Thermo Prima PRO and Prima BT Process Mass Spectrometers - Quantitative analysis of bioethanol in biofuel production processes

Importance of the Topic

Bioethanol is a key renewable fuel derived by fermenting sugars from lignocellulosic biomass or synthesis gas. Continuous monitoring of off-gas composition (oxygen, carbon dioxide, ethanol) is critical for optimizing fermentation kinetics, maximizing yields and ensuring process control across scales from laboratory to industrial production.

Study Objectives and Overview

This application note evaluates the performance advantages of Thermo Scientific’s Prima BT and Prima PRO magnetic sector mass spectrometers for on-line quantitative analysis of bioethanol production. It compares precision, stability and linearity against quadrupole instruments and describes enhancements in ethanol detection via a glass-lined ion source.

Methodology and Instrumentation

Both systems employ a magnetic sector analyzer which accelerates ions through a flight tube and separates them by mass-to-charge ratio in a variable magnetic field. Key features include:

• Flat-topped ion peaks for high tolerance to mass drift
• High acceleration voltage reducing space-charge and contamination effects
• Extended calibration intervals (monthly vs weekly for quadrupoles)
• GasWorks software for multi-stream, per-stream optimization

The Prima BT is optimized for process development, while the Prima PRO is designed for industrial plant monitoring. A redesigned ion source with a glass-lined gas inlet dramatically improves ethanol response times.

Main Results and Discussion

Comparison tests using inert gas mixtures (He, Ar, Kr, Xe) demonstrate that magnetic sector instruments achieve approximately tenfold better stability and accuracy than quadrupole units. Typical performance specifications for fermentation monitoring are:

• N₂, O₂: 0–100 mol% with ±0.005 mol% standard deviation
• CO₂: 0–10 mol% with 0.1 % relative or 0.0003 mol% precision
• Ethanol, methanol: 0–1 mol% with 2 % relative or 0.001 mol% precision

Stability tests on reference air show O₂ readings stable within ±0.01 mol% and CO₂ within ±5 ppm over one week without re-calibration. Ethanol quantitation exploits the CH₃O⁺ fragment at m/z 31, with interference from O₂ tailing corrected by calibration. Linearity from 100–1 000 ppm ethanol in mixed gas matrices yielded errors below 6 %.

Glass-lined ion source tests with 100 ppm and 400 ppm ethanol demonstrate:

• Build-up time reduced from 12 min (stainless steel) to <1 min
• Settling time reduced from 90 s to <20 s
• Accurate steady-state readings at low ethanol levels (20–100 ppm)

These improvements enable faster sampling rates and reliable low-level ethanol detection.

Benefits and Practical Applications

Online magnetic sector MS provides:

• Real-time monitoring of metabolic activity (O₂ uptake, CO₂ evolution)
• Continuous ethanol production tracking correlated to broth concentration
• Reduced off-line sampling and maintenance downtime
• Enhanced process development speed and scale-up consistency

Used Instrumentation

• Prima BT benchtop mass spectrometer
• Prima PRO process mass spectrometer
• Magnetic sector analyzer
• Rapid Multistream Sampler (RMS) inlet
• GasWorks software for data acquisition and control

Future Trends and Potential Applications

Advances may include integration with process analytical technology (PAT), automated strain screening in high-throughput fermentors, real-time multivariate data analytics and expansion to other volatile bio-products beyond ethanol.

Conclusion

Thermo Scientific’s Prima BT and Prima PRO magnetic sector mass spectrometers deliver superior precision, stability and low-level ethanol detection compared to quadrupole systems, enabling robust online control of bioethanol fermentation from development to large-scale production.

References

1. Renewable Fuels Association website, World Fuel Ethanol Production
2. Traynor P., Wright R., Conroy N., "Optimization of next generation bioethanol production," Hydrocarbon Engineering, June 2008