Analysis of volatile organic compounds in indoor environments using thermal desorption with comprehensive two‐dimensional gas chromatography and high‐resolution time‐of‐flight mass spectrometry

Building‐related health effects are frequently observed. Several factors have been listed as possible causes including temperature, humidity, light conditions, presence of particulate matter, and microorganisms or volatile organic compounds. To be able to link exposure to specific volatile organic compounds to building‐related health effects, powerful and comprehensive analytical methods are required. For this purpose, we developed an active air sampling method that utilizes dual‐bed tubes loaded with TENAX‐TA and Carboxen‐1000 adsorbents to sample two parallel air samples of 4 L each. For the comprehensive volatile organic compounds analysis, an automated thermal desorption comprehensive two‐dimensional gas chromatography high‐resolution time‐of‐flight mass spectrometry method was developed and used. It allowed targeted analysis of approximately 90 known volatile organic compounds with relative standard deviations below 25% for the vast majority of target volatile organic compounds. It also allowed semiquantification (no matching standards) of numerous nontarget air contaminants using the same data set. The nontarget analysis workflow included peak finding, background elimination, feature alignment, detection frequency filtering, and tentative identification. Application of the workflow to air samples from 68 indoor environments at a large hospital complex resulted in a comprehensive volatile organic compound characterization, including 178 single compounds and 13 hydrocarbon groups.     

A switchable ionic liquid with polarity swing-assisted regeneration properties used for the preconcentration of cadmium in biological samples

In the present study the cadmium (Cd) was determined in serum samples of psoriatic patients. The severity of psoriasis was evaluated according to criteria based on standard clinical diagnosis using Psoriasis Area Severity Index (PASI) score. In present study, an innovative tunable green solvent system based microextraction (TSS-ME) was applied for the enrichment of Cd in acid digested serum samples prior to determination with flame atomic absorption spectrometry. The hydrophobic complex of Cd-ammonium pyrrolidine thiocarbamate was extracted in a tunable solvent system which was prepared from a polybasic amine (N, N, N′, N′-tetramethyl-1, 4-diaminobutane), decanol and water system. The tunable green solvent system (TSS) which has zero ionic strength was converted to homogeneous monophasic polar hydrophilic phase via exposure to CO₂ at different pressure and time duration. Then hydrophobic enriched Cd- ammonium pyrrolidine thiocarbamate was back extracted, using HNO₃ (0.1 to 0.5 mol L⁻¹) then the second round of TSS-ME was applied. The acidic aqueous phase enrich with analyte was separated from tunable solvent. The separated TSS was easily reused for up to 10 time for preconcentration purposes without loss of its enrichment character. The smoker and nonsmoker psoriatic patients at PASI >10, have two to three folds higher Cd levels in serum samples than healthy persons.     

Ensuring robustness in the quality of antibiotic susceptibility test discs for four novel antibiotics

Antibiotic susceptibility test (AST) discs are used as an in-vitro diagnostic tool to select the appropriate antibiotic to treat an infection. Generally, the concentration of the drug loaded on to the AST discs is measured by studying its activity against quality control organisms. This methodology has several limitations—it is time consuming, requires trained manpower, has a wider acceptance criteria of zone of inhibitions—causing ambiguity in judging smaller variations in drug concentration. To overcome these issues, we have developed and validated high-performance liquid chromatographic (HPLC) methods for the determination of strength of AST discs for in-house researched antibiotics, namely Levonadifloxacin/WCK 771, Nafithromycin/WCK 4873, Cefepime-Tazobactam/WCK 4282, and Cefepime-Zidebactam/WCK 5222. The drugs were extracted from the AST discs using an appropriate solvent. The developed methods are simple, accurate, precise, reproducible, rugged, and robust. They are efficient in terms of time, and can be easily conducted in a quality control laboratory during release as well as stability evaluation of AST disc. Application of HPLC methods for the determination of strength of AST discs ensures flawless quality and, consequently, a better selection of drugs to treat bacterial infections in clinics.     

科研成果向教学实验的转化设计与实践成效*

围绕学校高水平应用型人才培养目标,依托省级重点实验室与省级化学化工大学生创新训练中心等科研教学平台,将“零排放型化学镀镍及其废液资源化为掺杂型LiFePO₄/C复合材料”的科研成果进行拆解和提炼,设计为分阶段、多层次的10个教学实验项目,并予以实践。结果表明,该科教融合模式营造出良好的科研氛围,有利于学生科研素养与创新意识的培养、实践能力与创新能力的提升。     

Topological “interfacial” polymer chemistry: Dependency of polymer “shape” on surface morphology and stability of layer structures when heating organized molecular films of cyclic and linear block copolymers of n‐butyl acrylate‐ethylene oxide

The “topological polymer chemistry” of amphiphilic linear and cyclic block copolymers at an air/water interface was investigated. A cyclic copolymer and two linear copolymers (AB‐type diblock and ABA‐type triblock copolymers) synthesized from the same monomers were used in this study. Relatively stable monolayers of these three copolymers were observed to form at an air/water interface. Similar condensed‐phase temperature‐dependent behaviors were observed in surface pressure–area isotherms for these three monolayers. Molecular orientations at the air/water interface for the two linear block copolymers were similar to that of the cyclic block copolymer. Atomic force microscopic observations of transferred films for the three polymer types revealed the formation of monolayers with very similar morphologies at the mesoscopic scale at room temperature and constant compression speed. ABA‐type triblock linear copolymers adopted a fiber‐like surface morphology via two‐dimensional crystallization at low compression speeds. In contrast, the cyclic block copolymer formed a shapeless domain. Temperature‐controlled out‐of‐plane X‐ray diffraction (XRD) analysis of Langmuir–Blodgett (LB) films fabricated from both amphiphilic linear and cyclic block copolymers was performed to estimate the layer regularity at higher temperatures. Excellent heat‐resistant properties of organized molecular films created from the cyclic copolymer were confirmed. Both copolymer types showed clear diffraction peaks at room temperature, indicating the formation of highly ordered layer structures. However, the layer structures of the linear copolymers gradually disordered when heated. Conversely, the regularity of cyclic copolymer LB multilayers did not change with heating up to 50 °C. Higher‐order reflections (d₀₀₂, d₀₀₃) in the XRD patterns were also unchanged, indicative of a highly ordered structure. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 486–498     

Estimator of a change point in single index models

This paper considers the problem of change point in single index models. In order to obtain asymptotically valid confidence intervals for the estimation of the change point, the convergence rate and asymptotic distribution of the change point estimate is studied. Some simulation results are presented which show that the numerical performance of our estimator is satisfactory.     

On molecular topological properties of hex‐derived networks

Topological indices are numerical parameters of a molecular graph, which characterize its topology and are usually graph invariant. In quantitative structure–activity relationship/quantitative structure–property relationship study, physico‐chemical properties and topological indices such as Randić, atom–bond connectivity (ABC), and geometric–arithmetic (GA) index are used to predict the bioactivity of chemical compounds. Graph theory has found a considerable use in this area of research. In this paper, we study hex‐derived networks HDN1(n) and HDN2(n), which are generated by hexagonal network of dimension n and derive analytical closed results of general Randić index R_α(G) for different values of α, for these networks of dimension n. We also compute the general first Zagreb, ABC, GA, ABC₄, and GA₅ indices for these hex‐derived networks for the first time and give closed formulae of these degree‐based indices for hex‐derived networks. Copyright © 2016 John Wiley & Sons, Ltd.     

Decomposability index of tournaments

Given a tournament $T$, a module of $T$ is a subset $X$ of $V\left(T\right)$ such that for $x,y\in X$ and $v\in V\left(T\right)?X$, $(x,v)\in A\left(T\right)$ if and only if $(y,v)\in A\left(T\right)$. The trivial modules of $T$ are $?$, $\left\{u\right\}$ $(u\in V\left(T\right))$ and $V\left(T\right)$. The tournament $T$ is indecomposable if all its modules are trivial; otherwise it is decomposable. The decomposability index of $T$, denoted by $\delta \left(T\right)$, is the smallest number of arcs of $T$ that must be reversed to make $T$ indecomposable. For $n\ge 5$, let $\delta \left(n\right)$ be the maximum of $\delta \left(T\right)$ over the tournaments $T$ with $n$ vertices. We prove that $?\frac{n+1}{4}?\le \delta \left(n\right)\le ?\frac{n?1}{3}?$ and that the lower bound is reached by the transitive tournaments.