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Ultraviolet (UV) resonance Raman spectra of Bacillus subtilisendospores have been excited at 244 nm. Spectra can be interpreted in terms of contributions from calcium dipicolinate and nucleic acid components. Differences between spectra of spores and vegetative cells are very large and are due to the dominance of the dipicolinate features in the spore spectra. Because the DNA and RNA composition of B. subtilisspores is known and because the cross-sections of Raman bands belonging to DNA and RNA bases are known, it is possible to calculate resonance Raman spectral cross-sections for the spore Raman peaks associated with the nucleic acids. The cross-sections of peaks associated with calcium dipicolinate have been measured from aqueous solutions. Cross-section values of the dominant 1017 cm−1calcium dipicolinate peak measured from the Bacillus spores have been shown to be consistent with a calcium dipicolinate composition of ten percent or less by weight in the spores. It is suggested that spectral cross-sections of endospores excited at 244 nm can be estimated to be the sum of the cross-sections of the calcium dipicolinate, DNA, and RNA components of the spore. It appears that the peaks due to DNA and RNA can be used as an internal standard in the calculation of spore Raman peak cross-sections, and potentially the amount of calcium dipicolinate in spores. It is estimated on the basis of known nucleic acid base cross-sections that the most intense Raman band of the Bacillus subtilis sporespectra has a cross-section of no more than 4 × 10−18cm2/mol-sr.

A dimension reduction fiber-optic array is used to measure the response of a stacked-layer, image-guide CO2/O2sensor, simultaneously at several different wavelengths. Two different image-guide CO2/O2sensor configurations are described: a stacked-layer sensor, where luminescence indicators for CO2and O2are uniformly coated on the tip of the sensor; and a side-by-side coated sensor where the two indicators are coated on different halves of the fiber tip. It is shown that a single image-guide measurement, made by using the dimension reduction array, can be used to generate response plots, intensity profiles, and reconstructed images at different luminescence wavelengths. The spatial resolution of an image guide sensor is limited by the number of fibers used to construct the dimension reduction array.

A single-frame approach to chemical imaging with high spectroscopic resolution is described that makes use of a second-generation dimension-reduction fiber-optic array. Laser-induced plume images are focused onto a 17 × 32 rectangular array of square close-packed 25 μm cross-sectional f/2 optical fibers that are drawn into a 544 × 1 distal array with serpentine ordering. The 544 × 1 side of the array is imaged with an f/2 spectrograph equipped with a holographic grating and a gated intensified charge-coupled device (ICCD) camera for spectral analysis. Software is used to extract the spatial/spectral information contained in the ICCD images and de-convolute them into wavelength-specific univariate reconstructed images or position-specific spectra that span an 86 nm wavelength space. Temporal resolution is provided by imaging sequential laser plumes with varying time delays after each laser pulse on the gated intensifier.

In addition to the previously reported vibrational frequencies of NO stretch at 1591–1650 cm−1and 1770–1800 cm−1on Pt(100) surface at 300 K, we observed an infrared spectral band centered around 1689–1692 cm−1. With the use of two-dimensional IR correlation analysis, we were able to distinguish the various adsorption sites of NO under the present experimental conditions. The infrared band at 1689–1692 cm−1developed independently of the band at 1639–1654 cm−1. By varying the pressure of NO and the surface temperature, we were able to demonstrate that the 1689–1692 cm−1band grows only at higher NO pressure and lower surface temperature.

Partial least-squares regression (PLSR) was used to generate wheat moisture content predictive models from eight-frequency microwave attenuation (A) and phase (P) spectra in the 10.36 to 18.0 GHz range, as obtained by a free-space technique with a 10.4 cm thick sample. Spectra (n =379) were measured for a set of grain samples that had been treated to span the agriculturally practical ranges of moisture content (M) (10.6 to 19.2% g/gwet), temperature (K) (–1 to 42°C), and bulk density (D) (0.72 to 0.88 g/mL). The sample– property space formed by M, K, and D was used to prune redundant samples and select representative subsets for calibration (n= 279), cross-validation (n =40 segments), and testing (n =31). Twelve model types are reported and vary from attenuation or phase alone to the combination of attenuation, phase, temperature, and density (i.e., APKD). For optimization of each PLSR model, the raw spectral, temperature, and density data were preprocessed with variable ratios, mathematical transformations, and/or variable scaling. The lowest moisture prediction errors were for temperature-and density-corrected models with variables AKD or APKD; these produced root-mean-square cross-validation and prediction errors (RMSECV and RMSEP) of 0.19 to 0.20% in moisture content units. The more practical unifrequency models, APK at 15.2 GHz, and AK at 18.0 GHz, yielded RMSECV values of 0.21% and 0.35%, respectively. Addition of temperature to dielectric data always substantially reduced the model error. However, the multiplicative effect of density is well corrected by using the ratio A/P, or partly corrected by using the features in the attenuation spectra. Data trends suggest that dual-frequency PK models might benefit from a wider frequency range, and unifrequency AK models might be better at frequencies higher than 18.0 GHz. The results presented make it possible to evaluate a wide variety of instrumental configurations that might be proposed to suit particular engineering criteria such as measurement accuracy, range of operating conditions, and hardware complexity.

The interactions of α, β, and -γ-cyclodextrins and selected naphthalene derivatives as observed through fluorescence lifetime measurements are discussed in detail. These systems can be quickly characterized with the use of the parameters obtained from experimental fluorescence decay curves. The formation of inclusion complexes can be followed with the appearance of a long-lived fluorophore which contributes to the total fluorescence according to the cyclodextrin concentration. This fluorophore is determined to be an inclusion complex between a naphthalene and cyclodextrin.

Resonance Raman spectra are reported for aqueous suspensions of nine clones of marine plankton algae representing three classes, five genera, and seven species. Spectra are obtained easily either directly from culture or from samples concentrated by sedimentation. Spectra taken at 488 or 457.9 nm are of high quality and are sufficiently distinct to differentiate clones at the algal class level, and possibly also at the genus level. Strongest peaks occur near 1527 and 1158 cm−1associated with ν(c = c) and ν(c – c) of carotenoid pigments, but information is contained in the entire region between 900 and 3000 cm−1due to associated overtone and combination bands which can be assigned along with fundamental vibrations. Chlorophyll peaks also are quite pronounced. Spectra obtained using rapid flow techniques match those taken using slurries in sealed tubes if low laser power is used. The sensitivity and rapidity of the technique suggest that it may be useful in remote sensing applications.

The intrinsic steady-state fluorescence and fluorescence decay of Staphylococcus epidermidis, Pseudomonas fluorescens, Enterobacter cloacae, Escherichia coli, and Bacillus subtilishave been observed. Excitation spectra were obtained while emission at 430, 455, 487 and 514 nm was being monitored. Emission spectra were obtained with the use of excitation wavelengths of 340, 365, 405, 430 and 460 nm. Fluorescence lifetimes were measured at 430, 487, and 514 nm while selective excitation was caused at 340, 405, and 430 nm. The complex nature of the excitation and emission spectra reflects the presence of a number of different fluorophores. Attempts have been made to describe portions of the bacterial fluorescence in terms of the measured fluorescence properties including lifetimes of molecular components known for their widespread occurrence in bacteria and their relatively high quantum yields. Candidate fluorophores which have been considered include the pteridines, the structurally related flavins, and the pyridine coenzymes. The observation that characteristic sets of lifetimes have been obtained for each organism suggests that measurements of fluorescence lifetimes may be helpful in the rapid characterization of bacteria. Results are especially definitive in cases such as Pseudomonas fluorescens, where one marker fluorophore, a pteridine, is produced in large amounts.

High-quality resonance Raman spectra in the visible region can be obtained from very small aggregates of chromobacteria, and very useful spectra can be obtained from individual cells. Individual cells in bacterial mixtures have been clearly identified by argon-laser-excited resonance Raman spectra taken with a commercially available Spex Micramate. Organisms present in the vicinity of the laser beam and in the beam itself can be observed and counted with ease by means of a television image obtained via a vidicon tube attached to a microscope. The method appears capable of identification at the species level.

A novel optical approach to single-shot chemical imaging with high spectroscopic resolution is described with the use of a prototype dimension-reduction fiber-optic array. Images are focused onto a 30 × 20 array of hexagonally packed 250 μm o.d. f/2 optical fibers that are drawn into a 600 × 1 distal array with specific ordering. The 600 × 1 side of the array is imaged with an f/2 spectrograph equipped with a holographic grating and a charge-coupled device (CCD) camera for spectral analysis. Software is used to extract the spatial/spectral information contained in the CCD images and de-convolute them into wavelength-specific reconstructed images or position-specific spectra that span a 190 nm wavelength space. “White light” zero-order images and first-order spectroscopic images of laser plumes have been reconstructed to illustrate proof-of-principle. Index Headings: Fiber optics; Chemical imaging; Spectroscopic imaging; Charged-coupled device (CCD); Laser-induced breakdown spectroscopy (LIBS).

Two-dimensional (2D) FT-IR correlation analysis was applied to both the mid-IR (MIR) and near-IR (NIR) regions to investigate changes in the secondary structures of β-lactoglobulin in D2O (or H2O) solvent systems consisting of varying concentrations of bromoethanol. Mid-IR correlation spectra indicate that the amide I bands corresponding to different structures (i.e., α-helical structures at 1650 cm−1, aggregated β-strands at 1620 cm−1, and β-sheet at 1636 cm−1) exhibit apparently different spectral response towards varying concentrations of bromoethanol. We propose that the mechanism for the conversion of the β-sheet into α-helix occurs in terms of two parallel pathways, i.e., (1) β-sheets → aggregated β-strands →α-helix, and (2) β-sheets →α-helix. Although the amide B/amide II combination bands give no spectral features relating to the secondary structure, changes were found in the C–H combination bands that suggest an interaction between the solvent and the protein.

Bacteria grown on trypticase soy agar (TSA), trypticase soy broth (TSB), and Davis minimal media, and harvested at times ranging from 4.5 to 48 h have been excited at 242.54 and 222.65 nm for the purpose of generating resonance Raman spectra. When excitation with 242.54-nm light occurs, simple spectra of tyrosine and tryptophan and various nucleic acids are observed. Large changes in the relative intensities of major nucleic acid peaks at 1485 and 1575 cm−1, on the one hand, as compared to a prominent protein tyrosine + tryptophan peak at 1616 cm−1, on the other, have been attributed to very large variations in the RNA content of bacterial cells from culture to culture. The spectral changes are observed whenever differences in growth rates or variations in cultural media result in substantial changes in the amount of ribosomal RNA. In spite of very large cultural effects on peak intensities it has been possible to obtain bacterial G + C/A + T ratios from these spectra. Specifically, the ratio of the intensity of the C (1530 cm−1) peak to the intensity of the A + G peak (1485 cm−1) when plotted against the known molar percent G + C of the corresponding bacterial DNA produces a straight line. Plots have been shown to be very nearly growth-time and media independent for fourteen different types of bacteria, which range in DNA G + C content from 32 to 66%. Spectra obtained with 222.65-nm light, in contrast with spectra obtained with 242.54-nm excitation, have been found to be nearly growth-rate and media independent. The excitation wavelength, 222.65 nm, appears to be the best yet found for use in rapid Raman identification of bacteria. All strong peaks which have been assigned have been attributed to protein modes. Relative intensities of 1556-cm−1tryptophan and 1616-cm−1tryptophan + tyrosine bands have been found to be strongly correlated with bacterial Gram type and nearly independent of cultural media or stage of growth.

High-quality, UV-excited (218–242 nm), fluorescence-free conventional Raman spectra have been generated from UV-transparent polymers such as polytetra-fluoroethylene (Teflon®), polyethylene, polypropylene, and polyoxymethylene (Delrin®). Spectra can be generated with the use of low exciting power (<1 mW), but even at low power, precautions have to be taken to prevent photo-oxidation and thermal degradation of samples. Polyvinylchloride polymers especially have been found to be prone to degradation. Weakly absorbing polymers such as nylon and polybutadiene show special promise for Raman analysis, because they exhibit significant preresonance enhancement of structurally significant modes, and because they still retain information derived from conventional Raman spectra. Strongly preresonance-enhanced ethylenic modes of polybutadiene isomers can be resolved, allowing the easy identification of cisand transisomers. In contrast, strongly absorbing polymers such as polystyrene, polycarbonate, and polyphenolics show only intense, resonance-enhanced Raman spectra. Unfortunately, Raman spectra of these materials are limited to phenyl ring modes, and all valuable conventional Raman spectra are totally lost due to internal absorption.

UV resonance Raman spectra of Bacillus cereus, Bacillus megaterium, and Bacillus subtilisendospores have been excited at 222.7,230.7,242.5, and 251.1 nm, and spectra have been compared with those of vegetative cells. The resonance Raman spectra of aqueous solutions of dipicolinic acid and calcium dipicolinate have been measured at the same wavelengths. Spectra of endospores and their corresponding germinated spores show only modest differences when excited at 222, 231, and 251 nm. However, very substantial differences appear when excitation occurs at 242 nm. Difference spectra obtained at 242 nm by subtracting spectra of germinated spores of Bacillus cereusfrom spectra of their corresponding endospores are attributed almost entirely to dipicolinate. Vegetative cells and endospores show large spectral dissimilarities at all exciting wavelengths. These spectral differences, which vary strongly with exciting wavelength, appear to be the result of large differences in the amounts and composition of proteins and nucleic acids, especially ribosomal RNA. The very substantial resonance enhancement of Raman spectra has been obtained from aqueous solutions of pure dipicolinic acid and of sodium and calcium dipicolinate salts, as well as spores at the various exciting wavelengths. The strong enhancement of dipicolinate spectra in spores, however, was noted only with 242-nm excitation. Consequently, only with 242-nm light was it possible to selectively and sensitively excite and study calcium dipicolinate in spores. Resonance enhancement of the dipicolinate spectra with 242-nm excitation appears due primarily to resonance interactions with n-π* electronic transitions associated with the pyridine ring and/or the carboxylate group.

Domoic acid, an amino acid neurotoxin, produces a single intense resonance Raman peak observed at 1652 cm−1from aqueous solution when excited at either 242 or 257 nm. The detection limits for domoic acid in water are found to be well within those concentrations determined to be representative of values in toxic phytoplankton cells. Examination of cells known to contain identified large amounts of domoic acid shows that domoic acid spectra are sufficiently intensely excited to allow detection in the presence of normal phytoplankton cell constituents within the cell. Single cells from species established as producers of domoic acid, cultured under controlled conditions favorable to the production of domoic acid, produce spectra consistent with the presence of domoic acid in low concentrations.

The Raman spectra of cis, trans, and vinyl isomers of crotyl chloride (i.e., cisand trans1-chloro-2-butene, and 3-chloro-1-butene) have been excited at 218 nm and at 231 nm. With 218-nm excitation the ethylenic mode belonging to the vinyl isomer is only modestly preresonance enhanced. On the other hand, the preresonance enhancement of the peaks belonging to the cisand transisomers is very noticeable and nearly identical in energy to the peaks of cisand transpolybutadiene, which occur at 1655 and 1665 cm−1, respectively. However, with 231-nm excitation the vinyl-isomer ethylenic mode at 1633 cm−1is very strongly enhanced, while the cisand transisomer modes show no corresponding enhancement, but appear to decrease in relative intensity. Responsibility for the strong vinyl group enhancement is assigned to an electronic transition observed as a broad shoulder near 230 nm. By exciting at 231 nm it is possible to detect small amounts of the vinyl isomer in the presence of cisand transcrotyl chloride. Remarkably strong enhancement under 231-nm excitation has been noted as well for the first overtone of the vinyl ethylenic mode observed at 3263 cm−1.

The use of FT-IR gas-phase difference spectroscopy for the determination of isotopically labeled species in the study of catalytic reaction mechanisms is illustrated. Applications are based on the study of the mechanism of oxidative coupling of methane over oxide catalysts and include determinations of: (1) deuterated and partially deuterated ethylenes and ethanes from experiments with 2H labeling of the methane; (2) 18O contents of CO and CO2from experiments with 18O labeling of O2, CO, and CO2; (3) 13C/12C ratios in hydrocarbons and carbon oxides from experiments with 13C labeling of C2hydrocarbons. The major limitation of the technique is in regions of strong absorption where nonlinear effects make subtraction difficult; however, this limitation could be alleviated by judicious choice of pathlength. This technique is a powerful supplement to measurements based on mass spectrometry.

Time-resolved fluorescence spectra have been obtained for Escherichia coli, Pseudomonas fluorescens, Staphylococcus epidermidis, and Enterobacter cloacae. Pseudomonas fluorescenshas been shown to have distinctly different time-resolved spectra. Fluorescence excitation spectra for the three other organisms showing similar time-resolved spectra are very nearly alike, while spectra of Pseudomonas fluorescensare markedly different. This suggests that the changes in the average fluorescence lifetime with emission wavelength are due to the separate contributions from fluorophores of distinctly different lifetimes which have emission maxima at different wavelengths.

Resonance Raman spectra of the gram-negative organism, Escherichia coli, have been obtained with 222.5-, 230.6-, and 251.0-nm excitation, and the results have been compared with those reported earlier for 242.4-nm excitation. Major changes in bacterial spectra have been observed with changes in exciting wavelength. The origins of the major peaks in each spectrum have been explained primarily in terms of contributions of nucleic acid bases and aromatic amino acids. As an aid in making assignments, spectra of aromatic amino acids, nucleosides, and mixtures of the two have been obtained at each wavelength used to excite bacterial spectra. Background fluorescence has been observed to be negligible below 251 nm. Selective excitation of bacterial nucleic acid and protein components has been done with ease. Results suggest that an extension of the exciting wavelength range to 190–220 nm will allow the selective excitation of additional cell components.

The intrinsic steady-state fluorescence due to tryptophan has been obtained from monospecific cultures of fourteen plankton algae of various genera. Fluorescence decay profiles of protein tryptophan residues were obtained for eight marine plankton algae. Each organism exhibits a strong maximum in its emission spectrum at 320–340 nm when excited at 290 nm. Iodide quenching and denaturization experiments with 8 M urea provide strong evidence for the assignment of the 320–340 nm fluorescence to protein tryptophan. Most importantly, the decay of this bacterial protein tryptophan fluorescence has been described. The observation that characteristic protein-tryptophan fluorescence lifetimes have been obtained for each organism suggests that measurements of fluorescence lifetimes may be helpful in the rapid characterization of algae. Direct application will likely be found in combination with the measurement of other luminescence parameters.

A scanning algorithm for condensed-phase CARS and folded BOXCARS along with the necessary optical alignment hardware for folded BOXCARS have been developed. Due to the unique geometry of the folded BOXCARS beams, the CARS signal is sufficiently isolated from the pump and Stokes beams such that extended spectra with a lower frequency limit of 70 cm−1have been obtained.

Ultraviolet-excited (242 nm) resonance Raman spectra have been obtained for the first time for five types of bacteria: Escherichia coli, Pseudomonas fluorescens, Staphylococcus epidermidis, Bacillus subtilis, and Enterobacter cloacae. Detailed, highly reproducible spectra show substantial differences in both the intensities and the energies of peaks, which suggests that such spectra provide unique “fingerprints” reflecting the unique combinations of chemotaxonomic markers present in each type of organism. Many of the spectral features excited by 242-nm radiation probably arise from cellular RNA, DNA, and the amino acids tyrosine and tryptophan. Background fluorescence has been shown to be negligible.

Resonance Raman spectra have been obtained with 218-nm excitation for Escherichia coliand Staphylococcus epidermidis.Large intensity differences seen in the tryptophan-associated 1556-cm−1peak appear to be strongly related to Gram type. Unlike E. coli, S. epidermidispossess a very intense peak at 1658 cm−1which varies in intensity with cultural conditions. Spectra excited from E. coliand Enterobacter aerogeneswith 200-nm light show peaks which strongly reflect nucleic acid composition, unlike spectra excited at 218 nm. Purified, separated ribosomes of E. coliproduce spectra which are dominated by nucleic acid vibrations when excited at 242 nm, but have peaks belonging nearly exclusively to protein aromatic amino acids when excited at 222 nm. The relative weakness of bacterial RNA modes excited at 222 nm from whole cells and ribosomes is attributed to nucleic acid hypochromism.

An electrothermal fountain is used to heat gas-phase samples in the range of 300 to 400°C in order to observe their near-infrared (NIR) emissions. In conjunction with the fountain, a 1/8-m Ebert monochromator and an uncooled PbS detector are shown to be sufficiently sensitive for recording the NIR fingerprints of CH4, CO2, N2O, and C2H6. At fountain temperatures of approximately 400°C, the molecular emission is confined to the long wavelength NIR region (1600–2500 nm) and yields limits of detection in the range of 4 to 10% v/v (3–10 mg/s). Reproducibilities have relative standard deviations of 3.0%. The calibration curves for the gases examined in this study have small linear dynamic ranges (factors of 2 to 10) and exhibit some degree of upward curvature. Ramifications of the application of NIR molecular emission spectroscopy to the qualitative and quantitative analyses of mixtures are discussed.

Fourier transform (FT)-Raman spectroscopy has been used to obtain high-quality spectra of 32 explosive materials. The majority of the spectra of these explosives have not previously been reported. Twenty-eight of the explosives have been categorized into three classes (nitrates esters, nitro-aromatics, and nitramines) based on their chemical structure, the position of the antisymmetric and symmetric stretching vibrations of the nitro group, and the shapes of the band envelopes. The spectra of exceptional explosives are discussed in terms of their unique structures or compositions.

The implementation of neural, fuzzy, and statistical models for the unsupervised pattern recognition and clustering of Fourier transform (FT)-Raman spectra of explosive materials is reported. In this work a statistical pattern recognition technique based on the concept of nearest-neighbors classification is described. Also the first application of both fuzzy clustering and a fuzzified Kohonen clustering network for the analysis of vibrational spectra is presented. Fuzzified Kohonen networks were found to perform as well as or better than the traditional fuzzy clustering technique. The unsupervised pattern recognition techniques, without the need for a prioristructural information, yielded results which were comparable with those obtained by using a combination of a prioristructural information and manual group-frequency analysis. This work demonstrates, via the use of a nitro-containing explosive data set, the utility of unsupervised pattern recognition techniques for the clustering, novelty detection, prototyping, and feature mapping of Raman spectra. The results of this work are directly applicable to the characterization of Raman spectra of explosives recorded with fiber-optic sampling.

The light-induced yellowing of the surface of paper made from a Eucalyptus regnanschemimechanical pulp has been studied by using second-derivative diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy in the region 1550 to 1800 cm−1. The observed reflectances were transformed to Kubelka-Munk units and the second derivatives obtained. Use of the second derivative technique has resulted in reduced bandwidths, enabling bands such as that at 1612 cm−1arising from exocyclic C=C bonds in lignin to be resolved from the broad envelope of the strong C=C ring stretching band at 1591 cm−1. The improved resolution has enabled the effects of UV light on the population of potential chromophoric C=0 and C=C groups in paper surfaces to be studied more precisely.

Resonance Raman spectra are reported for 16 types of carotene-containing bacteria and algae in aqueous dispersion. Spectra are obtained with ease from organisms grown in culture and collected by centrifugation. In many instances spectra produced with 488 nm incident radiation are sufficiently unique to provide a basis for identification. While most information is contained in the 900 to 1600 cm−1region, several bacteria exhibit pronounced carotenoid overtone and combination bands which can be assigned along with the fundamental vibrations.

The intrinsic steady-state fluorescence and fluorescence decay of Staphylococcus epidermidis, Pseudomonas fluorescens, Enterobacter cloacae, Escherichia coli, and Bacillus subtilishave been observed. Each organism exhibits a strong maximum in its emission spectrum at 330–340 nm when excited at 290 nm. Iodide quenching and denaturization experiments with 8 Murea provide strong evidence for the assignment of the 330–340-nm fluorescence to protein tryptophan. Most importantly, the decay of this bacterial protein-tryptophan fluorescence has been described by two exponential functions in all cases. The observation that characteristic protein-tryptophan fluorescence lifetimes have been obtained for each organism suggests that measurements of fluorescence lifetimes may be helpful in the rapid characterization of bacteria. Direct application will most likely be found in combination with the measurement of other luminescence parameters.

By using some of the excellent background material available from the literature, the tool of the statistically designed experiment is applied in the development and evaluation of spectrographic methods A preliminary design is carried through to determine the major factors affecting a method's total variability Further designs then study these gross variables in greater detail Eventually a reliable method, of known precision and bias, is developed, and the method is ready for routine use During the routine use, a quality control program is carried on to maintain a check on the results and yield a realistic estimate of variability over a period of timeThe paper gives a bibliography of books and articles that the author has found particularly useful

Airborne halogen compounds have been found to greatly increase the intensity of the N2and NO molecular spectra of air in an ac spark. Chlorinated materials cause the largest enhancement followed by brominated, iodinated, and fluorinated compounds. This phenomenon can effectively be used to measure the presence of many volatilized halogen compounds present in concentrations as low as 1 ppm.

Low-grade carbonaceous gold ore (0.01 to 1.8 oz/ton of gold) from the Carlin mine in Elko county, Nevada, has been characterized by a variety of analytical and spectroscopic techniques with emphasis on vibrational spectroscopy. A particular concern was determining the nature of the carbon-containing material in the ore. It was found that in addition to the anticipated carbonate, finely disseminated elemental carbon is present in amounts ranging from 0.062 to 0.43 wt. %. Contrary to previous reports, no detectable amounts of humic acid materials or organic hydrocarbons are present in any of the samples investigated.