Insights on the Working Principles of Secondary Electrospray Ionization High-Resolution Mass Spectrometry for Quantitative Analysis of Aerosol Chemical Composition

Real-time mass spectrometry (MS) has attracted increasing interest in environmental analysis due to its advantages in high time resolution, minimization of sampling artifact, and avoidance of time-consuming sample pretreatment. Among real-time MS methods, secondary electrospray ionization MS (SESI-MS) is showing great promise for the detection of organic compounds in atmospheric particulate matter. In this study, we demonstrated the working principles of secondary nanoelectrospray ionization (Sec-nESI) for real-time measurement of laboratory-generated organic aerosols using l-tartaric acid (TA) as a model compound. Factors affecting the detection of TA particles using a homemade Sec-nESI source coupled with a high-resolution mass spectrometer are systematically investigated. Temperature of ion transport capillary (ITC) was found to be the key factor in determining the ion signal intensity, which shows an increase of intensity by a factor of 100 from ITC temperature of 100–300 °C and could be attributed to more efficient desolvation and ionization. The characteristic fragment ion at m/z 72.99 was selected for quantitative analysis of TA at normalized collision energy of 50%, the optimal value applied during MS/MS analysis. Detection limit of 0.14 µg/m3 and a linear range of 0.2–2.97 µg/m3 are achieved. Satisfactory correlations between ion signal intensity and particle surface area (R2 = 0.969) and mass concentration (R2 = 0.967) were obtained. Although an equally good correlation was observed between signal intensity and particle surface area, the good correlation between signal intensity and particle mass concentration indicates that high solubility of TA ensures efficient dissolution of TA in the primary ESI droplets for further ionization.

Glycine–Nitrate Combustion Synthesis of Cu-Based Nanoparticles for NP9EO Degradation Applications

Copper-based nanoparticles were synthesized using the glycine–nitrate process (GNP) by using copper nitrate trihydrate [Cu(NO3)2·3H2O] as the main starting material, and glycine [C2H5NO2] as the complexing and incendiary agent. The as-prepared powders were characterized through X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy analysis. Using Cu(NO3)2·3H2O as the oxidizer (N) and glycine as fuel (G), we obtained CuO, mixed-valence copper oxides (CuO + Cu2O, G/N = 0.3–0.5), and metallic Cu (G/N = 0.7). The XRD and BET results indicated that increasing the glycine concentration (G/N = 0.7) and reducing the particle surface area increased the yield of metallic Cu. The effects of varying reaction parameters, such as catalyst activity, catalyst dosage, and H2O2 concentration on nonylphenol-9-polyethoxylate (NP9EO) degradation, were assessed. With a copper-based catalyst in a heterogeneous system, the NP9EO and total organic carbon removal efficiencies were 83.1% and 70.6%, respectively, under optimum operating conditions (pH, 6.0; catalyst dosage, 0.3 g/L; H2O2 concentration, 0.05 mM). The results suggest that the removal efficiency increased with an increase in H2O2 concentration but decreased when the H2O2 concentration exceeded 0.05 mM. Furthermore, the trend of photocatalytic activity was as follows: G/N = 0.5 > G/N = 0.7 > G/N = 0.3. The G/N = 0.5 catalysts showed the highest photocatalytic activity and resulted in 94.6% NP9EO degradation in 600 min.

Exposure to Submicron Particles and Estimation of the Dose Received by Children in School and Non-School Environments

In the present study, the daily dose in terms of submicron particle surface area received by children attending schools located in three different areas (rural, suburban, and urban), characterized by different outdoor concentrations, was evaluated. For this purpose, the exposure to submicron particle concentration levels of the children were measured through a direct exposure assessment approach. In particular, measurements of particle number and lung-deposited surface area concentrations at “personal scale” of 60 children were performed through a handheld particle counter to obtain exposure data in the different microenvironments they resided. Such data were combined with the time–activity pattern data, characteristics of each child, and inhalation rates (related to the activity performed) to obtain the total daily dose in terms of particle surface area. The highest daily dose was estimated for children attending the schools located in the urban and suburban areas (>1000 mm2), whereas the lowest value was estimated for children attending the school located in a rural area (646 mm2). Non-school indoor environments were recognized as the most influential in terms of children’s exposure and, thus, of received dose (>70%), whereas school environments contribute not significantly to the children daily dose, with dose fractions of 15–19% for schools located in urban and suburban areas and just 6% for the rural one. Therefore, the study clearly demonstrates that, whatever the school location, the children daily dose cannot be determined on the basis of the exposures in outdoor or school environments, but a direct assessment able to investigate the exposure of children during indoor environment is essential.

Heterogeneous formation of HONO and its impacts on haze formation in the YRD region of China

<p>A suite of instruments were deployed to simultaneously measure nitrous acid (HONO), nitrogen oxides (NO<sub>x</sub>= NO + NO<sub>2</sub>), carbon monoxide (CO), ozone (O<sub>3</sub>), volatile organic compounds (VOCs, including formaldehyde (HCHO)) and meteorological parameters near a typical industrial zone in Nanjing of the Yangtze River Delta region, China. High levels of HONO were detected using a wet chemistry-based method. HONO ranged from 0.03-7.04 ppbv with an average of 1.32 ±0.92 ppbv. Elevated daytime HONO was frequently observed with a minimum of several hundreds of pptv on average, which cannot be explained by the homogeneous OH + NO reaction (P<sub>OH+NO</sub>) alone, especially during periods with high loadings of particulate matters (PM<sub>2.5</sub>). The HONO chemistry and its impact on atmospheric oxidation capacity in the study area were further investigated using a MCM-box model. The results show that the average hydroxyl radical (OH) production rate was dominated by the photolysis of HONO (7.13×10<sup>6</sup>molecules cm<sup>-3 </sup>s<sup>-1</sup>), followed by ozonolysis of alkenes (3.94×10<sup>6</sup>molecules cm<sup>-3 </sup>s<sup>-1</sup>), photolysis of O<sub>3</sub>(2.46×10<sup>6</sup>molecules cm<sup>-3 </sup>s<sup>-1</sup>) and photolysis of HCHO (1.60×10<sup>6</sup>molecules cm<sup>-3 </sup>s<sup>-1</sup>), especially within the plumes originated from the industrial zone. The observed similarity between HONO/NO<sub>2</sub>and HONO in diurnal profiles strongly suggests that HONO in the study area was likely originated from NO<sub>2</sub>heterogeneous reactions. The averagenighttimeNO<sub>2</sub>to HONO conversion ratewas determined to be ~0.9% hr<sup>-1</sup>. Good correlation between nocturnal HONO/NO<sub>2</sub>and the products of particle surface area density (S/V) and relative humidity (RH), S/V×RH,supports the heterogeneous NO<sub>2</sub>/H<sub>2</sub>O reaction mechanism. The other HONO source, designated as P<sub>unknonwn</sub>, was about twice as much as P<sub>OH+NO </sub>on average and displayed a diurnal profile with an evidently photo-enhanced feature, i.e., photosensitized reactions of NO<sub>2</sub>may be an important daytime HONO source. Nevertheless, our results suggest that daytime HONO formation was mostly due to the light-induced conversion of NO<sub>2</sub>on aerosol surfaces but heterogeneous NO<sub>2</sub>reactions on ground surface dominated nocturnal HONO production. Concurred elevated HONO and PM<sub>2.5</sub>levels strongly indicate that high HONO may increase the atmospheric oxidation capacity and further promote the formation of secondary aerosols, which may in turn synergistically boost NO<sub>2</sub>/HONO conversion by providing more heterogeneous reaction sites.</p>

Formation of boron – silica based mesoporous and studies of its adsorption ability for curcuminoids

The development aims of mesoporous silica formation in pharmaceutical fields were its uses as a drug delivery vehicle and in separation. It is possible because of the large particle surface area, the presence of pores, and the possibility to modify functional groups in the mesoporous materials. In this study, the formation of silica-based mesoporous and boron-silica-based mesoporous materials was carried out by sol-gel techniques and modification of functional groups was carried out by the co-condensation method. Mesoporous material characterization was carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR). Adsorption ability of curcuminoid onto the mesoporous was carried out through isotherm adsorption study approaches using adsorption models including Langmuir, Freundlich, and Temkin model. The results of the isotherm adsorption study showed that the Freundlich model is the best model for isotherm adsorption with an r2 value of 0.997.