Isotope Ratio Spectrometry With Reference Intensity Drift Estimation
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Solution Overview
Problem
Long Integration Dual Inlet (LIDI) isotope ratio mass spectrometry systems face challenges in accurately measuring isotope ratios due to non-linearity and limited sample volume, making it difficult to maintain consistent signal intensities and correct for instrumental drift, which affects the precision of measurements, especially for clumped isotopologues like 13C18O16O.
Innovation Solution
The method involves measuring reference gas isotope ratios before and after the sample gas measurement, determining relationships between isotope ratios and signal intensities, and using these relationships to estimate reference gas isotope ratios during the sample measurement, allowing for post-processing intensity matching and correction for instrumental drift, even when sample and reference gases are measured at different times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference gas pressure is adjusted to match sample gas signal intensity, then measurement precision is improved, but sample gas is consumed during pressure adjustment
Solution Approach 1:
The patent performs preliminary matching of reference gas signal intensity to sample gas signal intensity before the actual isotope ratio measurement. By establishing the relationship between reference gas pressure and signal intensity in advance, and adjusting the reference gas pressure to match the sample gas intensity beforehand, the system eliminates the need for continuous pressure adjustments during measurement, thereby preventing sample gas consumption while maintaining measurement precision.
2Reliability
If sample and reference gases are measured alternately with short integration times, then instrumental drift correction is enabled, but measurement precision deteriorates due to non-linearity
Solution Approach 1:
The patent changes the integration time parameter from short intervals to long integration periods, allowing both sample and reference gases to be measured continuously over extended times. This enables the system to capture the non-linear relationship between signal intensity and isotope ratio more accurately, while still permitting drift correction by comparing trends between sample and reference measurements over the long integration period.
Solution Approach 2:
The patent replaces the mechanical approach of alternating measurements with a computational approach using post-processing data analysis. By measuring sample and reference gases simultaneously or in continuous sequence and then applying mathematical corrections to account for non-linearity and drift in the data processing stage, the system achieves both drift correction and high precision without the limitations of alternating short-integration measurements.
3Measurement precision
If signal intensity is maintained constant for sample and reference, then isotope ratio comparison accuracy is improved, but device complexity increases due to pressure adjustment mechanisms
Solution Approach 1:
The patent implements a self-service approach where the system automatically determines the relationship between reference gas pressure and signal intensity, and autonomously adjusts the reference gas pressure to match the sample gas intensity without requiring complex manual intervention or sophisticated control mechanisms. This automated self-adjustment maintains signal intensity matching for accurate isotope ratio comparison while minimizing the complexity of the pressure adjustment mechanism.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the precision of isotope ratio measurements by enabling accurate normalization and correction for instrumental drift, even with significant decay in signal intensities, enhancing the accuracy of clumped isotopologue measurements and reducing the demand for precise capillary matching.
Implementation Method 1
In an isotope ratio mass spectrometer, the signal from detected ions of a specific mass-to-charge (m/z) ratio
Implementation Method 2
measuring two separate spectral absorption lines, typically in the infrared region, one line for each different isotopic species
Data Source
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AI summary
An isotope ratio spectrometer is operated for measurement of a sample. First isotope ratios and first signal intensities are measured for a reference in the spectrometer, over a first measurement time period. A first relationship comprising a relationship between the first isotope ratios and the first signal intensities is determined. Sample isotope ratios and sample signal intensities are measured in the spectrometer, over a second measurement time period subsequent to the first measurement time period. Second isotope ratios and second signal intensities for a reference are measured in the spectrometer, over a third measurement time period subsequent to the second measurement time period. A second relationship comprising a relationship between the second isotope ratios and the second signal intensities is determined. A reference isotope ratio is estimated for a time X within the second measurement time period, based on the first relationship and the second relationship.