Analytical Sciences最新文献

In this research, a green approach utilizing deep eutectic solvent liquid-liquid microextraction is combined with smartphone digital image colorimetry for the determination of boron in nut samples. A smartphone camera was used to capture the image of the analyte extract located in a custom-made colorimetric box. Using ImageJ software, the images were split into RGB channels, with the green channel identified as the optimum. The distance between the cuvette containing the analyte extract and the detection camera was determined to be 8 cm, while the brightness of the light source was 30%. All the images were obtained at 585 nm monochromatic light positioned as a background source. The extraction was achieved with 450 µL of a 1:4 choline-chloride to phenol mole ratio within 60 s and another minute of centrifugation. The limits of detection and quantification were found to be 0.02 and 0.06 µg mL^-1, respectively. The method linearity, as indicated by the relative coefficient, was greater than 0.9955 and the relative standard deviations were below 5.4%. Lastly, the application of chemometrics in the form of artificial intelligence (AI)-based models and hybrid machine learning methodologies has been incorporated with SDIC for the quantitative simulation of SDIC parameters. The results gathered showed that these models are capable of predicting the quantitative SDIC parameters.

As one of the most harmful heavy metal pollutants, hexavalent chromium Cr(VI) is becoming a serious threat to human health. Thus pursuing a remarkably sensitive method to monitor the Cr(VI) concentration in natural conditions is favored for the fast response to prevent harm. In the present work, an ethylenediamine (En) and SiO₂-modified wool keratin-based carbon quantum dot (CQD)(En@CQDs@SiO₂) fluorescent sensor is prepared, and the En is found to improve the discrimination ability by binding the Cr(VI) with the surface carboxyl groups. Based on these designs, the En@CQDs@SiO₂ achieves a significant improvement in the Cr(VI) detection ability, with a detection limit of 6.08 × 10^-4 mg/L, which succeeded 6 times over CQDs, and is better than conventional UV-Vis and flame atomic absorption (AAS) techniques. Furthermore, the fluorescent sensor has good relative sensitivity, selectivity, good spectral reproducibility, and excellent structural stability. These properties make the sensor suitable for environmental Cr(VI) detection, which undoubtedly improves the economy and environmental friendliness of the fluorescent sensor.

Glutathione (GSH) is a tripeptide and natural reducing agent composed of glutamic acid, glycine, and cysteine. Its level in the human body is closely linked to human health, such as diabetes, Alzheimer's disease, and cancer. The supplementation of exogenous GSH could bring health benefits and GSH detection in food is of considerable importance. However, the existing assays for GSH detection such as high-performance liquid chromatography/mass spectrometry, electrochemiluminescence and fluorescent nanoprobe were not satisfactory because of the disadvantages of equipment and site requirements. In this study, a multiple-colorimetric detection assay for GSH was developed based on GSH's reaction with gold nanorods. During the reaction with varying concentrations of GSH, the gold nanorods degraded into spherical nanoparticles with multiple color changes, which could be used to determine GSH concentrations. The transverse surface plasmon resonance absorption peak of gold nanorods (AuNRs) significantly shifted, indicating a novel mechanism distinct from etching or surface coating, which typically altered the longitudinal surface plasmon absorption peak. Under optimized conditions, the assay exhibited commendable specificity and reliability in actual samples. The assay accurately quantified GSH ranging from 1 to 10 µM, with detection limits of 439 nM and 260 nM for spectrophotometry and visual analysis, respectively. It was firstly to use GSH as a reducing agent to react with AuNRs in the presence of AgNO₃ and the mechanism was different from etching or surface coating. The study's assay shows potential for detecting GSH in food samples and provides an alternative approach for the development of colorimetric detection assays based on AuNRs.

The diverse functional roles of RNA within cells have led to a growing interest in developing RNA-binding fluorescent probes to investigate RNA functions. In particular, the probes for double-stranded RNA (dsRNA) structures are of significant value given the importance of the secondary and tertiary RNA structures on their biologic functions. This review highlights our recent efforts on the development of triplex-forming peptide nucleic acid (TFP)-based probes for fluorescence sensing of dsRNA structures. We demonstrated that the forced intercalation of asymmetric cyanine dyes integrated as base surrogate within the probes was useful for achieving significant light-up response toward target dsRNAs. We also showed that the TFP probes conjugated with small RNA-binding molecules facilitated the fluorescence sensing of biologic relevant dsRNAs containing unpaired nucleobases. The binding and fluorescence signaling functions of such probes were discussed, emphasizing their potential as analytical tools for studying dsRNA structures.

A digital-movie-based flow colorimetry for pH measurement using a universal indicator has been applied to the end point detection of acid-base titrations. A two-channel flow system of feedback-based flow ratiometry, primarily consisting of two peristaltic pumps, a digital microscope-based detector, and a laptop computer, was constructed; a Visual Basic.NET program written in-house was used for automating the analytical processes. While maintaining the total flow rate (F_T) constant, a titrand solution was merged with a titrant solution, both containing the same concentration of Van Urk's universal indicator, under varying flow ratios. Downstream, the video image was captured with a digital microscope and its color was expressed as RGB values, hue, and luminance. The end point was determined from the rapid change of hue reflecting the color transition of the universal indicator around the equivalence point. A stepwise titration of multivalent acid (i.e., H₃PO₄) was also possible by setting hue values corresponding to the first (1st) and second (2nd) equivalence points as criteria to determine the respective end points. The hue-based approach was validated by the titrations of CH₃COOH and H₃PO₄ (1st and 2nd equivalence points) with 0.1 mol dm^-3 NaOH and to those of NaOH and NH₃ with 0.1 mol dm^-3 HCl. The method was applied to determine Japanese Pharmacopoeia (JP) borax and JP citric acid. The respective assay results were 100.0 ± 0.0% and 100.0 ± 0.0%, both meeting the JP specifications. The developed method is simple, high throughput (1 titration/min), versatile, and does not require indicator replace depending on the equivalence point pH.

"Liquid gold" has been traditionally used for over a century to decorate ceramicware, but its chemical composition has not been thoroughly investigated. One of the keys to successfully characterizing liquid gold, which is a complex mixture, is to distinguish Au-containing products from other chemicals. In this paper, we propose a separation based on the difference in collision cross section, of which chemicals with heavy atoms are relatively smaller than those without in ion mobility-mass spectrometry (IM-MS). Chemicals containing a single Au atom (and Pt atom) were successfully separated from other species in the two-dimensional distribution map for IM-MS. By a detailed analysis of the spectra obtained by IM-MS/MS with collision-induced dissociation before and after IM separation, we found that liquid gold (gold resinate) was a mixture of a series of (1) Au reacted with α-pinene-related units and (2) Au reacted with abietic acid units. α-Pinene and abietic acid are the main components of turpentine and rosin, the raw materials of liquid gold as reported previously (Anal. Sci. 2024, 40, 133-139). All Au-containing species contain sulfur atoms. Species of Au reacted with α-pinene-related units with different degrees of unsaturation and oxidation have also been identified. Liquid gold, a complex mixture of chemicals containing Au, has been successfully analyzed compositionally.

We synthesized a squaraine dye (F-0) to develop a method for detecting pyrophosphate (PPi) and alkaline phosphatase (ALP) by modulating the fluorescence of F-0. The fluorescence intensity of the F-0 system was quenched upon the addition of Cu²⁺ ions; however, it was restored when PPi was introduced due to the formation of a complex between PPi and Cu²⁺. Since ALP can hydrolyze PPi, the fluorescence of the system was quenched again upon the addition of ALP. Based on these principles, we established a fluorescent probe that exhibits an "off-on-off" fluorescence response. The detection limits of this method for PPi and ALP were 103 nmol dm^-3 and 0.18 U dm^-3, respectively. Moreover, this method demonstrates good selectivity and specificity and can be applied to the detection of PPi in actual samples.

A biosensor for biochemical oxygen demand (BOD) was developed based on intracellular 5'-adenosine triphosphate (ATP) measurements in Saccharomyces cerevisiae. Intracellular ATP was measured using an engineered protein named ATeam, comprising a bacterial F₀F₁-ATP synthase ε subunit sandwiched between cyan fluorescent protein and mVenus, a modified yellow fluorescent protein. Because the binding of ATP to ATeam induces changes in the fluorescence spectra owing to Fӧrster resonance energy transfer, S. cerevisiae expressing ATeam is expected to show spectral changes owing to the intracellular ATP produced by the metabolism of the BOD sample. A glycogen phosphorylase knockout S. cerevisiae strain expressing ATeam was prepared, and the fluorescence spectra of the strain were analyzed. Changes in the fluorescence spectra of glucose in the medium were observed, which exhibited a linear relationship with the glucose concentration (0-100 mg/L, R² = 0.970). Responses to lactose, fructose, sucrose, Glu, Asp, His, and Gly were evaluated and compared with typical BOD measurements. The results of this comparison suggest that a BOD biosensor based on intracellular ATP can be used for BOD measurements. A BOD standard solution comprising glucose and glutamic acid (GGA) was calibrated across a concentration range of 0 to 100 mg/L. Finally, simulated real samples were prepared using real pond water and GGA was measured. The correlation between the BOD value evaluated using intracellular ATP and that evaluated using the 5-day BOD test showed a linear relationship with R² = 0.944.