研究目的
Investigating the qualitative and quantitative distinction of ortho-, meta-, and para-fluorotoluene by means of chirped femtosecond laser ionization.
研究成果
The study successfully demonstrated the qualitative distinction of structural isomers of fluorotoluene using chirped fs-LIMS and the quantitative in situ analysis of ternary isomeric mixtures with an accuracy of 5%. The approach paves the way for isomer analysis without chromatographic separation steps.
研究不足
The accuracy of the quantitative analysis is limited by the difference between the measured and the weight-in composition, likely due to the difference in vapor pressures of the isomers. Additionally, the choice of equations for the quantitative analysis is neither unique nor critical, suggesting room for methodological improvement.
1：Experimental Design and Method Selection:
The study employs femtosecond-laser ionization mass spectrometry (fs-LIMS) with systematic variation of the spectral phase of fs-laser pulses to analyze the fragmentation patterns of fluorotoluene isomers.
2：Sample Selection and Data Sources:
Pure samples of ortho-, meta-, and para-fluorotoluene were introduced into the chamber via an effusive gas supply for reference studies, followed by premixed ternary mixtures for quantitative analysis.
3：List of Experimental Equipment and Materials:
A home-built linear time-of-flight mass spectrometer, a chirped pulse amplification system (Odin, Quantronix), a femtosecond oscillator (Synergy, Femtolasers), and a liquid crystal display (SLM-S640, Jenoptik) for pulse shaping.
4：Experimental Procedures and Operational Workflow:
Laser pulses were focused into the ion source, and ions were accelerated toward the detector. Mass spectra were recorded while systematically varying the spectral phase.
5：Data Analysis Methods:
Principal component analysis (PCA) was used for statistical analysis of the data sets. Ion yield ratios (IYR) were derived from the mass spectra for qualitative and quantitative analysis.
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