Analytical Sciences最新文献

This study developed a rapid screening method to determine residual solvents contained in a tablet formulation using a needle-type extraction device. For this, the tablet formulation was pulverized and the powdered sample was rapidly inserted into a pipette tip. After fixing the sample with quartz wool, the pipette tip was capped with a silicon septum. A needle-type extraction device packed with Carbopack X and a carbon molecular sieve was inserted into the pipette tip through the septum, and the gas sample was collected. During this gas sampling, pure N₂ gas was introduced into the pipette tip. The extraction time for collecting 100 mL of the sample was approximately 10 min. After gas sampling, the extraction needle was connected to a gas-tight syringe and 0.5 mL of pure N₂ gas (desorption gas) was collected. The extraction needle was then inserted into a heated gas chromatographic injection port. The extracted residual solvents were then thermally desorbed and determined using a gas chromatograph-flame ionization detector. The detector response is very low for carbon tetrachloride, although the proposed method showed sufficient sensitivity for five Class 1 compounds. Additionally, this study clearly indicated that the purge efficiency of residual solves with dynamic extraction is different between powdered pharmaceutical formulations.

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In this study, we investigated a solid-phase dispersive extraction (SPDE) method and solid-phase derivatization method using the same solid-phase gel to extract methamphetamine (MA) from urine samples more efficiently and perform trifluoroacetic acid (TFA) derivatization for MA analysis by gas chromatography/mass spectrometry (GC/MS). N-Methylbenzylamine (NMe-BA) was added to the urine sample as a surrogate, and MA was extracted by SPDE using Oasis^® HLB gel as a solid-phase agent. After drying the solid-phase gel of the SPDE, anhydrous TFA was added to the MA-absorbed HLB gel in order to derivatize MA with TFA on the solid-phase, followed by elution of the TFA derivative from this gel using ethyl acetate. As a validation of the analytical method, the limit of detection (S/N = 3) and the limit of quantification (S/N > 10) of MA were 0.002 µg/mL and 0.01 µg/mL, respectively. And the average recovery rate was 97.6–100.1%, repeatability was 5.6–10.7%, and intermediate precision was 10.1–11.4% for low (0.02 µg/mL), intermediate (0.1 µg/mL), and high (1 µg/mL) concentrations of MA added in urine. The developed pretreatment method enabled continuous extraction, cleanup, and TFA derivatization of urinary MA on the same solid-phase. Thus, urinary MA can be analyzed easily, rapidly, and with high sensitivity and accuracy.

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In this study, a novel covalent organic framework-modified silica-gel composite (Si-COF) was synthesized for the adsorption of palladium [Pd(II)], zirconium [Zr(IV)], and molybdenum [Mo(VI)] from nitric acid solutions and its adsorption behaviors were systemically investigated under the effects of contact time, nitric acid concentration, solution temperature and others. The pseudo-second-order kinetic model governed the adsorption of these metal ions onto the Si-COF composite, and the Langmuir isotherm model well-matched with the experimental data, with maximum adsorption capacities of 0.588, 0.221, and 0.417 mmol/g for Pd(II), Zr(IV) and Mo(VI), respectively. The adsorption of these metal ions was clarified to originate from the interaction with the abundant nitrogenous groups on the Si-COF composite by the X-ray photoelectron spectroscopy (XPS) method.

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Recently, the misuse of organic arsenic feed additives, such as roxarsone (ROX), has increasingly jeopardized both human health and the environment. In response, a unique electron-rich pyrazine-cored fluorescent covalent organic framework (COF) nanosheet, named as COF-TMP, was synthesized using an alkali-catalyzed reaction between 2, 3, 5, 6-tetramethylpyrazine (TMP) and terephthalaldehyde (TPA). Characterization demonstrated that COF-TMP boasted high porosity, pronounced fluorescence, and an abundance of (E)-2-styrylpyrazine (SPA) groups. These attributes render it an exceptional fluorescent sensor for the ultrahigh sensitivity detection of electron-deficient ROX molecules. The limit of detection (LOD) for COF-TMP in detecting ROX was found to be 0.015 ppb through fluorescence-quenching titration experiments-surpassing all previously reported fluorescent sensors. A combination of experimental results and theoretical calculations suggests that the extraordinary detection capability of COF-TMP for ROX arises from a static quenching mechanism. This study paves the way not only for a novel pyrazine-based fluorescent COF nanosheet with high porosity, exceptional fluorescent capabilities, and abundant SPA groups suitable for highly sensitive and selective ROX detection but also hints at its potential application as a fluorescent sensor for environmental pollution management and related domains.

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The novel highly fluorescent pyrazine-based covalent organic frameworks with abundant SPA groups is specifically combined to ROX for highly sensitive and selective ROX detection.

Kanamycin (KAN) is widely used as a growth hormone analog and an antibacterial agent. However, abuse of this substance has resulted in the accumulation of excessive residue levels in foods of animal origin, which presents a significant risk to human health. A chemiluminescent aptasensor was constructed for the rapid quantitative detection of KAN by combining the properties of Co₃O₄ nanoparticles (Co₃O₄ NPs) nanozyme activity and DNA aptamer with high specificity. The DNA aptamer/Co₃O₄ NPs nanozyme regulated the chemiluminescence signal by exploiting the chemiluminescent properties of luminol oxidation by H₂O₂. Specific binding of KAN to the aptamer led to the formation of a steric hindrance block in the solution, which inhibited the activity of nanozyme and reduced signal intensity. The degree of signal reduction is related to the concentration of KAN. Under optimal conditions, there was good linearity between KAN concentration and chemiluminescence signal intensity in the range of 0.5–8.0 μΜ, with a detection limit of 0.26 μΜ. The detection system performed well in the presence of competing antibiotics and was virtually unaffected. The method was also suitable for the detection of KAN in milk samples with sample recoveries of 97.8%–99.1%. The chemiluminescence sensor has the advantages of low cost, specificity, and sensitivity, and does not require an external light source or modification of the nucleic acid aptamer which makes it a promising candidate for applications in the field of food detection.

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Schematic diagram of the chemiluminescence for KAN detection based on Co₃O₄ NPs/KAN-apt.

Staphylococcal enterotoxin B (SEB), a potent enterotoxin produced by Staphylococcus aureus, has been implicated in incidences of Staphylococcal food poisoning in the Philippines. The use of lateral flow immunoassay devices to detect this toxin in solid food samples, like durian candy, at the point of sampling is constrained by the requirement for sample purification (e.g. centrifugation). This problem is also true with the other applications of LFIA devices on food samples. To overcome this challenge, a lateral flow immunoassay (LFIA) device capable of detecting SEB in unpurified durian candy sample was developed in this study. A modified LFIA device was assembled with three layers of glass fiber pads functioning as sample pads instead of a conventional cellulose fiber pad. Unlike with the cellulose fiber pad, the glass fiber sample pads acted as filter and allowed the flow of a 1:5 dilution of durian candy. The LFIA device applied to spiked 1:5 diluted durian candy samples achieved a visual limit of detection of 5 ng/mL for SEB, which is twofold lower than reported for previous LFIA devices designed to detect SEB in food samples.

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Despite the fact that there are already a number of solid-contact-based ion-selective electrodes designed for atrazine detection, our ground-breaking contribution lies in introducing the first-ever atrazine potentioselectrode, enabling the ultra-sensitive detection of atrazine at nanomolar levels. Solid-contact ion-selective electrodes can offer advantages, such as improved stability, reproducibility, sensitivity, and selectivity compared to their liquid-contact counterparts. Here, a biomimetic potentiometric sensor for Atrazine was developed using economic, light weight, and flexible carbon cloth as solid-contact material. Our methodology entails the synthesis of a molecularly imprinted polymer (MIP) through straightforward precipitation polymerization, showcasing a streamlined and efficient method for creating highly specific molecular recognition elements. The validation of template removal is confirmed via meticulous analysis employing EDX and FTIR techniques, ensuring the efficacy of our methodology. The resulting sensing membrane are casted by dispersing the MIP in 2-nitrophenyl octyl ether plasticizer and embedding it within a PVC matrix containing sodium tetraphenyl borate as a lipophilic additive. The developed sensor responds to atrazine in the pH range of 2.8–3.3 over a wide concentration range of 1 × 10^–8 M to 1 × 10^–5 M & 1 × 10^–5 M to 1 × 10^–1 M with respective slopes of 29.2 mv & 58.7 mV and a limit of detection of 1 × 10^–9 M. An impressive feature of this sensor lies in its swift response time, registering a rapid reaction within a mere 10 s. Emphasize the sensor’s commendable attributes of reproducibility, selectivity, and sensitivity underscoring its successful application in field monitoring.

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To develop a clean-up material suitable for high-fat food matrices for detecting mycotoxins in yak ghee, an octadecyl-bonded hectorite (Hectorite@NHCO(CH₂)₁₇CH₃) was synthesized through multi-step chemical reactions. A modified QuEChERS–HPLC–MS/MS method for detecting ten mycotoxins in sesame oil in yak ghee was established using Hectorite@NHCO(CH₂)₁₇CH₃ as clean-up agent. It involved extracting mycotoxin contaminants using acidified acetonitrile and employing the Hectorite@NHCO(CH₂)₁₇CH₃ to remove interfering substances from the extract. The purified samples were then analyzed using HPLC–MS/MS. Within a linear range of 1.0–500 μg/kg, there was a good linear relationship between the quantification ion peak area of the target analytes and the corresponding concentrations (R² ≥ 0.9991). The limit of detection (LOD) ranged from 0.10 μg/kg to 18.62 μg/kg and the limit of quantitation (LOQ) ranged 0.32–62.07 μg/kg. The recoveries at low, medium and high concentrations (25, 100 and 500 μg/kg) ranged from 72.2% to 113.9%, with relative standard deviations (RSD) between 3.2% and 17.5%. The intra-day and inter-day precision met experimental requirements. The proposed method was characterized by a high accuracy and precision, and it could cater to the current demand for detecting ten mycotoxins in yak ghee.

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In this work, for the first time, the potentiometric method was used to determine the antioxidant capacity (AOC) of compounds of different hydrophilicity in the joint presence using mixed solvents and surfactants. The AOC of model solutions of antioxidants of different hydrophilicity was determined separately and in the joint presence in the media of phosphate buffer-surfactant and mixed solvents–surfactant, using as an example the ascorbic acid and the α-tocopherol. It was shown that the surfactant Triton X-100 is able to solubilize α-tocopherol under the selected conditions, allows to obtain reproducible and accurate results, and has less effect on the equilibrium rate of the K₃[Fe(CN)₆]/K₄[Fe(CN)₆] system. Phosphate buffer-ethanol and phosphate buffer-acetonitrile media in the 3:2 ratio with Triton X-100 (5 mmol/dm³) were chosen as the analysis conditions (RSD ≤ 6%). The range of determined concentrations was (0.006–0.5) m mmol/dm³ in phosphate buffer-ethanol and (0.006–0.3) m mmol/dm³ in phosphate buffer-acetonitrile. AOC of raw materials infusions was determined in selected media. The positive correlation with the well-known Folin-Ciocalteu assay was obtained.

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