An efficient tool for the continuous monitoring on adsorption of sub-ppm level gaseous benzene using an automated analytical system based on thermal desorption-gas chromatography/mass spectrometry approach.

It became an important task to effectively adsorb volatile organic compounds (VOCs) at or near real-world levels for efficient control of airborne pollution in ambient environments. Nonetheless, most studies carried out previously for the control of VOCs are confined to significantly polluted conditions (e.g., >100 ppm) that are far different from real-world or ambient conditions. To help acquire the meaningful data for the adsorptive removal of VOCs at near real-world levels, a new approach was designed and implemented to measure adsorption of gaseous benzene (as a representative or model VOC) at trace-level quantities (as low as 0.14 ng (0.43 ppb) for a 100 mL sample) using activated carbon (sieved to 212 µm mesh size) as a model sorbent. With the aid of a thermal desorption-gas chromatography/mass spectrometry system, the key adsorption performance metrics (such as 10% breakthrough volume (10% BTV) points: 10% as the key reference) were determined: 1018 L atm g-1 at 0.1 ppm benzene with the corresponding partition coefficient of 3.85 mol kg-1 Pa-1. If the adsorption capacity values (at 10% BTV) are compared across the varying concentration levels of benzene, the maximum value of 1.07 mg g-1 was observed at 1 ppm benzene (within the concentration range selected in this work). As such, it was possible to quantitatively assess the sorbate-sorbent interactions at significantly low concentrations of VOCs that actually prevail under the near real-world conditions.

The transfer characteristics of heavy metals in electronic cigarette liquid.

In this research, the concentrations of six heavy metals (Zn, Pb, Ni, Fe, Cd, and Cr) in electronic cigarette (EC) solutions were determined to assess their association with EC use patterns. To this end, their contents were analyzed under three conditions: (1) ECL I: EC liquid was directly taken from EC liquid bottles as purchased from retail, (2) ECL II: EC liquid simply stored in the EC clearomizer for a certain period was collected without any puffing, and (3) ECL III: EC liquid remaining in the EC clearomizer after puffing. Each of all three types of electronic cigarette liquid (ECL) samples selected in this study was analyzed after being stored for up to seven days (at elapsed intervals of 1, 3, and 7 days). Zn and Pb were detected in all types of samples while Cd was all below method detection limit (MDL). Fe, Ni, and Cr were generally below MDL in ECL I, while it was not the case for ECL II and III samples. Especially, Zn, Pb, and Ni levels increased significantly with the use of EC. If the consumption of EC causes alterations in elemental content, such changes can be assessed in terms of ratio values such as "after/before use". The maximum ratio values for each target, when assessed using ECL III samples, were seen in the following order: 463 (Zn) > 315 (Ni) > 131 (Fe) > 47.9 (Cr) > 36.0 (Pb). As such, EC use is clearly demonstrated as the transfer route of heavy metals.

Quantitative insights into major constituents contained in or released by electronic cigarettes: Propylene glycol, vegetable glycerin, and nicotine.

Generally, the liquid used in electronic cigarettes (E-cigarettes), which is also called E-liquid, is composed of propylene glycol (PG), vegetable glycerin (VG), and nicotine, with many other miscellaneous ingredients. E-liquid is consumed mainly in the form of aerosol via inhalation by the e-cigarette user. The amount and composition of the aerosol generated during its consumption depend on various factors. In this study, the three major constituents (PG, VG, and nicotine) of E-cigarettes were analyzed in both liquid and aerosol samples from 50 commercial products. Their concentrations in the liquid (and aerosol at 3.4 V) samples were 538 (4 6 7), 482 (4 4 9), and 8.75 mg g-1 (7.91 mg g-1), respectively. The nicotine levels in the E-liquids measured in this study were normally 1.2 times greater than those specified by the manufacturers. Furthermore, the amount of liquid consumed increased proportionally as the voltage of the E- cigarette increased. The consumption rate of VG increased as the voltage of the E-cigarette increased, whereas that of PG and nicotine decreased. The results of our study confirm that the amounts of PG and VG generated through the use of E-cigarettes are noticeably larger than those from other tobacco products (such as traditional tobaccos and heat-not-burn products), although no such trend was evident in case of nicotine.

High-performance materials for effective sorptive removal of formaldehyde in air.

As formaldehyde (FA) is well-known for its carcinogenic potential, various techniques for its removal have been developed based on recovery (e.g., adsorption/absorption and condensation) or destructive treatment (e.g., incineration and thermal/ catalytic oxidation). Among them, adsorption has been one of the most preferable options due to its low price and simplicity. In this review, we summarize state-of-the-art knowledge about adsorption mechanisms with respect to its key controlling variables (e.g., surface chemical properties of adsorbent, temperature, and relative humidity) and adsorption performance of materials with particular emphasis on advanced materials (e.g., carbon nanotubes, metal-organic frameworks, graphene oxides, and porous organic polymers) and their modified forms in comparison with conventional sorbents (e.g., AC and zeolite). However, it is yet difficult to assess the adsorption capacity of each material on a parallel basis because adsorption experiments of each material were conducted under different conditions (e.g., large differences in the initial loading concentrations). The partition coefficient (PC) was employed for evaluating adsorption performance between different materials at an equivalent level to overcome the limitation based on adsorption capacity concept. For instance, among the list of the surveyed materials, the highest PC was recorded by γ-CD-MOF-K (31.2 mol kg-1 Pa-1). This study should offer valuable insights into the selection and development of outstanding materials for the sorptive removal of FA.