Donald F. Gurka

Environmental applications of gas chromatography/atomic emission detection.

A gas chromatograph/atomic emission detector (GC/AED) system has been evaluated for its applicability to environmental analysis. Detection limits, elemental response factors, and regression analysis data were determined for 58 semivolatile environmental contaminants. Detection limits for injected analytes ranged from 0.17 to 3.0 ng on the hydrogen 486-nm channel, from 1.0 to 5.0 ng on the nitrogen 174-nm channel, from 0.65 to 11.7 ng on the oxygen 777-nm channel, from 0.071 to 3.0 ng on the chlorine 479-nm channel, and from 0.023 to 0.038 ng on the sulfur 181-nm channel. Mean elemental response factors (ERFs) measured on these channels, relative to the carbon 496-nm channel, were hydrogen, 0.084 (mean %RSD = 6.6); nitrogen, 0.246 (mean %RSD = 19); oxygen, 0.459 (mean %RSD = 16); and chlorine, 0.417 (mean %RSD = 3.6). The higher precision obtained for hydrogen and chlorine, relative to that for nitrogen and oxygen, is attributed to the ability to scan these elemental channels in the same GC run as the carbon 496-nm channel (diode array wavelength range limitation of ∼40 nm/run). Mean ERFs of standard compounds were used to determine the molecular formulas of chlorinated hydrocarbons and chlorinated organosulfur compounds in a contaminated environmental soil sample. These formulas are in good agreement with the molecular weights and chlorine isotopic data obtained from low-resolution gas chromatography/mass spectrometry.

Qualitative and quantitative environmental analysis by capillary column gas chromatography/lightpipe Fourier-transform infrared spectrometry.

rn A new state-of-art commercial gas chromatography/ Fourier transform infrared (GC/FT-IR) lightpipe-containing system has been evaluated for its applicability to qualitative and quantitative environmental analysis of typical environmental contaminants. This system exhibited minimum identifiable quantities, for many compounds, in the 10-50-ng range. On a wide-bore capillary column, quantitation curves generated from chromatogram peak areas were linear over the 10-250-ng range. The mean correlation coefficient for 38 quantitation calibration curves on 24 standards was 0.976. The selectivity of the new system was evaluated with standards, soil, and stillbottom samples. It was demonstrated with 27 standards that no discernible loss in identification selectivity occurred when a narrow-band infrared detector (spectral cutoff 750 cm-l) was used in place of a midband detector (cutoff 700 cm-l). This allows the meaningful utilization of the extra sensitivity associated with narrower frequency range infrared detectors.

QUANTITATIVE DETECTION OF ENVIRONMENTALLY IMPORTANT DYES USING DIODE LASER/FIBER-OPTIC RAMAN SPECTROSCOPY

A compact diode laser/fiber-optic Raman spectrometer is used for quantitative detection of environmentally important dyes. This system is based on diode laser excitation at 782 nm, fiber-optic probe technology, an imaging spectrometer, and a state-of-the-art scientific CCD camera. The dyes studied include trypan blue, acid black 1, acid blue 40, and basic blue 7. Detection sensitivities (at rms S/N = 2) ranged from 0.2 ppm (3.24 × 10−7 M) for acid black 1, to 25 ppm (4.86 × 10−5 M) for basic blue 7.

Micro-Diffuse Reflectance and Matrix Isolation Fourier Transform Infrared Techniques for the Identification of Tetrachlorodibenzodioxins

Micro-diffuse reflectance Fourier transform infrared (DRIFT) and matrix isolation (MI) Fourier transform infrared spectra of the 22 tetrachlorodibenzodioxin (TCDD) isomers have been recorded. The DRIFT and MI techniques required about four minutes and one-half minute, respectively, of signal averaging to produce high signal-to-noise (S/N) spectra on low-nanogram-level samples. Spectral subtraction was employed to remove DRIFT solvent impurity interferences. The validity of the DRIFT subtraction technique was demonstrated by comparison of the corrected DRIFT, with the chromatographically pure, MI spectra. The reproducibility of DRIFT frequencies and intensities was tested by comparison of the 1,3,7,8-TCDD spectra from samples independently prepared by two analysts. The MI technique successfully identified 2,3,7,8 in environmental samples. MI spectral subtraction was applied to one sample to remove a coeluting impurity. The DRIFT and MI spectral techniques, used in conjunction with modern chromatographic separation and spectral subtraction, are very promising for the on-line or off-line differentiation of low-level toxic isomeric compounds.

Volatile organic analysis by direct aqueous injection

Gas chromatographic environmental analysis by direct aqueous injection (DAI) was studied for 24 volatile organic analytes (VOAs). Internal standardization was used to determine the precision of analysing these compounds by DAI. Aqueous samples were directly introduced to a gas chromatograph using fused-silica, mega-bore capillary column separation with subsequent full-scan ion trap mass spectral detection. Triplicate injections at seven levels of VOA standard solutions over a 10(3) concentration range were performed using an autosampler set up for on-column injection of 0.2 microl. Comparison of single-ion response curves to triple-ion response curves showed that triple-ion quantitation was more sensitive and precise than single-ion quantitation. Of the 24 VOAs determined at the 20 parts per billion (ppb) level, 19 and 20 were detected by the single-ion calibration and triple-ion calibration, respectively. The weighted and non-weighted regression correlation coefficients, r(2), for the 24 responses curves by the two methods, ranged from 0.910 to 0.998, with 76 of 96 being greater than 0.990. Precision, as measured by per cent relative standard deviation, was shown to be best for later eluting compounds and for higher concentrations. Analysis of an environmental sample by DAI was accomplished in 12 min and indicated the presence of benzene at 80 ppb and chlorobenzene at 2 ppm. This demonstrated the feasibility of applying this technique for screening. Several chlorinated benzenes were also detected, establishing the potential for expanding the method to include higher boiling compounds.

Interim Protocol for the Automated Analysis of Semivolatile Organic Compounds by Gas Chromatography/Fourier Transform Infrared (GC/FT-IR) Spectrometry

The application of gas chromatography/Fourier transform infrared (GC/FT-IR) data to regulatory decisions requires, among other things, the availability of validated analytical protocols. Such protocols are necessary for the generation of reliable analytical data. A GC/FT-IR protocol is described which is applicable to the determination of semivolatile organic compounds in wastewater, soils, sediments, and solid wastes. The protocol is designed for the high-throughput automated analysis of multicomponent environmental and hazardous waste extracts. Wastewater analysis for semivolatile organic compounds is based upon the extraction of 1 L of sample with methylene chloride and the concentration of the extract to 1 mL. The analysis of the semivolatile fraction derived from solid waste analysis is based upon the extraction of 50 grams of sample and concentration of the sample extract to 1.0 mL. A gel permeation cleanup option is included to further purify those extracts which cannot be concentrated to the specified final volume. With the use of capillary GC/FT-IR techniques, wastewater identification limits of 150 to 400 ppb can be achieved with this method, while the corresponding identification limits for solid samples are 3 to 88 ppm. Automated packed-column GC/FT-IR identification limits are approximately a factor of five higher than the corresponding capillary GC/FT-IR values. The most frequent obstacle to the achievement of these identification limits is expected to be the presence of large quantities of interfering high-boiling coextractants. These coextractants would raise the identification limits by preventing the concentration of extracts to the desired final volume, thereby necessitating gel permeation cleanup, and/or by decreasing the spectral signal-to-noise of GC-volatile analytes by raising the spectral background intensity.

The Measurement of On-the-Fly Fourier Transform Infrared Reference Spectra of Environmentally Important Compounds

The United States Environmental Protection Agency (U.S. EPA) requires reference spectra to support its gas chromatography/Fourier transform infrared (GC/FT-IR) routine environmental monitoring program. Although on-the-fly (OTF) techniques are needed to satisfy the Agencys high sample throughput requirements, the FT-IR vapor-phase reference spectra produced by the Agency thus far have been measured under static conditions. Accordingly, the OTF spectra of 47 environmentally important compounds have been measured by packed-column GC/FT-IR under carefully controlled conditions. The compounds selected for spectral measurement are currently regulated by the U.S. EPA and generally represent compound classes which are absent, or poorly represented, in the current U.S. EPA data base (e.g., organochlorine and organophosphorus pesticides). Where feasible, the Co-blentz Society guidelines for the measurement and recording of vapor-phase infrared reference spectra and supporting data were followed. The sensitivity order of the reference compounds as determined by the strongest spectral band and the quantity of compound injected on-column was, organophosphorus and thio-organophosphorous > aliphatic organochlorine ≥ polynuclear aromatic.

Identification of pollutants in a municipal well using high resolution mass spectrometry.

An elevated incidence of childhood cancer was observed near a contaminated site. Trace amounts of several isomeric compounds were detected by gas chromatography/mass spectrometry (GC/MS) in a concentrated extract of municipal well water. No matching library mass spectra were found and Fourier transform IR and NMR analyses were not feasible due to the low concentration of the compounds. Mass peak profiling from selected-ion-recording data (MPPSIRD) provided the sensitivity and scan speed necessary to acquire mass peak profiles at mass resolutions of 10,000 to 20,000 for the molecular ion (M+) and 10 fragment ions as capillary GC peaks eluted. Using a profile generation model (PGM), the elemental composition of the molecular ion was determined from the exact masses and abundances of the M, M + 1 and M + 2 profiles. Fragment ion compositions were determined from their exact masses based on the elements in the molecular ion. Exact mass differences between the molecular and fragment ions corresponded to unique combinations of atoms for the neutral losses. Consequent reduction of the number of possible structures for the fragment ions simplified mass spectral interpretation. After inspecting library mass spectra for smaller molecules, isomeric structures were hypothesized with cyano and alkylcyano groups attached to tetralin. A literature search found such isomers produced by an industrial polymer synthesis. Three isomers in a standard form polymerization of styrene and acrylonitrile provided the same mass spectra and GC retention times as isomers in the extract.

Optimization of a Fourier transform infrared spectrometer during on-site pollution analysis

The field transportable Fourier transform infrared (FT-IR) spectrometer system developed at Kansas State University is now finishing the testing stage. The testing stage consisted of three parts: the measurements of (1) controlled releases of volatile organic compounds (VOC), (2) uncontrolled VOC releases at well documented sites, and (3) uncontrolled VOC releases at complex sites with little or no precharacterization1. Some measurements have been acquired in all three categories with most of the data acquisition taking place in the first two categories, which are discussed in these proceedings. These tests were developed to validate the qualitative and quantitative capabilities while enhancing the versatility and detection limits of the spectrometer system. The controlled VOC releases, for the most part, took place at the University of Kansas (KU). The KU tests utilized a co-monitoring technique, evacuated stainless steel canisters followed by GC/FID analysis, during the acquisition of the infrared data. The ability to monitor the concentrations of the released plume with another technique allowed for the comparison and examination of how varying parameters can affect the infrared spectrometer technique. The varying parameters that were addressed were wind, path length, temperature, barometric pressure, water and carbon dioxide concentration, and air borne particulates. One set of uncontrolled releases occurred at an active production facility. A list of the possible compounds that might be observed from the facility directly due to production was obtained. Infrared measurements were acquired at two different setup geometries down wind and one setup geometry up wind. The three path lengths were 390 meters, 500 meters, and 412 meters respectively. During these measurements two series of canister samples were obtained down wind and one series of canister samples were obtained up wind. The analyses of these canisters, on-going at this writing, is being performed by GC/FT-IR (matrix isolation). When the analysis from this method is complete the results will be compared. These two different data acquisitions have led to much insight into the capabilities of the spectrometer system and how varying parameters can affect the FT-IR spectrometers performance. Preliminary analysis of the spectroscopic data from both data acquisitions will be discussed.

Applications of infrared spectroscopy to dioxin analyses of environmental samples

Abstract The gas chromatography/matrix isolation/Fourier transform-infrared spectra of 2,3,7,8-TCDD and its totally C-13 labeled isotopomer have been obtained at levels in the low nanogram range, and a problem with the infrared spectrum of this isotopomer has been cleared up. Potential future applications of infrared spectroscopy to dioxin analyses are also discussed.