Application of Nutech Preconcentrator Coupled with GC-MS in the Analysis of Trace Impurities in Fuel Hydrogen

Background Introduction

Hydrogen fuel cell vehicles are a key application of hydrogen energy. The purity and impurity content of hydrogen fuel have a significant impact on the discharge performance and lifespan of hydrogen fuel cells. Among the impurities that must be controlled for hydrogen used in fuel cells, sulfur-containing compounds are severe catalyst poisons, causing irreversible declines in fuel cell performance even at extremely low concentrations. Formaldehyde and halogenated compounds can adsorb onto the catalyst, negatively affecting the power performance of the fuel cell. The China standard “Hydrogen Fuel for Proton Exchange Membrane Fuel Cell Vehicles” (GB/T 37244-2018) specifies strict limits for sulfur-containing compounds (<4 nmol/mol), formaldehyde (<0.01 μmol/mol), and halogenated compounds (<0.05 μmol/mol).

To enable accurate and efficient measurement of these ultra-trace impurities in hydrogen, the National Standardization Administration released the standard “Determination of Sulfur-Containing Compounds, Formaldehyde, and Organic Halides in Hydrogen for Proton Exchange Membrane Fuel Cell Vehicles by Gas Chromatography” (GB/T 44243-2024) on July 24, 2024, which came into effect on November 1, 2024. This standard provides a validated method for the determination of sulfur-containing compounds, formaldehyde, and organic halides in fuel cell hydrogen.

The GB/T 44243-2024 standard employs a pre-concentrator to enrich target analytes. The desorbed sample is separated using a GC column and then directed through a splitting assembly and connection column. One pathway is analyzed by a sulfur chemiluminescence detector (SCD) for sulfur-containing compounds, while the other pathway is analyzed by a mass spectrometer (MS) for formaldehyde and organic halides. This method requires a GC-SCD/MS or a GC-SCD system to analyze sulfur-containing compounds as specified in the standard. For laboratories equipped only with a GC-MS, modifications are necessary, including the addition of a splitting assembly, connection column, and SCD detector, or the procurement of an additional GC-SCD. This imposes high demands on instrument configuration and operator proficiency.

Nutech Testing Solution

After optimizing and upgrading its existing 8910 preconcentrator, Nutech has developed a solution that, when paired with a GC-MS, enables simultaneous separation and analysis of sulfur-containing compounds, formaldehyde, organic halides, and dozens of other target analytes using only a mass spectrometer. This solution features simple operation and excellent sensitivity.

The analytical system requires no modifications to the GC-MS, allowing for direct integration with GC-MS systems. It can also be flexibly combined with existing GC-SCD/MS or GC-SCD systems, offering versatile configurations and reducing overall costs.

Figure 1 Workflow Diagram of the Pre-Concentrator

The pre-concentrator employs liquid nitrogen cooling and uses a specially designed spiral cold trap to capture target compounds. All tubing, valves, and other flow path components are inert-treated, with a streamlined and rational workflow design to minimize adsorption losses of analytes and ensure complete recovery of target compounds. With a concentration factor exceeding 1000-fold, the system effectively lowers the detection limits of analytical instruments, achieving precision that meets standard requirements. The system features:

1. Fully inert-treated flow paths with the shortest route to the trap, reducing adsorption losses in tubing.
2. Specialized cold trapping and secondary focusing, enhancing sensitivity for target compounds.
3. Single MS detector analysis, enabling all target compounds to be analyzed in one injection.

Analysis Results

The sample is introduced into the pre-concentrator, where target compounds are captured, focused, and desorbed. The desorbed sample is then introduced into a gas chromatograph equipped with a non-polar capillary column. After separation by the column, the analytes are directed into a mass spectrometer for detection of target compounds, with quantification performed using an external standard method.

The total ion chromatogram (TIC) of a mixed standard containing sulfur-containing compounds, formaldehyde, and organic halides, after enrichment by the pre-concentrator and analysis by the gas chromatography-mass spectrometry system, is shown in Figure 2.

Figure 2 Total Ion Chromatogram (TIC) of Sulfur-Containing Compounds, Formaldehyde, and Organic Halides

Nutech offers a comprehensive mass spectrometry-based solution for analyzing sulfur-containing compounds, formaldehyde, and organic halides in hydrogen for fuel cells. The correlation coefficients, detection limits, and precision of the target components fully meet the requirements of the standard.

Table 1: Test Data for Selected Compounds

Conclusion

This solution uses the Nutech 8910 series pre-concentration instrument combined with GCMS to analyze 13 sulfur-containing compounds, formaldehyde, and 35 organic halides in fuel hydrogen. The method’s detection limits range from 0.003 to 0.108 nmol/mol, with linear correlation coefficients (R2) between 0.9944 and 0.9999, and precision ranging from 0.5% to 2.3%. The method’s detection limits, linearity, and precision meet the requirements of the “Proton Exchange Membrane Fuel Cell Vehicle Hydrogen – Determination of Sulfur Compounds, Formaldehyde, and Organic Halides by Gas Chromatography” (GB/T 44243-2024) standard. This solution provides a reference for impurity analysis in fuel hydrogen, offers data support for instrument selection such as gas concentrators in hydrogen impurity analysis, and ensures robust hydrogen quality control.