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Why Process Analysis

Direct Liquid Sampling Mass Spectrometry – Towards Quantitation of Trace Components in Liquid Process Streams. Steve Lancaster BP Chemicals Hull Research & Technology Centre. 25 April 2002. Why Process Analysis. Improve process efficiency & optimise product quality.

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Why Process Analysis

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  1. Direct Liquid Sampling Mass Spectrometry – Towards Quantitation of Trace Components in Liquid Process Streams.Steve LancasterBP ChemicalsHull Research & Technology Centre.25 April 2002

  2. Why Process Analysis • Improve process efficiency & optimise product quality. • Reduce requirement for laboratory analysis. • Reduce waste production. • Minimise operator exposure to samples. Future requirements • On-line QC. • Reduce or eliminate the need for intermediate storage.

  3. Process Analysis at BP Chemicals • 8 NIR Spectrometers on line. • 1 Raman spectrometer on-line. • Spectrometers are multiplexed. • Over 50 on-line applications. • 1 mass spectrometer monitoring atmosphere for 1 potential pollutant in case of accidental release. • Over 20 GCs on-line – many more at plant.

  4. Potential advantageous of Process MS • Rapid, sensitive, information rich. • Ideally suited to multistream analysis. • Detailed compositional analysis at trace levels. • Final product analysis possible.

  5. Why is mass spectrometry not more widely used? • Liquid introduction generally utilises hplc type interfaces. • Not appropriate for analysis in the matrices of interest – poor ionisation. • Membrane interfaces not appropriate for analytes with very similar properties to matrix. • Total liquid evaporation reported as HPLC interface but little experience. • Cost. • Fear of mass spectrometry.

  6. Development requirements: MS technology • Efficient EI ionisation. Large repeller potential required. • Stable MS response. Liquid interface: • Must allow vaporization of flowing stream. • Allow controlled amount of material into source. • Facilitate easy cleaning/maintenance. Data handling • Univariate and multivariate calibration.

  7. Optimum System Design Liquid Interface • Optic PTV Injector • Split or splitless inlet. • Temperature/pressure controllable. Mass Spectrometer • ThermoOnix magnetic sector instrument. • Square topped peaks. • Ion repeller plate at 1 KV • Highly stable response – square topped peaks.

  8. Liquid Sampling Interface To gas supply PTV control Unit and power supply to Heated block Nitrogen carrier in Glass liner Hinged base plate Syringe drive Heated capillary to Massspectrometer Septum Heated injector block Aluminium box

  9. Project Aims • Prove PTV Interface. • Prove stability of sector instrument. • Develop laboratory methods. • Assess instrument reliability. • At-plant applications. • Ultimately on-line if sufficiently robust

  10. Analysis of simple mixtures where the analyte has one or more unique ions.

  11. Analysis of Propanoic Acid in Acetic Acid • Ratio of 74/60 plotted against concentration. • 30 scans per sample averaged (2 seconds per scan) • Detection limit 20 ppm. • Lab GC analysis 300 ppm ± 21 ppm (n=2, analysis time 25 min). • Fast GC 220.9 ppm ±3.2 (n=1, 2 minutes) • MS analysis 300 ppm ±5 ppm (n=30, analysis time 1 minute).

  12. Analysis of complex samples where no significant unique ions are present.

  13. Multivariate Calibration foran Acetate process stream. • Significant ions scanned for each component. • Analyte ions ratio to matrix mass ion. • 25 second run covers the range of ions present. • Signals averaged over 10 minutes. • Eight standards prepared with varying concentrations of the components over the range 0 ppm to 100 ppm.

  14. Model validity

  15. Multicomponent Analysis of Acetate Ester Product Stream • 24 scans per sample averaged (25 seconds per scan) • Detection limit 10 to 20 ppm. • MS analysis of acrolein 27 ppm ±0.24 ppm (n=24, analysis time 10 minutes).

  16. Conclusions • Direct liquid introduction MS analysis is feasible for trace analysis. • Instrument running for 7 months with little maintenance required. • Univariate calibration for propanoic acid in acetic acid gives good results. • Multivariate calibration demonstrated in the lab on two process streams. • Long term stability to be evaluated. • Excellent for trace determination of molecules with significant spectral differences from the matrix. • Less good for molecules with similar fragments to matrix.

  17. Future Work • Long term stability of calibration models. • Continue validation of multivariate data against real samples. • More laboratory based applications with both uni- and multivariate calibration. • Possibility of soft ionisation to minimise interference from similar fragments. • Investigate other means of sample delivery e.g., mass flow controller.

  18. Acknowledgments. Thermo Onix Robert Wright, Chris Walker & Alasdair Crawford. BP Chemicals. Tom Lynch Tom Dutton Mathieu Noe Ian Beningfield

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