Microscopic organic analysis using two-step laser mass spectrometry: application to meteoritic acid residues

Abstract

We have developed a mlcroanalytlcal Instrument to analyze the organk constltuonts of partlculates and Inhomogeneous samples wtth aspaUal ramlutbn ol approxlmatdy 40 pm. Om method, two-step laser desorptlon/laser lonlzatlon mass spectrometry (L2MS), uses an Infrared laser to volatlllze constttuent mokuks Intact and an ultraviolet law to lonlze desorbed molecules In a selective manner with Imle or no frcrqrwntcrtion. In partlcular, our lnrtrwnent Is currently tuned to detect polycycllc aromatic hydrocarbons (PAHs), whlch have a strong aboorptlon cross section at the lonlzatlon laser wavelength of 266 m. The detection lhnlt of our Instrmnt k approxbnately 6 hnol for the compound wonene (CUH,*). We demonstrate the use of thk Instrument to analyze acld reddues from SIX motrltw the samples cor#kt of particles that are about 200 pm In dlameter. Quantltatlve and qualltatlve trends In PAH comporltlon are IdentHled for different classes of metwrltes. SgnHIcant dMeronces are seen between the carbonaceous and ordlnary chondrftes. Moreover, wlthln a rlngk clam of ordlnary chondrltes we see an Increase h dkybtbn wtth Increasing petrographk type (thennal metamorphlsm).