Core-shell structured magnetic covalent organic frameworks for magnetic solid-phase extraction of diphenylamine and its analogs.

Core-shell structured magnetic covalent organic frameworks (Fe3O4@COFs) were synthesized via a facile approach at room temperature using 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 2,5-dibromo-1,4-benzenedicarboxaldehyde (DBDA) as two building blocks for the first time. The Fe3O4@COFs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), nitrogen adsorption-desorption isotherms, and zeta potentiometric analysis. The Fe3O4@COFs had a high specific surface area (141.94 m2·g-1) and uniform pore size distribution (average 4.53 nm). They also demonstrated good magnetic response (32.49 emu·g-1) and good thermal and chemical stabilities. Furthermore, adsorption experiments were conducted to evaluate the adsorption capacities and adsorption times of Fe3O4@COFs to diphenylamine (DPA) and its analogs, including benzidine (BZ), 1-naphthylamine (1-NA), 4-phenylphenol (4-PP), and O-tolidine (O-TD). From the experimental results, the maximum adsorption capacities of DPA, 1-NA, 4-PP, BZ, and O-TD were calculated as 246.25, 95.20, 85.85, 107.20, and 123.55 mg·g-1, respectively. A duration of 20 min was sufficient for adsorption. The Fe3O4@COFs were explored as adsorbents for magnetic solid-phase extraction (MSPE) of DPA and its analogs, and the MSPE parameters, including adsorbent dosage, extraction time, pH, ionic strength, desorption solvent, desorption time, and desorption frequency were optimized. Combined with HPLC using diode-array detection, a simple, fast, and sensitive method was proposed to detect DPA and its analogs, which exhibited good linearity (r >0.9946) in the range of 0.1-100 µg·mL-1. Moreover, the low limits of detection (ranging from 0.02 to 0.08 µg·mL-1, S/N = 3), low limits of quantitation (ranging from 0.05 to 0.30 µg·mL-1, S/N = 10), good precision with low relative SDs (<5.86% for intra-day and <6.44% for inter-day) were obtained. Finally, Fe3O4@COFs were applied to the effective MSPE of DPA and its analogs in actual samples chosen from the natural environment, and good recoveries (ranging from 79.97 to 122.52%) were observed.

Determination of Diphenylamine in Agricultural Products by HPLC-FL.

A method for the determination of diphenylamine in agricultural products was developed. Diphenylamine was extracted with acetonitrile from a sample under an acidic condition, passed through a C18 cartridge column, re-extracted with n-hexane, cleaned up on a PSA cartridge column, determined by HPLC with fluorescence detector and confirmed by liquid chromatography with tandem mass spectrometry. Average recoveries (n=5) from brown rice, corn, soybeans, potato, cabbage, eggplant, spinach, orange, apple and green tea were in the range from 76.7 to 94.9%, and the relative standard deviations were from 0.6 to 5.8% at concentrations equal to the maximum residue limits (MRLs). The quantification limits were 0.01 mg/kg, which is the uniform limit in the positive list system for agricultural chemical residues in food in Japan.

Dynamic planar solid phase microextraction-ion mobility spectrometry for rapid field air sampling and analysis of illicit drugs and explosives.

A preconcentration device that targets the volatile chemical signatures associated with illicit drugs and explosives (high and low) has been designed to fit in the inlet of an ion mobility spectrometer (IMS). This is the first reporting of a fast and sensitive method for dynamic sampling of large volumes of air using planar solid phase microextraction (PSPME) incorporating a high surface area for absorption of analytes onto a sol-gel polydimethylsiloxane (PDMS) coating for direct thermal desorption into an IMS. This device affords high extraction efficiencies due to strong retention properties at ambient temperature, resulting in the detection of analyte concentrations in the parts per trillion range when as low as 3.5 L of air are sampled over the course of 10 s (absolute mass detection of less than a nanogram). Dynamic PSPME was used to sample the headspace over the following: 3,4-methylenedioxymethamphetamine (MDMA) tablets resulting in the detection of 12-40 ng of piperonal, high explosives (Pentolite) resulting in the detection of 0.6 ng of 2,4,6-trinitrotoluene (TNT), and low explosives (several smokeless powders) resulting in the detection of 26-35 ng of 2,4-dinitrotoluene (2,4-DNT) and 11-74 ng of diphenylamine (DPA).

Nakijiquinones E and F, new dimeric sesquiterpenoid quinones from marine sponge.

Two new dimeric sesquiterpenoid quinones, nakijiquinones E (1) and F (2), have been isolated from an Okinawan marine sponge, and the structures and relative stereochemistry of 1 and 2 were elucidated on the basis of the spectral data. Nakijiquinones E (1) and F (2) were the first dimeric sesquiterpenoid quinones possessing a 3-aminobenzoate moiety.

Laccase-catalyzed removal of diphenylamine from synthetic wastewater.

The priority pollutant lists of both the U.S. Environmental Protection Agency (U.S. EPA) and the European Union (EU) include diphenylamine (DPA), a contaminant found in wastewater of various industries. This work demonstrates the potential of using enzymatic treatment to remove DPA from buffered synthetic wastewater. This treatment method includes oxidative polymerization of DPA using laccase from Trametes villosa, followed by removal of those polymers via adsorptive micellar flocculation (AMF) using sodium lauryl sulfate (SDS) and alum. Researchers investigated the effects of pH, laccase concentration, molecular mass, and concentration of polyethylene glycol (PEG) in continuously stirred batch reactors to achieve 95% substrate conversion in three hours. Treatment of 0.19 mM DPA was best at pH 7 and an enzyme concentration from 0.0025 to 0.0075 standard activity unit/mL. Except for PEG400 optimum enzyme and PEG concentrations decreased with an increase in PEG molecular mass. Optimum AMF conditions were pH 3.0 to 6.5, 200 mg/L of SDS, and 150 mg/L of alum.

Enzymatic treatment of sulfonated aromatic amines generated from reductive degradation of reactive azo dyes.

Anaerobic degradation, an effective treatment process of textile industry effluent, generates sulfonated aromatic amines, which are carcinogenic, mutagenic, and resistant to microbial degradation. These aromatic amines can be effectively removed by oxidative polymerization catalyzed by peroxidase enzyme. The amines, generated in this study from the anaerobic reduction by zero-valent iron of two reactive azo dyes (Reactive Red 2 [RR2] and Reactive Black 5 [RB5]), were successfully removed (90%) by Arthromyces ramosus peroxidase (ARP). For better understanding of the process, enzymatic treatment of two model compounds, diphenylamine (DPA) and 2-amino-8-naphthol-3,6-disulfonic acid (ANDSA), were also studied. Diphenylamine has a similar diarylamine bond as RR2. The ANDSA has a similar structure as the dye reduction products. The secondary amine bond in DPA and RR2 were oxidized by ARP. Enzymatic reaction of sulfonated aromatic amines generated soluble colored compounds, which were removed by coagulant. Optimum reaction parameters were also determined.

Adsorption behaviour of some aromatic amines on pyrolusite and activated carbon and recovery of beta napthylamine from water sample.

The adsorption behaviour of Diphenylamine (DPAM), beta napthylamine (beta NAM), alpha napthylamine (alpha NAM) and aniline on pyrolusite and activated carbon has been studied. Pyrolusite shows remarkable sorption capacity for DPAM and beta NAM as compared to aniline; (the adsorption followed the order: Activated Carbon:--> DPAM = beta NAM > alpha Aniline; Pyrolusite: DPAM: --> beta NAM > alpha NAM > Aniline) The maximum adsorption of beta NAM occurred in the concentration range 4-20 microg mL(-1) on pyrolusite (95%) and 4-50 microg mL(-1) on activated carbon (100%). The effect of various doses of activated carbon on the adsorption of beta NAM confirm Langmuir and Freundlich isotherms where as Freundlich isotherm is obeyed by pyrolusite. The adsorption of beta NAM on both the absorbents is not affected in presence of DPAM over a wide range of their initial concentrations (20-60 microg mL(-1)). The desorption studies of beta NAM on pyrolusite was carried out by batch as well as column processes. Excellent results were obtained when a mixture of n-hexane and isopropanol (91:1) was used as eluent.

Diphenylamine, an antihyperglycemic agent from onion and tea.

Diphenylamine has been isolated as one of the active antihyperglycemic agents of onion. It was identified by ir, uv, cmr, pmr, and mass spectra. It attained the highest percentage in mature onion bulbs; other onion organs contained diphenylamine in lower percentages. Green and black teas were found to contain relatively high percentages of diphenylamine, being higher in the former. Cooking was found to decrease the diphenylamine content.