Response of nanogravimetric detector is based on adsorption of molecules on the surface of a vibrating beam. For any compound, NGD temperature (originally from 40 to 200°C) is the main operating parameter to control its sensitivity. Introduction of a cooling unit to enlarge the operating temperature range (down to -100°C) led to a substantial improvement in detection sensitivity and a significant reduction in quantification limits. The response of tetrahydrothiophene (THT) over a wide temperature range was deeply investigated: peak height increased exponentially as temperature decreased, while noise was slightly lowered. Consequently, the limit of quantification (LOQ) of THT can be reduced from 22 ppm at 50°C to 0.16 ppm at -65°C. However, significant peak tailing was observed at very low temperatures, which may compromise the separation of complex mixtures. THT chromatographic peaks were successfully modeled using an Exponentially Modified Gaussian (EMG) function, and the temperature dependence of the EMG adjusted parameters has been discussed.

Vegetable oil adulteration in essential oils is a common practice to increase artificially the volume of production of these natural raw materials and reduce the production cost. With the case study of cypriol oil, an overview of the different analytical tools was established to identify the fraud. The analytical strategy implemented analytical approaches suitable for the detection of heavy compounds such as triglycerides in vegetable oils to detect at least 3% of addition. This methodology includes stable isotope analyses IRMS δ 13 C, thermogravimetric analyses, spectroscopic techniques (FTIR and NMR) and the study by GC–MS (high temperature columns and derivatization). Depending on the adulteration performed, some techniques will be more effective. δ 13 C measurement is useful for the authentication of essential oils from C 4 plants; thermogravimetric analysis is the simplest to implement and allows for a quick detection of fraud but does not allow for the identification of the adulterant, in which case a complementary spectroscopic analysis will be necessary.

Lung cancer remains one of the deadliest cancers worldwide, which highlights the urgent need for new diagnostic tools to detect reliable biomarkers. To enable scalable and cost-effective production, we developed reusable PDMS stamps patterned with electrodes to print flexible electrodes on PET substrates using a microcontact printing (µCP) approach. PET was chosen not only for its flexibility but also as a more sustainable alternative to conventional rigid materials. On these electrodes, three sensing platforms were tested for neuron-specific enolase (NSE) detection: APTES-based monolayers, electrospun PVA/alginate nanofibers, and electropolymerized polypyrrole (PPy) films. Voltammetric and fluorescence/AFM analyses confirmed that all three platforms could recognize the target analyte, with the PPy-CdTe configuration showing the strongest signal variation. Impedance spectroscopy further supported this finding, revealing a clear linear correlation between charge transfer resistance (RCT) and NSE concentration. The PPy-CdTe sensor demonstrated high sensitivity and consistent performance for NSE detection, achieving a detection limit (LOD) of 8.05 pg·µL−1 and a quantification limit (LOQ) of 26.84 pg·µL−1.

The main objective of this research is to prepare and characterize silica-coated magnetic capsules and investigate them for DNA extraction via adsorption and desorption process as a function of pH and DNA concentration. A novel approach was used to synthesize and emulsify ferrofluid, followed by silica coating of the resulting nanoparticles using sol-gel process consuming TEOS and APTES as silica precursors separately. TEM, XRD, DLS, FTIR, and TGA are employed to determine the size distribution, crystallinity, morphology, and chemical composition of the nanoparticles. The ferrofluid contains magnetic nanoparticles stabilized with oleic acid in octane. O/W (oil-in-water) magnetic emulsion and silica-coated capsules have an average size of 280, 290, and 320 nm, respectively. The successful extraction of DNA using these capsules is evidenced by the quantification of immobilized DNA on the particles. This research work shows positive results regarding DNA immobilization and separation methodologies, suggesting potential avenues for practical biomedical applications.

Polyvinyl chloride (PVC) recycling is crucial for mitigating the environmental impact of PVC wastes, which take decades to decompose in landfills. This review examines the current state of PVC recycling processes, focusing on challenges and future research opportunities. It explores the types and sources of PVC wastes, including post‐consumer, industrial, and construction wastes. Conventional recycling methods such as mechanical, thermal, and chemical recycling are discussed, highlighting their advantages, limitations, and successful applications. Furthermore, recent advances in PVC recycling, including biological, plasma‐assisted, and solvent‐based recycling, are explored, considering their potential benefits and challenges. The review emphasizes the European context of PVC recycling, as the region has implemented regulatory initiatives and collaborations. It points out the Circular Economy Action Plan and directives targeting PVC waste management, which have promoted recycling and established a supportive framework. Challenges of current PVC recycling methods and technologies, such as low yield and high energy consumption, are identified. The review calls for the development of efficient and cost‐effective recycling technologies, along with improvements in recycling infrastructure and consumer awareness. Assessing the environmental and economic impacts, PVC recycling significantly reduces greenhouse gas emissions and conserves resources compared to virgin PVC production. The economic benefits include job creation and reduced raw material costs.

Hydrodynamics, efficiency, and loading capacity of two semi-packed columns with different cross sections (NANO 315 µm x 18 µm; CAP 1000 µm x 28 µm) and similar pillar diameter and pillar-pillar distance (respectively 5 µm and 2.5 µm) have been compared in high-pressure gas chromatography. A flow prediction tool has been first designed to determine pressure variations and hold-up time across the chromatographic system taking into account the rectangular geometry of the ducts into the semi-packed columns. Intrinsic values of Height Equivalent to Theoretical Plate were determined for NANO and CAP columns using helium as carrier gas and similar values have been obtained (30 µm) for the two columns. Loading capacity of semi-packed columns were determined for decane at 70 °C using helium, and the highest value was obtained from CAP column (larger cross section and stationary phase content). Finally, significant HETP improvement (down to 15 µm) and peak shape were observed when carbon dioxide was used as carrier gas, suggesting mobile phase adsorption on stationary phase in high pressure conditions.

The transformative impact of recent advancements in gas sensor technologies, crucial for industrial safety, environmental monitoring, quality assessment, healthcare, and consumer electronics, has been extensively investigated. Gas sensors play a pivotal role across various domains by offering real-time gas monitoring and detection capabilities. This review summarises the latest developments in gas sensor technologies, encompassing various sensor types employed in breath analysis and common nanomaterials for sensing. It provides insight into their performance evaluation based on sensitivity, selectivity, detection limit and response time and their applications in medical and environmental contexts. Also, we offer perspectives on the challenges and future direction imperative for the ongoing innovation of gas sensors as a smart tool for disease diagnosis, various industrial applications and environmental monitoring and management.

The integration of semi-packed columns in gas chromatography has garnered significant interest in recent years. This review investigates various aspects of semi-packed columns, encompassing their fundamental concept, fabrication process, coating techniques, and exploration of various designs employed in gas chromatography. Diverse applications of semi-packed columns in gas chromatography are presented to showcase their practical significance and potential. By examining the current state of research and advancements in semi-packed column technology, this review aims to provide valuable insights for researchers seeking to enhance the capabilities of gas chromatography systems using innovative column designs.

In this paper, a microconductometric sensor has been designed, based on a chitosan composite including alcohol dehydrogenase—and its cofactor—and gold nanoparticles, and was calibrated by differential measurements in the headspace of aqueous solutions of ethanol. The role of gold nanoparticles (GNPs) was crucial in improving the analytical performance of the ethanol sensor in terms of response time, sensitivity, selectivity, and reproducibility. The response time was reduced to 10 s, compared to 21 s without GNPs. The sensitivity was 416 µS/cm (v/v%)−1 which is 11.3 times higher than without GNPs. The selectivity factor versus methanol was 8.3, three times higher than without GNPs. The relative standard deviation (RSD) obtained with the same sensor was 2%, whereas it was found to be 12% without GNPs. When the air from the operator’s mouth was analyzed just after rinsing with an antiseptic mouthwash, the ethanol content was very high (3.5 v/v%). The background level was reached only after rinsing with water.

Urban air pollution is partly due to exhaust emissions from road transport. Vehicle emissions have been regulated for more than 30 years in many countries around the world. Each motor type is equipped with a specific emission control system. In gasoline vehicles, a three-way catalytic converter (TWC) is implemented to remove at the same time hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). However, TWCs are only efficient above 200 °C and at a stoichiometric air-to-fuel ratio in the exhaust. However, deviations from stoichiometry occur during fast accelerations and decelerations. This study reports the analysis of unregulated VOCs commercial mini-TWC fed by model gasoline gas mixtures. A synthetic gas bench was used to control the model exhaust containing two model hydrocarbons (propene and propane) to identify the conditions at which VOCs are created under non-optimal conditions. Most of the pollutants such as N2O and VOCs were emitted between 220 and 500 °C with a peak at around 280 °C, temperature which corresponds to the tipping point of the TWC activity. The combination of different mass spectrometric analysis (online and offline) allowed to identify many different VOCs: carbonated (acetone, acetaldehyde, acroleine), nitrile (acetonitrile, propanenitrile, acrylonitrile, cyanopropene) and aromatic (benzene, toluene) compounds. Growth mechanisms from propene and to a lesser extend propane are responsible for the formation of these higher aromatic compounds that could lead to the formation of secondary organic aerosol in a near-field area.

A stable emulsion of organic ferrofluid in an aqueous medium, known as oil-in-water (o/w) magnetic emulsion, was successfully prepared and characterized. The present study introduces a novel approach to synthesize and emulsify ferrofluid, followed by silica coating of the resulting nanoparticles using sol–gel process. The ferrofluid consisted of magnetic nanoparticles stabilized with oleic acid in octane. Both the ferrofluid and the emulsion exhibited spherical morphology, with average sizes of 20 nm and 200 nm, respectively. Characterization methodologies for instance TEM (transmission electron microscopy), DLS (dynamic light scattering), XRD, FTIR, and magnetic measurements were employed to determine the size distribution, crystallinity, morphology, and chemical composition of the nanoparticles. Chemical composition analysis of the prepared nanoparticles was performed using thermogravimetric analysis (TGA). This research work demonstrates the possibility of encapsulating o/w magnetic emulsion, promising potential for future bioapplications, emphasizing the importance of efficient and stable o/w magnetic emulsions.

Thin-film composite of chitosan/nickel phthalocyanine (NiPc) was electrochemically deposited on the fingers of interdigitated gold electrodes, applying chronoamperometric polymerization technique. The presence of crystallized NiPc in the chitosan was confirmed by EDX and FTIR analysis. Acetone, ethanol, and methanol gas-sensing properties of the films prepared at optimum conditions were studied at atmospheric temperature, through differential measurements at an optimized frequency of 10 kHz, using a lock-in amplifier. The conductometric sensor presents the highest sensitivity of 60.2 mu S.cm(-1)(v/v) for methanol and 700 ppm as the limit of detection. For validation, the methanol content of a commercial rubbing alcohol was determined.

A conductometric microsensor for measuring methanol was conceived, based on electrospun composite nanofibers of polyvinyl chloride (PVC) doped with nickel phthalocyanine (NiPc) deposited on interdigitated electrodes (IDEs) as transducers. The nanofiber's shape, structure, percent atomic content and thermal properties were studied. The methanol sensor showed good sensitivity (505µS/cm(v/v) -1) , low LOD (15 ppm), short response time (13 s), and short recovery time (25 s). The sensor was 4 times more sensitive to methanol than to ethanol and 19 times more sensitive to methanol than to acetone. Furthermore, the sensor response was unaffected by the interfering water vapor, making it more suitable for VOC sensing in the presence of humidity. The sensor was applied for conductometric detection of methanol in rubbing alcohol.

Nano-gravimetric detector (NGD) has been recently introduced as miniaturized gas chromatography detector. The NGD response is based on an adsorption-desorption mechanism of compounds between the gaseous phase and the NGD porous oxide layer. The NGD response was characterized by hyphenating NGD in-line with FID detector and a chromatographic column. Such method led to the full adsorption-desorption isotherms of several compounds in a single run. Langmuir model was used to describe the experimental isotherms, and the initial slope of the isotherm (Mm.KT) obtained at low gas concentration was used to compare the NGD response for different compounds (good repeatability was demonstrated with a relative standard deviation lower than 3%). The column-NGD-FID hyphenated method was validated using alkane compounds according to the number of carbon atoms in the alkyl chain and to the NGD temperature (all results agreed with thermodynamic relations associated to partition coefficient). Furthermore, relative response factor to alkanes, for ketones, alkylbenzenes, and fatty acid methyl esters have been obtained. These relative response index values led to easier calibration of NGD. The established methodology can be used for any sensor characterization based on adsorption mechanism.

A novel and ideal immunosensor platform with customized tailored chemistry is suggested by combining the characteristics of nanofibers (NFs) and dendrimers. Polystyrene (PS) NFs were doped with polyamidoamine (PAMAM) dendritic polymer and utilized for covalent immobilization of FITC-labeled anti-human TNF-alpha antibodies by activation of the amine groups of dendrimer on the surface of NFs using a glutaraldehyde (GA) coupling agent. SEM, ATR-FTIR, contact angle, EDX, XPS, TGA, and fluorescence microscopy were performed. The findings demonstrated that (1) PS-PAMAM NFs were produced with significantly smaller diameters (295 +/- 94 nm), more uniform morphology, and more hydrophilic (44 +/- 5.5 degrees) with dendrimer amine groups on the surface that can provide a better path for antibodies to be immobilized compared to pure PS NFs, (2) the PAMAM was distributed evenly throughout the NFs, (3) GA was uniformly applied to the surface of NFs via covalent bonding, (4) the PAMAM played a critical role in substantially increasing antibody immobilization at the surface of each NFs without causing agglomeration. According to the findings, the P5-PAMAM electrospun mat is suitable for immobilizing biomolecules and may be utilized as a support to boost immunosensor sensitivity.

A new nanocomposite, named A-CNF/DT, is prepared based on anionic cellulose nanofibrils (CNFs) treated with the (2, 2, 6, 6-tetramethyl piperidine-1-yl) oxyl (TEMPO) and diatomite (DT) via hydrothermal alkaline synthesis. The A-CNT/DT adsorbant was characterized by N-2 adsorption at 77 K, FTIR, XRD, TGA, SEM and TEM analysis and used to removal of methylene blue (MB) and indigo carmine (IC) dyes from water. The effects of solution pH, temperature, initial concentration, and contact time were investigated. The corrected Akaike Information Criterion (AICc) was found to rank adsorption isotherm and kinetic models better than error functions (R-2). Based on the AICc values, the adsorption isotherm data of IC and MB onto A-CNT/DT were well fitted by Langmuir and Sips isotherms, respectively. The maximum monolayer adsorption capacity (q(max)) of A-CNT/DT for the adsorption of IC and MB was 375.6 and 175.2 mg/g, respectively. The experimental kinetic data fitted very well to pseudo-first order model for adsorption of IC and pseudo-second order model for adsorption of MB onto A-CNT/DT. Thermodynamic parameters indicate endothermic (MB) and exothermic nature (IC) of dyes adsorption onto A-CNT/DT. In addition, the interaction between the dyes molecules and A-CNT/DT surface has been investigated by using Monte-Carlo calculation method (MC). The results have shown that the interaction of the dyes onto A-CNT/DT occurred through both polar and nonpolar interactions. The overall study shows that the synthesized A-CNT/DT was proved to act as a promising adsorbent to remove the dyes from the aqueous solutions proficiently. (C) 2022 Elsevier B.V. All rights reserved.

Increasing population and urbanization have direct consequences on the sewer functioning. In order to identify and quantify gases and VOCs likely to be present in the sewers, methodological studies of sampling in sewer using airbags, canisters and adsorbent tubes were assessed, and methods of analysis by GC-MS were developed. The results obtained lead to propose improvements to sampling protocols in the sewers. The gas quantification is complicated by low gas concentrations, environment heterogeneity and a high hygrometry.

Volatile organic compounds (VOCs) must be identified and measured for a range of applications, including breath analysis-based disease diagnosis, air quality monitoring, food quality monitoring, and air pollution assessment, among others. The monitoring of VOCs in various application areas can help to maintain good health and safety. Chemical sensor arrays have the capabilities to offer the essential VOC identification and measurement. Gas micro-sensors built from nanostructures of chitosan doped nickel phthalocyanine as the basis sensing material have several advantages, including tunable characteristics, room temperature sensing, and the potential to be amenable to a wide range of applications. Using the Chronoamperometric electropolymerization process, a thin-film hybrid of chitosan/NiPc was electrochemically deposited across the fingers of interdigitated gold electrodes. Scanning electron microscopy is used to characterize the surface of the pure chitosan and the chitosan doped with NiPc (SEM). Acetone, ethanol, and methanol gas-sensing properties of the films prepared at optimum conditions were studied at atmospheric temperature using lock-in amplifier differential measurements at an optimized frequency of 10 kHz. The methanol sensor has the highest sensitivity of $12.3\mu \text{Scm}-1(\mathrm{v}/\mathrm{v})$ and 700 ppmv as the limit of detection. In a situation where, methanol poisoning is not detected in time, it can cause blindness, organ failure, and even death. There is currently no methanol detector available for early breath analysis diagnosis or screening of contaminated beverages. Chemical sensors, on the whole, are unable to distinguish methanol from the significantly greater ethanol background. We describe a non-invasive, low-cost, and portable sensor for highly selective methanol sensing in this paper. The innovative conductometric chitosan doped NiPc sensor can be used to separate methanol from interferants such as ethanol, acetone, or hydrogen in a separation column before actual detection in gas chromatography.

A conductometric transducer is proposed for the first time for the detection of ethanol vapor. This ethanol microsensor is prepared by encapsulation of alcohol dehydrogenase (ADH) in chitosan. Interdigitated electrodes fabricated by silicon technology were used. The electrodeposition of chitosan allows the addressing of the chitosan film on the microconductometric devices and to encapsulate ADH and nicotinamide adenine dinucleotide (NAD+), which was monitored by FTIR. The analytical performance of the ethanol microsensor was determined in gaseous methanol, ethanol, and acetone samples, collected from the headspace above aqueous solutions of known concentration. The response time (tRec) of the sensor varies from 7 to 21 s from lower concentrations to higher concentrations. The detection limit is 0.12v/v % in the gas phase, corresponding to 0.22 M in the liquid phase. The relative standard deviation for the same sensor is from 12% for lower concentrations to 2% for higher concentrations. The ethanol sensor presents 2.6 times lower sensitivity for methanol and 28.3 times lower sensitivity for acetone. A detection of ethanol in the headspace of a red wine sample lead to an alcohol content in good agreement with the value given by the producer.

Compared to conventionnal bench top instruments, on-line GC analyzers require specific characteristics. On one hand, for some applications operating with a reactor pressure as high as several tens of bars, sample pressure has to be reduced before GC separation, or specific valves and columns have to be designed to perform separation with high carrier gas inlet pressure. On the other hand, informative detectors such as mass spectrometer are valuable but low maintenance detectors are prefered. To fit these two requirements (sampling at high pressure without decompression stage, and informative detector with low maintenance), short monolithic silica capillary column operated with inlet pressure as high as 60 bar has been hyphenated to VUV detector. Injection and column performance have been first investigated. The system has been optimized by adjusting split ratio at high pressure and by tuning two main VUV detector parameters ("average number" linked to data point averaging and make-up gas pressure) to decrease the limit of quantification. The optimization stage led to a set of experimental parameters which is a good compromise between signal-to-noise ratio and chromatographic efficiency. Finally, the hyphenated monolithic column has be used to partially separate a mixture of methane, ethane, carbon monoxide and carbon dioxide within 15 s, and the VUV deconvolution capabilities have been exploited to overcome coelution and finally separate individual signals.