Crude oil is used widely among refineries to produce products that are useful to the public. However, due to the increased popularity of harvesting crude oil from tar sands and other unmanned wells, more polar toxins are expected to be present in these mixtures and thus make it difficult for the refinery processing. As a part of the efforts to develop an analytical procedure based on MRR for fast detection of polar impurities in the oil mixture, a benchtop K-Band molecular rotational resonance spectrometer, which operates in the 18-26GHz frequency range, has been employed to record rotationally resolved spectra of crude oil. Preliminary analysis of the observed rotational spectra reveals the presence of multiple polar toxins, including small Sulfur-Oxygen-Nitrogen containing compounds, due to K-Band MRR’s sensitivity to only small polar compounds. The complex hydrocarbon matrix, which in many chromatographic methods obscures the signals from low concentration impurities, is eliminated. Plans to improve this analytical procedure are underway and results will be given in this talk.

We have been pursuing several applications of molecular rotational resonance (MRR) spectroscopy in quantitative analysis relevant to the pharmaceutical industry. These applications include chiral analysis (absolute configuration and enantiomeric excess), diastereomer identification, regioisomer identification, and isotopologue/isotopomer analysis. Because this work requires quantitative determination of species abundances, we have examined issues related to signal-to-noise determination and quantitation in the low signal regime. Models for the noise distribution in broadband, chirped-pulse Fourier transform microwave (CP-FTMW) spectrometers where the spectra are reported as the magnitude Fourier transform will be presented. The noise distribution is also found to be the same in cavity FTMW spectrometers. We have also modeled the accuracy of signal levels observed in the magnitude Fourier transform as a function of signal-to-noise ratio. This modeling shows that measured transition intensities are accurate down to the root-mean-squared noise level of the instrument without the need to correct for noise power in the signal channel. Finally, using the proper definitions for the noise in magnitude FTMW spectra, we have determined the performance metric introduced by Porterfield et al.J.P. Porterfield, L. Satterthwaite, S. Eibenberger, D. Patterson, M.C. McCarthy, Rev. Sci. Instrum. 2019, 90, 053104.or the UVA 6-18 GHz broadband spectrometer. The CP-FTMW instrument speed metric is S = 36,000,000 MHz/min using OCS as the test sample. The reported value for the cryogenic buffer gas cell instrument described in Ref. 1 is S = 4,400,000 MHz/min. These results are in strong disagreement with the CP-FTMW speed metric reported in Ref. 1, S = 60,360 MHz/min, that was the basis for claiming that buffer gas cooling spectrometers have almost a factor of 100 better performance than CP-FTMW instruments. J.P. Porterfield, L. Satterthwaite, S. Eibenberger, D. Patterson, M.C. McCarthy, Rev. Sci. Instrum. 2019, 90, 053104.f

We investigate the capability of temperature measurement by pure rotational femtosecond coherent anti-Stokes Raman spectroscopy (fs CARS) of O₂ through a chirped probe pulse (CPP) technique. The electronic ground state of O₂ is known to have a ³Σ⁻_g symmetry. As a result, both total nuclear angular momentum quantum number N, as well as total angular momentum quantum number J=N±1 are used for O₂ rotational level characterization. The selection rules for O₂ pure rotational Raman transitions are ∆N=0, ±2, ∆J=0, ±1, ±2. The simplifications of the theoretical modeling are possible, for example, by neglecting the 3-J splitting structures or by considering only the ∆N=2, ∆J=2 (S^S branch) transitions. We validate the accuracy of those assumptions by comparing to the correspondingly simulated rotational CARS spectra as well as by comparing to the experimental measurements. The experimental measurements will be performed in O₂ jet flow as well as in flames established over a Hencken burner. In the latter case, the interference from N₂ pure rotational CARS signals will become important, thus it will also be accounted for our spectroscopic analysis. r0 pt Figure

Molecular rotational resonance (MRR) spectroscopy was used to identify and quantitate the relative abundance of cyclohexene isotopologues prepared from a tungsten-benzene complex. Of the 1024 possible deuterium isomers, 992 of the geometries are pairs of rotationally equivalent geometries producing only 496 isomers with distinguishable rotational spectra. In addition, there are 32 species that yield identical structure for C2-rotation. Therefore, there are 528 different deuterium isomers that have distinguishable rotational spectra. Due the transient chirality associated with the ring pucker of cyclohexene, each isotopomer typically has two rotationally distinct forms in the sample. A rotational spectroscopy methodology was developed to perform automated isotopologue and isotopomer analysis of the synthetic samples. The analysis uses a single reference geometry to identify the isomers. The reference structure is obtained from the singly-substituted ¹³C, doubly-substituted ¹³C, and singly-substituted deuterium isotopomer rotational constants that are obtained from measurements in natural abundance using a commercial cyclohexene sample. In total, 26 deuterium isomers were identified in various samples of isotopically enriched cyclohexene. Of these 26 isomers represent 15 chemically distinct species. The confidence of the identification is assessed by comparing the root-mean-squared (RMS) error for the three rotational constants of each species. In all cases, the experimental rotational constants can be attributed to a single isotopomer with high confidence. This analysis demonstrates the potential for routine, fast isotopomer identification that provides site-specific information of deuterium incorporation. For the cyclohexene samples prepared using the tungsten complex, rotational spectroscopy verified high stereoselectivity in the synthesis with about 1% or less over- and under-deuteration in most cases.

Analysis of the crude reaction mixture of the arylation product of cyclohexanone with 5-bromo-2-(trifluoromethyl)pyridine was performed by molecular rotational resonance (MRR) spectroscopy. This reaction was part of a recent study to investigate the use of decatungstate photocatalysis to perform direct arylation of aliphatic C-H bonds in order to provide a single-step access to multiple pharmaceutically relevant molecules. [1] Although this approach enables a simpler approach of molecular construction, the prevalence of C-H bonds in any given molecule often results in several arylation regioisomers. For the reaction presented here, prior analysis identified the main reaction product as the 3-substituted arylation product, with the minor component being the 4-substiuted arylation product. In the initial analysis, the isomers were identified using nuclear magnetic resonance (NMR) spectroscopy and separated using ultra performance liquid chromatography (UPLC) in order to determine the relative composition. The crude reaction mixture was subsequently analyzed by broadband molecular rotational resonance spectroscopy. In order to identify the reaction products in the crude reaction mixture using MRR, low energy conformers of the reaction products were identified and the MRR structural parameters were calculated. Species were identified by agreement between theoretical and experimental rotational constants. In addition to the detection of the known reaction species and staring material, several other previously unknown impurities were identified in the sample, including the 2-substituted reaction product and a solvent derived byproduct. These species were verified in the analysis by NMR and UPLC data after identification by MRR spectroscopy. Quantitation of the relative abundance of the regioisomer products by MRR was performed by comparing the line intensity of the experimental transitions to the predictions from theory. The quantitative MRR results were in good agreement with the chromatographic results. This work demonstrates the capability of MRR to perform analysis of complex mixtures, simplifying the workflow of analysis. [1] Perry, I. B.; Brewer, T. F.; Sarver, P. J.; Schultz, D. M.; DiRocco, D. A.; MacMillan, D. W. C., Direct arylation of strong aliphatic C–H bonds. Nature 2018, 560 (7716), 70-75.

Fourier Transform Raman (3500-100 cm⁻¹) and Fourier Transform infrared spectra (4000-400 cm⁻¹) were measured for Pentabromophenol (PBP) and Pentaflurophenol (PFP). UV-Visible (200-400 nm) spectrum, along with 1H and 13C NMR spectra were also recorded, for PBP. Torsional potentials, optimized structure parameters, barrier height to internal rotation, harmonic vibrational frequencies, general valance force field, potential energy distribution (PED), along with infrared and Raman intensities were evaluated, for PBP and PFP. DFT was used in conjunction with B3LYP functional with 6-311++G(d,p) basis set, for the computations. Scaling process was employed to get a better fit between the measured and computed frequencies. The rms error between them was 9.7 and 7.0 cm⁻¹, for PBP and PFP, respectively. Unambiguous vibrational assignments were arrived at by using PED and eigenvectors. In order to understand the nature of intermolecular hydrogen bond in these molecules geometry optimization was made for dimers of PBP and PFP. Further, using Gauge Independent Atomic orbital (GIAO) approach 1H and 13C NMR chemical shifts were evaluated and compared with corresponding experimentally measured shifts for PBP. In the same way, Time-dependent Density Functional Theory (TD-DFT) was used to simulate UV-Visible spectrum of PBP and compared with its experimental spectrum. HOMO and LUMO energies along with associated electronic parameters were generated. In order to find reactive sites in PBP and PFP molecular electrostatic surface potential (MESP) diagrams were drawn. The values of dipole moment, polarizability and hyperpolarizability of these molecules were computed to determine their NLO behavior. To understand the stability of the molecules (PBP and PFP) caused by charge delocalization, natural bond orbital (NBO) analysis was made for both PBP and PFP. Thermodynamic parameters were also evaluated for both the molecules.
Key words: Pentabromophenol, Pentaflurophenol, Vibrational spectra, Intermolecular hydrogen bond, DFT, Hyperpolarizability # A part of this work appeared in J. Mol. Struct. 1180 (2019) 665-675

Cancer mortalities are common due to the lack of diagnostic at the early stages in many countries. Recent studies discovered that the heavy metals in the human colon could cause the colon cancer. The conventional cancer detection techniques suffer from the insensitiveness, imprecision, slowness, cumbersomeness of sample preparation, and some time show conflicting results. Hence an accurate, reliable, and rapid detection technique is essential for the early diagnostic and prevention of heavy metals accumulation induced colon cancers. In this work, calibration-free laser-induced breakdown spectrometer (LIBS) was applied on several cancerous and normal colon tissues collected from the colon cancer infested patients aged 40 — 60 years. The results showed the presence of carcinogenic heavy metals including lead (Pb), chromium (Cr), and mercury (Hg) in the malignant colon tissues, while the healthy tissues were devoid of these elements. The accuracy of the LIBS results was validated by comparing the results obtained using a standard inductively coupled plasma atomic emission spectroscopy (ICP-OES). This study demonstrated that LIBS technique is very effective for rapid, precise early detection of the heavy metals accumulation in malignant colon tissues.

Detecting cancer cells before any symptoms appear is essential for successful treatment, especially for epithelial ovarian cancer (EOC) with few or no symptoms at the early stages. Although there are methods that have been developed to identify the cancer cells, scientists are looking for other novel promising methods to detect that early stage, also cheap and user-friendly. Here, we cross-link elemental particles to a specific functional group of the targeted biomolecules based on a covalent and non-covalent linking chemistry to improve the sensitivity and the selectivity of biomarker detection. In this presentation, we look into the sandwich type of micro-particle immunoassay with pair of Fe3O4 and silicon micro-particles used for highly-selective detection of specific cancer antigen human epididymis protein-4 (HE4) in which U.S. Food and Drug Administration (FDA) accepted recently as a biomarker for monitoring EOC patients. The cancer biomarkers are quantified via detecting the silicon using Laser-induced breakdown spectroscopy (LIBS).

A novel photoacoustic spectrophotometer (PAS) for study the UV-visible absorption spectrum of gallbladder stone is described. Photoacoustic spectroscopy detects sound waves induced by absorption and periodic heating of a thin layer of gas above a sample placed in a PA cell. This heat results from non-radiative transitions following periodic illumination of the sample. Thus, in the present paper molecular composition of gallbladder stone has been investigated by means of PAS as it does not require any sample preparation. The PA spectrum of gallbladder stone is compared with the UV–Visible absorption spectrum of same gallbladder stone. The presence of cholesterol, calcium carbonate, bile acid and bilirubin in the photoacoustic spectrum, have been directly recognized. The results of this investigation demonstrate that PAS is more suitable to identify the chemical compounds present in gallbladder stones than the conventional absorption spectroscopy.