Photoinduced evolution of optical properties and compositions of methoxyphenols by Fe(III)-carboxylates complexes in atmospheric aqueous phase

The changes in optical properties and chemical compositions of methoxyphenols, which acted as an important aromatic compound from the biomass burning, were investigated in the presence of Fe(III)-carboxylates under aqueous phase conditions. The light was confirmed to be a key factor for stimulating the reaction of methoxyphenols and Fe(III)-carboxylates. The photoinduced evolution of optical properties of methoxyphenols was dependent on various factors, including irradiation intensity, types of carboxylates, dissolved oxygen and pH. The changes in the mass absorption efficiency at 306 nm (MAE₃₀₆) positively relied on irradiation intensity and dissolved oxygen. The acceleration effects of carboxylates on the decreases in MAE₃₀₆ of methoxyphenols followed the order of oxalate > citrate > malonate. The change amplitude of MAE₃₀₆ decreased with an increasing pH (3.5-9), while that of the mass absorption efficiency at 364 nm (MAE₃₆₄) increased with pH ranging from 3.5 to 7. The compositional evolutions of methoxyphenols by the photochemical aging were analyzed with the attenuated total reflection infrared spectroscopy (ATR-IR), confirming the decrease of CO groups and the increase of O-H and C-O groups. The photochemical reaction pathways of methoxyphenols with Fe(III)-carboxylates were proposed according to optical properties and compositions measurements.

Ready Biodegradability Ring Testing of 4-Isopropylphenol in Different Laboratories for Critical Evaluation of a Biodegradable Reference Substance

Ready biodegradability is a key property for studying the environmental and ecological risks posed by chemicals, and a reference substance is used to check the reliability of the test results. Traditional reference substances such as aniline, sodium benzoate, and ammonium acetate rapidly degrade even in test systems without inoculum. In this study, 4-isopropylphenol was investigated as a reference candidate. Aerobic biodegradation of 4-isopropylphenol was studied using different methods, and repeatability tests were performed in multiple laboratories. 4-Isopropylphenol met the ready biodegradability passing level in a closed bottle test (OECD 301D) and manometric respirometry test (OECD 301F). No obvious toxicity was found in activated sludge respiration inhibition and biodegradable toxicity control tests. The results of 301F tests performed in 15 Chinese laboratories were compared using statistical robustness analyses and Z-scores. The robust average 28-d biodegradability rate for 4-isopropylphenol was 80.3%, and the relative standard deviation was 9.20%. The data from the 15 laboratories consistently indicated that 4-isopropylphenol was readily biodegradable, except for an "unsatisfactory" outlier result from 1 laboratory. The degradation kinetics of 4-isopropylphenol were derived from a logistic model, which had a good fit for the degradation curve. The biodegradation lag phase was 2.3 d (range 2-5 d), and the pass level was attained at 6.5 d on average (range 2-9 d), which met the 10-d window requirement. The biodegradation rate at 28 d was 75.3% (range 64.0%-95.1%). The ready biodegradability of 4-isopropylphenol indicates that it will be more appropriate as a reference chemical than other reference compounds used for investigating the biodegradability of chemicals. Integr Environ Assess Manag 2021;17:562-572. © 2020 SETAC.

Ion-Trap Mass Spectrometric Analysis of Bisphenol A Interactions With Titanium Dioxide Nanoparticles and Milk Proteins

Quantitative analysis of endocrine-disrupting molecules such as bisphenol A (BPA) in freshwater to determine their widespread occurrence in environmental resources has been challenged by various adsorption and desorption processes. In this work, ion trap mass spectrometry (ITMS) analysis of BPA was aimed at studying its molecular interactions with titanium dioxide (TiO2) nanoparticles and milk whey proteins. Addition of sodium formate prevented TiO2 nanoparticles from sedimentation while enhancing the electrospray ionization (ESI) efficiency to produce an abundance of [BPA + Na]+ ions at m/z 251.0. More importantly, the ESI-ITMS instrument could operate properly during a direct infusion of nanoparticles up to 500 μg/mL without clogging the intake capillary. Milk protein adsorption of BPA could decrease the [BPA + Na]+ peak intensity significantly unless the proteins were partially removed by curdling to produce whey, which allowed BPA desorption during ESI for quantitative analysis by ITMS.