Rapid and simultaneous determination of ultrashort-, short- and long- chain perfluoroalkyl substances by a novel liquid chromatography mass spectrometry method.

Per- and Polyfluoroalkyl Substances (PFAS) are a group of persistent organic pollutants that have received considerable attention from public and regulatory groups. Due to regulations of long-chain PFAS, the use of short-chain and ultrashort-chain PFAS is rapidly growing. Thus, there is an urgent need to develop quantitative methods for determining PFAS with different chain lengths in various environmental matrices. This study introduces an innovative liquid chromatography-mass spectrometry (LC-MS) system combining large volume injection (LVI) and online solid phase extraction (SPE). This system incorporates three columns: a reverse-phase (RP) column, a weak anion exchange (WAX) trap column, and a hybrid HILIC/ion-exchange (HILIC/IE) column, controlled by two valves. With valve switching, ultrashort-chain PFAS that are not retained by the RP column are enriched by the trap column, while other PFAS are separated by the RP column. The trapped ultrashort PFAS are then transferred to the HILIC/IE column for further separation. The LVI significantly enhances the method's sensitivity, allowing for rapid and simultaneous determination of ultrashort-, short- and long- chain PFAS in aqueous samples. The matrix effects from various environmental samples were evaluated, and the results indicate that this unique LC-MS method is suitable for analyzing all chain-length PFAS in various matrices, including surface water, sewage effluent, and seawater. Finally, this novel LC-MS method was applied to quantify PFAS in various water samples.

Comprehensive analysis of cyanobacterial secondary metabolites distribution and toxicity in urban water bodies.

This study addresses the increasing concern regarding cyanotoxin contamination of water bodies, highlighting the diversity of these toxins and their potential health implications. Cyanobacteria, which are prevalent in aquatic environments, produce toxic metabolites, raising concerns regarding human exposure and associated health risks, including a potential increase in cancer risk. Although existing research has primarily focused on well-known cyanotoxins, recent technological advancements have revealed numerous unknown cyanotoxins, necessitating a comprehensive assessment of multiple toxin categories. To enhance the cyanotoxin databases, we optimized the CyanoMetDB cyanobacterial secondary metabolites database by incorporating secondary fragmentation patterns using the Mass Frontier fragmentation data prediction software. Water samples from diverse locations in Shanghai were analyzed using high-resolution mass spectrometry. Subsequently, the toxicity of cyanobacterial metabolites in the water samples was examined through acute toxicity assays using the crustacean Thamnocephalus platyurus. After 24 h of exposure, the semi-lethal concentrations (LC50) of the water samples ranged from 0.31 mg L-1 to 1.78 mg L-1 (MC-LR equivalent concentration). Our findings revealed a critical correlation between the overall concentration of cyanobacterial metabolites and toxicity. The robust framework and insights of this study underscore the need for an inclusive approach to water quality management, emphasizing continuous efforts to refine detection methods and comprehend the broader ecological impact of cyanobacterial blooms on aquatic ecosystems.

Development of a Five-Chemical-Probe Method to Determine Multiple Radicals Simultaneously in Hydroxyl and Sulfate Radical-Mediated Advanced Oxidation Processes.

Advanced oxidation processes (AOPs), such as hydroxyl radical (HO•)- and sulfate radical (SO4•-)-mediated oxidation, are attractive technologies used in water and wastewater treatments. To evaluate the treatment efficiencies of AOPs, monitoring the primary radicals (HO• and SO4•-) as well as the secondary radicals generated from the reaction of HO•/SO4•- with water matrices is necessary. Therefore, we developed a novel chemical probe method to examine five key radicals simultaneously, including HO•, SO4•-, Cl•, Cl2•-, and CO3•-. Five probes, including nitrobenzene, para-chlorobenzoic acid, benzoic acid, 2,4,6-trimethylbenzoic acid, and 2,4,6-trimethylphenol, were selected in this study. Their bimolecular reaction rate constants with diverse radicals were first calibrated under the same conditions to minimize systematic errors. Three typical AOPs (UV/H2O2, UV/S2O82-, and UV/HSO5-) were tested to obtain the radical steady-state concentrations. The effects of dissolved organic matter, Br-, and the probe concentration were inspected. Our results suggest that the five-probe method can accurately measure radicals in the HO•- and SO4•--mediated AOPs when the concentration of Br- and DOM are less than 4.0 µM and 15 mgC L-1, respectively. Overall, the five-probe method is a practical and easily accessible method to determine multiple radicals simultaneously.

Mechanistic and Kinetic Consideration of the Photochemically Generated Oxidative Organic Radicals in Dissolved Black Carbon Solutions under Simulated Solar Irradiation.

The photochemically generated oxidative organic radicals (POORs) in dissolved black carbon (DBC) was investigated and compared with that in dissolved organic matter (DOM). POORs generated in DBC solutions exhibited higher one-electron reduction potential values (1.38-1.56 V) than those in DOM solutions (1.22-1.38 V). We found that the photogeneration of POORs from DBC is enhanced with dissolved oxygen (DO) increasing, while the inhibition of POORs is observed in reference to DOM solution. The behavior of the one-electron reducing species (DBC•-/DOM•-) was employed to explain this phenomenon. The experimental results revealed that the DO concentration had a greater effect on DBC•- than on DOM•-. Low DO levels led to a substantial increase in the steady-state concentration of DBC•-, which quenched the POORs via back-electron reactions. Moreover, the contribution of POORs to the degradation of 19 emerging organic contaminants (EOCs) in sunlight-exposed DBC and DOM solutions was estimated. The findings indicate that POORs play an important role in the photodegradation of EOCs previously known to react with triplets, especially in DBC solutions. Compared to DOM solutions, POOR exhibits a lower but considerable contribution to EOC attenuation. This study enhances the understanding of pollutant fate in aquatic environments by highlighting the role of DBC in photochemical pollutant degradation and providing insights into pollutant transformation mechanisms involving POORs.

Quantification of aflatoxin B1 in vegetable oils using low temperature clean-up followed by immuno-magnetic solid phase extraction.

In the present study, a convenient and highly efficient method was developed to quantify aflatoxin B1 (AFB1) in oil samples. Low temperature clean-up (LTC) followed by immuno magnetic solid phase extraction (IMSPE) was used to clean up oil samples. LTC assisted in freezing out the interference from the oil matrix while IMSPE further helped to preconcentrate the targeted analyte. For IMSPE, we synthesised and characterised anti-AFB1 monoclonal antibody-functionalised magnetic nanoparticles. Oil sample extraction was then carried out using LTC-IMSPE. The proposed method showed satisfactory efficiency and reproducibility with recovery rates being within the range of 79.6-117.9%, with a relative standard deviation below 11.48%. The sensitivity of the method was satisfactory with the limits of detection and quantification being as low as 0.0048 and 0.0126 ng·g-1, respectively. Real sample analysis was carried out for five kinds of different vegetable oils. The results suggest that the method developed is very sensitive and accurate.