Analytical Methods最新文献

Telomerase activity has piqued scientists' interest for the reason that it has the potential to be employed for early-stage cancer detection, anticancer therapy and studies related to cancer progression and metastasis. Several approaches have been developed to detect telomerase activity. However, these approaches were lengthy, challenging to quantify, of limited sensitivity and prone to polymerase chain reaction (PCR)-related artefacts. We herein developed a novel nanoplasmonic sensing platform for colorimetric detection of telomerase activity relying on the telomere elongation of telomerase at the 3' end, structure-specific cleavage activity of exonuclease III that removes mononucleotides from the 3'-hydroxyl termini of double-stranded DNA, and electrostatic interaction of elongated telomeres with plasmonic nanoparticles. Using HeLa cells as a model for colorimetric detection of telomerase activity, this biosensor could detect telomerase activity with a detection limit of ∼100 cells per reaction by visible inspection and ∼5 cells per reaction by spectroscopic measurement and analysis time within about three hours. The proposed sensing method provided a novel tool for simple, rapid, and low-cost detection of telomerase activity, eliminating the necessity for thermal cycling, primers in PCR-based assays, and amplification of telomerase extension products. It exhibits significant potential as a label-free, simple, ultrasensitive strategy for on-site detection of telomerase activity in proteomics and clinical diagnostics.

During the pharmaceutical synthesis process, it is essential to control the reaction time to avoid by-product formation and the reduction of yield. In this study, a Raman spectroscopic platform based on online sampling was integrated to collect Raman spectra in real time and realize process monitoring. Considering its attractive features of strong light transmittance and resistance to acids, alkalis and high temperatures, polyfluoroalkoxy (PFA) tubes rather than cuvette-type flow cells or similar devices were used to transfer solutions and as a flow cell for collecting Raman spectra, therefore not requiring an in situ Raman probe, and significantly reducing the cost of equipment. The peristaltic pump is controlled by the sampling software to realize automatic sampling, and it automatically pushes the reaction solution back into the reaction vessel after the spectra are collected. Taking the aspirin synthesis reaction as an example, the platform was employed to monitor the chemical reaction in real-time. The internal standard method was adopted to minimize the interference of spectral oscillation and baseline drift during online monitoring. The characteristic peak of the PFA tube at 731 cm^-1 was selected as the internal standard peak, which formed the relative intensity ratio R with the characteristic peak of the product acetylsalicylic acid at 1606 cm^-1. The endpoint of the reaction was identified based on the trend of the relative intensity ratio with the reaction time. The results indicate that the method is feasible for monitoring the aspirin synthesis reaction and provides a research basis for real-time monitoring of other pharmaceutical processes.

A novel near-infrared fluorescent probe TM2 based on a rhodamine-bearing framework was disclosed with a large Stokes shift (100 nm). TM2 exhibits highly selective recognition for Cu²⁺ in EtOH/H₂O (1 : 1, v/v) solution with a low detection limit (2.3 μM) and a wide detection range (0-50 μM). Detection of Cu²⁺ is undisturbed at physiological pH levels of 5-9. This recognition mechanism is attributed to the formation of a 1 : 1 complex between TM2 and Cu²⁺, validated by Job's plot, ¹H NMR titration, and LC-MS experiments. Moreover, the successful fluorescence imaging of Cu²⁺ both in vitro and in vivo was also accomplished.

Taylor Dispersion Analysis (TDA) is explored to measure the hydrodynamic sizes of full and half generation PAMAM dendrimers up to generation 4.5 in various buffer solutions. A method was used to minimize the interaction between the capillary and cationic dendrimers. The effects of generation, surface functionality, pH and ionic strength on the hydrodynamic radii of PAMAM dendrimers were investigated. Our results show that TDA can accurately measure the sizes of PAMAM dendrimers with a relatively low standard deviation especially for half generations. It was found that the ionisation of functional groups at various pH values led to a conformational change due to electrostatic repulsion or back-folding of the branches. Furthermore, adding salt to a half-generation dendrimer (G4.5) can lead to a profound size change that is dependent on ionic strength. A 17% increase in the size of the G4.5 dendrimer was observed in a 1 M NaCl solution compared to that in a 0.1 M solution. Compared to dynamic light scattering, TDA is more reliable and tolerant to large particles in the solutions. The findings of this study indicate that TDA could serve as a viable alternative technique for assessing dendrimer size and conformation, as well as studying their binding behavior.

Exposure to aromatic amines may occur via tobacco smoke, hair dyes or tattoo inks, but also in the workplace during certain manufacturing processes. As some aromatic amines are known or suspected carcinogens, human biomonitoring (HBM) is essential to assess their exposure. Aromatic amines were among the selected chemicals in HBM4EU, a European-wide project to harmonise and advance HBM within 30 European countries. For this purpose, the analytical comparability and accuracy of participating laboratories were assessed by a QA/QC programme comprising interlaboratory comparison investigations (ICIs) and external quality assurance schemes (EQUASs). This paper presents the evaluation process and discusses the results of three ICI/EQUAS rounds for the determination of aromatic amines in urine conducted in 2019 and 2020. The final evaluation included ten participants which analysed the following six targeted aromatic amines over three rounds: aniline, ortho-toluidine (TOL), 4,4'-methylenedianiline (MDA), 4,4'-methylenebis(2-chloroaniline) (MOCA), 2,4-diaminotoluene (2,4-TDA), and 2,6-diaminotoluene (2,6-TDA). Most participants achieved satisfactory and highly comparable results, although low quantification limits were required to quantify the parameters at the level of exposure in the general population. Hydrolysis of the sample followed by liquid-liquid extraction and subsequent analysis of the derivatised analytes by means of GC-MS/MS were preferred for the sensitive and precise determination of aromatic amines in urine. This QA/QC programme succeeded in establishing a network of laboratories with high analytical comparability and accuracy for the analysis of aromatic amines in Europe.

Low-density lipoprotein (LDL) is a key biomarker for cardiovascular disease (CVD) risk assessment. Monitoring LDL for the early diagnosis of CVD and its complications is an important clinical analysis tool. In this work, a novel colorimetric aptasensor for LDL detection was constructed via reduced graphene oxide@molybdenum disulfide-ferrocene-carboxylic nanosheets (rGO@MoS₂-Fc) with excellent peroxidase-like activity. On this basis, the LDL aptamer (LDLapt) immobilized on the surface of rGO@MoS₂-Fc served as a signal probe (rGO@MoS₂-Fc/LDLapt), while the unmodified LDLapt served as a capture probe. When LDL was present, it was recognized by the LDLapt and rGO@MoS₂-Fc/LDLapt to form an rGO@MoS₂-Fc/LDLapt/LDL/LDLapt sandwich-type conjugate with excellent enzymatic catalytic properties that can catalyze the generation of hydroxyl radicals (·OH) from hydrogen peroxide (H₂O₂), which in turn oxidized the colorless substrate o-phenylenediamine (OPD) to the yellow compound 2,3-diamino phenothiazine (DAP). In addition, the catalytic mechanism of the reaction was confirmed to be induced by ·OH through free radical experiments. The aptasensor had a linear range of 15.0 to 200.0 μg mL^-1, and a limit of detection (LOD) of 2.199 μg mL^-1. Overall, the assay has high selectivity, sensitivity and operability, showing broad application prospects in the clinical diagnosis of CVD.

Despite the efficacy of strong emission control plans that have been implemented the last few decades, polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) may still be released from anthropogenic sources such as sinter plants, and municipal and hazardous waste incinerators. Monitoring for PCDDs and PCDFs in gaseous emissions from such facilities is important due to the acute toxicity of these compounds even at trace levels. Currently, most of these samples from the African continent are being analysed abroad at high cost, with the direct consequence that the number of measurements are kept to a minimum. In this context, we developed a more affordable analytical approach for the measurement of PCDD/Fs sampled onto Amberlite XAD-2 sorbent, which relies on a novel extraction, clean-up, and analysis method with the aim of reducing both the cost and the complexity of standard methods while maintaining high quality results. A simple, sequential, 3 hour end-over-end tumbling extraction procedure was developed employing acetone : n-hexane (1 : 9) as extraction solvent. This was combined with a dimethyl sulfoxide (DMSO) clean-up to remove aliphatic interferences, prior to direct analysis by gas chromatography triple quadrupole mass spectrometry. The Unites States Environmental Protection Agency Method 23, in contrast, requires a 16 hour Soxhlet extraction with toluene and multiple column chromatography steps. The end-over-end tumbling extraction yielded an average recovery of 79% for PCDD/Fs usually monitored in gaseous samples, whilst an average recovery of 89% was achieved for the DMSO clean-up procedure. In addition, an overall average recovery of 78% and a Z-score of -1.1 was obtained using the developed method for the proficiency testing of a solid reference material, proving the method is fit for purpose. It was then successfully applied to the analysis of air emissions from a medical waste incinerator, which further showed that the alternative approach may deliver quality, fast, and cost-effective analysis of gaseous PCDD/Fs sampled onto Amberlite XAD-2 sorbent in a developing country context.

A new fluorescent probe for detecting hydrogen sulfide (H₂S) was developed through the thiolation reaction of 2-chloro-1,4-naphthoquinone. Rhodol was employed as the fluorophore, while 2-chloro-1,4-naphthoquinone acted as the reactive group for H₂S. The probe remains non-fluorescent under sunlight but emits a strong fluorescence upon reaction with H₂S, accompanied by a visible color change in the solution. This selective H₂S probe features rapid detection (under 1 minute), high photostability, and a very low detection limit (LOD = 44.3 nM), well below the levels that trigger physiological responses. The probe's mechanism was confirmed through ¹H-NMR, HR-MS, and DFT analysis. With low cytotoxicity and high biocompatibility, the probe has been effectively applied for fluorescent bioimaging of H₂S in living cells.

This study presents a refined method that uses liquid chromatography with a fluorescence detector (LC-FD) to quantify trace amounts of dimethylamine in particulate matter (PM). This method was optimized to prioritize simplicity, cost-effectiveness and practicality. To ensure accurate and reliable analysis, strict protocols and procedures were followed to minimize cross-contamination. Separate workspaces were designated for preparing control blanks and sample treatments in one area and standard solutions in another, thus mitigating the risk of cross-contamination. An evaluation was conducted on different concentrations of 9-fluorenylmethyl chloroformate to derivatize dimethylamine. The results showed that a concentration of 3 μg mL^-1 was effective in derivatizing dimethylamine concentrations up to 300 ng mL^-1. Increasing the concentration of the derivatization reagent from 2.9 to 7.3 μg mL^-1 resulted in slightly elevated dimethylamine levels in blank measurements. Also, during the preparation of standards at low concentrations, high analytical coefficients of variation were observed. This highlights the importance of checking for potential sources of contamination. Method precision and quantification limits were evaluated through blank analysis, yielding values of approximately 20% and 20 ng mL^-1, respectively, consistent with chromatographic determination for environmental analysis. The suitability of the method for environmental analysis was demonstrated by analyzing eight PM_2.5 samples. The concentrations of methylamine and dimethylamine were found to range from 0.8 to 3 ng m^-3 and 1.4 to 7.1 ng m^-3, respectively, in accordance with the literature. Comparison with concurrent carbonyl measurements revealed similar concentration profiles. Both types of analyses can be performed using affordable methodologies that involve prior derivatization using a reduced concentration of the derivatization reagent.

A novel compact potentiometric electrode specifically designed for pH monitoring, featuring a good construction on a glass substrate coated with a cerium-doped tin oxide (Ce-doped SnO₂) layer. The Ce-doped SnO₂ thin film was created by spray-pyrolysis it on a glass substrate. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) were used to characterize the deposited metal oxide coating. As a miniature potentiometric electrode, the synthesized Ce-doped SnO₂/glass substrate was utilized to measure a broad pH range (pH 2-12) in aqueous solutions. The electrode had a perfect near-Nernstian response (slope of -58.6 ± 0.7 mV per decade), high potential stability, mechanical durability, and great selectivity towards some common interfering cations and anions. These characteristics made it ideal for quality control and assurance purposes. The electrode's performance parameters and validation measurements were assessed using established procedures. The Ce-doped SnO₂-based electrode satisfactorily monitored the pH of several genuine water, drink, and fruit juice samples, and the data compared well with those obtained using a traditional pH glass electrode. The integration of Ce-doped SnO₂ as the active material marks a significant advancement, providing enhanced electrochemical stability, improved sensitivity, and a wider pH detection range compared to conventional electrodes. The compact design not only reduces the sensor's footprint but also facilitates its application in miniaturized and portable pH monitoring devices, making it highly suitable for advanced analytical and environmental sensing applications.