Analytical Methods最新文献

Phosphate anion (PPi) as hydrolysis products of adenosine triphosphate (ATP), is related to various biochemical reactions, particularly energy storage and transfer, nucleotide metabolism, and cellular signaling. In this paper, a binuclear zinc complex (Zn₂L) was prepared for the PPi sensing in Tris-HCl solution. The results showed a clear fluorescence change from blue to green (425 nm → 500 nm) with the addition of PPi to the probe. The probe Zn₂L demonstrated a remarkable selectivity for PPi in comparison to common anions, with an estimated limit of detection (LOD) of 0.29 μM within a working range of 0-9 μM. UV titration experiments showed two binding steps from 1 : 1 to 1 : 2 complex (Zn₂L-PPi). Density-functional theory (DFT) studies were further conducted to find an energy gap that decreases with complex (probe + 2PPi) formation, resulting in a redshift of the absorption spectrum (360 nm → 430 nm). In addition, the Zn₂L probe was also used for PPi sensing in a urine sample, in which relative standard deviation values (1.19-2.17%) and recoveries (95.00-103.00%) were obtained.

Nutritional trials often yield inconsistent results due to the lack of standardised study designs, especially when evaluating the health benefits of fruits and vegetables. Apple phenolics, linked to various health benefits, have particular challenges in human nutritional studies due to compositional changes influenced by factors like fruit maturity, growing conditions, tissue type, and processing methods. This study applied an 'orchard-to-fork' approach to evaluate Monty's Surprise apple phenolics in the skin and flesh, controlling for harvest procedures, fruit maturity, and seasonal impact. It further assessed processing methods to preserve phenolic content, with the goal of developing a standardised material for dietary intervention trials. Monty's Surprise apples were collected over two seasons following standardised harvesting protocols and various fruit maturity parameters (firmness, starch pattern, and total soluble solids) were controlled and measured for various apple sizes. Phenolic content in the skin and flesh was analysed with LC-HRAM-MS and compared across seasons. The impacts of processing (pureeing, air drying, and slicing) on phenolic content were also evaluated. Cold storage for four weeks reduced maturity variability across apple sizes. Monty's Surprise apple skin (5270.49 ± 214.95 mg kg^-1 FW) had significantly (p < 0.0001) higher phenolic concentrations than the flesh (863.69 ± 12.71 mg kg^-1 FW), with procyanidins as the main phenolic group. No seasonal impact was observed. Pureed apples retained significantly higher phenolics compared to sliced or dehydrated samples. Monty's Surprise apple is a rich source of health-beneficial phenolics, and pureeing effectively preserves these compounds. This study offers guidance for the development of standardised apple material for dietary intervention trials to more accurately investigate the health benefits of apples.

In this study, an approach involving gas chromatography-mass spectrometry (GC-MSMS) combined with a modified QuEChERS method was developed for the detection of 13 novel fungicides in chicken and beef samples, in accordance with the regulatory limits proposed by Japan, South Korea, Codex Alimentarius, and the EU in recent years. The regulatory limits and detection methods for these fungicides in foods of animal origin are yet to be established in China. These 13 fungicides were linearly correlated in a range of 0.1-200 ng mL^-1 with a coefficient of determination (R²) of >0.999. The limits of detection (LODs) and limits of quantification (LOQs) for the 13 fungicides were found to be in a range of 0.16-1.50 ng mL^-1 and 0.54-5.00 ng mL^-1, respectively. The recovery of the spiked samples exhibited a range of 79.51-111.39% (RSD ≤ 10.51%), demonstrating satisfactory accuracy and precision. This study establishes a foundation for the identification of novel fungicides in foods of animal origin and provides technical references for the investigation of novel fungicides.

Quantification of exopolysaccharide (EPS) production in fermentation broth requires solvent precipitation of the polymer, followed by acid or enzymatic hydrolysis, and colorimetric or chromatographic analysis. This lengthy multistep sample preparation and analysis is a major bottleneck in bioprocess monitoring. The development of a nondestructive analytical method requiring minimal sample preparation is warranted. In this study, partial least squares (PLS) regression models were developed to quantify pullulan in cell-free supernatant (PCS) and precipitated pullulan redissolved in distilled water (PDW) from spectral data (204-400 nm). Genetic algorithm, particle swarm optimization, competitive adaptive reweighted sampling, and adaptive bottom-up space exploration strategies were employed to select optimal spectral regions. The full-spectrum model on the PCS (5 latent variables, RMSE_CV: 0.020 g l^-1, R_CV²: 0.997) outperformed the PDW (3 latent variables, R_CV²: 0.990). Adaptive bottom-up space exploration achieved the lowest RMSE_CV (0.009 g l^-1 for the PCS, 0.027 g l^-1 for the PDW), retaining just 16 and 21 spectral variables, respectively. The residual predictive deviation (RPD) for all PLS model variants remains satisfactory (>6.559). The method's limit of detection (0.021 g l^-1) was suitable for quantifying pullulan in fermentation broth. The proposed method can be extended to other structurally similar biopolymers where PLS-based soft sensor integration would enable real-time monitoring and bioprocess control.

Advanced glycation end products (AGEs) in food and biological samples have been analyzed using several chromatographic and immunological methods, but no studies have quantitatively analyzed the major AGEs, N^ε-carboxy-methyl-lysine (CML) and N^ε-carboxy-ethyl-lysine (CEL), in muscle tissue. In this study, a quantitative profiling method using ultra-performance liquid chromatography-tandem mass spectrometry in mouse muscle tissue was developed and validated. For extraction, acid hydrolysis and solid-phase extraction were performed. The CML and CEL were well separated and analyzed within 5 min in multiple reaction monitoring mode. The method was validated against ICH guidelines to evaluate the linearity, limits of detection and quantification, matrix effects, recovery, accuracy, and precision, and the validated approach was applied to muscle tissue from aged mice to establish a baseline for the typical range of CML and CEL. This quantitative profiling method has the potential to be applied in the study of diseases influenced by AGEs.

In recent years, the residue of psychotropic drugs such as diazepam in aquatic products has attracted widespread attention and is one of the important hidden dangers to the quality and safety of agricultural products. This study developed a modified QuEChERS method combined with UPLC-MS/MS to determine the residues of diazepam and its active metabolites, nordiazepam, oxazepam, and temazepam, in aquatic products and aquaculture environments. The important variables of the QuEChERS procedure were screened and optimized through single-factor experiments and response surface methodology. The recoveries of analytes in five aquatic products, pond water, and sediment were 87.4-97.8%, 90.4-96.4%, and 85.2-94.7%, respectively, with relative standard deviations of less than 15%. The limits of quantification were 0.1 μg kg^-1 for the four analytes in aquatic products and sediments, and 5 ng L^-1 in pond water. This method has been successfully applied to the analysis of diazepam and its active metabolite residues in 28 freshwater aquaculture farms in South China. The detected concentrations of the four analytes in aquatic products, sediments and pond water were 0.18-3.03 μg kg^-1, 0.21-17.5 μg kg^-1 and 5.56-391 ng L^-1, respectively. The illegal abuse of diazepam in fishing bait may be an important source of pollution in aquatic products. The risk assessment results showed that the residues of diazepam in aquaculture posed an acceptable risk to human health and a medium risk to the ecosystem. These results confirmed that the established method is suitable for the simultaneous analysis of diazepam and its active metabolites in aquatic products and aquaculture environments.

Carbon Quantum Dots (CQDs) have gained significant attention as versatile nanomaterials in analytical chemistry due to their strong fluorescence, high sensitivity, and biocompatibility features. This review explores the synthesis, functionalization, and broad applications of CQDs in various analytical domains, including bioimaging, diagnostics, and environmental monitoring. CQDs' unique properties, such as tunable emission and ease of surface modification, enhance their performance in fluorescence and electrochemical sensing. CQDs present emerging applications in single-cell analysis, point-of-care diagnostics, and food safety. Technological advancements in green synthesis and hybrid nanomaterial integration are paving the way for more sustainable, efficient, and scalable analytical tools. However, challenges related to reproducibility, stability, and large-scale production persist, highlighting the need for continued research. The present review provides a comprehensive overview of CQDs' impact, emphasizing their potential to transform analytical chemistry through innovative applications and future breakthroughs.

Propionic acid-polyethylene glycol-propionic acid (PA-PEG-PA) is a commonly used biocompatible polymer in drug delivery systems. Unraveling the in vivo pharmacokinetic behavior of PA-PEG-PA polymer is important for the safety evaluation of PA-PEG-PA related drug delivery systems. In this research, a highly sensitive ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) assay was developed for detection of PA-PEG₈-PA polymers in complex biological matrices. Methoxy-polyethylene glycol propionic acid polymers with 6 subunits (mPEG₆-PA) were used as the internal standard (IS). The multiple reaction monitoring (MRM) transitions at m/z 513.4 ([M - H]^- precursor ions) → 441.2 (fragment ions) and m/z 367.3 ([M - H]^- precursor ions) → 118.8 (fragment ions) were chosen to determine PA-PEG₈-PA and mPEG₆-PA, respectively. The analysis time was only 5 min for each sample. Numerous parameters like specificity, sensitivity, accuracy, precision, recoveries, matrix effects and dilution effect were validated for the developed assay. The UPLC-MS/MS assay showed excellent linearity over the range of 30-1500 ng mL^-1(r > 0.995). The assay was successfully applied to quantify the concentration of PA-PEG₈-PA polymers in rat plasma.

The development and research of electrochemical immunoassays have attracted considerable attention. However, traditional electrochemical immunoassays inevitably require the participation of biological enzymes, which suffer from high cost, poor stability, inconvenient storage and easy inactivation. Herein, we constructed a bio-enzyme-free electrochemical immunoassay system specifically for the detection of aflatoxin B1 (AFB₁). This method was based on the traditional antigen-antibody immune recognition system utilizing the nanosilver particles (NSPs) as signal markers to replace conventional natural enzymes. Subsequently, the labeled NSPs were transferred to silver ions in the presence of nitric acid. The concentration of silver ions was determined using anodic stripping voltammetry (ASV), which correlates closely to the concentration of the target. The current intensity measured by the bio-enzyme-free electrochemical sensor exhibited a negative correlation with the concentration of AFB₁. Under optimized conditions, the electrochemical sensor was used to detect AFB₁ in the dynamic concentration range of 0.01-100 ng mL^-1, and the limit of detection was 0.4882 pg mL^-1. The spiked recovery range of AFB₁ in corn starch was determined to be between 100.98% and 109.42%, while the relative standard deviation (RSD) range was found to be from 0.34% to 3.82%. These results indicate that the electrochemical immunosensor without biological enzyme labeling has reliable accuracy, and the sensor has a broad application prospect in AFB₁ detection.

Pseudomonas aeruginosa (P. aeruginosa), a Gram-negative pathogenic bacterium, is one of the most common bacteria that causes severe infectious diseases. However, accurate and efficient detection of P. aeruginosa in clinical samples is a huge challenge. Therefore, in this study, we developed a Cas9 derivative (dCas9)/sgRNA-mediated competitive assay for the sensitive and precise characterization of genomic materials from P. aeruginosa. Our approach involved the identification of target genomic sequences using the dCas9/sgRNA complex, which occupied the "sensing probe" (SP) binding site, resulting in an increased availability of free SP. SP subsequently facilitated DNA polymerase/endonuclease-mediated signal cycles and signal production, enabling highly sensitive detection of P. aeruginosa. The proposed competitive assay demonstrated a robust linear response to P. aeruginosa within a concentration range from 10 CFU mL^-1 to 10⁶ CFU mL^-1, leveraging numerous signal amplification processes and competitive target recognition while exhibiting robust anti-interference capacity. Compared with former strategies, the proposed competitive assay enabled the accurate detection of P. aeruginosa by directly identifying and binding genomic sequences, which could be easily extended to the detection of other bacteria by simply changing the sgRNA. In addition, the proposed approach exhibits significant clinical potential for early disease diagnosis owing to its excellent sensitivity and accuracy.