Analytical Sciences最新文献

Graphene-based pH sensors, acclaimed for their exceptional sensitivity to environmental variations, have garnered significant interest in scientific research. However, the sensor performance in high ionic concentration environments is limited, due to the Debye length ion screening effect. In this study, an innovative graphene channel pH sensing device was developed and modified by cross-linked poly(methyl methacrylate) (PMMA). Furthermore, even in high ionic concentrations, the pH value can be precisely measured by this sensor. The sensor has remarkable sensitivity, and high response rate of − 70.49 mV/pH within the pH range from 7 to 10. Notably, the sensors retain uniform response direction and sensitivity under different ionic concentrations environmental and maintain consistent reversibility and stability. This advancement in sensor technology paves the way for broader applications in complex ionic environments.

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Left : A graphene-based pH sensor modified with a cross-linked PMMA film; Right : Sensitivity comparison of graphene-based sensors to pH under different electrolyte concentrations. This work presents a cross-linked PMMA film-modified graphene-based pH sensor that maintains high sensitivity even in high ionic strength environments.

All-solid-state NO₃^–, K⁺, NH₄⁺, Na⁺, and Ca²⁺ ion-selective sensors (ISEs) were prepared using polyvinyl butyral (S-LEC®K KX-5). In the present case, polyvinyl butyral was used as a porous material to keep the internal solution of the respective ISE. All sensors exhibited near-Nernst responses in the concentration region between approximately 10^–5 and 0.1 mol dm^–3. To avoid the influence of KCl as interfering ions, MgSO₄ was used as an electrolyte within the salt bridge. Although the liquid junction potential was generated, the potential difference was stabilized within about few minutes. The NO₃^–-ISE showed high stability with no potential drift during 12 h of continuous measurements and maintained high sensitivity even after 3 weeks of storage in ultrapure water. Solidification of the internal solution is expected to make the sensor smaller and increase its mechanical strength. As an actual measurement, the sodium concentration in plasma samples using the Na⁺-ISE was measured to confirm agreement with literature values.

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The bimolecular photochemical quenching of the tris(2,2′-bipyridyl)ruthenium (II) complex by ferricyanide ions in water–ethylene glycol binary media was investigated using a spectrophotometric approach, as previously reported by our research group. Time-resolved spectroscopy revealed that dynamic photochemical quenching occurred via a diffusion-dominated pathway. The static quenching process was found to occur significantly when the concentration of ethylene glycol was greater than 40 wt%. The analysis of the Stern–Volmer plots revealed that the emitters and quenchers tended to show ionic associations in water–ethylene glycol compared to our previous results with a water–glycerol binary solvent system. This is attributed to hydrophobicity, which is consistent with pioneering works that report that the addition of ethylene glycol to pure water forms hydrophobic regions, leading to dehydration of the complex ions.

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Construct a sensitive and rapid detection fluorescence biosensor with the assistance of exonuclease III to achieve efficient detection of Hg²⁺. Nucleic acid aptamer H0 specifically recognizes Hg²⁺, and under the action of exonuclease III, H0 bound to Hg²⁺ is hydrolyzed, which in turn fails to trigger the catalytic hairpin self-assembly amplification reaction, resulting in a decrease in the number of double-stranded DNA bound to the fluorescent dye SYBR Green I in the solution, and a decrease in the fluorescence intensity. The results showed that the concentration of Hg²⁺ showed a good linear relationship with the fluorescence intensity of the sensing system within the range of 3.8–10 pmol/L, and the detection limit was 0.53 pmol/L. The recoveries of Xiangjiang River water used for the analysis of the actual samples were in the range of 99.57–103.58%, and the relative standard deviations of the determined values were 2.4–3.7%. The method is simple, sensitive, specific, cost-effective and can be applied to water samples.

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Monitoring the changes of food products with easily applicable technique is important for the quality control of the products. Cigar wrapper and filler easily get moldy due to the existence of the native bacterial in the material and the moisture storage/production condition. Herein, we investigate the volatile compounds produced during the culture of tobacco using chromatography–ion mobility spectrometry (GC–IMS). 114 and 112 volatile compounds are determined with GC–IMS for the cultured cigar wrapper and cigar filler, respectively. Detailed fingerprint analysis and principal component analysis identify a series of compounds that can be used for the evaluation of the degree of mold development on cigar wrapper/filler. The results reported in this work may provide useful information for the quality evaluation of food products.

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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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