Coverage‐ and Temperature‐Dependent Metalation and Dehydrogenation of Tetraphenylporphyrin on Cu(111)

Using temperature‐programmed desorption, supported by X‐ray photoelectron spectroscopy and scanning tunneling microscopy, a comprehensive overview of the main reactions of 5,10,15,20‐tetraphenyl‐21H,23H‐porphyrin (2HTPP) on Cu(111) as a function of coverage and temperature is obtained. Three reactions were identified: metalation with Cu substrate atoms, stepwise partial dehydrogenation, and finally complete dehydrogenation. At low coverage the reactions are independent of coverage, but at higher coverage metalation becomes faster and partial dehydrogenation slower. This behavior is explained by a weaker interaction between the iminic nitrogen atoms and the Cu(111) surface in the high‐coverage checkerboard structure, leading to faster metalation, and the stabilizing effect of T‐type interactions in the CuTPP islands formed at high coverage after metalation, leading to slower dehydrogenation. Based on the amount of hydrogen released and the appearance in STM, a structure of the partially dehydrogenated molecule is suggested.     

Mercury forms and their transformation in pyrite under weathering

Pyrite is considered to be the major carrier of mercury in coal. Here, the chemical characteristics of two natural pyrite samples of different weathering degrees were characterized by time-of-flight secondary ion mass spectrometry (TOF-SIMS). Thermal stability of Hg was also analyzed via temperature programmed desorption experiment (TPD). Characteristic ions such as S⁻, Fe⁺, FeS⁻, and FeS₂⁻ were detected on the surface of fresh pyrite. The release temperature of Hg ranged between 180°C and 300°C, and the characteristic peak of black HgS was recorded. In addition, abundant Fe₂O₃⁻, FeSO⁻, SO₄⁻, and HSO₄⁻ were detected on the surface of weathered pyrite, and the release temperature of Hg therein was mainly distributed at 260°C to 380°C and 520°C to 600°C, corresponding to the characteristic peaks of red HgS and HgSO₄, respectively. The results show that pyrite is acidified during weathering and that Hg forms in pyrite are transformed from the original state (HgS) to HgSO₄.     

解析电喷雾质谱法对感冒药中对乙酰氨基酚的快速检测

基于常压质谱的直接、快速、无需样品预处理检测的优势,该文拓展了其在药物质检领域的应用。采用自行搭建的解析电喷雾(DESI)装置,对常用感冒药对乙酰氨基酚片进行快速质谱检测,无需样品预处理,直接获得药片中有效成分的分子结构信息。为克服基质差异对定量分析的影响,以淀粉为基质构建对乙酰氨基酚模拟药片,在优化的基础上进行定量实验。针对实际药片中高浓度对乙酰氨基酚检测的需要,研究了其在较高浓度范围的定量关系,结果显示,方法对0.35~4.52 mg/mm^2范围内的对乙酰氨基酚具有较好的线性关系(r^2=0.9982),定量下限为1.903 ng/mm^2,检出限为0.237 ng/mm^2,加标回收率为102%~114%。对3种市售的对乙酰氨基酚片进行直接检测,与厂家提供的标准数据相比,相对标准偏差(RSD)为7.2%~12%,表明方法具有较好准确度。该工作很好地证明了DESI-MS在药品快检中的优势,从而为药品质检提供了潜在的高效、可靠的检测手段。     

新型表面辅助激光解吸附/离子化质谱基质及其在生物检测中的应用

表面辅助激光解吸附/离子化质谱(Surface-assisted laser desorption/ionization mass spectrometry,SALDI-MS)是一种利用无机纳米粒子或纳米结构表面作为基质,辅助待测分子的解吸附和离子化的质谱技术。由于其具有灵敏度高、耐盐性好、操作简便、重现性好、检测通量高等优势,已经被广泛应用于食品安全、环境监测、生命科学等诸多领域。该文总结了近5年来,SALDI基质材料(金属及金属氧化物材料、碳材料、硅材料、金属有机骨架化合物材料等)的最新研究进展及其在生物检测领域中的应用,并对SALDI-MS基质材料的发展及应用进行了展望。     

PSMA@Ag复合微球的制备及其在MALDI-MS分析小分子化合物中的应用研究

基质辅助激光解吸电离质谱(MALDI-MS)作为一种有力的分析手段,在生物分子分析中有着广泛的应用,但很难应用于分子量小于500的待测物的分析。该文利用聚多巴胺修饰还原法制备了核壳结构的聚苯乙烯-马来酸酐共聚物@银纳米壳层(PSMA@Ag)复合微球。采用傅立叶红外光谱法验证了聚多巴胺(PDA)的成功修饰。结合扫描电子显微镜(SEM)和紫外-可见光谱(UV-Vis)分析结果,发现Ag纳米壳层成功地包覆在PSMA微球的表面。将制备的PSMA@Ag复合微球作为辅助基质直接应用于MALDI-MS,成功地从0.5μL待测物样品中检测到2 pmol脯氨酸(M_w=115)和1 pmol丝氨酸(M_w=105)。研究结果证明PSMA@Ag微球对MALDI的离子化过程有促进作用,为解决MALDI-MS在分析小分子待测物时背景噪声过大,信号无法分辨的问题提供了一个有效途径。     

Mechanistic aspects of magnetic MgAlNi barium-ferrite nanocomposites enhanced adsorptive removal of an anionic dye from aqueous phase

The mechanistic aspects of improved aqueous removal of methyl orange (MO) dyes using high performance novel magnetic MgAlNi barium-ferrite (MgAlNi-BaFe) ternary double layer hydroxide (LDH) nanocomposites is reported in this study. Detailed surface characterization coupled with kinetic, equilibrium, thermodynamics and regeneration studies were undertaken under different operational conditions of temperature (298–318 K), initial concentration (20–100 mg/L), pH (2–6). The kinetic results show that MO sorption was mainly, associated with pseudo-second order and intra-particular diffusion process. The MO adsorption onto the MgAlNi-BaFe nanocomposites suggests a multi-layered sorption process that is endothermic and spontaneous in nature. The MO adsorption mechanism insight taken in cognizance of FTIR, XRD, pKa, zeta potential, the adsorbates surface functional groups and the adsorbate-adsorbent surface charges interactions suggest involvement of hydrogen bonding and n-π interactions, predominantly via physisorption process (ΔG° = −7.406 to −5.69 kJ/mol). The excellent adsorptive performance of the MgAlNi-BaFe adsorbents for removal of MO from water compared with other magnetic LDH nanocomposites was further elucidated via the MgAlNi-BaFe nanomaterials high rates of regeneration and superior performances for three successive desorption-adsorption cycles. This study demonstrates the high potentials of employing MgAlNi-BaFe nanomaterials for removal of dyes from water and wastewater.     

The Molecular Composition of Soot

Soot (sometimes referred to as black carbon) is produced when hydrocarbon fuels are burned. Our hypothesis is that polynuclear aromatic hydrocarbon (PAH) molecules are the dominant component of soot, with individual PAH molecules forming ordered stacks that agglomerate into primary particles (PP). Here we show that the PAH composition of soot can be exactly determined and spatially resolved by low‐fluence laser desorption ionization, coupled with high‐resolution mass spectrometry imaging. This analysis revealed that PAHs of 239–838 Da, containing few oxygenated species, comprise the soot observed in an ethylene diffusion flame. As informed by chemical graph theory (CGT), the vast majority of species observed in the sampled particulate matter may be described as benzenoids, consisting of only fused 6‐membered rings. Within that limit, there is clear evidence for the presence of radical PAH in the particulate samples. Further, for benzenoid structures the observed empirical formulae limit the observed isomers to those which are nearly circular with high aromatic conjugation lengths for a given aromatic ring count. These results stand in contrast to recent reports that suggest higher aliphatic composition of primary particles.     

Preconcentration of trace nickel lons from aqueous solutions by using a new and low cost chelating polystyrene adsorbent

A simple and reliable method has been developed using chelating polymeric adsorbent (PSAHSB) to preconcentration of trace amount of Ni(II) ions from aqueous solutions under static loading conditions, and their determination by Ultraviolet and visible (UV–Vis) absorption spectroscopy. The influences of some analytical adsorption parameters, such as pH, temperature and contact time, the ionization constants of chelating groups in the adsorbent and desorption process were investigated. Maximum adsorption ≥98% was achieved at pH 3–7 after 20 min of contact time and the relative standard-deviation values were ≤5%. Adsorbed metal ions have been desorbed with 10 mL of 2 M HCl acid with the detection limit of 0.0157 μg m⁻¹. The Langmuir and Freundlich isotherm equations were used to describe adsorption behavior of the system at different temperatures. Kinetic and thermodynamic behavior of the adsorbent for Ni(II) ion preconcentration was also studied. The possible adsorption mechanism of Ni (II) ions onto modified adsorbent is also discussed. This method was applied efficiently to remove Ni (II) ions from environmental water samples.     

Investigation of ion-pair precipitates of selected alkoxylates and complex salts of specific metal cations by liquid secondary ion mass spectrometry

Liquid secondary ion (LSI) mass spectra of ion-pair precipitates obtained for Triton X-100 with strontium, lead, cadmium and mercury tetraphenylborates and for selected butoxylene-ethoxylene monoalkyl ethers with barium tetraiodobismuthate(III) are discussed. On the basis of LSI mass spectra, recorded in both positive and negative modes, the formulae of the ion-pair precipitates were determined. On the basis of B/E mass spectra, the fragmentation routes of [M - H + Ba](+) ions for butoxylene-ethoxylene monoalkyl ether complexes of barium and [M - H + Cd](+) ions for the Triton X-100 complex of cadmium are proposed.