Application of reflectance micro-Fourier transform infrared analysis to the study of coal macerals: an example from the late jurassic to early cretaceous coals of the Mist Mountain Formation, British Columbia, Canada

lnternationaf

ELSEVIER

Journal

of

International Journal of Coal Geology 32 (1996) 55-67

Application of reflectance micro-Fourier Transform infrared analysis to the study of coal macerals: an example from the Late Jurassic to Early Cretaceous coals of the Mist Mountain Formation, British Columbia, Canada M. Mastalerz a, R.M. Bustin b ” Indiana Geological Survey, Indiana University, 611 North Walnut Grove, Bloomington, IN 47405.2208, USA b The UniversiQ of British Columbia, Department of Geological Sciences, 6339 Stores Rd., Vancouver, BC V6T 12.4, Canada

Received 31 May 1995; accepted 3 November 1995

Abstract The applicability of the reflectance micro-Fourier Transform infra-red spectroscopy (FTIR) technique for analyzing the distribution of functional groups in coal mace& is discussed. High quality of spectra, comparable to those obtained using other FUR techniques (KBr pellet and transmission micro-FTIR), indicate this technique can be applied to characterizing functional groups under most conditions. The ease of sample preparation, the potential to analyze large intact samples, and ability to characterize organic matter in areas as small as 20 pm are the main advantages of reflectance micro-FTIR. The quantitative aspects of reflectance micro-FTIR require further study. The examples from the coal seams of the Mist Mountain Formation, British Columbia show that at high volatile bituminous rank, reflectance micro-FUR provides valuable information on the character of aliphatic chains of vitrinite and liptinite macerals. Because the character of aliphatic chains influences bond disassociation energies, such information is useful from a hydrocarbon generation viewpoint. In medium volatile bituminous coal liptinite macerals are usually not detectable but this technique can be used to study the degree of oxidation and reactivity of vitrinite and semifusinite. Keywords: Coal; Macerals;

FTIR techniques;

0166-5162/96/$15.00 Copyright PZZ SOl66-5162(96)00030-4

Mist Mountain

Formation

0 1996 Elsevier Science B.V. All rights reserved.

56

M. Mastalerz, R.M. Bustin / International Journal of Coal Geology 32 (1996) 55-67

1. Introduction

There is a growing awareness that bulk coal analyses, although very useful for industrial needs, cannot provide information on coal structure because coal is composed of heterogeneous entities. There is also increasing concern that individual macerals are more chemically heterogeneous than originally thought based on their optical characteristics and that information of this heterogeneity may be necessary to evaluate the bulk properties of coal. The determination of maceral properties can be achieved by analyzing mechanical separates or by studying macerals in-situ using a micro-technique. Mechanical separation of macerals based on specific gravity have proven to be fairly successful (Dyrkacz et al., 1984, 19911, but it is time-consuming and absolutely pure maceral fractions are impossible to obtain (Stankiewicz et al., 1994). In-situ micro-techniques permit the analyses of individual types of organic matter. Several in-situ techniques have been used to study macerals. These include the electron microprobe (Bustin et al., 1993; Mastalerz and Bustin, 1993a,b), laser micro mass spectroscopy (Lyons et al., 1987; Morelli et al., 1988), laser micro-pyrolysis (Stout, 1992; Eglinton, 1994) and microFourier Transform infra-red spectroscopy (FTIR) (Landais and Rochdi, 1990; Pradier et al., 1992; Mastalerz and Bustin, 1993a,b) and Scanning Transmission X-ray microscopy (Botto and Cody, 1994). Infrared (IR) spectroscopy registers changes in dipole moment resulting from bond vibration upon absorption of IR radiation, thus allowing the identification of functional groups in organic samples. Older instruments measured absorbance over only a few wavelengths at a given time, requiring several minutes to cover the entire IR spectrum once. FTIR permits measurements of IR absorbance simultaneously over the entire infrared spectrum. As a result, many spectra can be collected and summed, which reduces random noise and enhances absorbance peaks. In micro-FTIR techniques, an infra-red spectrometer is linked to a microscope, and the sample can be either analyzed optically when an IR beam is blocked or subjected to IR radiation when a beam blocker is removed from the system. Micro-FTIR analyses can be performed in transmission or reflected modes. Transmission micro-FTIR yields high quality spectra (Landais and Rochdi, 1990; Rochdi et al., 1991; Stasiuk et al., 1992; Mastalerz and Bustin, 1995); however, the preparation of sample sections sufficiently thin for this technique is difficult and by no means routine. Reflectance micro-FTIR was rarely applied to study coal macerals until recently because of difficulty of obtaining high quality spectral signals. As a result of recent advances in detector sensitivity and correction routines, it is now possible to collect good quality reflected FTIR spectra (Pradier et al., 1992; Lin and Ritz, 1993a,b; Mastalerz and Bustin, 1995). The purpose of this paper is: (1) to evaluate the applicability of reflected micro-FTIR to coal macerals by summarizing methodology and discussing the quality of spectra and (2) to discuss a range of chemical variations in functional groups in selected macerals using Upper Jurassic/Lower Cretaceous coals from the Mist Mountain Formation of British Columbia as examples.

M. Mastalerz,R.M. Bustin/IntemationalJoumal ofCoal Geology 32 (1996) 55-67

51

2. Quality of reflectance micro-FTIR spectra A Nicolet 710 micro-FTIR spectrometer equipped with a NICPLAN microscope (a 35 x IR objective) was used in this study. All spectra were obtained at a resolution of 4 cm-‘, using a gold plate as background. Coal samples were prepared as polished blocks, using standard procedures as described by Bustin et al. (1985). A program FOCAS@ was used for spectral deconvolution, curve fitting and determination of peak integration areas. Basic operating parameters and conditions important for reflectance micro-FTIR analysis are discussed in Mastalerz and Bustin (1995) and they will be only briefly reviewed here. These include: (1) reproducibility of spectra with time; (2) signal-to-noise ratio as a function of the number of scans; (3) influence of an area size on the resultant spectrum; (4) selection of background and (5) application of Kramers-Kronig transformation. Reflectance micro-FTIR spectra are very reproducible, regardless of the aperture size, with regard to peak locations and ratios between integration areas of individual bands. The spectra collected on the same maceral (the same spot) every second day look almost identical (Fig. 1). Slight differences between spectra seem to result only from scattering effect and can, to large extent, be eliminated by baseline correction. MicroFTIR spectra have an excellent signal-to-noise ratio at a scan number of 500, with basically no improvement with further increase in the number of scans (Fig. 2). A scan number as low as 128 still has some noise but the quality of spectra is adequate to analyze individual functional groups. The Kramers-Kronig transformation is a necessary element of reflectance micro-FI’IR analysis on polished surfaces. Non-transformed spectra exhibit a shift in band location towards higher wavenumbers. This spectral distortion results probably from the contribution of a volume component (Fuller, 1992) to the spectra, suggesting that the mirror-like reflection from the polished surface is not

Vitrinite

1

2

I,1

3

, 4000

, 3600

3200

2800

2400

2000

1600

1200

800

400

WAVENUMBER (cm-‘)

Fig. 1. Reproducibility of spectra; spectra l-3 same operating conditions on different days.

were collected

on the same maceral (the same spot) under the

58

M. Mastalerz, R.M. Bustin /International

Journal of Coal Geology 32 (1996) 55-67

1500 scans

500 scans 128 scans

4000

3600

3200

2800

2400

WAVENUMBER

2000 1600

1200

800

400

(cm-‘)

Fig. 2. Quality of spectra as a function of scan number; note improvement 10 and 128 scans.

in the signal-to-noise

ratio between

the only component responsible for the signal sent to a spectrometer for analysis. The Kramers-Kroning transformation corrects for transflectance and shifts bands to the positions comparable to those in transmission or KBr pellet spectra. Reflectance FTIR spectroscopy yields spectra of somewhat poorer quality than transmission FI’IR (Fig. 3). Specifically, there is lower absorbance of all spectral bands and less resolution of aliphatic stretching bands in reflectance FIIR spectra (Mastalerz and Bustin, 1995). However, bands representing all functional groups of importance for organic matter are easily detectable, and they appear at similar wavenumbers in both transmission and reflectance micro-FTIR modes following Kramers-Kronig transformation. The advantages of the procedure are greater ease of sample preparation for reflectance micro-FTIR and possibility of analyzing changes in functional groups in large intact samples. This makes this method especially valuable and far outweighs the lower absorbances, which to a great extent can be compensated for by adjusting the instrument gain and the absorbance scale or adding more spectra. A drawback of the reflectance micro-FIIR technique is that because it is a surface technique, reflectance FTIR spectra should be collected soon after sample polishing in order to minimize the effects of surface oxidation. In general, reflectance FTIR spectra compare adequately to those from KBr pellet techniques (Mastalerz and Bustin, 1995; Fig. 4). Band absorbances and peak locations by these two methods are similar, except for anthracite. Some differences between the spectra obtained by these two methods, however, make correlation between reflectance and KBr techniques somewhat difficult. The major difference is that aromatic bands in the 700-900 cm-’ region are more prominent when obtained with reflectance microFTIR than with the KBr pellet technique, whereas aliphatic bands in the 2750-3000 cm-’ region are weaker in the reflectance mode than in the KBr mode. The aromatic C = C band (N 1600 cm-’ ) has very similar absorbances in both reflectance and KBr techniques, except in subbituminous coal (Fig. 4) and anthracite (Mastalerz and Bustin,

M. Mastalerz,

VITRINITE

SPORINITE

b

4ow

.

.

3x0

-

5Y

R.M. Bustin /International Journal of Coal Geology 32 (1996) 55-67

-

24ca

-

.

l&l0

.

.

4

8W

.um

3200

2400

,600

800

WAVENUMBER (cm“)

WAVENUMBER (cm-‘)

Fig. 3. Comparison between transmission (TRANS) and reflectance (REFL) spectra of vitrinite and sporinite from high volatile bituminous coal (after Mastalerz and Bustin, 1995).

1993b), Although effective as such, macerals

where the absorbance of this band is much higher in the reflectance mode. the KBr pellet technique still proves to yield better spectra and is very in coal studies (Sobkowiak and Painter, 1992) it remains a bulk technique and, does not compete with micro-FTIR in the cases where data on individual or submacerals are required.

2.1. Semi-quantitative

aspect of reflectance

micro-FTIR

Because calibrations have not been made between reflectance micro-FTIR spectra and absolute values of aromatic and aliphatic hydrogen in coals of various ranks, at present this technique cannot be regarded as quantitative. Ratios of spectral band integration areas (or peak height) can be calculated instead to quantify functional group variations (Pradier et al., 1992; Mastalerz and Bustin, 1993a,b). The commonly used ratios are: (1) CH,/CH, in the 2800-3000 cm-’ region; this ratio reflects length of aliphatic chains and indicates if they are straight or branched (Lin and Ritz, 1993b; Pradier et al., 1992); (2) C = O/C = C ratio of oxygenated groups in 1700 cm-’ region (carboxyl/carbonyl bands) to aromatic carbon (N 1600 cm-] ); (3) C = O/CH groups -- a high value of this ratio may indicate consumption of aliphatic groups by oxidation (Calemma et al., 1988) and (4) ratios of individual aromatic bands in the out-of-plane (700-900 cm-‘) region, reflecting a type of hydrogen substitution. These and other spectral band area ratios in use are valuable for studying the evolution of the molecular structure of organic matter in coal as well as for classifying kerogen type and evaluating

60

M. Mastalerz, R.M. Bustin/Intemational

Journal of Coal Geology 32 (1996) 55-67

SUBBITUMINOUS

9

COAL

I Ref.

.

, 4000

,

. 3200

3ew

2400

2m

Moo

1600

1200

SW

400

WAVENUMBER (cm -‘)

MEDIUM VOLATILE BITUMINOUS COAL

KBr Ref.

4000

x00

3203

2eca

2400

2Mx)

WAVENUMBER (cm-’

Fig. 4. Comparison between volatile bituminous coal.

KEIr and reflectance

spectra

tsw

1200

en0

4al

)

of vitrinite

in subbituminous

coal and medium

hydrocarbon generation potential, even though absolute contents of functional groups are not known. The reflectance micro-FTIR spectra can be calibrated by using KBr pellet spectra and potentially yield quantitative information on functional groups in macerals. If the content of particular functional groups in a coal is known, for example, based on the KBr technique, and a reflectance micro-FIIR spectrum of the same material is available, the micro-FTIR spectrum can be used as a reference spectrum for other micro-FTIR spectra

M. Mastalerz, R.M. Bustin / International Journal of Coal Geology 32 (1996) 55-67

61

of the same type of organic matter at the same maturation level. To make such a calibration meaningful, however, a reference spectrum and all other spectra have to be collected under the same experimental conditions so that the depth penetrated by the IR radiation is constant. Having reference spectra for coals of various rank, then concentration of any functional group in coal can be determined quickly and with the same precision as with the KBr technique (Mastalerz and Bustin, 1995).

3. Variation Formation

in functional

groups in macerals;

an example from the Mist Mountain

FTIR characteristics of macerals of the Mist Mountain Formation presented in this paper show the kind of information that can be obtained using reflectance micro-FTIR. Two distinct sets of coal samples were selected from the Mist Mountain Formation; the first set represents high volatile A bituminous coal with a random vitrinite reflectance of 0.84-l.OO%, and the second set represents medium volatile bituminous coal with a vitrinite reflectance of 1.17-l .41%. Vitrinite, sporinite, cutinite, semifusinite and fusinite were analyzed in high volatile bituminous coal, whereas vitrinite, semifusinite and fusinite were analyzed in the medium volatile bituminous coal (liptinite macerals were not present in this set probably because of higher rank). In the high uolutile A bituminous coal, the liptinite macerals - sporinite and cutinite -. have highest CHJCH, ratios (Tables 1 and 2, Fig. 51, reflecting the longest and least branched aliphatic chains. Vitrinite has a substantially lower CHJCH, ratio. The CH,/CH, ratios for semifusinite and fusinite are higher although the overall intensities of the CH, and CH, bands in the 2800-3000 cm-’ region decrease drastically. Vitrinite has relatively uniform CH,/CH, ratios compared to other macerals, whereas cutinite and semifusinite CHJCH, ratios have a wide reange of values (Tables 1 and 2). The C = O/C = C ratio is highest in liptinite macerals, reflecting high contributions from carboxyl/carbonyl groups, whereas vitrinite has the lowest C = O/C = C ratio. CH,/CH, and C = O/C = C ratios show a similar trend for macerals of high volatile bituminous coal (Fig. 5). The C = O/CH, + CH, ratio is lowest in liptinite macerals because of high CH, and CH, contents. This ratio varies most widely in vitrinite due to mainly to large differences in C = 0 band intensities (sometimes these bands are not detectable). In the medium volatile bituminous coal, there are also large variations in FTIR-derived ratios among vitrinite, semifusinite and fusinite (Fig. 6). CHJCH, is higher in vitrinite than in semifusinite (Tables 3 and 4, Fig. 6). In fusinite CH Z and CH, bands are very small, and the resultant high CH,/CH, values may be statistically unimportant. In vitrinite and fusinite, this ratio varies more than in the lower rank group (Tables 2 and 4). In vitrinite this ratio is generally higher than that of the vitrinite from high volatile bituminous coal, which suggests relative reduction in CH, content. The C = O/C = C ratio in vitrinite is higher than in the vitrinite of the lower rank. This ratio for vitrinite is lower than the ratios in semifusinite, suggesting higher relative abundance of oxygenated groups in semifusinite. In medium volatile bituminous coal, an increase in the CH,/CH, ratio is not associated with an increase in C = O/C = C but an increase in C = O/C = C is generally accompanied by an increase in C = O/CH, + CH,.

62

M. Mastalec, R.M. Bustin /International Journal of Coal Geology 32 (1996) 55-67

Table 1 Reflectance (random) and CH, /CH,, volatile bituminous coal

C = O/C

= C and C = O/CH,

+ CH,

ratios for macerals

Maceral

Sample

CH, /CH,

c=o/c=c

C = O/H,

Vitrinite

MM710 MM32 MM45 MM412 MM41 MM9Tl MM3TI MM3T2 MMTl MM37 MM310 MM3Ml MM3M2

0.95 1.2 0.58 0.47 0.71 0.97 1.62 0.91 0.97 0.83 0.92 1.8 0.87

0.3 0.27 0.34 0.39 0.3 0.56 0 0 0.32 0.37 0.58 0 0

1.62 1.99 0.91 2.54 1.25 3.02 0 0 1.79 0.73 1.11 0 0

0.9 0.94 1.01 0.95 0.97 0.93 0.94 0.93 0.93 0.89 0.84 0.89 0.88

Sporinite

MM7Sl MMS2

4.4 2.53

0.61 0.68

0.39 0.75

0.18 0.2

Cutinite

MM712 MM9C 1 MM3Cl MM3C2 MM7C 1

2.11 1.43 2.9 2.37 3.17

0.7 1 0.67 0 0.79 0.67

0.41 1.29 0 1.58 1.38

0.41 0.15 0.29 0.3 0.26

Semifusinite

MM78 MM9Sl MM9S2 MM46 MM413 MM410

1.75 3.05 2.2 1.12 0.88 1.6

0.49 0.54 0.57 0.4 0.42 0.52

1.25 1.59 2.48 2.12 3.08 2.35

1.35 1.36 1.52 1.16

MMFl MM3F2 MM3Fl MM9S3 MM49

1.94 0.78 1.94 2.1 0.58

0.6 0 0.68 0.55 0.61

1.76 0 1.51 0.95 0.78

2.1 1.81 1.67 1.4 I .73

+CH,

of high

R rand

1.32 1.16

The above example from the Mist Mountain Formation coals illustrates that in the high volatile bituminous coal data set, reflectance micro-FIIR analysis provides valuable information on the character of aliphatic chains and documents longer chains for cutinite and sporinite than for vi&mite. This agrees with the studies of Lin and Ritz (1993b), who documented higher CHJCH, ratios for cutinite (above 18) and alginite (2.8-20) than for vitrinite (0.2-4.6). In the cutinite studied here, this ratio is much lower (1.4-3.2) than the values calculated by Lin and Ritz, indicating large heterogeneity within this maceral. Because aliphatic chain character influences bond disassociation energies, this inhomogeneity may suggest that different cutinites can have different hydrocarbon generation potential. Semifusinite has low concentrations of CH, and CH,

M. Mustalerz, R.M. Bustin/ International Journal Table 2 Ranges, mean values and standard deviations macerals of high volatile bituminous coal

of reflectance

ofCoal Geology 32 (1996) 55-67

(random)

and FlTR-derived

Maceral

R rand

CH, /CH,

c=o/c=c

C =O/CH,

Vitrinite-range Mean h d.

0.84-1.00 0.92 0.04

0.47-1.8 0.98 0.37

0.0-0.58 0.26 0.21

0.0-2.54 1.15 1.01

Sporinite-range Mean S.d.

0.18-0.20 0.19 0.01

2.53-4.4 3.5 1.3

0.61-0.68 0.64 0.04

0.39-0.79 0.57 0.25

C‘utinite-range Mean s.d.

0.15-0.41 0.28 0.09

1.43-3.17 2.4 0.68

o-o.79 0.57 0.32

O-l.58 0.93 0.68

Semifusinite-range Mean s.d.

1.16-1.52 1.3 0.13

0.88-3.05 1.77 0.78

0.4-0.52 0.49 0.07

1.25-3.08 2.1 0.65

Fusinite-range Mean h.d.

1.4-2.1 1.7 0.25

0.58-2.1 1.47 0.73

O-0.68 0.49 0.28

0- 1.76 I .02 0.69

62

spectra1 ratios for

+CH,

C Wtnnite Spnnite Cutinite Semifusinite Fusinite

B

Spolinite

Semlfusinite

0

0.1

Fig. 5. FTIR-derived Formation.

0.2

0 3

0.4

0.5

0.6

spectra1 ratios for macerals

0.7

in high volatile bituminous

coal from the Mist Mountain

64

M. Mastalerz, R.M. Bustin /International

Table 3 Reflectance (random) and CH, /CH,, volatile bituminous coal

C = O/C

Journal of Coal Geology 32 (1996) 55-67

= C and C = O/CH,

+CH,

ratios for macerals

of medium

Maceral

Sample

CH, /CH,

c=o/c=c

C =0/H,

Vitrinite

LCMMllTl LCMMT 1 MM7Tl LCMMl17 LCMM1114 LCMM1118 LCMMIC LCMM9 1 LCMMIB

1.04 0.6 0.98 1.26 0.88 1.13 1.8 2.09 1.35

0.47 0.56 0.77 0.51 0.43 0 0.39 0.6 0.46

1.Ol 0.74 0.78 0.77 0.69 0 0.93 0.8 0.79

1.2 1.3 1.32 1.19 1.17 1.3 1.38 1.32 1.41

Semifusinite

LCMMllll LCMM1113 LCMM1116 LCMM1117 LCMM1119 LCMM8D LCMMIH LCMM8E LCMM8F LCMMSFl LCMMSF2 LCMMSFS LCMMl lS2 LCMMl 1S3 MM7SFl

2.56 1.47 0.42 1.1 1.12 3.11 0.81 0.69 0.8 1.03 0.87 0.66 0.69 0.49 1.03

0 0.58 0.53 0.6 0.62 0.47 0.43 0.41 0.37 0.78 0.6 0.95 0.76 0.7 0.65

0 0.57 0.62 0.56 1.17 0.54 0.93 1.16 1.23 1.67 1.33 1.01 1.5 1.51 0.68

2.23 2.92 1.44 1.87 2.29 2.58 2.35 2.67 2.64 1.97 1.67 2.08 1.76 2.23 1.97

Fusinite

LCMMl lF2 LCMMl lF1 LCMMllS4 LCMM95

1.46 6.7 2.57 0

0.56 0.6 0.24 0.64

0.63 0.79 0.45 0.73

3.02 3.01 2.92 2.02

Table 4 Ranges, mean values and standard deviations macerals of medium volatile bituminous coal

of reflectance

(random)

+CH,

and FTIR-derived

Maceral

R rand

CH, /CH,

c=o/c=c

C = O/H,

Vitrinite-range Mean s.d.

1.17-1.41 1.3 0.08

0.6-2.9 1.49 0.92

o-o.77 0.47 0.21

o-o.93 0.72 0.29

Semifusinite-range Mean s.d.

1.44-2.92 2.12 0.4

0.42-3.11 1.08 0.71

o-o.95 0.59 0.25

O-l.67 0.96 0.46

Fusinite-range Mean s.d.

2.02-3.0 2.74 0.48

O-6.7 2.68 2.87

0.24-0.64 0.51 0.18

0.45-0.79 0.65 0.15

R rand

spectral

ratios for

+ CH,

M. Mastalerz, R.M. Bustin /International Journal of Coal Geology 32 (1996) 55-67

65

2.5

0

Vitrinite Semifusinite

Fusinite

C=OIC=C

?? C=OICH, +CH, ?? CH21CHI Fig. 6. FTIR-derived Formation.

spectral ratios for macerals

in medium volatile bituminous

coal from the Mist Mountain

in both high volatile and medium volatile bituminous coals. However, it is noteworthy that there is a wide range of CHJCH, variations in both coals, which may have bearing on the reactivity (or non-reactivity) of this maceral. In general, the examples summarized here from the Mist Mountain Formation and our earlier studies (Mastalerz and Bustin, 1993b) show that there are not only substantial differences in functional groups between macerals but also within individual macerals. Clearly much more research is needed to document and understand how these molecular variations influence the physical and chemical properties of macerals, their hydrocarbon generation potential and their behaviour in technological processes.

4. Concluding

remarks

Reflectance micro-FTIR is one of the techniques that can be applied to the study of functional groups in coal macerals. Although this technique yields spectra of somewhat poorer quality than transmission micro-FTIR (i.e., lower spectral band absorbencies, less distinct aliphatic stretching bands), the ease of sample preparation and the possibility of studying large intact samples make reflectance micro-FTIR competitive. Reflectance micro-FTIR compares favourably with the KBr pellet technique; the main difference between these methods is the higher absorbance of aromatic out-of-plane bands in reflectance micro-FTIR. The quantitative aspect of reflectance micro-FTIR technique still awaits further development, however the combination of KBr and micro-FTIR techniques permits quantitative characterization of organic matter yielding aromatic and aliphatic H contents with the same precision as in the KBr pellet technique.

66

M. Mastalerz, R.M. Bustin/lntemational

Journal of Coal Geology 32 (1996) 55-67

The great advantage of using reflectance micro-FIIR spectroscopy is that other types of analysis, for example elemental composition using the electron microprobe technique or reflectance using a reflected light microscopy, can be readily obtained on the same areas (macerals) analyzed (Mastalerz and Bustin, 1993a,b). This is made possible because reflectance micro-FTIR uses standard polished sections for reflected light microscopy. The possibility of obtaining various types of data on the same spot is especially important because it can give better insight into coal structure, eliminate uncertainty about the identity of the material analyzed, and minimize the time (and cost) of further sample preparation. Reflectance micro-FTIR has proven to be a valuable tool for studying the evolution in molecular chemistry of mace& with increasing maturation and for determining molecular differences between mace& within iso-rank coals (Mastalerz and Bustin, 1993b). The presented examples from the Mist Mountain Formation document significant heterogeneity within individual macerals. Understanding of this heterogeneity requires further research.

Acknowledgements Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for partial support of this research. Comments by A.L. Bates, R.K. Kotra, P.C. Lyons and C.A. Palmer are greatly appreciated.

References Botto, R.E. and Cody, G.D., 1994. Scanning Transmission X-ray microscopy: a new “looking glass” into coal chemical structure. 207th ACS Natl. Meet., Book of Abstracts, 41. Bustin, R.M., Mastalerz, M. and Wilks, K.R., 1993. Direct determination of carbon, oxygen and nitrogen content in coal using the electron microprobe. Fuel, 72: 181-185. Bustin, R.M., Cameron A., Grieve D. and Kalkreuth W., 198.5. Coal Petrology, its Principles, Methods and Applications. Short Course Notes, 2nd ed. Geol. Assoc. Canada, Victoria, 230 pp. Calemma, V., Rausa, R., Margarit, R. and Girardi, E., 1988. FTIR study of coal oxidation at low temperature. Fuel, 67: 765-769. Dyrkacz, G.R., Bloomquist, C.A.A. and Solomon, P.R., 1984. Fourier transform infrared study of high-purity maceral types. Fuel, 63: 536-542. Dyrkacz, G.R., Bloomquist, C. and Rustic, L., 1991. An investigation of the vitrinite maceral group in microlithotypes using density gradient separation methods. Energy Fuels, 5: 155-163. Eglinton, L.B., 1994. Laser micro-pyrolysis: morphology to molecular structure of discrete kerogen components. In: 1 lth Annu. Meet. TSOP, Jackson, Wyoming, Abstracts, pp. 21-24. Fuller, M., 1992. Nicolet FT-IR Technical Note, TN-9035, 6. Landais, P. and Rochdi, A., 1990. Reliability of semiquantitative data extracted from transmission microscopy - Fourier transform infrared spectra of coal. Energy Fuels, 4: 290-295. Lin, R. and Ritz, G.P., 1993a. Reflectance FT-IR microspectroscopy of fossil algae contained in organic-rich shales. Appl. Spectrosc., 47: 265-271. Lin, R. and Ritz, G.P., 1993b. Studying the chemistries of individual macerals using infrared microspectroscopy, and the structural implications on oil vs. gas/condensate proneness and “low rank” generation. Org. Geochem., 20: 695-707.

M. Mastalerz, R.M. Bustin/ International Journal of Coal Geology 32 f 1996) 55-67

6;

Lyons, P.C., Hercules, D.M., Morelli, J.J., Sellers, G.A., Mattem, D., Thompson-Rizer, C.L., Brown. F.W. and Millay, M.A., 1987. Application of laser microprobe (LAMMA 1000) to “fingerprinting” of coal constituents in bituminous coal. Int. J. Coal Geol., 7: 185-194. Mastalerz, M. and Bustin, R.M., 1993a. Electron microprobe and micro-FTIR analyses applied to maceral chemistry. Int. J. Coal Geol., 24: 333-345. Mastalerz, M. and Bustin, R.M., 1993b. Variation in maceral chemistry within and between coals of varying rank: an electron microprobe and micro-Fourier transform infra-red investigation. J. Microsc.. I? l(2): 153-166. hlastalerz, M. and Bustin, R. M., 1995. Application of reflectance micro-Fourier transform infrared spectrometry in studying coal macerals: comparison with other Fourier transform infrared techniques. Fuel. 74: 536-542. Morelli, J.J.. Hercules, D.M., Lyons, P.C., Palmer, C.A. and Fletcher, J.D., 1988. Using laser micro Mass Spectroscopy with the LAMMAinstrument for monitoring relative elemental concentrations in vitrinite. Mikrochim. Acta, III: 105-l 18. Pradier, B., Landais, P., Rochdi, A. and Davis, A., 1992. Chemical basis of tluorescence of crude oils and kerogens-II. Fluorescence and infra-red micro-spectrometric analysis of vitrinite and liptinite. Org. Geochem., 18: 24 l-248. Rochdi. A., Landaia, P. and Bumeau, A., 1991. Analysis of coal by transmission FTIR microspectro\copy: methodological aspect. Bull. Sot. Geol. Fr., 162: 155-162. Sobkowiak, M. and Painter, P., 1992, Determination of the aliphatic and aromatic CH contents of coals by FT-i.r.: studies of coal extracts. Fuel, 71: 1105-I 125. Stankiewicz, B.A., Kruge, M.A. and Crelling, J.C., 1994. Geochemical characterization of maceral cc)ncentrates from Herrin No. 6 coal (Illinois Basin) and Lower Toarcian shale kerogen (Paris Basin). Bull. Centres Rech. Explor.-Prod. Elf Aquitaine, 18: 237-248. Stasiuk, L.D., Kybett, B.D. and Bend, S.L., 1992. Reflected light microscopy and transmission micro-FIIR of alginite in relation to petroleum generation, Upper Ordovician Kukersites, Saskatchewan. Canada, In: 9th Annu. Meet. Sot. Organic Petrology, Abstracts, University Park, Pennsylvania, pp. 76, 77. Stout. S.A., 1992. Chemical fingerprinting of individual macerals in situ using laser micropyrolysis-GCMS. In: 9th Annu. Meet. Sot. Organic Petrology, Abstracts, University Park, Pennsylvania. pp. 59. 60.