用热分析技术测定碳化硅粉体对聚乙二醇的吸附量

用热分析技术TG-DTA(thermal gravimetric and differential thermal analysis)测定浆料中碳化硅粉体对分散剂聚乙二醇PEG(polyethylene glycol)的吸附量. 结果显示PEG在Ar气氛中411.5 ℃时完全分解; 碳化硅表面分散剂PEG的吸附量随着pH的增大而下降, 在较高pH下大多数分散剂仍存在于溶液中; 分散剂PEG的吸附量通过公式(1)进行计算. 该方法简单方便, 可以应用于测量氧化物或非氧化物吸附紫外-可见分光光度法不能测定的一些有机聚合物分子.     

Grafting of functionalized silica particles with poly(acrylic acid)

Two different methods to graft silica particles with poly(acrylic acid) (PAA) were studied. In the first method PAA was reacted with 1,1′‐carbonyldiimidazole to give functionalized PAA. The resulting activated carbonyl group reacted easily with 3‐aminopropyl‐functionalized silica at low temperatures. In the second method 3‐glycidoxypropyl‐functionalized silica particles were reacted directly with PAA by using magnesium chloride as a catalyst. Different molecular weights of PAAs were used in order to investigate the effect of molecular weight on grafting yields in both methods. The grafting yields were determined with thermogravimetric analysis (TGA). All products were also investigated with IR. The results showed that the yields of reactions performed at ambient temperature by using 1,1′‐carbonyldiimidazole‐functionalized PAA were the same as with a direct reaction of unfunctionalized PAA and 3‐aminopropyl‐functionalized silica performed at 153°C. Also in reactions between 3‐glycidoxypropyl‐functionalized silica and PAA the yields were satisfactory. Copyright © 2006 John Wiley & Sons, Ltd.     

水中矿物元素的ICP-MS分析

用ICP－MS对地下水、地表水和饮用水中的矿物元素进行了分析测定，实验证明用ICP－MS可以同时测定地下水，地表水和饮用水中矿物元素；该法灵敏度、精密度和准确度都能满足有关标准的要求，具有多元素同时分析，样品前处理简单，干扰少，测定快速，省事省力等优点。     

Protein secondary structure and stability determined by combining exoproteolysis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

In the post-genomic era, several projects focused on the massive experimental resolution of the three-dimensional structures of all the proteins of different organisms have been initiated. Simultaneously, significant progress has been made in the ab initio prediction of protein three-dimensional structure. One of the keys to the success of such a prediction is the use of local information (i.e. secondary structure). Here we describe a new limited proteolysis methodology, based on the use of unspecific exoproteases coupled with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), to map quickly secondary structure elements of a protein from both ends, the N- and C-termini. We show that the proteolytic patterns (mass spectra series) obtained can be interpreted in the light of the conformation and local stability of the analyzed proteins, a direct correlation being observed between the predicted and the experimentally derived protein secondary structure. Further, this methodology can be easily applied to check rapidly the folding state of a protein and characterize mutational effects on protein conformation and stability. Moreover, given global stability information, this methodology allows one to locate the protein regions of increased or decreased conformational stability. All of this can be done with a small fraction of the amount of protein required by most of the other methods for conformational analysis. Thus limited exoproteolysis, together with MALDI-TOF MS, can be a useful tool to achieve quickly the elucidation of protein structure and stability.     

Simultaneous sample preparation for high-performance liquid chromatographic determination of Vitamin A and β-carotene in emulsified nutritional supplements after solid-phase extraction

Determination of small amounts of the fat-soluble species Vitamin A (VA) (2.5 μg/g) and β-carotene (9 μg/g) from emulsified nutritional supplements containing 50 kinds of co-existing compounds and a fat content between 2000 and 8000 times higher was performed by solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) with fluorescence detection set at ex. 350 nm and em. 480 nm, and visible detection at 450 nm using an Inertsil ODS 80A (5 μm) analytical column. Mobile phases of methanol-ethanol (50:50) and acetonitrile-ethanol (70:30) were used for the both vitamins. A Bond Elut C₁₈ cartridge was chosen for SPE after comparison with eight other types of SPE cartridge. Retention time of VA and β-carotene was 7 and 8 min, respectively, giving a limit of detection of ca. 0.1 ng per injection at a signal-to-noise ratio 3:1. Recoveries of VA and β-carotene were over 90% by the standard addition method. Relative standard deviation of VA and β-carotene were ca. 2.9 (n=5) and 2.3% (n=5), respectively.     

Routine determination of major anions in atmospheric aerosols by capillary electrophoresis

Capillary electrophoresis (CE) with indirect UV detection utilizing a pyromellitate-based electrolyte was used for the routine analysis of major anions in atmospheric aerosols collected on filters with high-volume (Hi-Vol) samplers. The long-term reliability of the CE system was checked over an 8-month period during which over 2900 samples were analyzed. In addition, approximately 1100 samples were analyzed in parallel by ion chromatography (IC). It has been shown that acceptable analytical performance can be routinely obtained. The agreement between the CE and IC results is good, generally better than 20% at concentrations larger than 1 mg l⁻¹.     

Tetrachloroferrate(III)-selective liquid membrane electrode based on crystal violet

An extract of crystal violet-tetrachloroferrate(III) in nitrobenzene was used to prepare a tetrachloroferrate(III)-selective liquid membrane electrode with a poly(vinyl chloride) support. The optimal conditions to determine 2.5 × 10^–5 – 5.0 × 10^–2 M iron(III) as tetrachloroferrate(III) (anionic slope 56 mV/decade, detection limit 7.9 × 10^–6 M) were found to be 4.0–5.5.M total chloride in 0.75–1.5M hydrochloric acid. The electrode was reliably applied to determine iron in human blood, haematite and mineralized vitamin syrup by direct potentiometry, standard and sample additions as well as standard subtraction techniques.     

CFB煤燃烧/热解双反应器中热解室对立管内气固流动特性的影响

考察了循环流化床煤燃烧/热解双反应器系统中热解室的存在对立管内的压力分布及气固流动状况的影响。提升管的内径100 mm、高6 m，立管的内径44 mm、高3 m，热解室的截面积200 mm×200 mm、高770 mm。结果表明，随着提升管内表观气速Ur的增加，有无热解室立管内均为负压差流动，负压差梯度随着Ur的增加而减小。有热解室时，热解室内要保持一定的料位高度，整个立管内固体颗粒的流动为负压差移动床流动；没有热解室时，立管内为稀相流动和移动床流动同时存在，立管内平衡料柱高度随Ur的增加而升高。随着循环量Gs的增加，两种类型的立管内负压差梯度均随之增大，也存在着流动形态的差别。循环量Gs的增加会引起立管内平衡料柱高度的降低。立管内气固相对滑移速度也随着循环量Gs的增加而增大。     

A simple flow injection-reduced volume column system for hemoglobin typing

A flow injection (FI)-reduced volume column system was developed for hemoglobin (Hb) typing to be used as an initial screening method for thalassemia. The column was packed with 140 μl diethylaminoethyl (DEAE)-Sephadex A-50 ion exchange beads. Hb can be separated using Tris–HCl buffer solution with pH gradient 8.5–6.5 and then monitored spectrophotometrically at 415 nm. The hemolysate of 40 blood samples from packed red cells were screened for thalassemia by determining the amount of HbA₂ and HbE present. The proposed system was able to predict positive test results from those samples with β, E-trait and EE homozygous thalassemia, Hb types that were independently identified following the conventional method at the hospital laboratory. Advantages of the proposed system over the conventional column technique include low amount of reagents and blood sample needed, short analysis time and low cost. Each analysis required only 80 μl of 50 times diluted packed cells, which is equivalent to 1.6 μl undiluted packed cells, and it can be completed in only 35 min. This simple FI-reduced volume column system was demonstrated to be an economic alternative system for Hb typing to initially screen some types of thalassemia such as β-trait, E-trait and EE-homozygous which are commonly found in Thailand.     

An attempt on the VOC oxidation using mechanically activated catalyst

A catalytic action of the mechanochemical products of copper hydroxocarbonate with calcium carbonate was investigated in n-butyl alcohol oxidation tests. The solid products of high-energy milling were identified using thermogravimetry supplemented by X-ray diffraction method. It was shown that the mechanical activation induces more effective tested catalyst because it promotes the alcohol conversion at lower temperatures than that unmilled one. This revised version was published online in July 2006 with corrections to the Cover Date.