Academic literature on the topic 'GC microchips'

This paper presents the synthesis and evaluation of a carbon molecular sieve membrane (CMSM) grown inside a MEMS-fabricated μ-preconcentrator for sampling highly volatile organic compounds. An array of µ-pillars measuring 100 µm in diameter and 250 µm in height were fabricated inside a microfluidic channel to increase the attaching surface for the CMSM. The surface area of the CMSM was measured as high as 899 m2/g. A GC peak amplification factor >2 × 104 was demonstrated with gaseous ethyl acetate. Up to 1.4 L of gaseous ethanol at the 100 ppb level could be concentrated without exceeding the capacity of this microchip device. Sharp desorption chromatographic peaks (<3.5 s) were obtained while using this device directly as a GC injector. Less volatile compounds such as gaseous toluene, m-xylene, and mesitylene appeared to be adsorbed strongly on CMSM, showing a memory effect. Sampling parameters such as sample volatilities, sampling capacities, and compound residual issues were empirically determined and discussed.

AbstractBACKGROUNDOrganophosphorus pesticides (OPs) were used in large quantities, and pesticide residues have caused different degrees of environmental pollution. Because the current laboratory detection techniques cannot meet the requirements of quickly and accurately monitoring pesticide concentration, there is an urgent need for a portable and accurate method to trace pesticide residues. This paper reports an effective electrochemical sensor composed of ZrO2@PDA electrode material and glassy carbon electrode (GCE).RESULTSThis sensor displayed optimal selectivity for dichloride among various OPs with a low limit of detection (LOD = 1.318 × 10−3 mg L−1). Wherein the accuracy and reliability of this electrochemical sensor were verified through the standard method of gas chromatography–mass spectrometry (GC–MS) (p = 0.977 > 0.05), as well as the stability and anti‐interference capabilities. In addition, the results of recovery experiments have shown that the recovery rate of the electrochemical sensor for dichlorvos ranged from 89.2% to 103.8%, with RSD less than 5%, indicating its practical application in the actual sample detection.CONCLUSIONSFinally, the portable sensing platform for on‐site analysis of dichlorvos concentration in farmland water samples was also demonstrated with excellent results. All the results suggested that the prepared ZrO2@PDA composites could serve as a prospective microchip sensor for the on‐site detection of dichlorvos. © 2024 Society of Chemical Industry (SCI).

Introduction: A new analytical method based on the coupling of microextraction and microfluidics was developed and investigated for the pre-concentration, separation, and electrochemical detection of fenitrothion (FT) and parathion (PA) at the sub-ppm concentrations. Method: In the first step, the microchip capillary electrophoresis technique was used to serve as a separation and detection system. Analytes were injected into the 40 mm long microchannel with 10 mm sidearms. Then, they were separated by applying a direct electrical field (+1800V) between buffer and detection reservoirs. 2-(n-morpholino)ethanesulfonic acid (MES) buffer (20 mM, pH 5) was used as the running buffer. The electrochemical detection was performed using three Pt microelectrodes with the width of working, counter, and reference electrodes (50, 250, and 250 µm, respectively) in the out channel approach. Results: The system was devised to have the optimum detection potential equal to -1.2 V vs. Pseudo Ref. electrode. The dimensions of the SU-8 channel have 20 µm depth and 50 µm width. In the second step, an air-assisted liquid-liquid microextraction technique was used for the extraction and preconcentration of analytes from human blood plasma. Then, 1, 2 di-bromoethan was used as extractant solvent, the analytes were preconcentrated, and the sedimented solvent (50 µL) was evaporated in a 60 ˚C water bath followed by substitution of running buffer containing 10% ethanol. The optimum extraction cycles were found 8 with adding 1% NaCl to the aqueous phase. Analyzing time of the mentioned analytes was less than 100s, and the precision range was 3.3 – 8.2 with the linear range of 0.8 – 100 ppm and 1.2 - 100 ppm for FT and PA, respectively. The extraction recoveries were about 91% and 87% for FT and PA, respectively. The detection limits for FT and PA were 240 and 360 ppb, respectively. Finally, the reliability of the method was investigated by GC-FID. Conclusion: The proposed method and device were validated and can be used as in situ and portable detection system for detecting fenitrothion and parathion insecticides.

La pollution des eaux est une problématique majeure qui affecte tant les écosystèmes aquatiques que sur la santé humaine. Par conséquent, la prévention et la surveillance des pollutions constituent donc un enjeu prioritaire afin d’éviter la dissémination de ces polluants. Dans ce contexte, il est essentiel de recourir à la miniaturisation des systèmes et à des méthodes analytiques afin de surveiller en temps réel l'évolution de la pollution sur le terrain. Dans le cadre de ces travaux de thèse, tout d’abord, la préparation et l’évaluation de µ-colonnes de types multicanaux en GC a été réalisée. Des dépôts avec différentes phases stationnaires ont été effectués et des tests en GC unidimensionnel puis un système bidimensionnel « GC×µGC » avec un modulateur microfluidique ont été réalisés avec succès. Par la suite, une méthode d’extraction par sorption sur barreau magnétique (SBSE) suivi d’une thermo-désorption (TD) et d’une analyse non ciblée par spectrométrie de masse à haute résolution (HRMS) a été développée. Afin de pallier les contraintes de la SBSE classique, de nouvelles phases ont été déposées sur les barreaux magnétiques visant ainsi à améliorer les rendements d’extraction des composés les plus polaires. Enfin, des extractions SBSE des polluants ont été effectuées sur des eaux naturelles provenant d’Algérie et de France suivies d’analyses non ciblées par TD-GC-HRMS OrbitrapTM. Des informations sur la qualité des eaux de surfaces en Algérie mais aussi en France quant au niveau de leur contamination ont pu être données et les différents polluants identifiés ont été ensuite classés selon des niveaux confiances basés sur une échelle d’identification récentes<br>Water pollution is a major problem that affects both aquatic ecosystems and human health. Therefore, the prevention and the control of the dissemination of contaminants in the environment has become a priority. To achieve that, the use of miniaturized analytical systems to control pollution in real-time on-site appears necessary. The evaluation of µ-columns with radially elongated pillars was performed using different stationary phases. Then the performances of the prepared µ-columns were evaluated on conventional GC and in a comprehensive two-dimensional system « GC×µGC » with a microfluidic modulator as a second columns. Afterwards, a stir bar sportive extraction (SBSE) method and a non-targeted analysis one using GC coupled to a high-resolution mass spectrometry (HRMS) were developed. In order to overcome the limitations of SBSE and improve the extraction yields, new SBSE phases were used for the coating of the stir bar. Finally, SBSE extractions of contaminants were performed on naturel waters collected from Algeria and France followed by a non-target analysis using TD-GC-HRMS OrbitrapTM. Information on the quality of surface waters and the level of pollution were collected for both countries and the annotation of the identified compounds were then classified according to levels of confidence

博士<br>國立交通大學<br>應用化學系所<br>94<br>Illicit and abused drugs are often known by street names that vary from area to area. A call to a local police station, or animal or human poison control center, can be extremely helpful in identifying the illicit substance. Most human hospitals, emergency clinics, or veterinary diagnostic laboratories have illicit drug screens available and can check for the presence of illicit drugs or their metabolites in different body fluids. The presence of a parent drug or its metabolites in blood or urine may help confirm the exposure in suspect cases. Veterinarians should contact these laboratories for the types of samples needed and time required for completion. Commonly available over-the-counter drug test kits may be helpful in ruling out a suspected case of illicit drug toxicosis. These test kits are inexpensive, efficient, and easy to use. They are designed to detect drug metabolites in the urine and can detect most commonly available illicit or recreational drugs such as amphetamines, cocaine, marijuana, opiates, and barbiturates. The sensitivities and specificities of these test kits may vary. The instructions provided with each kit should be followed carefully for best results. In this work, first, we have simultaneously determinated and quantified ketamine and its major metabolites, norketamine, 5,6-dehydronorketamine, and deaminonorketamine, in human urine and hair using liquid–liquid extraction (LLE) and solid phase extraction (SPE) in combination with gas chromatography/mass spectrometry (GC/MS) (Chapter 2). The next, we also have investigated a rapid, simple, and highly efficient on-line preconcentration method using in micellar electrokinetic chromatography (MEKC) for the analysis of abused drugs including ketamine (Chapter 3), flunitrazepam (Chapter 4), cocaine, heroine, opiates (Chapter 5), and their major metabolites. The optimized sweeping method was also used to examine a urine sample. We conclude that sweeping with micellar electrokinetic chromatography has considerable potential use in clinical and forensic analyses of flunitrazepam and its metabolites. Finally, we have devised a rapid and highly efficient separation method for the separation and analysis of amphetamine, methamphetamine, and ephedrine using micellar electrokinetic chromatography (MEKC) and dry-film-based microchip capillary electrophoresis (DFB-MCE) with electrochemical detection. These analytes were separated in a plastic microchip capillary electrophoresis with electrochemical detection. The capillary electrophoresis-based methods are extremely complementary to GC/MS-based forensic analyses (Chapter 6).