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Stability and long-term durability of Raman spectroscopy
D Lawson1, S Samanta, P T Magee
1Department of Anesthesiology, University of Virginia Health Sciences Center, Charlottesville 22908.
Journal of Clinical Monitoring
|September 1, 1993
Summary
Raman spectroscopy in the RASCAL gas analyzer shows reliable performance for CO2, O2, N2O, and N2. However, volatile agent readings can drift significantly upward over time without frequent calibration.
Area of Science:
- Medical instrumentation
- Analytical chemistry
- Gas analysis
Background:
- Raman spectroscopy is a technique used for gas analysis.
- The RASCAL multiple gas analyzer utilizes Raman spectroscopy.
- Assessing the reliability and stability of such analyzers in clinical settings is crucial.
Purpose of the Study:
- To evaluate the clinical reliability and long-term stability of the RASCAL multiple gas analyzer.
- To identify and analyze failure modes encountered during regular use of the RASCAL analyzer.
Main Methods:
- Twenty-one RASCAL analyzers were tested for accuracy and precision over 36 hours using standard gas mixtures.
- Service data spanning 29 months were analyzed to assess durability and failure modes.
- Bias residuals were calculated by comparing predicted and observed values.
Main Results:
- The RASCAL analyzer showed a tendency to overread high concentrations of volatile agents (isoflurane/enflurane).
- Four of 16 instruments misread agents by more than +/- 0.30%, and four failed to identify low concentrations.
- Water contamination was a significant issue, leading to sample set replacements.
- Despite some issues, linearity for CO2, O2, N2O, and N2 remained acceptable even without frequent calibration.
Conclusions:
- Manufacturer-recommended calibration intervals (30 days) are adequate for reliable gas analysis with Raman spectroscopy.
- Volatile agent quantification is prone to significant upward drift over time without frequent recalibration.