Analytical Sciences最新文献

Combination of organoclay sorption with manganese(IV) oxide (MnO₂) catalyzed catechol oxidation was studied for the removal of a dicarboximide fungicide, iprodione, from water. Iprodion in water was sorbed on didodecyldimethylammonium bromide (DDAB)-modified montmorillonite (MT) organoclay and converted into the degraded product, 3,5-dichloroaniline (DCA). The degree of sorption increased by the modification with DDAB, because of the formation of a hydrophobic region for the incorporation of iprodione and negligibly interfered by coexisting MnO₂. The half-life for the degradation of irodione in water at 25 °C was 7 days, whreas it reduced to 15 min in the organoclay. The activation energy, 65.4 ± 4.8 kJ mol^-1, for the first-order reaction in the aqueous solution (pH 7.0) decreased to 43.9 ± 1.8 kJ mol^-1 in the organoclay, indicating the catalytic activity of the organoclay that accelerates the hydrolysis reaction of iprodione. In the coexistence of appropriate amounts of MnO₂ and catechol, the degraded product, DCA, reacted with oxidized products of catechol to form a water-insoluble precipitate and was successfully eliminated from water. The results obtained in the present study strongly suggest the applicability of the combined method of organoclay sorption method and MnO₂-catalyzed oxidation for the diffusion control of toxic agrochemicals.

Present work reports, the development of a novel electrochemical sensor based on a diazonium-coupling reaction and covalent attachment of the -NH₂ group of cysteamine (Cyst) on screen-printed carbon electrode (SPCE), for simultaneous determination of Pb(II) and Cd(II). Initially, the in-situ generated 4-carboxyphenyl (4-CP) diazonium salt was electro-grafted to generate 4-CP/SPCE, followed by covalent bonding of terminal carboxylic group of 4-CP with -NH₂ group of Cyst to give Cyst/4-CP/SPCE. The modified electrode showed an enhanced selectivity and sensitivity toward the quantification of Pb(II) and Cd(II) using square wave anodic stripping voltammetry (SWASV) without mutual interference. Under optimal experimental conditions, the newly designed sensor showed a wide linear range of 0.01 µM to 0.7 µM. The limit of detection (LOD) obtained was 0.882 nM (0.09 ppb) and 0.65 nM (0.134 ppb) for Cd(II) and Pb(II), respectively. The modified SPCE exhibited good stability, selectivity, and reproducibility. Furthermore, the sensor was successfully applied for the determination of Pb(II) and Cd(II) ions in water samples which illustrated excellent recoveries in different spiked samples and the results were in line with the standard ICP-AES analysis.

Designing portable electrochemical sensors combined with highly efficient glucose oxidation electrodes offers a significant opportunity for convenient glucose detection. In this report, we present the design and preparation of platinum deposited Ni/NiFe₂O₄/Carbon composite (Pt/Ni/NiFe₂O₄/C) derived from Ni/Fe metal-organic frameworks (MOFs) followed by Pt deposition. Energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electron microscopy (EM) were utilized to analyze the crystal structure, morphology, and chemical composition of the resulting materials. The glucose sensing capabilities of the optimal Pt/Ni/NiFe₂O₄/C-3 were assessed using amperometry methods on a smartphone-based portable device. Acting as a nonenzymatic glucose sensor, the Pt/Ni/NiFe₂O₄/C-3 electrode demonstrated notable sensitivity and a low limit of detection for glucose. The portable sensor exhibits high sensitivities of 131.88 μM mM cm^-2 at low glucose concentration (3-500 μM) and 29.52 μA mM cm^-2 at high glucose concentration (700-4000 μM), achieving a low detection limit of 1.1 μM (S/N = 3). The sensor also demonstrates enhanced selectivity and stability for detecting glucose. Furthermore, the portable sensor exhibits a clear step-ampere response in the detection of serum samples with satisfactory recovery ranging from 99.30 to 101.32%. This suggests the significant potential of portable glucose sensing applications.

This study introduces a novel microfluidic polymer chip system that employs an embedded anionic surfactant (AS) ion-selective fluorescence optode (AS fluorescence optode) as a detector for measuring AS. The AS fluorescent optode comprises a lactone form of rhodamine B (L-RB) embedded in 2-nitrophenyl octyl ether plasticized poly (vinyl chloride) membrane. The AS fluorescence optode demonstrated a linear correlation between fluorescence intensity peak heights and AS concentrations within the range of less than 20 µM under optimal flow conditions. The limit of detection for AS was approximately 0.06 µM. The microfluidic system was utilized to measure AS levels in environmental samples, such as river water and tap water.

The main reason for the high mortality rate of non-small cell lung cancer is that patients are usually diagnosed at an advanced stage of the disease. Exosomes, small membrane vesicles secreted by normal cells or tumor cells, play a significant role in the progression of NSCLC. This study successfully optimized the preparation of artificial nanoenzymes self-coupling with horseradish peroxidase (IrO₂NPs@HRP-AptCD63), without adding any ligand, demonstrating remarkable catalytic activity suitable for detecting the EGFR protein on the surface of NSCLC exosomes. When fused with the CD63 aptamer for identifying NSCLC exosomes, IrO₂NPs@HRP showed enhanced catalytic activity in the 3,3',5,5'-tetramethylbenzidine-H₂O₂ oxidation-reduction system, thereby enhancing the colorimetric signal. This phenomenon can be distinguished by the naked eye and quantified using a UV-Vis spectrophotometer. Meanwhile, as the redox reaction occurs, the current signal of 3,3',5,5'-tetramethylbenzidine-H₂O₂, acting as an electrolyte, changes. The developed aptasensor generates dual-mode signal outputs, firstly, to visually assess the samples for their positive or negative status, and subsequently employ more in-depth electrochemical or colorimetric analysis methods for a detailed quantitative analysis of suspected positive samples. The detection limits of electrochemical analysis and colorimetric analysis were 0.9 × 10³ particles/mL and 0.14 × 10³ particles/mL, respectively. Compared with traditional biomarkers such as CA125, this method exhibits exceptional specificity, capable of simultaneously distinguishing serum exosomes of healthy volunteers, COPD patients, and NSCLC patients, promoting exosome detection in mouse models for tumor monitoring. Additionally, it elucidates the changes in EGFR protein expression on the surface of serum exosomes throughout the developmental trajectory.

The development of a highly selective and ultra-sensitive optical sensor for detecting scandium (Sc³⁺) ions involves incorporating the reagent 2,3-dichloro-6-(3-carboxy-2-hydroxy-1-naphthylazo)quinoxaline (DCHNAQ) into a silica sol-gel thin film on a glass substrate. This innovative approach utilizes tetraethoxy-silane (TEOS) as the precursor, maintaining a sol-gel pH level of 4.5, a water-to-alkoxide ratio of 5:1, and a DCHNAQ concentration of 5.0 × 10^-4 M. A detailed exploration of the impact of sol-gel parameters on the sensing capabilities of the developed sensor has been meticulously undertaken. This innovative sensor demonstrates remarkable selectivity in evaluating Sc³⁺ ions over a dynamic range of 7.5-170 ng/mL, with limits of quantification and detection recorded at 7.3 and 2.20 ng/mL, respectively. Consistent results are achieved with a minimal RSD of 1.47 and 0.94% for Sc³⁺ ions at 50 and 100 ng/mL, respectively, coupled with a swift response time of three min. Assessments of interference demonstrate a noteworthy preference for Sc³⁺ions, accomplished by enclosing DCHNAQ within the sol-gel framework and making optimal structural modifications to the doped sol-gel. The sensor offers straightforward regeneration using a 0.25 M EDTA solution, exhibiting complete reversibility. Comparative analysis with other methodologies underscores the efficacy in determining Sc³⁺ions in various reference materials, including plant leaves, fish, water, alloys, ores, and monazite samples.

This study introduces the α-rhamnose (Rham)-conjugated prodrug of SN-38 (Rham-SN-38) as a promising alternative to irinotecan. α-rhamnosidase, responsible for SN-38 release from Rham-SN-38, does not express in human cells, minimizing individual variability and side effects. The injection of the α-rhamnosidase into the tumor tissues makes it possible, for the first time, to activate the Rham-SN-38. Furthermore, α-rhamnosidase demonstrates significantly higher activity than carboxylesterase, the specific enzyme activating irinotecan. SN-38 release mediated by α-rhamnosidase completes within 2 h, with a k_cat/K_m value approximately 5.0 × 10⁴-fold higher than that of irinotecan. The 50% inhibition concentration (IC₅₀) of Rham-SN-38 against three types of cancer cells and one normal cell exceeds 4.5 × 10³ nM. The addition of α-rhamnosidase significantly increases cytotoxicity, with IC₅₀ comparable to free SN-38. The QIC₅₀, an index reflecting the difference in cytotoxicity with and without α-rhamnosidase, exceeds approximately 1.0 × 10²-fold. Rham-SN-38, synthesized in this study, demonstrates significant potential as a prodrug for cancer therapy.

This paper revealed a new strategy for citric acid (CA) detection using aggregation-induced emission (AIE)-based fluorescent gold nanoclusters (AuNCs). AuNCs was synthesized using glutathione (GSH) as the template and reducing agent and used as the fluorescent probe to detect CA under aluminum ion (Al³⁺) mediation. The fluorescence intensity of AuNCs increased about 4 times with the addition of Al³⁺, but the enhanced fluorescence was quenched after the addition of CA. Based on this fluorescence phenomenon, an "on-off" fluorescence strategy was designed for the sensitive determination of CA and a linear detection range for CA was achieved within 0-80.0 μM. In addition, the developed probe exhibited high selectivity and accuracy for determination of CA. The mechanism of fluorescence enhancement and quenching of AuNCs was explored in detail. The established probe was used successfully for CA detection in beverages. The spiked recoveries from 97.50% to 103.67% were gratifying, which indicated the probe had potential prospects for detecting CA in food.

In this study, a structure-induced aptamer targeting small molecules was selected using capillary sieving electrophoresis (CSE). CSE was conducted using a capillary filled with a background solution containing hydroxypropyl cellulose as a sieving matrix to separate the aptamer candidates by changing their structures via complexation. Before aptamer selection, the original random-sequence DNA library was used to create structure-not-preorganized DNA sub-library containing straight-chain-like structures using CSE. Next, a structure-induced aptamer targeting L-tyrosinamide was selected from the prepared sub-library. Six aptamer candidates were selected, one of which showed a binding ability comparable to that of the reported L-tyrosinamide aptamer and selectivity toward the analogs. These results indicated that the proposed method can be applied to select structure-induced aptamers that target small molecules.

Analyzing new psychoactive substances (NPSs) in forensic laboratories present a formidable challenge globally. Within illicit drug analysis, gas chromatography-mass spectrometry (GC-MS) emerges as a robust analytical tool. This study endeavors to assess and compare peak resolution in the analysis of illicit drugs, specifically focusing on 21 synthetic cathinones, encompassing 9 cathinone isomers. Varied GC-MS operating conditions, including distinct GC-MS columns and thermal gradients, were systematically employed for the simultaneous analysis of these synthetic cathinones. The study utilized HP-1 nonpolar and HP-5MS low-bleed columns to achieve optimal analyte resolution through modulation of GC-MS oven conditions. Mass spectra were meticulously recorded within a mass-to-charge (m/z) range spanning from 40 to 500 in full scan mode. The data showed that the cathinone isomers slightly differed in retention times and mass spectra. The GC oven conditions affected the peak resolution for chromatographic separation even with the same column. The peak resolution improved using a slower thermal gradient heat speed with a prolonged analysis time. Conclusively, the interplay of GC columns and thermal gradients emerged as pivotal factors impacting peak resolution in the analysis of illicit drugs. These empirical insights contribute to a nuanced understanding of peak resolution dynamics and facilitate the identification of synthetic cathinones, including their isomers, in seized materials through the judicious application of GC-MS methodologies.