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Thermodynamic characterization of interactions between environmental contaminants and room temperature ionic liquids using static headspace gas chromatography with vacuum ultraviolet detection. Anal Chim Acta 2023; 1264:341236. [PMID: 37230731 DOI: 10.1016/j.aca.2023.341236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 04/19/2023] [Accepted: 04/19/2023] [Indexed: 05/27/2023]
Abstract
Understanding the thermodynamic interactions between an analyte and the sample phase is of paramount importance when choosing a co-solvent in headspace analysis. A sample phase - gas phase equilibrium partition coefficient (Kp) is used fundamentally to describe the distribution of the analyte between the two phases. Kp determinations by headspace gas chromatography (HS-GC) were acquired by two methods: vapor phase calibration (VPC) and phase ratio variation (PRV). Here, we demonstrated a pressurized - loop headspace system in conjunction with gas chromatography vacuum ultraviolet detection (HS-GC-VUV) to directly calculate the concentration of analytes in the gas phase from room temperature ionic liquids (RTILs) sample phases, using pseudo-absolute quantification (PAQ). PAQ, an attribute of VUV detection, allowed for quick determination of Kp and other thermodynamic properties, such as enthalpy (ΔH) and entropy (ΔS) of the system through the use of van't Hoff plots in the temperature range of 70-110 °C. The Kp determinations by PAQ were comparable to those obtained using the VPC method with percent difference ranging from ≤ 1-33%. Kp determinations were made for analytes (cyclohexane, benzene, octane, toluene, chlorobenzene, ethylbenzene, m-,p-, and o-xylene) at the varying temperatures (70-110 °C) using different RTILs (1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][ESO4]), 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]), and tris(2-hydroxyethyl)methylammonium methylsulfate ([MTEOA][MeOSO3])) and (1-ethyl-3-methylimidazolium bis(trisfluoromethanesulfonyl)imide ([EMIM] [NTF2])). The results from the van't Hoff analysis revealed that [EMIM] cation-based RTILs exhibit strong solute-solvent interactions with analytes that have π- electrons.
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Limits of identification using VUV spectroscopy applied to C8H18 isomers isolated by GC×GC. Talanta 2023; 258:124451. [PMID: 36931058 DOI: 10.1016/j.talanta.2023.124451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 03/08/2023] [Accepted: 03/09/2023] [Indexed: 03/16/2023]
Abstract
The vacuum ultraviolet detector for gas chromatography can be used to identify structural differences between isomers with similar chromatographic elution times, which adds detail to characterization, valuable for prescreening of sustainable aviation fuel candidates. Although this capability has been introduced elsewhere, vacuum ultraviolet spectroscopy for saturated hydrocarbons has been examined minimally, as the similarities between their spectra are much less significant than their aromatic counterparts. The fidelity with which structural differences can be identified has been unclear. In this work, all possible structural isomers of C8H18 are measured and determined to have unambiguously unique vacuum ultraviolet spectra. Using a statistically based residual comparison approach, the concentration limits at which the spectral differences are interpretable are tested in both a controlled study and a real fuel application. The concentration limit at which the spectral differences between C8H18 isomers are unambiguous is below 0.40% by mass and less than 0.20% with human discretion in our experimental configuration.
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Analysis of complex drugs by comprehensive two-dimensional gas chromatography and high-resolution mass spectrometry: detailed chemical description of the active pharmaceutical ingredient sodium bituminosulfonate and its process intermediates. Anal Bioanal Chem 2022; 415:2471-2481. [PMID: 36401638 PMCID: PMC10149445 DOI: 10.1007/s00216-022-04393-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 10/14/2022] [Accepted: 10/19/2022] [Indexed: 11/21/2022]
Abstract
AbstractThe European pharmacopeia provides analytical methods for the chemical characterization of active pharmaceutical ingredients (APIs). However, the complexity of some APIs exceeds the limitations of the currently prevailing physicochemical methods. Sodium bituminosulfonate (SBS) is described by the collection of key parameters of generalizing criteria such as dry matter, sulfur and sodium content, and neutrality, but techniques to unravel the complexity on a molecular level are lacking. We present a study based on online derivatization with tetramethylammonium hydroxide in combination with comprehensive two-dimensional gas chromatography coupled to an electron ionization high-resolution time-of-flight mass spectrometer (GC × GC-HR-ToF–MS) for the chemical description of SBS as well as its process intermediates. The application of GC × GC allowed the comprehensive description of the chemical components in the API and the process intermediates for the first time. Furthermore, it was possible to classify peaks regarding their elemental and structural composition based on accurate mass information, elution behavior, and mass fragmentation pattern. This work demonstrates not only the general applicability, advantages but also limitations of GC × GC for the characterization of APIs for complex drugs.
Graphical Abstract
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4
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Make‐up gas influence on the signal behavior of the Vacuum ultraviolet detector for gas chromatography. SEPARATION SCIENCE PLUS 2022. [DOI: 10.1002/sscp.202200068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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5
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A Data Set Comparison Method Using Noise Statistics Applied to VUV Spectrum Match Determinations. Anal Chem 2022; 94:14861-14868. [PMID: 36264707 DOI: 10.1021/acs.analchem.2c01931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
It has been demonstrated that a pair of spectra exhibiting a coefficient of determination (R2) as low as 0.976 can originate from the same chemical species in one example, while a different pair of spectra exhibiting an R2 up to 0.9997 can originate from different chemical species. The R2 between spectra overlays depends on the signal-to-noise ratio, while the residual between any two spectra should look like noise only when the two spectra originate from the same chemical species. Numerical characteristics of the residual between two high-resolution spectra are invaluable toward the definitive elimination of many plausible matches of reference spectra to the sample spectra of analytes eluted from two-dimensional gas chromatography. Additionally, numerical characteristics beyond R2 facilitate a logical ranking of all plausible matches, making positive identification of a single-component analyte possible provided a reference spectrum exists for all plausible matches. Specifically, the experimental background noise is shown to follow a Gaussian distribution at all wavelengths, and a method is described to normalize the data such that the numerically adjusted noise distributions are independent of wavelength. The differences between matching spectra are further shown to exhibit numerical characteristics consistent with the background noise's Gaussian distribution, common to all wavelengths. Seven criteria are described for judging the similarity between spectra: R2 between the two spectra, R2 of a Q-Q plot with one axis being ideal Gaussian quantiles and the other axis being the distribution of the numerically adjusted residual quantiles, the maximum count of consecutive (by wavelength) signs in the residual, and the first four moments of the residuals. One exemplar application of the methodology is a definitive match of n-undecane, n-dodecane, and n-tridecane sample spectra to their corresponding reference spectrum, which is among the most challenging set of species within the volatility range of jet fuel to differentiate by spectral methods. While this example is a significant stress test of the approach, the utility of the methodology generally is in the subtle math and transparent criteria that unambiguously identify mismatches because the distributions of residuals between mismatching spectra are very clearly not Gaussian and have a high consecutive sign count, even in cases where the R2 between the compared spectra is ambiguous.
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Comparison of UNIFAC and LSER Models for Calculating Partition Coefficients in the Hexane–Acetonitrile System Using Middle Distillate Petroleum Products as an Example. Ind Eng Chem Res 2022. [DOI: 10.1021/acs.iecr.2c01093] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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7
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High Information Spectroscopic Detection Techniques for Gas Chromatography. J Chromatogr A 2022; 1676:463255. [DOI: 10.1016/j.chroma.2022.463255] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 06/10/2022] [Accepted: 06/14/2022] [Indexed: 01/14/2023]
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A systematic study of the absorbance of the nitro functional group in the vacuum UV region. Anal Chim Acta 2021; 1185:339042. [PMID: 34711315 DOI: 10.1016/j.aca.2021.339042] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 09/05/2021] [Accepted: 09/06/2021] [Indexed: 11/25/2022]
Abstract
The nitro functional group (NO2) features strongly in compounds such as explosives, pharmaceuticals, and fragrances. However, its gas phase absorbance characteristics in the vacuum UV region (120-200 nm) have not been systematically studied. Gas chromatography/vacuum UV spectroscopy (GC/VUV) was utilized to study the gas phase VUV spectra of various nitrated compounds (e.g., nitrate esters (-R-O-NO2), nitramines (R-N-NO2), nitroaromatics (Ar-NO2), and nitroalkanes (R-NO2)). The nitro absorption maximum appeared over a wide range (170-270 nm) and its wavelength and intensity were highly dependent upon the structure of the rest of the molecule. For example, the nitroalkanes exhibited a trend in that the ratio of the relative absorption intensity between these two absorption features between the alkyl group (<150 nm) and the nitro group (200 nm) increases as the molecular weight increases. It was observed that the addition of multiple nitro functional groups on benzene or toluene resulted in an increase in intensity and blue shift from approximately 240 nm-210 nm. Nitrate esters exhibited an absorption between 170 nm and 210 nm and absorbance increased with increasing nitrogen content. The relative diversity of the spectra obtained was analyzed by Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA). These calculations revealed that the spectra of all the compounds analyzed could be reliably differentiated without any misclassifications.
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Advanced data preprocessing for comprehensive two-dimensional gas chromatography with vacuum ultraviolet spectroscopy detection. J Sep Sci 2021; 44:4141-4150. [PMID: 34510756 DOI: 10.1002/jssc.202100528] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 08/13/2021] [Accepted: 09/06/2021] [Indexed: 11/08/2022]
Abstract
Comprehensive two-dimensional gas chromatography with vacuum ultraviolet detection results in sizable data for which noise and baseline drift ought to be corrected. As the data is acquired from multiple channels, preprocessing steps have to be applied to the data from all channels while being robust and rather fast with respect to the significant size of the data. In this study, we have described advanced data preprocessing techniques for such data which were not available in the existing commercial software solutions and which were dedicated primarily to noise and baseline correction. Noise reduction was performed on both the spectral and the time dimension. For the baseline correction, a morphological approach based on iterated convolutions and rectifier operations was proposed. On the spectral dimension, much less noisy and reliable spectra were obtained. From a quantitative point of view, mentioned preprocessing steps significantly improved the signal-to-noise ratio for the analyte detection (circa six times in this study). These preprocessing methods were integrated into the plugim! platform (https://www.plugim.fr/).
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Determination of vacuum ultraviolet detector response factors by hyphenation with two-dimensional comprehensive gas chromatography with flame ionization detection. J Sep Sci 2021; 44:3849-3859. [PMID: 34387030 DOI: 10.1002/jssc.202100459] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 07/21/2021] [Accepted: 08/09/2021] [Indexed: 11/10/2022]
Abstract
Two-dimensional comprehensive gas chromatography is an established technique, employed for the characterization of complex samples. Broadband vacuum ultraviolet absorption spectroscopy detection has recently attracted a lot of attention as it is a universal detection technique characterized by good selectivity but also ease of use and amenability to coupling with two-dimensional comprehensive gas chromatography. Vacuum ultraviolet spectroscopy is particularly interesting due to the possibility of performing spectral decomposition for species that coelute in gas chromatography analysis. This detector has quantitative capabilities, however not all species absorb vacuum ultraviolet radiation the same. Unfortunately, vacuum ultraviolet relative response factors for compounds are not always available. Methods to rapidly measure vacuum ultraviolet relative response factors and generate a large database that would allow calibration free quantitative analysis of complex mixtures are therefore of great interest. In this work, a universal methodology that permits rapid measurement of vacuum ultraviolet relative response factors is reported. It involves flow modulated two-dimensional comprehensive gas chromatography with dual vacuum ultraviolet and flame ionization detection. In this set-up, flame ionization detection is employed as a quantitative reference allowing to scale vacuum ultraviolet responses of investigated compounds. This approach was validated by flow measurements and by comparing relative response factors obtained for model compounds with literature data.
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A critical comparison of vacuum UV (VUV) spectrometer and electron ionization single quadrupole mass spectrometer detectors for the analysis of alkylbenzenes in gasoline by gas chromatography: Experimental and statistical aspects. Talanta 2021; 225:122081. [PMID: 33592794 DOI: 10.1016/j.talanta.2021.122081] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 12/17/2020] [Accepted: 12/31/2020] [Indexed: 11/24/2022]
Abstract
Recent advances in benchtop vacuum ultraviolet (VUV) spectrometers have yielded effective universal detectors for gas chromatography (GC). The ability of these detectors to acquire absorbance spectra from 125 nm to 430 nm poses an alternative to the gold standard of mass spectrometry (MS) as a sensitive and selective GC detector. The applications of GC/VUV extend into many areas. Featured here is the potential application of GC/VUV to the analysis of ignitable liquids, which may be found on debris from suspected arson fires. A particular compound class of interest is the alkylbenzenes, as they are a significant component in fuels such as gasoline, petroleum distillates, and aromatic solvents such as degreasers and cleaning solvents. To measure the sensitivity, selectivity and specificity of GC-VUV and GC-MS for alkylbenzenes we employed both library search methods and chemometric analysis using discriminant analysis. The GC-VUV detector was found to have superior specificity to the GC-MS detector in full scan mode. The GC-VUV detector was able to identify all alkylbenzenes correctly, including the correct identification of all structural isomers. LODs for both GC-VUV and GC-MS were found to be picograms on column.
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Gas chromatography-vacuum ultraviolet spectroscopic analysis of organosilanes. Talanta 2021; 223:121781. [PMID: 33298286 DOI: 10.1016/j.talanta.2020.121781] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 10/12/2020] [Accepted: 10/13/2020] [Indexed: 01/09/2023]
Abstract
Organosilanes are used in a broad range of industrial, cosmetic, and personal care products. They serve as bridges between inorganic or organic substrates and organic/polymeric matrices. They are also versatile intermediates and can be used for a variety of synthetic applications. They do not exist naturally and have to be synthesized. Evaluation of intermediates and products resulting from the synthesis processes of organosilanes can be challenging. In this study, gas chromatography with vacuum ultraviolet spectroscopic detection (VUV) was used to analyze Si-containing compounds that are commercially available or were synthetically prepared. VUV measures full scan absorption in the range of 120-240 nm, a region that provides unique absorption signatures for chemical compounds. VUV absorption spectra of organosilanes showed rich and featured characteristics in this wavelength range. Theoretical computations of VUV absorption spectra based on time-dependent density functional theory were also explored as a complementary tool for identification. In addition, the synthesis process of isomeric benzodioxasiline compounds (ortho-, meta-, and para-) was monitored by GC-VUV. It was demonstrated that GC-VUV can be used for easy and rapid differentiation of organosilanes, including structural isomers.
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Optimization of the qualitative and quantitative analysis of cocaine and other drugs of abuse via gas chromatography - Vacuum ultraviolet spectrophotometry (GC - VUV). Talanta 2021; 222:121461. [PMID: 33167202 DOI: 10.1016/j.talanta.2020.121461] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 07/23/2020] [Accepted: 07/24/2020] [Indexed: 12/21/2022]
Abstract
Gas Chromatography-Vacuum UV Spectroscopy (GC-VUV) has seen increased attention in many areas, however, a statistical optimization of VUV method parameters has not been published. This article presents the first statistical optimization of parameters influencing analytes such as cocaine in the VUV flow-cell. Flow-cell temperature, make-up gas pressure, and carrier gas flow rate from the GC were examined and optimized for the detection of controlled substances. The accuracy, precision, linearity, and optimized detection limits for drugs such as cocaine (98.5%, 1.2%, 0.9998, 1.5 ng), heroin (99.3%, 0.94%, 0.9998, 2.0 ng), and fentanyl (98.5%, 1.7%, 0.9752, 9.7 ng) are reported. In general, the limits of detection for cocaine, heroin, fentanyl, and methamphetamine after optimization were comparable to gas chromatography-mass spectrometry (GC-MS) in "scan mode", which had detection limits of 1.1-38 ng on column. The VUV absorption spectra of cocaine, PCP, lorazepam, and HU-210 are also reported. And three samples of "real world" cocaine are analyzed to demonstrate applicability to forensic drug analysis.
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Total-transfer comprehensive three-dimensional gas chromatography with time-of-flight mass spectrometry. J Chromatogr A 2020; 1634:461654. [DOI: 10.1016/j.chroma.2020.461654] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 10/19/2020] [Accepted: 10/26/2020] [Indexed: 12/25/2022]
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15
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Gas chromatography with dual cold electron ionization mass spectrometry and vacuum ultraviolet detection for the analysis of phenylethylamine analogues. Forensic Chem 2020. [DOI: 10.1016/j.forc.2020.100281] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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17
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Simulation of Vacuum Ultraviolet Absorption Spectra: Paraffin, Isoparaffin, Olefin, Naphthene, and Aromatic Hydrocarbon Class Compounds. APPLIED SPECTROSCOPY 2020; 74:72-80. [PMID: 31517520 DOI: 10.1177/0003702819875132] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The advent of a new vacuum ultraviolet (VUV) spectroscopic absorption detector for gas chromatography has enabled applications in many areas. Theoretical simulations of VUV spectra using computational chemistry can aid the new technique in situations where experimental spectra are unavailable. In this study, VUV spectral simulations of paraffin, isoparaffin, olefin, naphthene, and aromatic (PIONA) compounds using time-dependent density functional theory (TDDFT) methods were investigated. Important factors for the simulations, such as functionals/basis sets and formalism of oscillator strength calculations, were examined and parameters for future PIONA compound simulations were obtained by fitting computational results to experimental spectra. The simulations produced satisfactory correlations between experimental observations and theoretical calculations, and enabled potential analysis applications for complex higher distillate fuels, such as diesel fuel. Further improvement of the methods was proposed.
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Gas chromatography vacuum ultraviolet spectroscopy: A review. J Sep Sci 2019; 43:150-173. [PMID: 31750981 DOI: 10.1002/jssc.201900770] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 11/13/2019] [Accepted: 11/15/2019] [Indexed: 11/12/2022]
Abstract
Accelerated technological progress and increased complexity of interrogated matrices imposes a demand for fast, powerful, and resolutive analysis techniques. Gas chromatography has been for a long time a 'go-to' technique for the analysis of mixtures of volatile and semi-volatile compounds. Coupling of the several dimensions of gas chromatography separation has allowed to access a realm of improved separations in the terms of increased separation power and detection sensitivity. Especially comprehensive separations offer an insight into detailed sample composition for complex samples. Combining these advanced separation techniques with an informative detection system such as vacuum ultraviolet spectroscopy is therefore of great interest. Almost all molecules absorb the vacuum ultraviolet radiation and have distinct spectral features with compound classes exhibiting spectral signature similarities. Spectral information can be 'filtered' to extract the response in the most informative spectral ranges. Developed algorithms allow spectral mixture estimation of coeluting species. Vacuum ultraviolet detector follows Beer-Lambert law, with the possibility of calibrationless quantitation. The purpose of this article is to provide an overview of the features and specificities of gas chromatography-vacuum ultraviolet spectroscopy coupling which has gained interest since the recent introduction of a commercial vacuum ultraviolet detector. Potentials and limitations, relevant theoretical considerations, recent advances and applications are explored.
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Quantitation and identification of ethanol and inhalant compounds in whole blood using static headspace gas chromatography vacuum ultraviolet spectroscopy. J Chromatogr A 2019; 1611:460607. [PMID: 31668865 DOI: 10.1016/j.chroma.2019.460607] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 09/30/2019] [Accepted: 10/07/2019] [Indexed: 11/23/2022]
Abstract
Gas chromatography (GC) and vacuum ultraviolet spectroscopy (VUV) are powerful and complementary techniques for the analysis of small molecules in forensics. Most notably, flame ionization detection (FID) is commonly used with GC to identify and quantify volatile compounds. An FID's price point and ease of use makes it an attractive approach for routine laboratories that are in high demand for forensics analysis, but with the contingency that an FID relies on retention time for identification and quantification. A new and innovative method using static headspace gas chromatography coupled with vacuum ultraviolet (VUV) spectroscopy was developed for the quantitative determination of ethanol in blood and identification of inhalants. This study investigates the possibility of using VUV as an alternative technique to traditional methods that use FID and mass spectrometry (MS) in toxicology and forensic analysis. VUV brings both identification and quantitation based on Beer-Lambert's Law while using a simple single-column solution. This paper investigates 25 compounds, including ethanol, methanol, acetone, benzene, and toluene using a 130-240 nm wavelength range for identification and quantification using GC-VUV, even when coelutions occur. Ethanol was examined under a concentration range of 9 to 495 mg/dl, and the method was found to be linear with an r2 = 0.997 and a LOD of 3.1 mg/dl. Ethanol was fully separated from other volatile organic compounds (VOCs) as well as endogenous materials present in blood. Nonaromatic VOCs were analyzed at concentration ranges of 2.4 to 99 mg/dl with LODs around 0.2 mg/dl; aromatic VOCs were analyzed from 0.5 to 24 mg/dl with LODs ∼ 0.1 mg/dl.
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Generating highly specific spectra and identifying thermal decomposition products via Gas Chromatography / Vacuum Ultraviolet Spectroscopy (GC/VUV): Application to nitrate ester explosives. Talanta 2019; 195:580-586. [DOI: 10.1016/j.talanta.2018.11.060] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 11/18/2018] [Accepted: 11/19/2018] [Indexed: 10/27/2022]
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22
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Direct analysis of aromatic hydrocarbons in purified mineral oils for foods and cosmetics applications using gas chromatography with vacuum ultraviolet detection. J Chromatogr A 2019; 1590:113-120. [DOI: 10.1016/j.chroma.2019.01.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 12/04/2018] [Accepted: 01/07/2019] [Indexed: 01/22/2023]
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23
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Preparation and Characterization of Fe3O4@SiO2 Nanoparticles Incorporated Polymer Monolithic Column for Gas Chromatography. Chromatographia 2018. [DOI: 10.1007/s10337-018-3541-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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Vacuum Ultraviolet Spectroscopy and Mass Spectrometry: A Tandem Detection Approach for Improved Identification of Gas Chromatography-Eluting Compounds. Anal Chem 2018; 90:4878-4885. [DOI: 10.1021/acs.analchem.8b00531] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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25
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26
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Copper(i)-based oxidation of polycyclic aromatic hydrocarbons and product elucidation using vacuum ultraviolet spectroscopy and theoretical spectral calculations. NEW J CHEM 2018. [DOI: 10.1039/c8nj04740e] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Fluorinated 1,3,5-triazapentadienyl complexes of copper catalyze the oxidation PAHs to quinones using H2O2as an oxidant under mild conditions.
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Is vacuum ultraviolet detector a concentration or a mass dependent detector? J Chromatogr A 2017; 1530:171-175. [DOI: 10.1016/j.chroma.2017.11.028] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 11/13/2017] [Accepted: 11/14/2017] [Indexed: 01/04/2023]
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28
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Multidimensional Gas Chromatography: Advances in Instrumentation, Chemometrics, and Applications. Anal Chem 2017; 90:505-532. [DOI: 10.1021/acs.analchem.7b04226] [Citation(s) in RCA: 115] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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29
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Identification and deconvolution of carbohydrates with gas chromatography-vacuum ultraviolet spectroscopy. J Chromatogr A 2017; 1513:210-221. [DOI: 10.1016/j.chroma.2017.07.052] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2017] [Revised: 06/28/2017] [Accepted: 07/16/2017] [Indexed: 12/31/2022]
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Flow-modulated comprehensive two-dimensional gas chromatography combined with a vacuum ultraviolet detector for the analysis of complex mixtures. J Chromatogr A 2017; 1497:135-143. [DOI: 10.1016/j.chroma.2017.03.073] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 03/21/2017] [Accepted: 03/26/2017] [Indexed: 11/26/2022]
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31
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Resolution of isomeric new designer stimulants using gas chromatography - Vacuum ultraviolet spectroscopy and theoretical computations. Anal Chim Acta 2017; 971:55-67. [PMID: 28456284 DOI: 10.1016/j.aca.2017.03.023] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 03/10/2017] [Accepted: 03/12/2017] [Indexed: 11/29/2022]
Abstract
Distinguishing isomeric representatives of "bath salts", "plant food", "spice", or "legal high" remains a challenge for analytical chemistry. In this work, we used vacuum ultraviolet spectroscopy combined with gas chromatography to address this issue on a set of forty-three designer drugs. All compounds, including many isomers, returned differentiable vacuum ultraviolet/ultraviolet spectra. The pair of 3- and 4-fluoromethcathinones (m/z 181.0903), as well as the methoxetamine/meperidine/ethylphenidate (m/z 247.1572) triad, provided very distinctive vacuum ultraviolet spectral features. On the contrary, spectra of 4-methylethcathinone, 4-ethylmethcathinone, 3,4-dimethylmethcathinone triad (m/z 191.1310) displayed much higher similarities. Their resolution was possible only if pure standards were probed. A similar situation occurred with the ethylone and butylone pair (m/z 221.1052). On the other hand, majority of forty-three drugs was successfully separated by gas chromatography. The detection limits for all the drug standards were in the 2-4 ng range (on-column amount), which is sufficient for determinations of seized drugs during forensics analysis. Further, state-of-the-art time-dependent density functional theory was evaluated for computation of theoretical absorption spectra in the 125-240 nm range as a complementary tool.
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Gas chromatography-vacuum ultraviolet detection for classification and speciation of polychlorinated biphenyls in industrial mixtures. J Chromatogr A 2017; 1490:191-200. [DOI: 10.1016/j.chroma.2017.02.031] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 02/13/2017] [Accepted: 02/14/2017] [Indexed: 11/28/2022]
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Pseudo-absolute quantitative analysis using gas chromatography – Vacuum ultraviolet spectroscopy – A tutorial. Anal Chim Acta 2017; 953:10-22. [DOI: 10.1016/j.aca.2016.11.039] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 10/28/2016] [Accepted: 11/16/2016] [Indexed: 10/20/2022]
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Analysis of terpenes and turpentines using gas chromatography with vacuum ultraviolet detection. J Sep Sci 2017; 40:869-877. [PMID: 27983761 DOI: 10.1002/jssc.201601019] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 11/09/2016] [Accepted: 11/27/2016] [Indexed: 12/20/2022]
Abstract
The separation and identification of natural mixtures of terpenes is challenging and laborious. A gas chromatographic method based on vacuum ultraviolet spectroscopic detection, which is characterized by full-scan absorption in the range of 125-240 nm, was developed and applied to analyze terpenes. In this study, the vacuum ultraviolet absorption spectra of 41 different standard terpenes were investigated and compared. The spectra were found to be highly featured and easily differentiated. Several commercial turpentine samples were analyzed and the vacuum ultraviolet detector demonstrated good specificity for qualitative identification of constituent terpenes. A total of 31 terpenes were detected in the four turpentine samples. α-Pinene was the predominant terpene ranging from 744.2 ± 9.7 to 917 ± 21 mg/mL. The other major constituents in the turpentines included β-pinene, δ-3-carene, camphene, and p-isopropyltoluene. Deconvolution of co-eluting signals of terpenes was achieved utilizing the data analysis software. The technique has been demonstrated to be a powerful tool for reliable and accurate qualitative and quantitative analysis of terpenes from complex natural mixtures.
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Recent advances and applications of gas chromatography vacuum ultraviolet spectroscopy. J Sep Sci 2016; 40:138-151. [DOI: 10.1002/jssc.201601023] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 10/30/2016] [Accepted: 10/31/2016] [Indexed: 11/07/2022]
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Rapid Analysis and Time Interval Deconvolution for Comprehensive Fuel Compound Group Classification and Speciation Using Gas Chromatography–Vacuum Ultraviolet Spectroscopy. Anal Chem 2016; 88:11130-11138. [DOI: 10.1021/acs.analchem.6b03226] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Analysis and deconvolution of dimethylnaphthalene isomers using gas chromatography vacuum ultraviolet spectroscopy and theoretical computations. Anal Chim Acta 2016; 945:1-8. [PMID: 27968710 DOI: 10.1016/j.aca.2016.09.021] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 09/09/2016] [Accepted: 09/11/2016] [Indexed: 10/21/2022]
Abstract
An issue with most gas chromatographic detectors is their inability to deconvolve coeluting isomers. Dimethylnaphthalenes are a class of compounds that can be particularly difficult to speciate by gas chromatography - mass spectrometry analysis, because of their significant coelution and similar mass spectra. As an alternative, a vacuum ultraviolet spectroscopic detector paired with gas chromatography was used to study the systematic deconvolution of mixtures of coeluting isomers of dimethylnaphthalenes. Various ratio combinations of 75:25; 50:50; 25:75; 20:80; 10:90; 5:95; and 1:99 were prepared to test the accuracy, precision, and sensitivity of the detector for distinguishing overlapping isomers that had distinct, but very similar absorption spectra. It was found that, under reasonable injection conditions, all of the pairwise overlapping isomers tested could be deconvoluted up to nearly two orders of magnitude (up to 99:1) in relative abundance. These experimental deconvolution values were in agreement with theoretical covariance calculations performed for two of the dimethylnaphthalene isomers. Covariance calculations estimated high picogram detection limits for a minor isomer coeluting with low to mid-nanogram quantity of a more abundant isomer. Further characterization of the analytes was performed using density functional theory computations to compare theory with experimental measurements. Additionally, gas chromatography - vacuum ultraviolet spectroscopy was shown to be able to speciate dimethylnaphthalenes in jet and diesel fuel samples.
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Vacuum ultraviolet absorption spectroscopy in combination with comprehensive two-dimensional gas chromatography for the monitoring of volatile organic compounds in breath gas: A feasibility study. J Chromatogr A 2016; 1464:141-6. [PMID: 27545394 DOI: 10.1016/j.chroma.2016.08.024] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 08/09/2016] [Accepted: 08/10/2016] [Indexed: 12/17/2022]
Abstract
Vacuum ultraviolet (VUV) absorption spectroscopy was recently introduced as a new detection system for one, as well as comprehensive two-dimensional gas chromatography (GC×GC) and successfully applied to the analysis of various analytes in several matrices. In this study, its suitability for the analysis of breath metabolites was investigated and the impact of a finite volume of the absorption cell and makeup gas pressure was evaluated for volatile analytes in terms of sensitivity and chromatographic resolution. A commercial available VUV absorption spectrometer was coupled to GC×GC and applied to the analysis of highly polar volatile organic compounds (VOCs). Breath gas samples were acquired by needle trap micro extraction (NTME) during a glucose challenge and analysed by the applied technique. Regarding qualitative and quantitative information, the VGA-100 is compatible with common GC×GC detection systems like FID and even TOFMS. Average peak widths of 300ms and LODs in the lower ng range were achieved using GC×GC-VUV. Especially small oxygenated breath metabolites show intense and characteristic absorption patterns in the VUV region. Challenge responsive VOCs could be identified and monitored during a glucose challenge. The new VUV detection technology might especially be of benefit for applications in clinical research.
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