Complexation Gas Chromatography Research Articles

Compound-specific carbon isotope analysis of volatile organic compounds in complex soil extracts using purge and trap concentration coupled to heart-cutting two-dimensional gas chromatography–isotope ratio mass spectrometry

Compound-specific carbon isotope analysis (CSIA) is a powerful tool to track the origin and fate of organic subsurface contaminants including petroleum and chlorinated hydrocarbons and is typically applied to water samples. However, soil can form a significant contaminant reservoir. In soil samples, it can be challenging to recover sufficient amounts of volatile organic compounds (VOC) to perform CSIA. Soil samples often contain complex contaminant mixtures and gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) is highly dependent on good chromatographic separation due to the conversion to a single analyte. To extend the applicability of CSIA to complex volatile organic compound mixtures in soil samples, and to recover sufficient amounts of target compounds for carbon CSIA, we compared two soil extraction solvents, tetraglyme (TGDE) and methanol, and developed a heart-cutting two-dimensional GC-GC-C-IRMS method. We used purge & trap concentration of solvent-water mixtures to increase the amount of analyte delivered to the column and thus lower method detection limits. We optimized purge & trap and chromatographic parameters for twelve target compounds, including one suffering from poor purge efficiency. By using a 30 m thick-film non-polar column in the first and a 15 m polar column in the second dimension, we achieved good chromatographic separation for the target compounds in difficult matrices and high accuracy (trueness and precision) for carbon isotopic analysis. Tetraglyme extraction was shown to offer advantages over methanol for purge & trap concentration, leading to lower target compound method detection limits for CSIA of soil samples. The applicability of the developed method was demonstrated for a case study on soil extracts from a former manufacturing facility. Our approach extends the applicability of CSIA to an important matrix that often controls the long-term fate of contaminants in the subsurface.

Application of alternating trilinear decomposition-assisted multivariate curve resolution to gas chromatography-mass spectrometric data for the quantification of polycyclic aromatic hydrocarbons in aerosols.

For the first time, alternating trilinear decomposition-assisted multivariate curve resolution (ATLD-MCR) was applied to analyse complex gas chromatography–mass spectrometric (GC-MS) data with severe baseline drifts, serious co-elution peaks and slight retention time shifts for the simultaneous identification and quantification of polycyclic aromatic hydrocarbons (PAHs) in aerosols. It was also compared with the classic multivariate curve resolution-alternating least-squares (MCR-ALS) and the GC-MS-based external standard method. In validation samples, average recoveries of five PAHs were within the range from (96.2 ± 6.8)% to (106.5 ± 4.1)% for ATLD-MCR, near to the results of MCR-ALS ((98.0 ± 1.5)% to (106.7 ± 4.3)%). In aerosol samples, the concentrations of pyrene provided by ATLD-MCR were not significantly different from those of MCR-ALS. The other four PAHs including chrysene, benzo[a]anthracene, fluoranthene and benzo[b]fluoranthene were not detected by ATLD-MCR and the GC-MS-based external standard method. The results of figures of merit further demonstrated that ATLD-MCR achieved high sensitivities (8.9 × 104 to 1.7 × 106 mAU ml µg−1) and low limits of detection (0.003 to 0.087 µg ml−1), which were better than or similar to MCR-ALS, presenting a great choice to deal with complex GC-MS data for the simultaneous determination of targeted PAHs in aerosols.

ChemInform Abstract: Stationary Phases for Complexation Gas Chromatography and Microextraction Methods

AbstractReview: 84 refs.

Stationary Phases for Complexation Gas Chromatography and Microextraction Methods

AbstractThe main goal of this review is to provide an overview of the trends in the technological development of complexation gas chromatography. This kind of chromatography, despite the passage of years, continues to offer new opportunities. The authors would like to show how complexation gas chromatography evolved over the years, due to the variety of stationary phases with complexation properties, their ability to separate, very specifically, the structures of the molecules and chemical compounds, improving the quality of the obtained results, and continuously lowering the detection limits of the analysed compounds in very complex matrices, including environmental and medical samples. The work is dedicated to the memory of Professor E. Gil‐Av, whose scientific achievements were the inspiration for the improvement and widening of the research on the use of complexing metal ions and coordination metal compounds for selective separation in gas chromatography.

Recovery of shale oil condensate from different oil shales using a flow-through apparatus

Four oil shales from different locations and origins have been reacted in a flow-through system (425°C, with N2 or H2 as sweep gases at 1atm pressure) with a view to more closely simulating a practical process for oil shale conversion than can be achieved with a sealed autoclave system.It was observed that there was no general correlation between the yields in the two systems, nor was there a general correlation between the amount of condensate and the amount of volatiles obtained by thermogravimetric analysis.For all four oil shales, the condensate gave more complex gas chromatography–mass spectrometry total ion chromatograms (GC–MS TICs) than the CH2Cl2-solubles from sealed autoclave reactions. Surprisingly, the products from one of the Jordanian oil shales, Yarmouk, and an Australian Julia Creek oil shale were remarkably similar. The product from the lacustrine Colorado oil shale was much more similar to that from a lacustrine algal coal (torbanite) than to those from marine oil shales. The differences in yields and product characteristics between sealed autoclave and flow-through reactions suggest that yields and product distributions obtained from sealed autoclave reactions should be treated with caution.

A Technique for Rapid Gas Chromatography Analysis Applied to Ambient Organic Aerosol Measurements from the Thermal Desorption Aerosol Gas Chromatograph (TAG)

While automated techniques exist for the integration of individual gas chromatograph peaks, manual inspection of integration quality and peak choice is still required due to drifting retention times and changing peak shapes near detection limits. The feasibility of a simplified method to obtain multiple bulk species classes from complex gas chromatography data is investigated here with data from the thermal desorption aerosol gas chromatograph (TAG). Chromatograms were divided into many “chromatography bins” containing total eluting mass spectra (both from resolved species and unresolved complex mixture [UCM]), instead of only integrating resolved peaks as is performed in the traditional chromatography analysis method. Positive matrix factorization (PMF) was applied to the mass spectra of the chromatography bins to determine major factors contributing to the observed chemical composition. PMF factors are not highly sensitive to the specific PMF error estimation method applied. Increasing the number of chr...

Chemometric strategy for automatic chromatographic peak detection and background drift correction in chromatographic data

Peak detection and background drift correction (BDC) are the key stages in using chemometric methods to analyze chromatographic fingerprints of complex samples. This study developed a novel chemometric strategy for simultaneous automatic chromatographic peak detection and BDC. A robust statistical method was used for intelligent estimation of instrumental noise level coupled with first-order derivative of chromatographic signal to automatically extract chromatographic peaks in the data. A local curve-fitting strategy was then employed for BDC. Simulated and real liquid chromatographic data were designed with various kinds of background drift and degree of overlapped chromatographic peaks to verify the performance of the proposed strategy. The underlying chromatographic peaks can be automatically detected and reasonably integrated by this strategy. Meanwhile, chromatograms with BDC can be precisely obtained. The proposed method was used to analyze a complex gas chromatography dataset that monitored quality changes in plant extracts during storage procedure.

Investigation of novel immobilized 3-(perfluoroalkanoyl)-(1R)-camphorate nickel complexes in enantioselective complexation gas chromatography

Novel 3-(perfluoroalkanoyl)-(1R)-camphorate nickel complexes immobilized to poly(dimethylsiloxane) phases are presented. Immobilized 3-(perfluoroalkanoyl)-(1R)-camphorate nickel complexes with a trifluoromethyl (CF3; nickel(II)-bis[(1R,4S)-3-trifluoromethanoyl-10-propylenoxycamphor]-polysiloxane Ni(tfpc)2@PS) and a heptafluoropropyl-substituent (C3F7; nickel(II)-bis[(1R,4S)-3-heptafluorobutanoyl-10-propylenoxycamphor]-polysiloxane Ni(hfpc)2@PS) were synthesized, characterized and immobilized to polysiloxane. Ni(hfpc)2@PS was immobilized with a selector content of 38% and their enantioseparation ability was compared to selector concentrations of 4% and 20%. The influence of the perfluorinated moiety as well as the effect of the selector concentration on enantioseparations were investigated. Based on different functionalized organic compounds the quality of enantioseparation was analyzed and compared.

Characterizing odorous emissions using new software for identifying peaks in chemometric models of gas chromatography–mass spectrometry datasets

The task of identifying individual compounds within complex gas chromatography – mass spectrometry (GC–MS) chromatograms is made more difficult by interferences between peaks with similar mass spectra eluting at the same time, typically against a background of chemical and electronic noise. Although chemometric techniques like parallel factor analysis and multivariate curve resolution can help to purify spectra and improve correlations with reference compounds, file incompatibilities between GC–MS acquisition software and modeling software prevent the modeled spectra from being easily compared to spectra in reference libraries. In this paper we present an enhancement to OpenChrom, an open-source software for chromatography and mass spectrometry, which implements the automated cross-matching of modeled spectra to NIST08 and NIST11 mass spectral databases. The benefits of this approach are demonstrated using a complex environmental dataset consisting of non-methane volatile organic compound emissions sampled on an Australian poultry farm.

Straightforward Synthesis of Poly(dimethylsiloxane) Phases with Immobilized (1R)‐3‐(Perfluoroalkanoyl)camphorate Metal Complexes and Their Application in Enantioselective Complexation Gas Chromatography (Eur. J. Org. Chem. 21/2012)

AbstractThe cover picture shows the leaves and blossom of the camphor tree cinnamomum camphora (photo taken at the botanical garden of the Ruprecht Karls University Heidelberg), a natural source of (+)‐(1R)‐camphor, which is the chiral key moiety of immobilized (1R)‐3‐(perfluoroalkanoyl)camphorate metal complexes. The beautiful white blossom forms a structure with tetrahedral elements, which are “mirrored” in the model of the polymeric chiral stationary phase. This chiral stationary phase is accessible in large quantities and can be used in complexation gas chromatography, showing exceptional high separation factors for a large number of stereoisomers. Details are discussed in the article by O. Trapp et al. on p. 3929 ff. magnified image

Straightforward Synthesis of Poly(dimethylsiloxane) Phases with Immobilized (1R)‐3‐(Perfluoroalkanoyl)camphorate Metal Complexes and Their Application in Enantioselective Complexation Gas Chromatography

AbstractA straightforward synthesis of novel chiral polysiloxane‐based metal stationary phases immobilized through a propylenoxy linker (Chirasil‐Metal‐OC3) to the polymeric backbone is presented. Synthesis was accomplished in six steps with high overall yields starting from commercially available, enantiopure (+)‐(1S)‐camphorsulfonic acid. Two different approaches towards Chirasil‐Metal phases featuring either a propylenoxy or propylenthio linker used for immobilization through hydrosilylation are presented. Furthermore, a new protocol for the fluoroacylation, which is one of the key steps in the synthesis of (1R)‐3‐(perfluoroalkanoyl)camphorate metal complexes, was developed to improve the isolation and overall yield. The immobilization of (1R,4S)‐10‐(allyloxy)‐3‐(heptafluorobutanoyl)camphor – 10‐(allyloxy)‐hfbc – onto polysiloxanes as well as the incorporation of nickel(II), oxovanadium(IV), europium(III), and lanthanum(III) was characterized by FT ATR IR and NMR spectroscopy. Overall, seven different Chirasil‐Metal‐OC3 polymers with different separation properties were prepared by metal incorporation and variation of the amount of immobilized (1R,4S)‐10‐(allyloxy)‐3‐(heptafluorobutanoyl)camphor (10‐allyloxy‐hfbc: 3.5, 10.2, and 20.0 %). Their performance in enantioselective complexation gas chromatography was systematically studied and excellent enantioselectivity was found for Chirasil‐Nickel‐OC3. Separation of 29 small‐sized compounds, encompassing, among others, epoxides, substituted alkenes and alkynes as well as alcohols and amides, was achieved with high separation factors α. The synthetic strategy, enantiomer separations and thermal stability (up to 160 °C) demonstrates the versatility of the newly derived Chirasil‐Metal‐OC3 phases.

Predictions of Retention Factors for Some Organic Nucleuphiles in Complexation Gas Chromatography

In the present work, the quantitative structure-retention relationship (QSRR) was used to predict the gas chromatographic retention factors of some organic nucleuphile on chemically modified stationary phase by complexes of Cu (II) with amino groups. The gravitation index, relative negative charge surface area, C component of moment of inertia and weighted negative charged partial surface area are selected as the most relevant descriptors from the pool of descriptors. These descriptors were used for developing multiple linear regression (MLR) and artificial neural network (ANN) models as linear and nonlinear feature mapping techniques. The root mean square errors (RMES) in calculation of retention factors for training, internal and external test set are 0.242, 0.295, and 0.240, respectively for MLR model, and for ANN model the RMSE for training, internal and external test set are; 0.084, 0.108, and 0.176. The ANN and MLR model were further examined by cross validation test, which obtained statistics of Q2 = 0.82 and SPRESS = 0.22 for MLR model and Q2 = 0.97, SPRESS = 0.07 for ANN model. Comparison between these results and other statistics of ANN and MLR models revealed the superiority of ANN over MLR model.

Novel stationary phase for complexation gas chromatography originating from ionic liquid and metallomesogen

A metallomesogen of a polycatenar oxazoline copper(II) complex, [Cu( S-C 12) 2], that exhibited a columnar mesophase with a helical organization was prepared and employed as the stationary phase for the GC separation with polycyclic aromatic hydrocarbons (PAHs) as model compounds. For introducing the mesogen into the capillary column, an ionic liquid (BeMIM-TfO) was used as the vehicle. The results of thermal analyses and UV–vis spectroscopy indicated that some beneficial interactions occurred between the metallomesogen and the ionic liquid. Various parameters affecting the separation efficiency were studied. Different ratios of BeMIM-TfO and Cu( S-C 12) 2 (1:0, 1:1, 1:2 and 1:3 (w/w)) were tested for the separation of the PAHs. As the amount of Cu( S-C 12) 2 was increased, complete separation could be achieved. The stationary phase with the ratio of 1:1 provided the most satisfactory result having average theoretical plate number of 5.2 × 10 3 plates/m. With an optimized temperature program, 11 PAH mixtures were completely separated within 27 min. The interaction between PAH and these fascinating and interesting stationary phases was discussed.

Complexes of transition metals bonded to silica via β-diketonate groups — synthesis, structure, and catalytic activity

AbstractTransition metal complexes bonded to silica via silanes with β-diketonate groups can be used as packings for complexation gas chromatography or as immobilized homogenous metal complex catalysts. On basis of elemental analysis and the determination of surface area, possible structures of the complexes formed on the silica surface have been proposed. The possibility of using the immobilized complexes as catalysts has been indicated. Especially nickel complexes were taken into consideration. These immobilized complexes were used previously as packings for complexation gas chromatography.

Existence of a low isoenantioselective temperature in complexation gas chromatography: Profound change of enantioselectivity of a nickel(II) chiral selector either bonded to, or dissolved in, poly(dimethylsiloxane)

The gas chromatographic enantiorecognition of the two enantiomeric pairs of Z- and E-2-ethyl-dioxaspiro[4,4]nonane (chalcogran), respectively, critically depends on whether the chiral selector nickel(II) bis[3-(heptafluorobutanoyl)-(1 R)-camphorate] is chemically linked via a methylene spacer to poly(dimethylsiloxane) (Chirasil-Nickel 1), or is only dissolved in poly(dimethylsiloxane) (Chira-Nickel 2a). On 2a, the enantiomers are separated at ambient temperature with a large apparent enantioseparation factor α app whereas on Chirasil-Nickel 1 only a low α app is observed whereby the elution order of the enantiomers is reversed. Concise temperature-dependent studies show that on Chirasil-Nickel 1 a low isoenantioselective temperature, T isoenant, of 80 °C is experimentally observed as the result of enthalpy/entropy compensation. For thermodynamic measurements, the method of the retention-increment R′ has been employed. This concept separates achiral contributions to retention due to the poly(dimethylsiloxane) matrix, which are identical for enantiomers, from enantioselective contributions to retention, which are due to complexation of enantiomers with the chiral selector. From Van’t Hoff plots, concise thermodynamic data of enantioselectivity, −Δ D, L(Δ G), −Δ D,L(Δ H), Δ D,L(Δ S) and T isoenant were obtained. It was found that minute changes in the structure of the spiroketals as well as miniscule differences of the nature of the chiral selector present in the stationary phase (chemically bonded versus physically dissolved) led to profound differences in enantioselectivity. The observation of a low isoenantioselective temperature T isoenant represents are rare phenomenon in enantioselective gas chromatography which both complicates the study of chiral recognition mechanisms and the correlation of the absolute configuration and retention due to the temperature-dependent reversal of the elution order.

Separation of dialkyl sulfides by metallomesogenic stationary phases for complexation gas chromatography

A copper mesogenic side-chain polymer (P-C 15CuC 18) was cross-linked onto the capillary wall as a stationary film for gas chromatography (GC) separation of alkylsulfides. These organic sulfides are of interest for their large health impact because of their wide range of volatilities and high reactivities toward metals. Different GC parameters for optimal separation efficiency are discussed for use with a mesogenic polymer column along with flame photometric detection (FPD). Both the carrier gas flow-rate and column temperature were studied to determine the relationship of plate height to the chemical structure of the solutes, as well as to determine the morphology of the mesogenic polymer. Van ’t Hoff plots show phase transitions of the stationary mesophase as the column temperature was varied. The results reveal that the separation mechanism might be based on ligand exchange and polarity interaction between the analytes and the stationary phase, with the vapor pressure of the analytes also being important. The former interaction dominates in the lamellar crystalline phase and the latter interaction dominates in the hexagonal columnar-discotic phase. With high reproducibility for retention time (RSD ≤ 0.37%) and for peak area (RSD ≤ 5.16%), the GC–FPD system produced linear calibration graphs ( r ≥ 0.9918) for the determination of 13 sulfides with a detection limit below 2.5 ng.

A simple way to teach the physiological role of ethylene at school laboratories

Ethylene plays an important role in plant physiology, being responsible for the maturation of fruits. In specialised laboratories this gaseous plant regulator is quantified through complex and expensive gaschromatography equipment; this technology is not available in schools, so ethylene is neglected by teachersperforming an experimental study about the control of plant growth and development. To provide an indirect but reliable indication of ethylene production by fruits, we developed a simple bioassay based on the titrationof malic acid.

Modeling of Selected Enantioseparation Mechanisms in the Gas and Liquid Chromatography with the Aid of Molecular Mechanics

Three types of diastereomeric complexes formed between low molecular chiral selectors and enantiomeric analytes were modeled in order to simulate enantioseparation of these analytes via the complexation gas chromatography, chiral ligand exchange liquid chromatography and charge transfer complexation liquid chromatography. The diastereomeric complexes were submitted to optimization of geometry and to sequential search of low energy conformations. The differences of the total energy of interaction obtained for the two enantiomeric solutes, R and S, were correlated with the experimental values of the differences in the change in Gibbs free energy. The application of molecular mechanics could facilitate predicting of separation and the elution order of enantiomeric solutes on the accessible, and promote designing of new chiral stationary phases.

Polyamine complexes of copper (II) and chromium (III) for the analysis of nucleophilic compounds by complexation gas chromatography

The paper describes the synthesis and properties of gas chromatography new packings containing chemically bonded copper (II) and chromium (III) complexes. In the packings the chlorides of the metals are bonded to silica surface by means of the aminosilaneN-[3-(trimethoxysilyl)propyl]ethylenediamine. Measurement of retention data enabled characterization of specific interactions. For the different packings relationships were found between the molecular structure of the solute (aliphatic and aromatic halogenated hydrocarbons, ethers, thioethers and esters) and their retention times. The physical and chemical properties of the packings were determined.

Capillary complexation gas chromatography in analysis of cyclic and aromatic hydrocarbons

Results of studies on stationary phases containing copper(II), nickel(II) and cobalt(II) chloride chemically bonded via cyano—or thiol groups are presented. The retention parameters—i.e. retention factor (k), retention index (I) and molecular retention index (ΔMe) and specific retention volume (Vg)-enabled the characteristics of specific interaction between aromatic and cyclic hydrocarbons and metal complexes chemically bonded to stationary phases to be determined.