Trace Analysis of 10 Volatile Sulfur Compounds in Air Using Canister Sampling and Nutech 8910 Preconcentrator with GC–FPD

Overview

Volatile sulfur compounds are important target pollutants in ambient air and fugitive emissions. Their accurate determination can be technically challenging because compounds such as hydrogen sulfide and thiols are chemically reactive and susceptible to adsorption, surface loss and carryover. Consequently, the inertness of the sampling and analytical flow path is critical to method sensitivity, recovery and repeatability.

This application study evaluated the performance of a fully inertized Nutech 8910 preconcentration system for the determination of 10 volatile sulfur compounds using canister sampling, three-stage cryogenic preconcentration and gas chromatography with flame photometric detection (GC–FPD).

Under the selected analytical conditions, all 10 compounds were effectively separated. Correlation coefficients ranged from 0.9985 to 0.9996, while method detection limits ranged from 0.02 to 0.09 µg/m³. Precision and spike-recovery experiments at three concentration levels also demonstrated reliable quantitative performance.

Keywords: volatile sulfur compounds, canister sampling, Nutech 8910 preconcentrator, GC–FPD, ambient air, fugitive emissions

Target Compounds

The method covers the following 10 volatile sulfur compounds:

1. Hydrogen sulfide
2. Carbonyl sulfide
3. Methanethiol
4. Ethanethiol
5. Dimethyl sulfide
6. Carbon disulfide
7. Ethyl methyl sulfide
8. Thiophene
9. Diethyl sulfide
10. Dimethyl disulfide

Instrumentation

The analytical system consisted of:

• Nutech 8910 Preconcentrator
• Nutech 2208 Precision Static Dilutor
• Nutech 2104 Canister Cleaning System
• Nutech 3608L Autosampler
• Nutech sampling canisters
• Thermo Scientific TRACE 1600 gas chromatograph equipped with a flame photometric detector

Figure 1. Complete canister-based sulfur compound monitoring system integrating Nutech sample preparation instruments with GC–FPD.

Gases and Standards

A mixed sulfur-compound gas standard containing all 10 target compounds was used for calibration and method validation.

The gases used in the analytical system included:

• Vaporized nitrogen from a liquid-nitrogen Dewar, purity ≥99.999%
• High-purity hydrogen, purity ≥99.999%
• High-purity air

Analytical Conditions

Preconcentration Conditions

GC Conditions

Column: DB-624

Oven temperature program:

• Hold at 35°C for 10 min
• Ramp at 20°C/min to 120°C
• Hold at 120°C for 2 min
• Ramp at 25°C/min to 220°C
• Hold at 220°C for 2.5 min

Total GC run time: 22.75 min

Calibration Strategy

Two working-standard concentration levels were prepared using the Nutech 2208 Precision Static Dilutor.

The low-level working standard was introduced at 50, 100 and 200 mL. The high-level working standard was introduced at 100, 200 and 400 mL.

Equivalent calibration concentrations were calculated on the basis of a 400 mL sample volume:

Equivalent calibration concentration = Working standard concentration × (Introduction volume ÷ 400 mL)

Calibration Levels

Calibration curves were established using the logarithm of the analyte mole fraction as the x-axis and the logarithm of the corresponding chromatographic peak area as the y-axis.

Method Detection Limits

The lowest calibration level was analyzed seven consecutive times. The standard deviation was calculated, and the method detection limit was determined using:

MDL = t(n−1, 0.99) × s

where:

• n = 7
• t = 3.143
• s is the standard deviation of the seven replicate measurements

Precision and Spike-Recovery Evaluation

Blank samples were spiked at low, medium and high concentration levels. Six replicate analyses were performed at each level to determine method precision and spike recovery.

Results and Discussion

Chromatographic Separation

Under the selected preconcentration and GC conditions, all 10 target sulfur compounds were effectively separated. The chromatographic peaks were symmetrical, the baseline remained stable, and the separation between adjacent peaks was sufficient for qualitative identification and quantitative analysis.

1. Hydrogen sulfide；2. Carbonyl sulfide；3. Methanethiol；4. Ethanethiol；5. Dimethyl sulfide；6. Carbon disulfide；7. Ethyl methyl sulfide；8. Thiophene；9. Diethyl sulfide；10. Dimethyl disulfide

Figure 2. Chromatogram of the 10 target volatile sulfur compounds.

Calibration Performance and Detection Limits

The correlation coefficients obtained for the 10 target compounds ranged from 0.9985 to 0.9996, demonstrating a consistent calibration response over the evaluated concentration range.

Method detection limits ranged from 0.01 to 0.04 nmol/mol, corresponding to 0.02 to 0.09 µg/m³.

Figure 3. Calibration curves for the 10 target volatile sulfur compounds.

Precision and Spike Recovery

At the low, medium and high spike levels, the relative standard deviation ranges were:

• Low level: 1.10%–2.98%
• Medium level: 0.69%–6.14%
• High level: 0.17%–1.79%

The corresponding spike-recovery ranges were:

• Low level: 93.9%–107.9%
• Medium level: 90.6%–113.9%
• High level: 100.1%–124.3%

These results demonstrate repeatable enrichment and quantitative transfer across the evaluated concentration range.

Low-Level Spike Results

Medium-Level Spike Results

High-Level Spike Results

Conclusion

The Nutech 8910 Preconcentrator coupled with GC–FPD provided effective preconcentration, separation and quantification of 10 volatile sulfur compounds at trace concentrations.

The combination of a fully inertized sample flow path and three-stage cryogenic trapping helped minimize analyte adsorption, surface loss and carryover. The system achieved correlation coefficients of 0.9985–0.9996, method detection limits of 0.02–0.09 µg/m³, and repeatable performance across three spike levels.

The results demonstrate that the Nutech preconcentration system provides a reliable analytical platform for monitoring volatile sulfur compounds in ambient air and at fugitive-emission monitoring locations.