Energy & Fuels 1990,4, 747-748 characterized by the presence of protonated molecular ions. For functionalized tetrapyrroles, both porphyrins and chlorins, molecular weight information and characteristic fragment ions can be obtained in both positive and negative ionization modes. Thus, LC/MS should facilitate the identification of compounds without resort to the isolation of the individual component, through comparison with authentic standards. Hence, LC/MS provides a basis for the routine investigation of sedimentary tetrapyrrole
747
mixtures on the same level as GC/MS, which is used routinely to obtain, for example, sedimentary sterane or triterpane distributions. Acknowledgment. We thank the Deutsche Forschungsgemeinschaft (DFG Grant Ec 95/ 1-1) and the National Environmental Research Council (NERC Grant GR3/6619) for financial support. Samples were kindly provided by Dr. B. J. Keely and Mr. W. G. Prowse.
Communications Characterization of Geoporphyrins Using Plasma Desorption Mass Spectrometry
Sir: Plasma desorption mass spectrometry (PDMS), which utilizes a 252Cfionizing source with a time-of-flight mass spectrometer, has been shown to be useful for analyzing metalloporphyrins. The PDMS spectrum obtained from an Anna Shale indicated the presence of a vanadyl porphyrin series, Cza to CS2,which was consistent with isobutane chemical ionization (CI) results. The PDMS results had an improved signal-to-noise relative to the CI results and did not necessitate heating the sample to 350 OC, which was necessary in order to volatilize the metalloporphyrins to obtain CI results. The results suggest PDMS might be a viable screening method for metalloporphyrin analysis with minimal sample cleanup. The inability to distinguish deoxophylloerythroetioporphyrins(DPEP) and etioporphyrins (ETIO) due to the lack of mass resolution (on the PDMS instrument used in this study) is a limiting factor in assessing the potential of PDMS for determining the maturity of oils. Plasma desorption mass spectrometry (PDMS) has been utilized for obtaining molecular weight information on large proteins (to 30K d a l t ~ n s ) . ' - ~ Other compound classes, including oligonucleotides," have also been analyzed by PDMS. In this study we report the results of the relatively low molecular weight mass analysis (for PDMS) of metalloporphyrins in shale oil. A marine black shale, Anna Shale Member of the Carbondale Formation (Pennsylvanian), in the Illinois Basin: was used in this study. The metalloporphyrin containing polar fraction was obtained by extracting 25 g of pulverized shale with benzene in a modified Soxhlet extraction apparatus. The resulting extract was condensed and further separated into three fractions, aliphatic, aromatic, and polar, by use of silica gel and alumina column chromatography. These fractions were eluted with n-hexane, benzene, and benzene-methanol (1:l v:v), respectively. The polar fraction was dissolved in tetrahydrofuran (THF) prior to electrospraying onto a nitrocellulose-coated Mylar target. The sample target was inserted into the PDMS (1) Cotter, R. J. Anal. Chem. 1988, 60, 781A-793A. (2) Jardine, I.; Scanlon, G. F.; Tsarbopoulos, A. Anal. Chem. 1988,60, 1086-1088. (3) Nielsen, P. F.; Klarskov, K.; Hojrup, P.; Roepstorff, P. Biomed. Enuiron. Mass Spectrom. 1988, 17, 355-362. (4) Viari, A.; Ballini, J. P.; Meleard, P.; Vigny, P.; Dousset, P.; Blonski, C.; Shire, D. Riomed. Enuiron. Mass Spectrom. 1988, 16, 225-228. (5) Chou, M. M.; Chou, C. L.; Allen, R. A. Proceedings of the 1987
Eastern Oil Shale Symposium, Lexington, K Y , Nouember 1987; Kentucky Energy Cabinet Laboratory: Lexington, KY, 1988; pp 137-144.
2
C31
m O /
m/z
50 0
600
Figure 1. Plasma desorption mass spectrum of the polar fraction of an Anna Shale.
carousel for analysis. The plasma desorption mass spectrometer used in this study was the BIOION 20 (Bioion Nordic, Uppsala, Sweden). The acceleration potential used for these studies was 18000 V. Figure 1 is the mass spectrum of the Anna Shale polar fraction. As can be seen, the mass spectrum shows only slightly resolved peaks (the modest resolution is inherent in the BIOION 20 PDMS time-of-flight instrument) indicative of the DPEP/ETI06 doublet of vanadyl geoporphyrins. The most intense ions, mlz 486-542, correspond to the CZs through C32 vanadyl geoporphyrins. These results are in good agreement with the isobutane chemical ionization (CI) mass spectra of the polar fraction, which indicates the vanadyl geoporphyrin doublets. Of particular interest in this study was the improved signal-to-noise obtained in the PDMS results compared with the CI results obtained on a Finnigan 4000 mass spectrometer. In addition, the CI results were obtained by heating the probe to 350 "C, which caused rapid ion intensity deterioration due to the ion source becoming dirty. These results prompted investigating the viability for using PDMS for metalloporphyrin analysis with minimal sample cleanup. In a preliminary investigation the Anna (6) Gallegos, E. J.; Sundararaman, P. MQSSSpectrom. Reu. 1985, 4 , 55-85.
0007-0624/90/2~04-0747$02.50/0 0 1990 American Chemical Society
Energy & Fuels 1990,4, 748-754
748
Shale was placed in a screw-top vial and covered with benzene. The vial was shaken vigorously and allowed to stand for 1 day. The benzene was decanted from the vial and evaporated with a stream of nitrogen. The resulting residue was then dissolved in T H F and electrosprayed on a nitrocellulose-coated Mylar target. The initial PDMS results, while weak, indicated the C29through C,, vanadyl geoporphyrins to be the most abundant components (in agreement with the PDMS results obtained from the polar fraction). These preliminary results suggest that PDMS may be a viable simple and fast method for screening oil samples for metalloporphyrins due to the apparent transparent nature of many of the other components present in the extract. Further studies are needed to optimize the simple cleanup procedure thereby improving the PDMS spectra and to investigate the levels of detection of metalloporphyrins in oil samples using this simple
methodology. Also better control of the BIOION instrument parameters, which are designed for high mass determinations, may enable the two geoporphyrin components, D P E P and ETIO, to be resolved, enabling DPEP/ETIO ratios to be calculated. This would further enhance the screening capability of PDMS as relative maturation values could be determined.6 Karl V. Wood,* Connie C. Bonham Departments of Chemistry and Biochemistry Purdue University, West Lafayette, Indiana 47907 Mei-In M. Chou Illinois State Geological Survey Champaign, Illinois 61820 Received May 2, 1990 Revised Manuscript Received July 12, 1990
Articles Automated Image Analysis of Minerals and Their Association with Organic Components in Bituminous Coalst W. E. Straszheim*J and R. Markuszewskis Department of Civil and Construction Engineering, Department of Geological and Atmospheric Sciences, and Fossil Energy Program, Ames Laboratory, Iowa State University, Ames, Iowa 5001 1 Received April 16, 1990. Revised Manuscript Received September 26, 1990
Samples of 100-mesh Upper Freeport, Pittsburgh No. 8, and Illinois No. 6 seam coals from the Argonne Premium Coal Sample Program were analyzed by scanning electron microscopy based automated image analysis (SEM-AIA) for mineral composition, particle size, and association of the minerals with the organic matrix. The association results were used to predict cleanability, i.e., anticipated coal recovery versus mineral rejection, for density- and surface-based cleaning processes. Distributions showing the association of each mineral with coal indicate preferential liberation for calcite in all three coals and for some of the pyrite in Illinois and Pittsburgh coals. Generally, the Pittsburgh coal appeared to be the most easily cleaned, based on association considerations only. The predicted cleanabilities of the Upper Freeport and Illinois coals were similar for density-based processes, and the Upper Freeport coal appeared to be slightly more cleanable than the Illinois coal for surface-based processes.
Introduction Mineral matter in coal presents problems on a number of fronts. Of greatest significance during combustion is the emission of sulfur dioxide that results mostly from pyrite in the coal. In addition, mineral matter leads to wear of components in the coal-handling circuits, to boiler slagging and fouling problems, and to waste streams requiring disposal. Therefore, physical coal cleaning is em'This paper was originally scheduled to appear with the papers from the Symposium on Research with Argonne Premium Coal Samples [ E n e r g y Fuels 1990, 4 ( 5 ) ] , b u t missed that issue due to delays in the Editorial office. Ed. Department of Civil and Construction Engineering. !Department of Geological and Atmospheric Sciences.
ployed as a means for addressing these issues prior to combustion. Current planning and implementation of physical cleaning are typically based only on indirect or incomplete characterization data for the coal. Float-sink tests are often performed for a range of particle sizes and specific gravities to determine the cleanability of a coal. Laboratory-scale cleaning tests may also be run under a variety of conditions. However, it is not general practice to characterize the mineral matter in coal directly in order to determine the potential for its removal, i.e., the cleanability of the coal. Yet, physical separation fundamentally depends on the association of the individual mineral matter grains with the coal matrix. Large, liberated mineral particles may
o a a 7 - o s z ~ ~ ~ o ~ z ~ o ~ - o 7 ~ a0 ~ o1990 z . 5American o~o Chemical Society
