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Forland BM, Hughey KD, Wilhelm MJ, Williams ON, Cappello BF, Gaspar CL, Myers TL, Sharpe SW, Johnson TJ. Optimal Spectral Resolution for Infrared Studies of Solids and Liquids. APPLIED SPECTROSCOPY 2024; 78:486-503. [PMID: 38404070 DOI: 10.1177/00037028241231601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Due to a legacy originating in the limited capability of early computers, the spectroscopic resolution used in Fourier transform infrared spectroscopy and other systems has largely been implemented using only powers of two for more than 50 years. In this study, we investigate debunking the spectroscopic lore of, e.g., using only 2, 4, 8, or 16 cm-1 resolution and determine the optimal resolution in terms of both (i) a desired signal-to-noise ratio and (ii) efficient use of acquisition time. The study is facilitated by the availability of solids and liquids reference spectral data recorded at 2.0 cm-1 resolution and is based on an examination in the 4000-400 cm-1 range of 61 liquids and 70 solids spectra, with a total analysis of 4237 peaks, each of which was also examined for being singlet/multiplet in nature. Of the 1765 liquid bands examined, only 27 had widths <5 cm-1. Of the 2472 solid bands examined, only 39 peaks have widths <5 cm-1. For both the liquid and solid bands, a skewed distribution of peak widths was observed: For liquids, the mean peak width was 24.7 cm-1 but the median peak width was 13.7 cm-1, and, similarly, for solids, the mean peak width was 22.2 cm-1 but the median peak width was 11.2 cm-1. While recognizing other studies may differ in scope and limiting the analysis to only room temperature data, we have found that a resolution to resolve 95% of all bands is 5.7 cm-1 for liquids and 5.3 cm-1 for solids; such a resolution would capture the native linewidth (not accounting for instrumental broadening) for 95% of all the solids and liquid bands, respectively. After decades of measuring liquids and solids at 4, 8, or 16 cm-1 resolution, we suggest that, when accounting only for intrinsic linewidths, an optimized resolution of 6.0 cm-1 will capture 91% of all condensed-phase bands, i.e., broadening of only 9% of the narrowest of bands, but yielding a large gain in signal-to-noise with minimal loss of specificity.
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Affiliation(s)
- Brenda M Forland
- Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Kendall D Hughey
- Pacific Northwest National Laboratory, Richland, Washington, USA
| | | | | | | | - Connor L Gaspar
- Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Tanya L Myers
- Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Steven W Sharpe
- Pacific Northwest National Laboratory, Richland, Washington, USA
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Thompson CJ, Gallagher NB, Hughey KD, Dunlap MK, Myers TL, Johnson TJ. An Interactive Spectral Analysis Tool for Chemical Identification and Quantification of Gas-Phase Species in Complex Spectra. APPLIED SPECTROSCOPY 2023; 77:557-568. [PMID: 37097834 DOI: 10.1177/00037028231169304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
A spectral analysis tool has been developed to interactively identify and quantify individual gas-phase species from complex infrared absorbance spectra obtained from laboratory or field data. The SpecQuant program has an intuitive graphical interface that accommodates both reference and experimental data with varying resolution and instrumental lineshape, as well as algorithms to readily align the wavenumber axis of a sample spectrum with the raster of a reference spectrum. Using a classical least squares model in conjunction with reference spectra such as those from the Pacific Northwest National Laboratory (PNNL) gas-phase infrared database or simulated spectra derived from the HITRAN line-by-line database, the mixing ratio of each identified species is determined along with its associated estimation error. After correcting the wavelength and intensity of the field data, SpecQuant displays the calculated mixing ratio versus the experimental data for each analyte along with the residual spectrum with any or all analyte fits subtracted for visual inspection of the fit and residuals. The software performance for multianalyte quantification was demonstrated using moderate resolution (0.5 cm-1) infrared spectra that were collected during the time-resolved infrared photolysis of methyl iodide.
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Affiliation(s)
| | | | - Kendall D Hughey
- Chemical Physics and Analysis, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Megan K Dunlap
- Chemical Physics and Analysis, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Tanya L Myers
- Chemical Physics and Analysis, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Timothy J Johnson
- Chemical Physics and Analysis, Pacific Northwest National Laboratory, Richland, WA, USA
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Medina AS, Felmy HM, Vitale-Sullivan ME, Lackey HE, Branch SD, Bryan SA, Lines AM. Iodine and Carbonate Species Monitoring in Molten NaOH-KOH Eutectic Scrubber via Dual-Phase In Situ Raman Spectroscopy. ACS OMEGA 2022; 7:40456-40465. [PMID: 36385882 PMCID: PMC9647834 DOI: 10.1021/acsomega.2c05522] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Accepted: 10/14/2022] [Indexed: 06/16/2023]
Abstract
Molten hydroxide scrubbing of off-gas vapors is a potential process to improve safety during the operation of generation IV molten salt nuclear reactors (MSRs). MSRs produce off-gases that can be vented by the reactor core and treated via off-gas scrubbers. Molten hydroxide scrubbers focus on capturing volatile iodine radionuclides, and they can also be used to capture aerosols and particulates and to neutralize acidic species. The performance of these scrubbers depends on the chemical interactions of the scrubbing medium with the off-gas species. Knowledge of the concentration and speciation of scrubbed or target species, as well as process and environmental interferents, can enable advanced operation of MSR off-gas treatment systems. Optical online monitoring is an excellent technology to provide this information in real time, while limiting the need for operators to interact with radioactive samples through hands-on interrogation. Raman spectroscopy can provide crucial chemical information on the state of the molten eutectic during treatment in the molten phase, as well as the gas phase. In this work, Raman spectroscopy is used to detect iodine species, specifically iodate, in the molten phase of a NaOH-KOH eutectic and to construct a calibration curve of the Raman signal of those species. Additionally, a carbonate interferent is followed from the gas phase to the liquid phase as a basis for reaching a Raman-aided mass balance of the molten hydroxide eutectic scrubber system.
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Review of molten salt reactor off-gas management considerations. NUCLEAR ENGINEERING AND DESIGN 2021. [DOI: 10.1016/j.nucengdes.2021.111529] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Johnson TJ, Hughey KD, Blake TA, Sharpe SW, Myers TL, Sams RL. Confirmation of PNNL Quantitative Infrared Cross-Sections for Isobutane. J Phys Chem A 2021; 125:3793-3801. [PMID: 33904739 DOI: 10.1021/acs.jpca.1c01933] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Pacific Northwest National Laboratory (PNNL) gas-phase database is a compilation of quantitative experimental (5, 25, and 50 °C) infrared spectra of ca. 500 molecules, designed for in situ, standoff or remote sensing of gases and vapors at or near atmospheric pressure. The data are characterized by calibration on both the wavenumber and intensity axes. Recent papers have called into question the PNNL intensity values for isobutane, [2-methylpropane, HC(CH3)3], suggesting discrepancies of 30-40%. In this study, we remeasure and re-examine the intensity values of isobutane using both similar and alternate methods to those used to generate the original PNNL database spectra. Indirect confirmation from literature data of homologous molecules and direct confirmation from new results confirm that for many band integrals across the isobutane spectrum, the original PNNL data are indeed accurate to within the reported 3% experimental uncertainty.
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Affiliation(s)
- Timothy J Johnson
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Kendall D Hughey
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Thomas A Blake
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Steven W Sharpe
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Tanya L Myers
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Robert L Sams
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
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Clifford AJ, Lackey HE, Nelson GL, Bryan SA, Lines AM. Raman Spectroscopy Coupled with Chemometric Analysis for Speciation and Quantitative Analysis of Aqueous Phosphoric Acid Systems. Anal Chem 2021; 93:5890-5896. [PMID: 33780245 DOI: 10.1021/acs.analchem.1c00244] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Complex chemical systems that exhibit varied and matrix-dependent speciation are notoriously difficult to monitor and characterize online and in real-time. Optical spectroscopy is an ideal tool for in situ characterization of chemical species that can enable quantification as well as species identification. Chemometric modeling, a multivariate method, has been successfully paired with optical spectroscopy to enable measurement of analyte concentrations even in complex solutions where univariate methods such as Beer's law analysis fail. Here, Raman spectroscopy is used to quantify the concentration of phosphoric acid and its three deprotonated forms during a titration. In this system, univariate approaches would be difficult to apply due to multiple species being present simultaneously within the solution as the pH is varied. Locally weighted regression (LWR) modeling was used to determine phosphate concentration from spectral signature. LWR results, in tandem with multivariate curve resolution modeling, provide a direct measurement of the concentration of each phosphate species using only the Raman signal. Furthermore, results are presented within the context of fundamental solution chemistry, including Pitzer equations, to compensate for activity coefficients and nonidealities associated with high ionic strength systems.
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Affiliation(s)
- Andrew J Clifford
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Hope E Lackey
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Gilbert L Nelson
- Department of Chemistry, College of Idaho, Caldwell, Idaho 83605, United States
| | - Samuel A Bryan
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Amanda M Lines
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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Hughey KD, Tonkyn RG, Harper WW, Young VL, Myers TL, Johnson TJ. Preliminary studies of UV photolysis of gas-phase CH3I in air: Time-resolved infrared identification of methanol and formaldehyde products. Chem Phys Lett 2021. [DOI: 10.1016/j.cplett.2021.138403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Felmy HM, Clifford AJ, Medina AS, Cox RM, Wilson JM, Lines AM, Bryan SA. On-Line Monitoring of Gas-Phase Molecular Iodine Using Raman and Fluorescence Spectroscopy Paired with Chemometric Analysis. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:3898-3908. [PMID: 33411509 DOI: 10.1021/acs.est.0c06137] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Molten salt reactors (MSRs) have the potential to safely support green energy goals while meeting baseload energy needs with diverse energy portfolios. While reactor designers have made tremendous strides with these systems, licensing and deployment of these reactors will be aided through the development of new technology such as on-line and remote monitoring tools. Of particular interest is quantifying reactor off-gas species, such as iodine, within off-gas streams to support the design and operational control of off-gas treatment systems. Here, the development of advanced Raman spectroscopy systems for the on-line analysis of gas composition is discussed, focusing on the key control species I2(g). Signal response was explored with two Raman instruments, utilizing 532 and 671 nm excitation sources, as a function of I2(g) pressure and temperature. Also explored is the integration of advanced data analysis methods to enable real-time and highly accurate analysis of complex optical data. Specifically, the application of chemometric modeling is discussed. Raman spectroscopy paired with chemometric analysis is demonstrated to provide a powerful route to analyzing I2(g) composition within the gas phase, which lays the foundation for applications within molten salt reactor off-gas analysis and other significant chemical processes producing iodine species.
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Affiliation(s)
- Heather M Felmy
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Andrew J Clifford
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Adan Schafer Medina
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Richard M Cox
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Jennifer M Wilson
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Amanda M Lines
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Samuel A Bryan
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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