Micron-size tire tread particles leach organic compounds at higher rates than centimeter-size particles: Compound identification and profile comparison.

Tire tread particles (TTP) are environmentally prevalent microplastics and generate toxic aqueous leachate. We determined the total carbon and nitrogen leachate concentrations and chemical profiles from micron (∼32 µm) and centimeter (∼1 cm) TTP leachate over 12 days. Dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were used to measure the concentration of leached compounds. Nontargeted chemical analysis by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/TOF-MS) was used to compare the chemical profiles of leachates. After leaching for 12 days, DOC was 4.0 times higher in the micron TTP leachate than in the centimeter TTP leachate, and TDN was 2.6 times higher. The total GC×GC/TOF-MS chromatographic feature peak area was 2.9 times greater in the micron TTP leachate than the centimeter TTP leachate, and similarly, the total relative abundance of 54 tentatively identified compounds was 3.3 times greater. We identified frequently measured tire-related chemicals, such as 6PPD, N-cyclohexyl-N'-phenylurea (CPU), and hexa(methoxymethyl)melamine (HMMM), but nearly 50% of detected chemicals were not previously reported in tire literature or lacked toxicity information. Overall, the results demonstrate that smaller TTP have a greater potential to leach chemicals into aquatic systems, but a significant portion of these chemicals are not well-studied and require further risk assessment.

Screening p-Phenylenediamine Antioxidants, Their Transformation Products, and Industrial Chemical Additives in Crumb Rubber and Elastomeric Consumer Products.

Recently, roadway releases of N,N'-substituted p-phenylenediamine (PPD) antioxidants and their transformation products (TPs) received significant attention due to the highly toxic 6PPD-quinone. However, the occurrence of PPDs and TPs in recycled tire rubber products remains uncharacterized. Here, we analyzed tire wear particles (TWPs), recycled rubber doormats, and turf-field crumb rubbers for seven PPD antioxidants, five PPD-quinones (PPDQs), and five other 6PPD TPs using liquid chromatography-tandem mass spectrometry. PPD antioxidants, PPDQs, and other TPs were present in all samples with chemical profiles dominated by 6PPD, DTPD, DPPD, and their corresponding PPDQs. Interestingly, the individual [PPDQ]/[PPD] and [TP]/[PPD] ratios significantly increased as total concentrations of the PPD-derived chemical decreased, indicating that TPs (including PPDQs) dominated the PPD-derived compounds with increased environmental weathering. Furthermore, we quantified 15 other industrial rubber additives (including bonding agents, vulcanization accelerators, benzotriazole and benzothiazole derivatives, and diphenylamine antioxidants), observing that PPD-derived chemical concentrations were 0.5-6 times higher than these often-studied additives. We also screened various other elastomeric consumer products, consistently detecting PPD-derived compounds in lab stoppers, sneaker soles, and rubber garden hose samples. These data emphasize that PPD antioxidants, PPDQs, and related TPs are important, previously overlooked contaminant classes in tire rubbers and elastomeric consumer products.

An ultrasensitive molecularly-imprinted human cardiac troponin sensor.

Cardiac troponin T (TnT) is a highly sensitive cardiac biomarker for myocardial infarction. In this study, the fabrication and characterisation of a novel sensor for human TnT based on a molecularly-imprinted electrosynthesised polymer is reported. A TnT sensitive layer was prepared by electropolymerisation of o-phenylenediamine (o-PD) on a gold electrode in the presence of TnT as a template. To develop the molecularly imprinted polymer (MIP), the template molecules were removed from the modified electrode surface by washing with alkaline ethanol. Electrochemical methods were used to monitor the processes of electropolymerisation, template removal and binding. The imprinted layer was characterised by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). The incubation of the MIP-modified electrode with respect to TnT concentration resulted in a suppression of the ferro/ferricyanide redox process. Experimental conditions were optimised and a linear relationship was observed between the peak current of [Fe(CN)6](3-)/[Fe(CN)6](4-) and the concentration of TnT in buffer over the range 0.009-0.8 ng/mL, with a detection limit of 9 pg/mL. The TnT MIP sensor was shown to have a high affinity to TnT in comparison with non-imprinted polymer (NIP) electrodes in both buffer and blood serum.

Schedules of controlled substances: placement of ezogabine into Schedule V. Final rule.

With the issuance of this final rule, the Administrator of the Drug Enforcement Administration (DEA) places the substance ezogabine, including its salts, isomers, and salts of isomers whenever the existence of such salts, isomers, and salts of isomers is possible, into Schedule V of the Controlled Substances Act (CSA). This action is pursuant to the CSA which requires that such actions be made on the record after opportunity for a hearing through formal rulemaking.

Different results of the Salmonella umu test between three isomers of phenylenediamine (PDA) derivatives.

A post-treatment assay of the umu test was performed to detect genotoxicity of 10 phenylenediamine (PDA) derivatives using Salmonella typhimurium TA1535/pSK1002 with/without S9 mix. Seven chemicals (o-PDA, 4-chloro-o-PDA, 4-nitro-o-PDA, p-PDA, 2-chloro-p-PDA, 2-nitro-p-PDA, and 2,5-diaminotoluene) showed positive results with S9 mix, but three chemicals (m-PDA, 4-chloro-m-PDA, and 2,4-diaminotoluene) were negative with and without S9 mix. Four of 7 chemicals (o-PDA, 4-chloro-o-PDA, 4-nitro-o-PDA, and 2-nitro-p-PDA) that gave positive results with S9 mix were also positive without S9 mix. These results indicate that the genotoxicity of PDA derivative possessing m-position amino substituents was not detected in the umu post-treatment assay using TA1535/pSK1002.

Elucidation of the structures of 3-alkylthio-, 3-benzylthio-, 2-arylthio- and 2-heteroarylthio-N1-(1,3-dimethylbutyl)-N4-phenyl-1,4-phenylenediamines by one- and two-dimensional NMR spectroscopy.

Nucleophilic addition of alkyl- and benzylthiols to benzoquinone diimine (1) gave the corresponding 3-alkylthio- or 3-benzylthio-1,4-phenylenediamines (2-5). However, addition of aryl- or heteroarylthiols to 1 formed 2-arylthio- or 2-heteroarylthio-1,4-phenylenediamines (6-14). The structures of 2-14, obtained in 55-91% yields, were confirmed in CDCl3 or DMSO-d6 solution using 1D (NOE difference, coupled 13C NMR spectra, APT and DEPT) and 2D NMR techniques [DQCOSY, NOESY, HETCOR and heteronuclear multiple bond coherence (HMBC)] that resulted in unambiguous proton and carbon NMR resonance assignments. The substituent-induced 13C NMR chemical shift differences were calculated in 2-14 relative to carbon atoms in the model compound N1-(1,3-dimethylbutyl)-N4-phenyl-1,4-phenylenediamine (DMBPPD) (15) (a reduced form of benzoquinone diimine).