Analysis of Bisphenol A and Alkylphenols in Cereals by Automated On-line Solid-Phase Extraction and Liquid Chromatography Tandem Mass Spectrometry

An on-line solid-phase extraction (SPE) following a liquid chromatography–electrospray ionization–tandem mass spectrometry (LC–ESI–MS/MS) method was established for the simultaneous analysis of bisphenol A (BPA), nonylphenol (NP), and octylphenol (OP) in cereals (including rice, maize, and wheat). The target compounds were extracted by acetonitrile, purified by an automated on-line SPE cartridge, and analyzed by LC–MS/MS under the negative-ion mode. Mean recoveries fortified at three concentration levels ranged from 81.6 to 115.7%, and the coefficient of variation ranged from 4.6 to 19.9% (<i>n</i> = 6). The limits of quantification (LOQs) of the method were 0.5, 0.5, and 0.25 μg/kg for BPA, NP, and OP, respectively, in both rice and maize, while the LOQs in wheat were 0.5, 1.25, and 0.5 μg/kg for BPA, NP, and OP, respectively. This method was applied in the analysis of rice, maize, and wheat from a local market. As a result, NP occurred in all cereal samples at the concentration range of 9.4–1683.6 μg/kg and BPA was detected in a few samples

Geographical Distribution of Perfluorinated Compounds in Human Blood from Liaoning Province, China

Perfluorinated compounds (PFCs), such as perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA), have been identified widely in human. Monitoring of geographical distribution of PFCs in human blood can provide the information to better characterize the exposure source and pathway of these compounds. In this study, 13 PFCs were detected in 138 whole blood samples collected in 2008 from seven cities (Liaoning province, China) including Fuxin, Jinzhou, Shenyang, Anshan, Yingkou, Huludao, and Dalian. The highest geometric mean (GM) concentration of total PFCs was found in samples from Fuxin (17.27 ng/mL) followed by Shenyang (12.70 ng/mL) and Anshan (12.63 ng/mL). The composition profile of PFCs was varied in blood samples from seven cities. In Fuxin and Jinzhou, the percentage proportion of PFOA was significantly higher than that of perfluorohexanesulfonate (PFHxS) by about two times. By contrast, in Shenyang, Anshan, and Yingkou, the percentage proportion of PFHxS was about three times higher than that of PFOA. In Huludao and Dalian, the profile of PFCs in blood was very similar with comparable proportions of PFOA and PFHxS. The results suggested different human exposure sources and pathways of PFCs in Liaoning province, China

Determination of Triazine Herbicides in Drinking Water by Dispersive Micro Solid Phase Extraction with Ultrahigh-Performance Liquid Chromatography–High-Resolution Mass Spectrometric Detection

A novel dispersive micro solid phase extraction (DMSPE) method based on a polymer cation exchange material (PCX) was applied to the simultaneous determination of the 30 triazine herbicides in drinking water with ultrahigh-performance liquid chromatography–high-resolution mass spectrometric detection. Drinking water samples were acidified with formic acid, and then triazines were adsorbed by the PCX sorbent. Subsequently, the analytes were eluted with ammonium hydroxide/acetonitrile. The chromatographic separation was performed on an HSS T₃ column using water (4 mM ammonium formate and 0.1% formic acid) and acetonitrile (0.1% formic acid) as the mobile phase. The method achieved LODs of 0.2–30.0 ng/L for the 30 triazines, with recoveries in the range of 70.5–112.1%, and the precision of the method was better than 12.7%. These results indicated that the proposed method had the advantages of convenience and high efficiency when applied to the analysis of the 30 triazines in drinking water

A Colorimetric Sensor for the Visual Detection of Azodicarbonamide in Flour Based on Azodicarbonamide-Induced Anti-Aggregation of Gold Nanoparticles

Azodicarbonamide (ADA) in flour products can be converted into carcinogenic biurea and semicarbazide hydrochloride after baking. Thus, it is mandatory to determine ADA in flour. We herein developed a colorimetric method for the rapid and visual detection of ADA in flour based on glutathione (GSH)-induced gold nanoparticles (AuNPs) aggregation and specific reaction between ADA and GSH. The GSH can react to AuNPs via Au-SH covalent bond to form a network structure, which leads to AuNPs aggregation to produce color change, whereas ADA can specifically react with GSH to lead to the coupling of two GSH molecules, which makes GSH lose a −SH group and thus decreases the aggregation degree of AuNPs induced by GSH. This provided a platform for field-portable colorimetric detection of ADA. The colorimetric sensor can be used to detect as little as 0.33 μM (38.3 ppb) of ADA by naked eye observation and 0.23 μM (26.7 ppb) of ADA by spectrophotometry within 2 h. The method was successfully used to detect ADA in flour with a recovery of 91–104% and a relative standard deviation (RSD) < 6%. The visual detection limit of sensor is lower than the ADA limitation in flour (45 mg/kg), which makes the sensor a potential approach for the instrument-free visual and on-site detection of ADA in flour

Aggregation-Induced Emission Fluorophore-Incorporated Curcumin-Based Ratiometric Nanoprobe for Hypochlorite Detection in Food Matrices

The development of efficient, economic, reliable, and accurate monitoring of hypochlorite (ClO–) in food matrices is in great demand for food safety assessment, particularly during its massive use against the COVID-19 epidemic. Here, we prepared an aggregation-induced emission (AIE) fluorophore tetraphenylethylene (TPE)-incorporated curcumin-based hybrid ratiometric fluorescence nanoprobe (Curcumin/TPE@HyNPs) through amphiphilic phospholipid polymer-powered nanoprecipitation, which exhibited a fast, highly sensitive, and selective response to the residual ClO– in real food matrices. Because of the inner filter effect (IFE) from curcumin toward TPE inside the nanoprobe, the bright fluorescence of TPE aggregation at ∼437 nm was effectively quenched, along with an enhanced fluorescence of curcumin at ∼478 nm. Once there was a ClO– residue in food matrices, ClO– triggered the oxidation of o-methoxyphenol inside curcumin and led to the almost complete absorption collapse, thereby terminating curcumin fluorescence at ∼478 nm and the IFE process. Accordingly, the fluorescence of TPE at ∼437 nm was recovered. In this case, a ratiometric fluorescent response of Curcumin/TPE@HyNPs toward the residual ClO– in food matrices (e.g., milk) was proposed with a low detection limit of 0.353 μM and a rapid response time of 140.0 s. Notably, the phospholipid polymer as the protection layer effectively reduced/evaded the nonspecific binding of signal reporters inside the nanoprobe, facilitating it to directly monitor the residual ClO– in real food matrices. This work provided a novel approach to utilize the unconventional AIE luminophors for constructing the efficient and reliable early warning mechanisms toward various food contaminants

Enhanced Sensitivity and Effective Cleanup Strategy for Analysis of Neonicotinoids in Complex Dietary Samples and the Application in the Total Diet Study

Extensive residues of neonicotinoids (neonics) have been demonstrated in food and the environment by routine monitoring measurement, but little is known about the residue levels in “ready to eat” dietary samples. To obtain a more accurate picture of dietary exposure to total neonics, an ultrasensitive and effective cleanup analytical method for the quantification of neonics in dietary samples was established on the basis of cold-induced phase separation and pre-column dilution injection liquid chromatography–high-resolution mass spectrometry. A total of 10 neonics were quantified in ultratrace amounts (ng/kg) using stable isotope dilution, with calibration curves spanning 4 orders of magnitude. Satisfactory accuracy (73.5–109.2% for the recoveries) and precision (0.6–13.2% for the relative standard deviation ranges) were obtained in method validation. Moreover, tolerable absolute matrix effects (0.89–1.09) were also obtained in 12 kinds of dietary matrices with weak relative matrix effects (2.8–12.6%). The validated method was applied to the dietary samples collected from the Chinese Total Diet Study, and the results showed that 75% of the samples were contaminated with at least one neonicotinoid

Dual-Loading of Fe₃O₄ and Pd Nanoparticles on g‑C₃N₄ Nanosheets Toward a Magnetic Nanoplatform with Enhanced Peroxidase-like Activity for Loading Various Enzymes for Visual Detection of Small Molecules

Enzyme mimics now play a significant role in biochemistry. Especially, peroxidase mimics have been widely used for developing colorimetric sensors of blood glucose. The peroxidase mimics previously reported could not be recycled for reusing and may generate scattering to cause unwanted optical interference when it was used for fabricating colorimetric sensors. We herein prepared a broad-applicable and reusable magnetic enzyme-loading nanoplatform with enhanced peroxidase-like activity by simultaneously loading Fe3O4 nanoparticles (Fe3O4NPs) and palladium nanoparticles (PdNPs) on graphitic carbon nitride (g-C3N4) nanosheets (Fe3O4NPs/PdNPs/g-C3N4). The prepared Fe3O4NPs/PdNPs/g-C3N4 possesses stable and enhanced peroxidase-like activity and good enzyme-loading capacity and can be used to load various natural enzymes to form highly-efficient and stable double-active nanozyme for fabricating colorimetric sensors for the visual detection of small molecules. Especially, the magnetic feature facilitates the magnetic separation of Fe3O4NPs/PdNPs/g-C3N4 from sample solution, which is in favor of recycling and eliminating the optical interference caused by nanozyme in colorimetric sensors. The prepared Fe3O4NPs/PdNPs/g-C3N4 has been successfully used to load glucose oxidase (GOx) and cholesterol oxidase (Chox) to form magnetic peroxidase-GOx and peroxidase-Chox double-active nanozymes, which can be used to fabricate colorimetric methods for the detection of glucose and cholesterol, respectively, with a visual detection limit of 15 μM and a spectrometry detection limit of 1.0 μM. With the developed glucose and cholesterol detection methods, we have successfully detected glucose and cholesterol in serum with a recovery of 98–104% and a RSD (n = 5) < 5%. With high peroxidase-like activity, good stability, reusable features, and broad applicability of loading enzyme, the developed magnetic Fe3O4NPs/PdNPs/g-C3N4 provided a promising approach for fabricating cost-effective, sensitive, and simple colorimetric sensors for the visual detection of various small molecules

Occurrence of Chloramphenicol-Resistance Genes as Environmental Pollutants from Swine Feedlots

Chloramphenicol-resistance genes could be propagated to the surrounding environment via agricultural application of swine waste. This study investigated the potential risks of chloramphenicol-resistance genes from swine feedlots and their surrounding environment. We applied a culture-independent method to investigate levels of chloramphenicol-resistance genes in the wastewater from swine feedlots and the correspondingly impacted agricultural fields in Beijing. The <i>cml</i>A, <i>flo</i>R, <i>fex</i>A, <i>cfr</i>, and <i>fex</i>B genes were present in all samples, with the highest absolute concentrations of 1.50 × 10⁶ copies/g in soil and 6.69 × 10⁶ copies/mL in wastewater. The concentration of chloramphenicol residue was determined by ultra performance liquid chromatography-electrospray tandem mass spectrometry (UPLC-MS/MS), with the highest concentrations of 0.83 ng/g in soil and 11.5 ng/mL in wastewater. Significant correlations were found between chloramphenicol-resistance genes and chloramphenicol residues (<i>r</i> = 0.79, <i>p</i> = 0.0008) as well as between chloramphenicol-resistance genes in swine feedlots and corresponding agricultural soils (<i>r</i> = 0.84, <i>p</i> = 0.02). Consequently, swine feedlot wastewater could become a source of chloramphenicol-resistance genes, which could then lead to the spread of antibiotic resistance and eventually pose a risk to public health. To our knowledge, this is the first study to examine the occurrence of <i>flo</i>R, <i>fex</i>A, <i>cfr</i>, and <i>fex</i>B genes in the environment using a culture-independent method