used

• Gas chromatograph: Nexis GC-2030 with AOC-20i Plus auto-sampler
• Column: SH-Rtx-1 capillary (30 m × 0.25 mm I.D., 0.25 µm film)
• Injection: 0.5 µL split (1:50) at 220 °C
• Carrier gas: Helium, linear velocity 30 cm/s; purge 3 mL/min
• Oven program: 50 °C (3.5 min) to 200 °C at 30 °C/min, then to 250 °C at 25 °C/min (2 min)
• Detector conditions:
   SCD furnace 850 °C; H₂ 100 mL/min; N₂ 10 mL/min; O₂ 12 mL/min; O₃ 25 mL/min
• Comparative detector: Flame Photometric Detector optimized for sulfur

Mixed Standard Preparation

Three mixtures of sulfur compounds (10 µg/mL each) were prepared. Compounds contained one to three sulfur atoms per molecule to test linear scaling. Relative molar sensitivity (RMS) was calculated as peak area divided by moles of sulfur atoms, normalized to diisopropyl sulfide (one S atom).

Key Results and Discussion

• SCD Response Linearity: RMS values increased proportionally with sulfur atom count. Linear regression slope ~1.03 indicated near‐ideal equimolar sensitivity.
• FPD(S) Response Variability: No consistent linear relationship; responses for di- and tri-sulfides deviated due to reliance on S₂ chemiluminescence.
• Radar Chart Comparison: For single‐sulfur compounds, SCD exhibited more uniform sensitivities relative to FPD(S), highlighting superior equimolar behaviour.

Benefits and Practical Applications

• Unknown Sulfur Compounds: Enables approximate quantitation based on total sulfur atoms without pure standards of each species.
• Process Monitoring: Rapid total sulfur content determination in petroleum streams, environmental samples and food matrices.
• Quality Control: Improved accuracy and reproducibility in regulatory compliance testing.

Future Trends and Applications

• Coupling with High‐Resolution GC: Enhanced separation of trace sulfur species prior to equimolar detection.
• Automated Data Evaluation: Software algorithms to predict total sulfur content in complex matrices.
• Miniaturized and Field‐Deployable Systems: Portable SCD units for on‐site environmental monitoring.

Conclusion

The Shimadzu Nexis SCD-2030 demonstrates robust equimolar sensitivity for sulfur compounds containing one to three sulfur atoms. This characteristic enables reliable quantitation of total sulfur content without compound‐specific calibration, outperforming conventional FPD(S) in linearity and consistency.