Hydrogen content determination by picoSpin NMR

Importance of the Topic

Determination of hydrogen content in petroleum fuels is essential for assessing energy yield, fuel quality and compliance with industry standards. Higher hydrogen-to-carbon ratios correlate with greater combustion efficiency and lower oxidation states, making hydrogen quantification a key parameter in fuel characterization and process control.

Objectives and Overview

This application note evaluates the Thermo Scientific picoSpin 80 Series II benchtop NMR spectrometer as a cost-effective and flexible alternative to existing time-domain and high-field NMR methods. Reference compounds and standard fuel mixtures were analyzed to compare precision, accuracy and operational simplicity against established methods.

Methodology and Instrumentation

The study employed a pulsed 1H NMR spectrometer operating at 82 MHz with a 2 Tesla temperature-controlled permanent magnet held at 36 °C. Samples were introduced via a 40 µL capillary cartridge. Hexamethyldisiloxane (HMDSO) served as an internal standard due to its chemical inertness, high boiling point and non-overlapping 1H signal. Typical acquisition parameters included:

• 16 scans
• 4000 data points
• 40 s recycle delay

Hydrogen content was calculated from the relative integrated peak areas of sample and HMDSO signals, combined with their known masses and the 11.17 wt % H content of HMDSO.

Main Results and Discussion

Precision and accuracy were assessed on six reference compounds with theoretical hydrogen contents of 7–15 wt %. Five replicate measurements yielded relative standard deviations below 1 % (average 0.44 %). Relative errors versus theoretical values ranged from 0.56 % to 2.59 %, consistent with high-field NMR literature.

Three ASTM fuel standards (D5307, D5580, D5134) were also analyzed. Measured hydrogen contents were within ±1 % relative error of theoretical values, and precision ranged from 0.41 % to 0.83 % RSD. These results validate the picoSpin 80’s capability to match high-field performance in hydrogen determination.

Benefits and Practical Applications

The picoSpin 80 Series II spectrometer offers:

• Low cost of ownership and minimal maintenance
• Benchtop footprint with no dedicated facility requirements
• Non-destructive analysis allowing repeat measurements
• Comparable accuracy and precision to high-field NMR for hydrogen quantification

This makes it suitable for QC/QA laboratories, fuel production sites and research settings requiring routine hydrogen analysis.

Future Trends and Potential Applications

Emerging developments may include:

• Expanded pulse sequences for multi-nuclear or structural analysis
• Automated sample handling and integration with process analytics
• Portable or field-deployable benchtop NMR systems
• Application to alternative fuels, biofuels and complex hydrocarbon matrices

Conclusion

The Thermo Scientific picoSpin 80 Series II benchtop NMR spectrometer delivers reliable hydrogen content measurements in petroleum reference materials and fuel standards. It matches the accuracy and precision of high-field NMR while reducing cost and operational complexity, supporting its adoption for routine hydrogen analysis in diverse laboratory environments.

Used Instrumentation

• picoSpin 80 Series II benchtop NMR spectrometer
• 82 MHz pulsed Fourier transform 1H NMR
• 2 T temperature-controlled permanent magnet at 36 °C
• 40 µL capillary cartridge sample introduction

References

1. Mondal S.; Kumar R.; Bansal V.; et al. J. Anal. Sci. Technol. 2015, 6, 24.
2. ASTM D5291. Standard Test Methods for Instrumental Determination of Carbon, Hydrogen, and Nitrogen in Petroleum Products and Lubricants. ASTM, 1992.
3. ASTM D3701. Standard Test Method for Hydrogen Content of Aviation Fuels by Low Resolution Nuclear Magnetic Resonance Spectroscopy. ASTM, 1992.
4. ASTM D4808. Standard Test Methods for Hydrogen Content of Light Distillates, Middle Distillates, Gas Oils, and Residua by Low Resolution Nuclear Magnetic Resonance Spectroscopy. ASTM, 1992.
5. ASTM D7171. Standard Test Method for Hydrogen Content of Middle Distillate Petroleum Products by Low-Resolution Pulsed Nuclear Magnetic Resonance Spectroscopy. ASTM, 2011.
6. Khadim M. A.; Wolny R. A.; Al-Dhuwaihi A. S.; et al. Arab. J. Sci. Eng. 2003, 28 (2A), 147–162.