Quantitative analysis of perfumes in talcum powder by using headspace sorptive extraction

Quantitative analysis of perfume dosage in talcum powder has been a challenge due to interference of the matrix and has so far not been widely reported. In this study, headspace sorptive extraction (HSSE) was validated as a solventless sample preparation method for the extraction and enrichment of perfume raw materials from talcum powder. Sample enrichment is performed on a thick film of poly(dimethylsiloxane) (PDMS) coated onto a magnetic stir bar incorporated in a glass jacket. Sampling is done by placing the PDMS stir bar in the headspace vial by using a holder. The stir bar is then thermally desorbed online with capillary gas chromatography-mass spectrometry. The HSSE method is based on the same principles as headspace solid-phase microextraction (HS-SPME). Nevertheless, a relatively larger amount of extracting phase is coated on the stir bar as compared to SPME. Sample amount and extraction time were optimized in this study. The method has shown good repeatability (with relative standard deviation no higher than 12.5%) and excellent linearity with correlation coefficients above 0.99 for all analytes. The method was also successfully applied in the quantitative analysis of talcum powder spiked with perfume at different dosages.     

Acoustic emission spectra and sonochemical activity in a 36 kHz sonoreactor

During ultrasound-induced cavitation in liquids, acoustic emissions at fundamental and harmonic frequencies can be detected. The effect of acoustic emissions at harmonic frequencies on the sonochemical and sonophysical activities has not been explored, especially in large-scale sonoreactors. In this study, the acoustic emissions in the range, 0-250 kHz in a 36 kHz sonoreactor with varying liquid heights were studied and compared with the sonochemical activities. The acoustic pressures at both fundamental and harmonics decreased drastically as the liquid height was increased due to the attenuation of sound energy. It was observed that the increase in input power resulted in only an increase in the acoustic emissions at derivative frequencies such as, harmonics and subharmonics. The sonochemical activity, evaluated in terms of sonochemiluminescence and H₂O₂ yield, was not significantly enhanced at higher input power levels. This suggests that at higher power levels, the “extra” acoustic energy is not effectively used to generate primary cavitation activity; rather it is converted to generate acoustic emissions at harmonic and subharmonic frequencies. This is an important observation for the design of energy efficiency large-scale sonochemical reactors.     

Cytotoxicity of Exfoliated Transition‐Metal Dichalcogenides (MoS2, WS2, and WSe2) is Lower Than That of Graphene and its Analogues

Studies involving transition‐metal dichalcogenides (TMDs) have been around for many decades and in recent years, many were focused on using TMDs to synthesize inorganic analogues of carbon nanotubes, fullerene, as well as graphene and its derivatives with the ultimate aim of employing these materials into consumer products. In view of this rising trend, we investigated the cytotoxicity of three common exfoliated TMDs (exTMDs), namely MoS₂, WS₂, and WSe₂, and compared their toxicological effects with graphene oxides and halogenated graphenes to find out whether these inorganic analogues of graphenes and derivatives would show improved biocompatibility. Based on the cell viability assessments using methylthiazolyldiphenyl‐tetrazolium bromide (MTT) and water‐soluble tetrazolium salt (WST‐8) assays on human lung carcinoma epithelial cells (A549) following a 24 h exposure to varying concentrations of the three exTMDs, it was concluded that MoS₂ and WS₂ nanosheets induced very low cytotoxicity to A549 cells, even at high concentrations. On the other hand, WSe₂ exhibited dose‐dependent toxicological effects on A549 cells, reducing cell viability to 31.8 % at the maximum concentration of 400 μg mL^?1; the higher cytotoxicity displayed by WSe₂ might be linked to the identity of the chalcogen. In comparison with graphene oxides and halogenated graphenes, MoS₂ and WS₂ were much less hazardous, whereas WSe₂ showed similar degree of cytotoxicity. Future in‐depth studies should be built upon this first work on the in vitro cytotoxicity of MoS₂ and WS₂ to ensure that they do not pose acute toxicity. Lastly, nanomaterial‐induced interference control experiments revealed that exTMDs were capable of reacting with MTT assay viability markers in the absence of cells, but not with WST‐8 assay. This suggests that the MTT assay is not suitable for measuring the cytotoxicity of exTMDs because inflated results will be obtained, giving false impressions that the materials are less toxic.     

Enhancement in mineralization of a number of natural refractory organic compounds by the combined process of sonolysis and ozonolysis (US/O3)

As an advanced oxidation process, the combination of sonolysis (US)/ozonolysis (O(3)) was investigated on the treatment of tannic acid (TA) and humic acid (HA). In this study, biodegradable chemicals were found by the molecular weight and GC-MS analysis method, and mineralization rate and synergetic effects were also studied. For the water samples prior to the treatment of US/O(3), ratios of molecular size higher than 5000 and 2000 Da for HA and TA, detected by the ultra filtration method, were 90.25% and 89.53%, respectively. However, after 0.5h of reacting, this ratio rapidly reduced to 3% and 4%, and the ratios of molecules for HA and TA less than 500 Da rapidly increased from 0.8% to 41% and from 0.65% to 39%, respectively. In the results of chemical oxygen demand (COD(Cr)) and total organic carbon (TOC) reductions, the US/O(3) process also showed synergetic effect by US/O(3) for COD(Cr) of HA and TA were 19% and 11%, and those for TOC of HA and TA were 0% and 1%, respectively. The major by-products of the oxidation process included formaldehyde, acetone, hydroxylamine, etc. Biological decomposable materials could be indirectly inferred by measuring the molecular weights and intermediates.     

A Simplified Model and Similarity Solutions for Interfacial Evolution of Two-Phase Flow in Porous Media

For two-phase flows of immiscible displacement processes in porous media, we proposed a simplified model to capture the interfacial fronts, which is given by explicit expressions and satisfies the continuity conditions of pressure and normal velocity across the interface. A new similarity solution for the interfacial evolution in the rectangular coordinate system was derived by postulating a first-order approximation of the velocity distribution in the region that the two-phase fluids co-exist. The interfacial evolution equation can be explicitly expressed as a linear function, where the slope of the interfacial equation is simply related to the mobility ratio of two-phase fluids in porous media. The application of the proposed solutions to predictions of interfacial evolutions in carbon dioxide injected into saline aquifers was illustrated under different mobility ratios and operational parameters. For the purpose of comparison, the numerical solutions obtained by level set method and the similarity solutions based on the Dupuit assumptions were presented. The results show that the proposed solution can give a better approximation of interfacial evolution than the currently available similarity solutions, especially in the situation that the mobility ratio is large. The proposed approximate solutions can provide physical insight into the interfacial phenomenon and be readily used for rapidly screening carbon dioxide storage capacity in subsurface formations and monitoring the migration of carbon dioxide plume.

     

Development of new cleanup method of polychlorinated dibenzo-p-dioxins/dibenzofurans in fish by freezing-lipid filtration

Freezing-lipid filtration as a new method has been developed for the rapid determination of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) in biological samples. This method can effectively reduce the time of sample pretreatment, labor and amount of solvents compared with conventional methods. By freezing-lipid filtration procedure, about 90% of lipids in extract could be removed without any significant loss of PCDD/Fs. For further cleanup of extracts after freezing-lipid filtration, automatic parallel LC columns including silica gel, alumina and carbon columns were applied. During automatic parallel LC columns cleanup, most of co-extracted interferences such as residue lipids and fatty acids could be eliminated and dioxins could be separated from many other dioxin-like congeners such as polychlorinated biphenyls by this procedure. The extracts after cleanup were analyzed by high-resolution gas chromatography (HRGC)/high-resolution mass spectrometry (HRMS) using an isotope dilution method. The average recoveries and relative standard deviation (R.S.D.) of 17 native congeners in the spiked fish samples at 8-80 pg/g (n = 3) were ranged between 85.3 and 117.2% and 5.7-20.3%, respectively.     

Synthesis and Photovoltaic Properties of a Thienylenevinylene and Diketopyrrolopyrrole Copolymer with High Mobility

A novel donor–acceptor‐type polymer with a low band‐gap that alternates electron‐rich thienylenevinylene groups with electron‐deficient diketopyrrolopyrrole (DPP) units (PETVTDPP) has been synthesized by Pd‐catalyzed Stille cross‐coupling polymerization. The polymer shows a broad absorption band of wavelengths that range from 330 to 900 nm, and a low band‐gap value of 1.43 eV. The field‐effect mobility of an organic thin‐film transistor based on this polymer is 0.05 cm² · Vs⁻¹. Bulk‐heterojunction solar cells using a mixture of PETVTDPP and PC_[71]BM for the active layer show a power conversion efficiency (PCE) of 1.94% under simulated AM 1.5 G solar irradiation at 100 mW · cm⁻².

     

Application of Box-Behnken design with response surface methodology for modeling and optimizing ultrasonic oxidation of arsenite with H2O2

A combined ultrasound (US)/H₂O₂ process was used to oxidize arsenite to arsenate, yielding a synergistic effect value of 1.26. This showed that the combined process could be an effective method of oxidizing arsenite, instead of using either ultrasonic or H₂O₂ oxidation processes. This combined process was successfully modeled and optimized using a Box-Behnken design with response surface methodology (RSM). The effects of the US power density, the initial concentration of arsenite, and the H₂O₂ concentration on the sonochemical oxidation efficiency of arsenite were investigated. Analysis of variance indicated that the proposed quadratic model successfully interpreted the experimental data with coefficients of determination of R ² = 0.95 and adjusted R ² = 0.91. Through this model, we can predict and control the oxidation efficiency under different conditions. Furthermore, the optimal conditions for the oxidation of arsenite were found to be a US power density of 233.26 W L^?1, an initial arsenite concentration of 0.5 mg L^?1, and an H₂O₂ concentration of 74.29 mg L^?1. The predicted oxidation efficiency obtained from the RSM under the optimal conditions was 88.95%. A confirmation test of the optimal conditions verified the validity of the model, yielding an oxidation efficiency of 90.1%.      

Thermoelectric effect in the Kondo dot side-coupled to a Majorana mode

We investigate the linear thermoelectric response of an interacting quantum dot side-coupled by one of two Majorana modes hosted by a topological superconducting wire. We employ the numerical renormalization group technique to obtain the thermoelectrical conductance L in the Kondo regime while the background temperature T, the Majorana-dot coupling Γ _m , and the overlap ε _m between the two Majorana modes are tuned. We distinguish two transport regimes in which L displays different features: the weak- (Γ _m <T _K ) and strong-coupling (Γ _m >T _K ) regimes, where T _K is the Kondo temperature. For an infinitely long nanowire where the Majorana modes do not overlap (ε _m = 0), the thermoelectrical conductance in the weak-coupling regime exhibits a peak at T ~ Γ _m <T _K . This peak is ascribed to the anti-Fano resonance between the asymmetric Kondo resonance and the zero-energy Majorana bound state. In the strong-coupling regime, on the other hand, the Kondo-induced peak in L is affected by the induced Zeeman splitting in the dot. For finite but small overlap (0 <ε _m <Γ _m ), the interference between the two Majorana modes restores the Kondo effect in a smaller energy scale Γ′ _m and gives rise to an additional peak in Γ ~ Γ′ _m, whose sign is opposite to that at T ~ Γ _m . In the strong-coupling regime this additional peak can cause a non-monotonic behavior of L with respect to the dot gate. Finally, in order to identify the fingerprint of Majorana physics, we compare the Majorana case with its counterpart in which the Majorana bound states are replaced by a (spin-polarized) ordinary bound state and find that the thermoelectric features for finite ε _m are the genuine effect of the Majorana physics.