Gas Chromatographic Separation Research Articles

H2/D2 separation in gas chromatography through a MOF-on-MOF strategy using γ-AlOOH@Al(OH)(1,4-NDC)@ZIF-67 as the stationary phase via additive effects of chemical affinity quantum sieving and kinetic sieving.

The reaction of porous γ-Al2O3 particles acting as both a sacrificial template and an aluminum source with 1,4-naphthalene diacid (H2NDC) resulted in the formation of γ-AlOOH@Al(OH)(1,4-NDC) composites, in which ZIF-67 was then loaded by the in situ crystallization method, leading to the formation of γ-AlOOH@Al(OH)(1,4-NDC)@ZIF-67 composites. The deliberately designed composite was used to separate H2/D2 at 77 K in a 1 m chromatographic column. The results demonstrated that the optimized composite can achieve the effective separation of H2/D2 in gas chromatography due to the additive effects of kinetic sieving and chemical affinity quantum sieving of Al(OH)(1,4-NDC) and ZIF-67. By optimizing chromatographic separation conditions, the resolution R reached 2.02 with the separation time t = 7.72 min. The composite also showed satisfactory repeatability and reproducibility.

SEPARATION PERFORMANCE OF PEG-LINKED CALIX[4]ARENE AS STATIONARY PHASE FOR CAPILLARY GAS CHROMATOGRAPHY

This work presented a new PEG modified calix[4]arene stationary phase (C4A-PEG-2PTSC) for gas chromatographic (GC) separations. The statically coated C4A-PEG-2PTSC column exhibited moderate polarity and column efficiency of 2224 plates m-1 determined by 1-octanol at 120 oC. The results showed that the C4A-PEG-2PTSC column exhibited the good separation performance for various types of analytes containing halogenated benzenes, benzaldehydes, phenols, alcohols, anilines isomers and showed the different retention behavior with the comparative columns. Importantly, it showed the better separation capacity of toluidine and xylidine isomers than commercial HP-35 column. Moreover, it was applied in practical sample analysis to detect the content of isomer impurities. This work exhibited the good application potential of C4A-PEG-2PTSC stationary phase in GC analyses.

GC-MS Analysis of Phytocomponents in aqueous extract of Tulsi and Mulhethi

Extraction process specifically targets isolation of carbohydrates, glycosides, and secondary metabolites from leaves. These compounds play crucial roles in Mulethi and Tulsi’s biological activities, including antioxidant, antimicrobial, and anti-inflammatory properties. By extracting and analysing these components, a deeper understanding of these plants’ medicinal potential can be gained. The identification of the extracted compounds was done using various chromatographic techniques. Chromatography is a powerful tool that separates and characterizes complex mixtures. Techniques such as gas chromatography (GC) were employed to separate the individual components of the extract and determine their chemical structures. The aqueous extract was screened and qualitatively analysed to detect specific compounds. The analytical technique combines GC separation capabilities with MS detection and identification capabilities. It provides valuable information about the chemical composition of the extracts, allowing the identification of individual compounds present in the samples. These compounds are known for their pharmacological activities and are often responsible for plants’ medicinal properties.

Compact GC-QEPAS for On-Site Analysis of Chemical Threats.

This paper reports on a compact, portable, and selective chemical sensor for hazardous vapors at trace levels, which is under development and validation within the EU project H2020 "RISEN". Starting from the prototype developed for a previous EU project, here, we implemented an updated two-stage purge and trap vapor pre-concentration system, a more compact MEMS- based fast gas-chromatographic separation module (Compact-GC), a new miniaturized quartz-enhanced photoacoustic spectroscopy (QEPAS) detector, and a new compact laser source. The system provides two-dimensional selectivity combining GC retention time and QEPAS spectral information and was specifically designed to be rugged, portable, suitable for on-site analysis of a crime scene, with accurate response in few minutes and in the presence of strong chemical background. The main upgrades of the sensor components and functional modules will be presented in detail, and test results with VOCs, simulants of hazardous chemical agents, and drug precursors will be reported and discussed.

Top-Down Approach to Retention Time Prediction in Comprehensive Two-Dimensional Gas Chromatography-Mass Spectrometry.

In this contribution, we describe a novel modeling approach to predicting retention times (tr) in comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC × GC-ToF-MS) with a particular emphasis on the second-dimension (2D) retention time predictions (2tr). This approach is referred to as a "top-down" approach in that it breaks down the complete GC × GC separation into two independent one-dimensional gas chromatography separations (1D-GC). In this regard, both dimensions, that is, first dimension (1D) and second dimension (2D) are treated separately, and the cryogenic modulator is simply considered as a second consecutive injection device. Separate 1D-GC tr predictions are performed on both dimensions using the same flow rate as the one deployed in the conventional GC × GC system. The separate tr predictions are then combined to account for the two-dimensional separation. This model was applied to 24 analytes from 2 standard mixtures (Grob Test Mix and Fragrance Materials Test Mix) and assessed across 9 GC × GC chromatographic conditions. The experimental and predicted chromatographic retention space occupations were assessed by using the convex hull approach defined by the Delaunay triangulation. The predicted percentage of space occupation corresponded favorably with the experimental values. Furthermore, the top-down approach enabled an accurate prediction of the 2tr of all investigated analytes, providing an average 2tr modeling error of 0.26 ± 0.01 s.

A New Capillary Gas Chromatography Column Based on Poly(ethylene glycol) Methyl Ether-Functionalized Calix[4]arene.

In this work, a novel capillary column (C4A-mPEG) with a calixarene-based polymer stationary phase (poly(ethylene glycol) methyl ether-functionalized 4-tert-butylcalix[4]arene) was designed and used for gas chromatographic (GC) separations. The C4A-mPEG capillary column, prepared by the static coating method, showed moderate polarity and a column efficiency of 2332 plates/m, determined by 1-octanol at 120 °C. The separation features of C4A-mPEG stationary phase, resulting from its unique structure and multiple molecular recognition processes with analytes, including π-π, H-bonding, dipole-dipole, and van der Waals interactions, allowed to obtain high-resolution performances for a wide range of compounds and their isomers, especially benzaldehydes, phenols, and anilines. Moreover, compared with 4-tertbutyl calix[4]arene (C4A) and polyethylene glycol (PEG) stationary phases, a higher resolving capability was also observed for the separation of toluidine and xylidine isomers.

Comprehensive two-dimensional countercurrent chromatography × gas chromatography characterization of Artemisia argyi essential oil

A comprehensive two-dimensional (2D) countercurrent chromatography (CCC) × gas chromatography (GC) was investigated for characterization of chemical constituents of Artemisia argyi essential oil, and orthogonality for the 2D chromatographic system was evaluated. A solvent system composed of n-hexane/acetonitrile/methanol (2:2:1, v/v/v) was selected for first dimensional separation of Artemisia argyi essential oil. Then all CCC fractions were analyzed by GC, which provided a wealth of information regarding the composition of the essential oil. Visualization of chemical compositions obtained from the comprehensive 2D CCC × GC separation was achieved by creation of a 2D contour plot map. Total peak capacity was evaluated and approximately 1392 peaks were obtained through a comprehensive 2D CCC × GC separation. A high spatial coverage and a low linear correlation coefficient were achieved. Meanwhile, all compounds were identified by GC-MS. The obtained 2D contour plot could be divided into six zones to show the characteristic chemical compositions. Six zones could be divided into different component groups, including monoterpenes, sesquiterpenes, monoterpene alcohols, phenols, aldehydes, ketones and esters, which could be used to identify compounds that have not been reported, and to predict the structure of unknown compounds in Artemisia argyi essential oil and comprehensively characterize fingerprint peak.

Processing and Interpretation of Analytical Data with a High Degree of Uncertainty

Some analytical problems, which are often considered incorrect for objective reasons, are considered. The main of these reasons is an anomalously large scatter of the initial data. It can be due to either the low reproducibility of the characteristics of substances, their quantities, analytical signal intensities, process conditions, etc., or variability due to differences in the nature of the objects themselves. In the latter case, the nature of data interpretation is influenced by analytical hypotheses adopted for their consideration. The tasks considered include variations in the component composition of developers for black-and-white negative photographic materials, comparison of temperature parameters of the gas-chromatographic separation of various organic compounds, toxicity characterization (LD50) of homologues using C3–C12 1-alkanols as an example, and the possibility of predicting sample preparation operations in the determination of drugs in blood plasma based on their physicochemical characteristics. The main features of data interpretation characterized by a high degree of uncertainty are revealed. It is noted that important conclusions can be drawn based on the facts of low reproducibility (one-dimensional arrays) or poor correlation of variables (two-dimensional arrays).

Influence of modulator injection width on comprehensive two-dimensional gas chromatography peak dimensions.

This study examines how the height and width of peaks exiting the secondary column of a comprehensive two-dimensional gas chromatography (GC × GC) separation are affected by the width of the pulse introduced to the secondary column. A flow-modulated GC × GC apparatus was assembled that allowed input pulse widths to be controlled precisely over a range of 10 to 70ms. GC × GC chromatograms were obtained using secondary columns containing a polyethylene glycol stationary phase with internal diameters of 0.25 and 0.32mm. The area, height, and width of peaks emerging from the secondary column were found to be accurately modeled by the convolution of a rectangular function with a Gaussian distribution. The rectangular function represents the input pulse, and the Gaussian distribution represents the broadening that occurs in the secondary column. The minimum peak width that could be produced by the secondary column was determined for a wide range of compounds. Injection pulse widths that matched a compound's minimum peak width produced peaks that were 25% wider than the minimum width and had heights that were 76% of the maximum possible peak height. Increasing the injection width significantly above the minimum width yielded substantially broader peaks with only a modest increase (< 25%) in peak height.

Identification of the Degradation Products from α‐Tocopherol Used as Stabiliser in “Green” Propellants through its Lifetime

AbstractStabilisers are added to gun and rocket propellants to react with species responsible for nitrate ester degradation during storage. The degradation products can be toxic and therefore harmful. There is a need to replace such stabilisers by “green” molecules and to study their degradation patterns through ageing. Propellant powders must remain chemically stable for a minimum of ten years when stored at temperatures equivalent to 25 °C [1]. α‐Tocopherol is a natural product that has been known for decades in other fields (Vitamin E) such as the pharmaceutical, food and cosmetics industries. It can act as a ‘green’ stabiliser” for smokeless powders because its heat flow is stable over time. In this paper, we characterise its stabilisation mechanism by identifying its main degradation products that could form within the propellant in an oxidising environment and in the presence of nitric acid. Liquid chromatography (LC) and gas chromatography (GC) separations are performed in order to dissociate the compounds formed during ageing. Compounds are then analysed by APCI‐timsTOF to obtain the molecular ion masses and then perform fragmentation spectra (MS/MS) to characterise their structure. In addition, using preparative HPLC‐UV, the degradation products are collected and analysed by NMR, with the aim of identifying the molecules. These identification methods help to unravel the stabilisation mechanism under accelerated ageing conditions. A time‐related fluctuation of the degradation products amounts is also observed, which indicates that the decomposition products also have a stabilisation effect. The three major α‐tocopherol degradation products are identified as: 2,3‐epoxy‐α‐tocopherylquinone, 5,6‐epoxy‐α‐tocopherylquinone and α‐tocored.

Microplastic-Free Microcapsules to Encapsulate Health-Promoting Limonene Oil.

Fast-moving consumer goods (FMCG) industry has long included many appealing essential oils in products to meet consumers' needs. Among all, the demand for limonene (LM) has recently surged due to its broad-spectrum health benefits, with applications in cosmetic, detergent, and food products. However, LM is extremely volatile, hence has often been encapsulated for a longer shelf-life. To date, mostly non-biodegradable synthetic polymers have been exploited to fabricate the microcapsule shells, and the resulting microcapsules contribute to the accumulation of microplastic in the environment. So far, information on LM-entrapping microcapsules with a natural microplastic-free shell and their mechanism of formation is limited, and there is lack of an in-depth characterisation of their mechanical and adhesive properties, which are crucial for understanding their potential performance at end-use applications. The present research aims towards developing safe microcapsules with a core of LM fabricated via complex coacervation (CC) using gum Arabic (GA) and fungally sourced chitosan (fCh) as shell precursors. The encapsulation efficiency (EE) for LM was quantified by gas chromatography (GC) separation method. The morphology of microcapsules was investigated via bright-field optical microscopy and scanning electron microscopy, and their mechanical properties were characterised using a micromanipulation technique. Moreover, the adhesive properties of the resulting microcapsules were studied via a bespoke microfluidic device fitted with a polyethylene-terephthalate (PET) substrate and operating at increasingly hydrodynamic shear stress (HSS). Spherical core-shell microcapsules (EE ~45%) with a mean size of 38 ± 2 μm and a relatively smooth surface were obtained. Their mean rupture force and nominal rupture stress were 0.9 ± 0.1 mN and 2.1 ± 0.2 MPa, respectively, which are comparable to those of other microcapsules with synthetic shells, e.g., urea- and melamine-formaldehyde. It was also found that the fCh-GA complexed shell provided promising adhesive properties onto PET films, leading to a microcapsule retention of ~85% and ~60% at low (≤50 mPa) and high shear stress (0.9 Pa), respectively. Interestingly, these values are similar to the adhesion data available in literature for microplastic-based microcapsules, such as melamine-formaldehyde (50-90%). Overall, these findings suggest that microplastics-free microcapsules with a core of oil have been successfully fabricated, and can offer a potential for more sustainable, consumer- and environmentally friendly applications in FMCGs.

Single-Crystalline Imine-Linked Two-Dimensional Covalent Organic Frameworks Separate Benzene and Cyclohexane Efficiently.

Two-dimensional (2D) covalent organic frameworks (COFs) are composed of structurally precise, permanently porous, layered macromolecular sheets, which are traditionally synthesized as polycrystalline solids with crystalline domain lengths smaller than 100 nm. Here, we polymerize imine-linked 2D COFs as suspensions of faceted single crystals in as little as 5 min at moderate temperature and ambient pressure. Single crystals of two imine-linked 2D COFs were prepared, consisting of a rhombic 2D COF (TAPPy-PDA) and a hexagonal 2D COF (TAPB-DMPDA). The sizes of TAPPy-PDA and TAPB-DMPDA crystals were tuned from 720 nm to 4 μm and 450 nm to 20 μm in width, respectively. High-resolution transmission electron microscopy revealed that the COF crystals consist of layered, 2D polymers comprising single-crystalline domains. Continuous rotation electron diffraction resolved the unit cell and crystal structure of both COFs, which are single-crystalline in the a-b plane but disordered in the stacking c dimension. Single crystals of both COFs were incorporated into gas chromatography separation columns and exhibited unusual selective retention of cyclohexane over benzene, with single-crystalline TAPPy-PDA significantly outperforming single-crystalline TAPB-DMPDA. Polycrystalline TAPPy-PDA exhibited no separation, while polycrystalline TAPB-DMPDA exhibited poor separation and the opposite order of elution, retaining benzene more than cyclohexane, indicating the importance of improved material quality for COFs to exhibit properties that derive from their precise, crystalline structures. This work represents the first example of synthesizing imine-linked 2D COF single crystals at ambient pressure and short reaction times and demonstrates the promise of high-quality COFs for molecular separations.

Ionic liquids as stationary phases for the gas chromatographic separation of fentanyl analogues

The continuous emergence of novel fentanyl analogues has created a need for improved methods able to distinguish between fentanyl analogues and their isomers. In this study, the utility of commercially available ionic liquid columns is demonstrated for GC-FID and GC–MS separation and unambiguous identification of fentanyl, 22 fentanyl analogues and U-47700. The selectivity of the IL column towards these compounds was determined as well as the effectiveness of detection from complex illicitly synthesized drug samples. The results of this study were compared to a 5% diphenyl/95% dimethylpolysiloxane column to show increased selectivity and applicability towards seized illicit drug samples. 24 compounds were separated 36% faster with an elution window increase of 33% on the ionic liquid phase compared to the 5% diphenyl/95% dimethylpolysiloxane phase. The selectivity of 11 isomeric analogue sets (out of 12) increased by 2 to 25% over the 5% diphenyl/95% dimethylpolysiloxane phase showing an ionic liquid column is more favorable for separating fentanyl analogues. The ionic liquid column provides better signal to noise, and a faster and more selective option for forensic laboratories looking to identify confiscated illicit drug samples.

Nontargeted Screening for the Verification of Allergenic Ingredients and Perfume Authenticity by GC-ecTOF-MS

Fraudulent products are ubiquitous in all markets. Besides the financial aspect, a major issue regarding products adulteration for society and the environment is the missing regulation and control of these goods. Therefore, harmful and toxic compounds in fraudulent products may become a risk for human health and the environment. Even small amounts of toxic substances can still have damaging effects. Thus, a sensitive and reliable identification of compounds is needed. Novel technologies are necessary to use identifying and preventing fraud and related risks. Goods from the food, flavor, and fragrance markets often contain volatile organic compounds (VOCs), which include most allergenic fragrances. For the detection and identification of these substances, gas chromatographic separation hyphenated with high resolution mass spectrometry (GC–HRMS) is an ideal instrumental technique. GC–simultaneous electron and chemical ionization (ec) time-of-flight (TOF)-MS generates various types of information via simultaneous ec–HRMS. Advantages are given for target, known unknown, and unknown unknown data analysis by generating various types of ions within one single experimental GC–MS run. In this study, the experimental nontargeted screening approach and corresponding data analysis workflows—simultaneously using molecular ion information and structural information—are presented for the molecular identification and authenticity verification process from a brand perfume using GC–ecTOF-MS.

On-site GC-QEPAS analysis on the scene of crime: The RISEN project

The capability to provide timely forensic analytical information is of paramount importance in criminal investigations involving chemical substances of toxicological interest. Miniaturized Gas Chromatography (GC) systems are suitable sensors to be deployed on the scene of crime, allowing to analyse specimens there, providing timely information to protect security and safety of specialists on-site and saving the time needed to collect, transport and analyse them in a forensic laboratory. An innovative hand-portable point sensor has been recently developed using a fully Micro-Electro-Mechanical-System (MEMS)-based compact-GC platform of the size of a few cm3 coupled to a miniaturized detector based on InfraRed Quartz Enhanced Photo Acoustic Spectroscopy (QEPAS). Sensing is based on the piezoelectric transduction of the photo-acoustic signal that is generated when laser radiation is absorbed by molecules in vapour phase in the QEPAS cell. Signal intensity is proportional to laser intensity, to the absorption cross section of the substance, and to its concentration. QEPAS spectra are very similar to the spectra obtained by classical IR absorption spectroscopy (IRAS), but, unlike IRAS cells, QEPAS cells can be designed as very cheap components of miniature size. The GC-QEPAS prototype is built upon a patented compact-GC architecture integrating three silicon micro-machined chips for sample pre-concentration, injection and GC separation and a QEPAS sensor based on a new ultra-wide tunability Quantum Cascade Laser (QCL) source, designed and assembled into a package matching the needs of hand-portability by the operator. The system was equipped with a compact air sampler, which also contains a first stage of pre-concentration, to allow vapour analysis on-site. Preliminary tests were carried out in a 60 litres glass box, where vaporizing solutions (between 1 and 100 microlitres) using a syringe of target substances. Sampling time was less than 60 seconds. The GC-QEPAS sensor was used to successfully analyse ppm and sub-ppm amounts of two nerve agent simulants: dimethyl methyl phosphonate (DMMP) and dipropylene glycol methyl ether (DPGME). Methyl salicylate (a blister agent simulant) and sulfur mustard (a real blister agent sample) were also tested. Other substances of interest in forensic toxicology where tested, including precursors of drugs of abuse. The sensor showed also its capability of analyzing amphetamine types stimulants (ATS) and drug precursors both as pure compounds and as mixtures. LoDs measured were in the order of about 10 ng for many precursors, and ten times larger for target compounds containing an amino group. Ethanol, propanol, gasoline and paint vapours at much higher concentrations, up to saturation vapor pressure, compared to the target chemical substances of forensic interest were also analysed to study the selectivity of the system in a real scenario. The miniature size of the column has allowed the separation of substances in cycle times of 2–3 minutes, to be compared with chemical substances eluting after retention times in the order of tens of minutes with traditional GC systems commonly used in forensic laboratories for casework. The total absorption chromatograms and the photoacoustic absorption spectra related to chromatographic peaks of both pure compounds and mixture will be shown, to demonstrate how the approach developed in the RISEN project will be able to support an improved approach to crime scene activities in the near future.

A chiral metal-organic cage [Fe4L6](ClO4)8 used for capillary gas chromatographic separations

Metal-organic cages (MOCs), as a promising class of crystalline porous materials with well-defined cavities, have attracted wide attention due to their multifarious potential applications in gas storage, host-guest chemistry, molecular recognition, separation, catalysis, sensing, and drug delivery and so on. Herein, we report that a chiral MOC [Fe4L6](ClO4)8 coated capillary column was fabricated for high-resolution gas chromatographic separation of various analytes, including n-alkanes, n-alcohols, positional isomers, aromatic hydrocarbon mixture, especially for racemic compounds. A series of racemic compounds such as alcohols, epoxides, aldehydes, ketones, ethers, esters, alkenes, sulfoxides and amino acid derivatives could be well separated on the [Fe4L6](ClO4)8 coated capillary column with high enantioselectivity and good reproducibility. Comparing the chiral resolution ability of the MOC [Fe4L6](ClO4)8 coated column with the commercial β-DEX 120 column and the porous organic cage (POC) CC10 coated column, the chiral MOC column can be complementary to the two different types of columns. The results show that the chiral MOC [Fe4L6](ClO4)8 exhibited excellent separation performance toward a wide range of organic compounds, which will be very attractive as a new chiral separation media and has potential application prospects in separation science.

Preparation and evaluation of a chiral porous organic cage based chiral stationary phase for enantioseparation in high performance liquid chromatography

Porous organic cages (POCs) are a new kind of porous molecular materials, which have gained widespread interest in many fields due to their intriguing properties, including excellent molecular solubility, inherent molecular cavity and rich host-guest chemistry. To date, many chiral POCs have been explored as chiral stationary phases (CSPs) for gas chromatographic (GC) separation of enantiomers. However, the applications of chiral POCs for high performance liquid chromatography (HPLC) enantiomeric separation is extremely rare. In this study, we report the construction of thiol-ene click reaction for the preparation of CSP for HPLC by using a [4+8]-type chiral POC NC4-R as chiral selector. The fabricated CSP showed good chiral resolution performance not only in normal-phase HPLC (NP-HPLC) but also in reversed-phase HPLC (RP-HPLC). Seventeen and ten racemates were well resolved in the two separation modes, respectively, including ketones, esters, alcohols, phenols, amines, ethers, organic acids, and amino acids. Moreover, the fabricated column also shows good chiral recognition complementarity to two popular chiral HPLC columns (Chiralpak AD-H and Chiralcel OD-H columns) and previously reported chiral POC NC1-R-based HPLC column, which can resolve some racemates that unable to be resolved by the two commercially available chiral HPLC columns and NC1-R-based column. The relative standard deviation (RSD) values (n = 4) of retention time and resolution (Rs) of analytes separated on the column were less than 0.3 % and 0.5 % after it was subjected to different injections, showing the good reproducibility and stability of the NC4-R-based column. This work demonstrated high potentials of chiral POCs for HPLC enantioseparation and the applicability of chiral POC-based HPLC columns can be broadened by developing more chiral POCs with diverse structures as chiral selector for HPLC.

Analysis of Thermoplastic Copolymers by Mild Thermal Degradation Coupled to Ion Mobility Mass Spectrometry.

Thermal desorption/degradation with an atmospheric solids analysis probe (ASAP) and ion mobility (IM) separation are coupled with mass spectrometry (MS) analysis and tandem mass spectrometry (MS/MS) fragmentation to characterize thermoplastic elastomers. The compounds investigated, which are used in the manufacture of a wide variety of packaging materials, are mainly composed of thermoplastic copolymers, but also contain additional chemicals ("additives"), like antioxidants and UV stabilizers, for enhancement of their properties or protection from degradation. The traditional method for analyzing such complex mixtures is vacuum pyrolysis followed by electron or chemical ionization mass spectrometry, often after gas chromatography separation. Here, an alternative, faster approach, involving mild degradation at atmospheric pressure (ASAP) and subsequent characterization of the desorbates and pyrolyzates by IM-MS, and if needed, MS/MS is presented. Such multidimensional dispersion considerably simplifies the resulting spectra, permitting the conclusive separation, characterization, and classification of the multicomponent materials examined.

Selectivity Map of Stationary Phases: A Graphical Method for Systematizing and Searching for Conditions for the Gas Chromatographic Separation of Polar Substances

Selectivity Map of Stationary Phases: A Graphical Method for Systematizing and Searching for Conditions for the Gas Chromatographic Separation of Polar Substances

In-Situ Intercalating of Silica Nanospheres into Polypyrrole During Its Electropolymerization to Prepare a Sorbent for Headspace Microextraction of Aldehydes in Edible Oils

The quality of edible oils is significantly affected by autoxidation of lipids, which alters their flavor and nutritional quality through production of toxic materials like aldehydes (an important class of oil deterioration markers). Herein, an amino-silica nanospheres/polypyrrole (ASNS/PPy) nanocomposite sorbent was synthesized and used as the fiber coating for headspace solid-phase microextraction (HS-SPME) of aldehydes in edible oils, followed by gas chromatography (GC) separation and determination. Amino-silica nanoparticles were prepared by an amended Stöber method and composited with polypyrrole during its electropolymerization on the surface of a platinized stainless-steel fiber. The synergy between in-situ electropolymerization and rough surface of the platinized metal substrate created a durable fiber coating with unique uniformity, cohesiveness, and adsorption properties. The synthesized nanocomposite was characterized using Fourier transform infrared spectroscopy and scanning electron microscopy techniques. The performance of the prepared fiber was optimized by investigating the affecting variables including extraction temperature and time, stirring rate, and desorption conditions. The obtained limits of detection for hexanal and heptanal in sunflower oil were 0.005-0.009 µg mL-1. The prepared fiber exhibited excellent repeatability and reproducibility with the intra-fiber and inter-fiber relative standard deviations in the ranges of 3.9-8.8% and 7.3-15.1%, respectively. The proposed HS-SPME-GC strategy was successfully applied for the analysis of aldehydes in commercial edible oil samples.