MICROSCOPIC ORGANIC-ANALYSIS USING 2-STEP LASER MASS-SPECTROMETRY - APPLICATION TO METEORITIC ACID RESIDUES

被引:90
作者
KOVALENKO, LJ
MAECHLING, CR
CLEMETT, SJ
PHILIPPOZ, JM
ZARE, RN
ALEXANDER, CMO
机构
[1] STANFORD UNIV,DEPT CHEM,STANFORD,CA 94305
[2] WASHINGTON UNIV,MCDONNELL CTR SPACE SCI,ST LOUIS,MO 63130
关键词
D O I
10.1021/ac00030a021
中图分类号
O65 [分析化学];
学科分类号
070302 ; 081704 ;
摘要
We have developed a microanalytical instrument to analyze the organic constituents of particulates and inhomogeneous samples with a spatial resolution of approximately 40-mu-m. Our method, two-step laser desorption/laser ionization mass spectrometry (L2MS), uses an infrared laser to volatilize constituent molecules intact and an ultraviolet laser to ionize desorbed molecules in a selective manner with little or no fragmentation. In particular, our instrument is currently tuned to detect polycyclic aromatic hydrocarbons (PAHs), which have a strong absorption cross section at the ionization laser wavelength of 266 nm. The detection limit of our instrument is approximately 8 fmol for the compound coronene (C24H12). We demonstrate the use of this instrument to analyze acid residues from six meteorites; the samples consist of particles that are about 200-mu-m in diameter. Quantitative and qualitative trends in PAH composition are identified for different classes of meteorites. Significant differences are seen between the carbonaceous and ordinary chondrites. Moreover, within a single class of ordinary chondrites we see an increase in alkylation with increasing petrographic type (thermal metamorphism).
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页码:682 / 690
页数:9
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