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Antibiotic residues in foods have aroused wide public concern because of their potential side-effects. It is imperative to develop a simple, accurate and reliable method for the detection of antibiotic residues in foods. In this paper, we report a novel, facile and sensitive method for the detection of ampicillin in milk using a commercial personal glucose meter (PGM). Magnetic beads (MBs) were employed as the platform, an ampicillin aptamer was used as the recognition element and streptavidin was utilized as the bridge to link invertase and the aptamer. After the hydrolysis of sucrose to glucose, the concentration of glucose was quantitatively measured using the PGM. The difference of PGM signals with and without addition of ampicillin exhibits a good linear correlation with the logarithm of ampicillin concentrations in the range of 2.5 × 10 ?10 mol L ?1 to 1.0 × 10 ?7 mol L ?1 with a detection limit of 2.5 × 10 ?10 mol L ?1 (S/N = 3). Finally, the proposed method was successfully applied for the detection of ampicillin residue in milk.

In this study, aggregation-induced emission luminogens (AIEgen) are used for the detection of per- and poly-fluoroalkyl substances (PFAS) including perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS) and 1 H ,1 H ,2 H ,2 H -perfluorooctanesulfonic acid (6:2FTS). A solution of acetone–water (solvent) containing AIE-PFAS is first formulated. From this solution, one droplet (1–2 μL) is dropped and trapped into a hole in a chip made of glass slide. When the droplet is exposed to air, both water and acetone can vaporise, but acetone vaporises much more quickly than water does due to its higher vapour pressure. Consequently, with the solvent volume shrinking, the concentrations of AIE and PFAS increase in the shrinking droplet while the water percentage increases. At a certain stage of this process, the micelle of PFAS surfactant forms, accompanied by AIE aggregation. After completely vaporising and drying on the bottom of the chip-hole, the aggregated AIE features fluorescence, the density of which can be effectively linked to the concentration of PFAS surfactant. Thus, a simple sensor is developed for PFAS detection in the range of 0.1–100 μM (41 ppb to 41 ppm for PFOA) within around 1 min using a 1–2 μL PFAS sample.

In this work a fully automated catalytic–spectrophotometric method for determination of copper at trace levels using a multisyringe flow injection system (MSFIA) and a multipumping flow system (MPFS) coupled to a micro-chip (Chip–MSFIA–MPFS) is presented. The reaction is based on the catalytic effect of Cu( II ) on the oxidation of the in situ reduced form of 2,6-dichlorophenolindophenol (DCPI) r , by hydrogen peroxide. Due to the importance of the mixing order of the reagents, a new design of the chip is proposed. DCPI, ascorbic acid and buffer are first propelled to mix in the front section of the chip using MPFS. Then this reagent mixture, together with hydrogen peroxide and the sample, is simultaneously dispensed to the rear section of the chip by using a multisyringe for mixing, heating and absorbance measurement of the product at 600 nm. The optimum conditions are 0.9 mmol L ?1 DCPI, 3.6 mmol L ?1 ascorbic acid, 0.8 mol L ?1 ammonium chloride buffer, pH 10.5, and 0.3 mol L ?1 H 2 O 2 . The proposed system is simple, rapid, selective and sensitive. We can determine trace levels of Cu( II ) at room temperature (25 °C). The main analytical characteristics of the proposed method are a detection limit of 0.12 μg L ?1 of Cu( II ), a working range of 0.4–35.0 μg L ?1 of Cu( II ), and a relative standard deviation of 0.79% (10 μg L ?1 Cu( II ), n = 15). The system was successfully applied to water samples, certified reference materials (CRMs) of river and waste water, acid digested multivitamins and animal tissues with a sample throughput of 31 injections h ?1 .

The analysis of complex mixtures by NMR is a challenge in (bio)chemistry due to signal overcrowding making the analysis difficult. Thus, new advanced quantitative 2D NMR techniques that lead to better resolved and more intense signals have been applied to extracts of plants for tracking biomarkers of the photosynthesis and photorespiration cycles.

An eco-friendly, sensitive and selective high-performance thin-layer chromatographic method was developed and validated for analysis of eszopiclone in bulk powder and formulation. The method employed HPTLC aluminium plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of methanol–water (6?:?4, v/v). Densitometric analysis of eszopiclone was carried out at 300 nm. This system was found to give a compact spot for eszopiclone ( R f value of 0.48 ± 0.02). The proposed method was validated for linearity, precision, robustness, LOD, LOQ, specificity and accuracy in accordance with ICH guidelines. Linearity was found to be in the range of 0.2–1.2 μg per band with a significantly high value of correlation coefficient r = 0.9997. Statistical comparison with a reported reference method showed similar results with respect to accuracy and precision. The study of the eszopiclone water-induced degradation kinetics was carried out by the proposed HPTLC method. The activation energy and degradation rate constant at room temperature were calculated after the construction of the Arrhenius plot.

Methyl mercury (MeHg) is a common contaminant worldwide. Health authorities keep monitoring MeHg levels in biological and environmental samples to assess the corresponding exposure in the population. So far, a basic leaching has been mostly used for the MeHg extraction. In this study, it was demonstrated that methanesulfonic acid, commonly used for amino acid extraction, can be used for MeHg extraction. Species-specific isotope dilution was employed to achieve accurate results. The method was validated by analysis of dogfish liver certified reference material (DOLT-4). The derivatized extracts were then analyzed with gas chromatography-inductively coupled plasma-mass spectrometry (GC-ICP-MS). Results obtained for MeHg in DOLT-4 are in agreement with the certified value ( t -test, P = 0.05), confirming that methanesulfonic acid extraction is suitable for extraction of MeHg in biological tissues. This new procedure could be of particular interest in biological and toxicological studies where a simultaneous determination of MeHg and certain amino acids is sometimes required.

Isotope techniques can be applied to discover the migration and transformation of metal elements in plants. However, only a few studies on Cd isotopes in plants have been carried out so far. In this study, an optimized analytical method consisting of digestion, purification and determination of Cd isotopes in plants was developed. Three Cd standard solutions as well as four plant species ( Solanum nigrum , Ricinus communis , Cyperus alternifolius and Pteris vittata ), which were grown in soil or hydroponic cultures, were repeatedly analyzed for Cd isotopes using Multiple Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS). The factors that affected the accuracy of Cd isotopic determination, such as isobaric interference and instrumental mass fractionation, have been carefully evaluated and corrected. The purification procedure yielded a Cd recovery of not less than 95% and effectively eliminated the spectral interference of Pd, In and Sn as well. The analysis of pure Cd standard materials showed accurate isotope values, which matched with the results of previously published methods. This technique provided an average long-term external reproducibility of ±0.09‰ for δ 114/110 Cd (2SD). The overall δ 114/110 Cd values of four plant species ranged from ?0.39‰ to ?0.08‰ and provided direct evidence for Cd isotopic fractionation in herbaceous plants.

In this research, 16 polycyclic aromatic hydrocarbons (PAHs) in bread samples were simultaneously determined using microwave-assisted extraction and dispersive liquid–liquid microextraction (MAE–DLLME) coupled with gas chromatography-mass spectrometry (GC-MS). Effective parameters of MAE–DLLME were investigated and optimized using a response surface methodology based on central composite design (CCD). Under optimum conditions, linearity was obtained in the range of 1–200 ng g ?1 for 16 PAHs, with a correlation coefficient ( R 2 ) better than 0.9833. The limits of detection and limits of quantitation for PAHs in real samples were over the ranges 0.1 to 0.3 ng g ?1 and 0.3–1 ng g ?1 , respectively. The performance of the proposed method was investigated for the determination of PAHs in various bread samples and acceptable results were obtained.

An electrochemical analyzer based on a potentiostat/galvanostat (PG004) was developed and applied to perform in situ Pb 2+ and Cd 2+ determination in water samples with on-line data transmission, and a global positioning system (GPS), to acquire the geographical coordinate of the place being monitored. For this, a flow-batch analysis (FBA) and a thermostated electrochemical flow cell (EFC) coupled with a boron-doped diamond electrode (BDD) were developed to measure these ions by employing square-wave anodic stripping voltammetry (SWASV). To study the Pb 2+ and Cd 2+ ions by in situ analysis, mainly for temperature variation, the PG004 was evaluated and the limits of detection were 0.08 μg L ?1 and 0.18 μg L ?1 , respectively, for simultaneous analysis. Then, the PG004 was used for in situ determination of analytes in lake water samples, and voltammograms with good resolution and low noise were obtained. Recoveries ranged from 93.3% to 109%, and the waste generated was as low as 700 μL per determination. The accuracy of the method was checked by determination of Cd 2+ and Pb 2+ in certified water (NIST), t -unpaired test was applied for n = 3, and the values found were in close agreement at a confidence level of 95%. Besides the geographical coordinates obtained by using a GPS receiver, and experimental data sent via wireless, the device used a solar board as renewable energy. The developed system proved to be a useful tool to measure Pb 2+ and Cd 2+ in lake samples with a fast, on-line, and environmentally friendly analytical method.

Although UV-Vis spectroscopy has been applied in many fields, it still encounters some challenges in multi-component mixture analysis due to severe spectral overlapping and different interferences. In this paper, a Tchebichef curve moment (TM) approach has been developed and proposed for the quantitative analysis of five skin-whitening agents in several cosmetic products with different substrates based on conventional UV-Vis determination for the first time. First, the TMs were calculated from the raw UV-Vis spectra of mixed standard samples, and employed to establish linear quantitative models by stepwise regression. Then, the obtained models were applied to the analysis of real samples. The leave-one-out correlation coefficients ( R loo-cv ) of the established models were more than 0.9948 within the linear ranges. The proposed approach was evaluated using intra- and inter-day precision (less than 5.98%) and recovery (ranging from 88.3 ± 2.8% to 109.2 ± 2.3%). The LODs and LOQs were less than 0.13 mg L ?1 and 0.45 mg L ?1 , respectively. Compared with the classical methods, the proposed approach is not only more accurate, reliable and robust in the quality control analysis of cosmetic products, but also can extend effectively the application of conventional UV-Vis determination.