固相萃取-石墨炉原子吸收法光谱分析铝合金中痕量铍的研究

建立了固相萃取-石墨炉原子吸收光谱法测定铝合金中铍的方法。利用偶氮砷酸类试剂7-(2′-胂酸基-5′-羧酸)苯偶氮-8-羟基喹啉-5-磺酸(H2L)与Be2+形成螯合物,该螯合物可用C18固相萃取柱富集,而Al3+则不被保留。采用石墨炉原子吸收光谱法(GF-AAS)测定C18柱洗脱液中的Be2+的螯合物,从而实现铝合金中铍的分离检测。最佳实验条件为:采用pH=3.0的5%H2L水溶液螯合Be2+,水相上柱,用2mL体积比为50%的甲醇/水溶液作为洗脱液。结果表明:经过C18柱固相萃取可以去除Al3+的干扰,Be2+的测定范围为0.05～16μg/L,检出限为0.025μg/L,加标回收率为92%～108%。应用该法于铝合金标样中铍的测定,结果与认定值相符。     

Nickel(II) N‐Benzyl‐N‐methyldithiocarbamato Complexes as Precursors for the Preparation of Graphite Oxidation Accelerators

The nickel(II) N‐benzyl‐N‐methyldithiocarbamato (BzMedtc) complexes [Ni(BzMedtc)(PPh₃)Cl] ( 1 ), [Ni(BzMedtc)(PPh₃)Br] ( 2 ), [Ni(BzMedtc)(PPh₃)I] ( 3 ), and [Ni(BzMedtc)(PPh₃)(NCS)] ( 4 ) were synthesized using the reaction of [Ni(BzMedtc)₂] and [NiX₂(PPh₃)₂] (X = Cl, Br, I and NCS). Subsequently, complex 1 was used for the preparation of [Ni(BzMedtc)(PPh₃)₂]ClO₄ ( 5 ), [Ni(BzMedtc)(PPh₃)₂]BPh₄ ( 6 ), and [Ni(BzMedtc)(PPh₃)₂]PF₆ ( 7 ). The obtained complexes 1 – 7 were characterized by elemental analysis, thermal analysis and spectroscopic methods (IR, UV/Vis, ³¹P{¹H} NMR). The results of the magnetochemical and molar conductivity measurements proved the complexes as diamagnetic non‐electrolytes ( 1 – 4 ) or 1:1 electrolytes ( 5 – 7 ). The molecular structures of 4 and 5· H₂O were determined by a single‐crystal X‐ray analysis. In all cases, the Ni^II atom is tetracoordinated in a distorted square‐planar arrangement with the S₂PX, and S₂P₂ donor set, respectively. The catalytic influence of selected complexes 1 , 3 , 5 , and 6 on graphite oxidation was studied. The results clearly indicated that the presence of the products of thermal degradation processes of the mentioned complexes has impact on the course of graphite oxidation. A decrease in the oxidation start temperatures by about 60–100 °C was observed in the cases of all the tested complexes in comparison with pure graphite.     

Preparation and Characterization of Graphite‐Epoxy Composite Modified with Zinc Hexacyanoferrate and Their Electrochemical Behaviour in Presence of Substituted Anilines

The growth of zinc hexacyanoferrate (ZnHCF) hybrid film on the surface of graphite‐epoxy composite (GEC) electrodes was demonstrated by cyclic voltammetry. Surface morphology of the hybrid film was investigated by using scanning electron microscopy. The effect of the type of monovalent cations on the redox behaviour of hybrid film was also studied. This effect indicated that the radius of the hydrated cation mainly determines the ion permeability of the film.     

氧化钛-氧化石墨插层结构及其光催化性能(英文)

采用氧化石墨(GO)和硫酸钛作为初始反应物,在低温下(80℃)制备了纳米级的氧化钛-氧化石墨插层(TiO2-GO)复合材料,研究了这一复合材料的紫外光催化性能.结果表明,在采用TiO2-GO插层复合材料对甲基橙溶液进行紫外光催化降解时,其降解效率η=1.17mg·min-1·g-1,明显优于德固赛P25氧化钛粉.通过对TiO2-GO插层复合材料进行X射线衍射(XRD)、傅里叶红外(FT-IR)光谱、X射线光电子能谱(XPS)和场发射扫描电子显微镜(FESEM)等测试,表征了产物的晶相结构、界面状况及其显微结构.结果表明:插层结构中的TiO2晶粒为锐钛矿和金红石的混合相,且锐钛矿相含量大于金红石相含量;氧化石墨层间的含氧基团如C襒O,基本被还原.对TiO2-GO插层复合材料的形成机理以及该材料具有优越光催化性能的原因进行了探讨.     

高分辨连续光源石墨炉原子吸收光谱法测定面制食品中的铝

使用微波消解-高分辨连续光源石墨炉原子吸收光谱法测定四种面制食品(挂面、饺子皮、油条和梳打饼干)中铝的含量.样品置于密闭聚四氟乙烯消解罐中经HNO3和H2O2混合溶液完全消解.对微波消解条件、灰化温度和原子化温度进行了优化.确定最佳实验条件为:消解液HNO3和H2O2体积比7∶1,微波功率1 000 W,190℃消解4...     

Synthesis of Acrylamide Molecularly Imprinted Polymers Immobilized on Graphite Oxide through Surface-Initiated Atom Transfer Radical Polymerization

A novel acrylamide (AA) molecularly imprinted polymer was synthesized by atom transfer radical polymerization (ATRP) on graphite oxide (GO) particles. Propionamide (PAM) was used as a dummy template molecule, hydroxy ethyl acrylate (HEA) as a functional monomer, ethylene glycol dimethacrylate (EDMA) as a crosslinking agent, and acetonitrile as both solvent and dispersion medium. Scanning electron microscopy (SEM) images and infrared spectroscopy (IR) confirmed that the molecularly imprinted polymers (MIP) were successfully grafted onto the surface of the GO particles. The corresponding adsorption kinetic curves and adsorption isotherms showed that the AA adsorption reached equilibrium after 5 h, with large amounts of AA being adsorped in the first 100 min. The maximum AA adsorption capacity was 123.48 µmol g^?1 according to Scatchard analysis, which indicated that the MIP possesses good AA adsorption capacity. This MIP-GO material was used to selectively determine AA in fried food samples.     

Interferences in Thermospray Flame Furnace AAS: Co and Mn Behavior

ABSTRACT

The effects caused by concomitants [Na(I), K(I), Ca(II), and Mg(II)] on the atomization of cobalt and manganese by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) were here studied. The main concomitants were chosen according to typical major elements found in foods and beverages. Severe interference effects were caused by all concomitants. The interferences varied from ?101.0% to +360.0% and ?117.5% to +175.5% for Co and Mn, respectively. These data demonstrated a frequently paradoxical situation in spectrochemical analysis, that is, efforts are directed toward the introduction of a higher amount of sample, however, when this condition is attained, there is the manifestation of severe processes of interferences. These interference processes require the application of either previous separation steps or special strategies of calibration.     

石墨炉原子吸收光谱法测定铅和铜中记忆效应的消除

对石墨炉原子吸收光谱法测定Pb和Cu中 ,不同构形的石墨管存在的记忆效应问题进行了探索研究,并对石墨管采取改进措施,取得了良好的效果,有效地消除了记忆效应。     

Determination of Lead in Human Hair by High Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry with Microwave Digestion and Solid Sampling

The content of lead in human hair was measured by high resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS) combined with microwave-assisted digestion (MAD) and direct solid sampling (DSS). Hair strands were washed, dried, and then cut into three parts (root, middle portion, and tip). For MAD-GFAAS assays, approximately 0.25 g of hair was completely digested using a mixture of concentrated nitric acid and hydrogen peroxide in a closed system. In the DSS-GFAAS assays, 0.1–0.2 mg of dried hair was directly introduced into a graphite furnace using a solid autosampler. The temperature programs were optimized and the effects of various added modifiers were compared. The results indicated that NH₄H₂PO₄ was the optimal modifier for analysis of Pb using GFAAS. Use of the optimal modifier and temperature program gave similar limits of detection for MAD-GFAAS and DSS-GFAAS of 1.16 ng/g and 0.82 ng/g, respectively. Both methods also produced satisfactory recoveries ranging from 98.69% to 103.14%. There was no significant difference observed between the Pb contents of hair strands determined by the MAD-GFAAS and DSS-GFAAS assays, which both indicated that the Pb levels increased along the hair strands. Comparison of the two methods revealed that DSS-GFAAS had several advantageous characteristics over MAD-GFAAS, including the need for much less sample material and having a less time-consuming procedure, lower sample blank absorbance, lower memory effect, and no risk of environmental pollution by digesting chemicals. The direct solid sampling technique can be employed as a good alternative to conventional wet digestion in AAS assays.