气相色谱法测定面粉中过氧化苯甲酰

面粉中的过氧化苯甲酰经乙醚提取浓缩后,被碘化钾还原反应生成苯甲酸,利用气相色谱法对其进行分离测定,并与标准品比较定性、定量.该方法的最低检出含量为0.3 mg/kg,加标回收率在90%～99%之间.该方法分离效率高,样品用量少,检测灵敏度高.     

氢原子能谱进展

介绍氢原子能谱的规律性及其发展，并对能级图进行比较，力求得到清晰的物理图像。     

琼脂糖固定化过氧化氢酶的电化学性能研究

利用琼脂糖（agarose）将过氧化氢酶（Cat）固定在热裂解石墨电极表面,制备Cat—agarose膜修饰电极．包埋在琼脂糖中妁过氧化氢酶与电极直接传递电子,在pH6．0的缓冲溶液中可得一对可逆的氧化还原峰,式电势为-0．343V（vs SCE）,这是过氧化氢酶辅基血红素Fe（Ⅲ）／Fe（Ⅱ）电对的氧化还原．其式电势随溶液的pH值增加而负移且成线性关系,直线斜率为-36．8mV／pH,说明过氧化氢酶的电子传递过程伴随有质子的转移．过氧化氢酶修饰电极．在16．5—278μmol／L的范围内,催化电流与过氧化氢浓度成线性关系．     

Expression and proteolytic activity of calpain in lens epithelial cells of oxidative cataract

INTRODUCTION The association between oxidative stress andcataract formation is well known from both clinicaland experimental data. The mechanism throughwhich oxidative stress causes cataract has not yetbeen established. It is known that many kinds ofcataract are related to increased levels of calcium.This has raised interest in the involvement of cal-cium-activated proteases. Calpains are non-lysosomal, cysteine prote-ases activated by calcium, which are found in mostmammalian…     

Degradation of chlorophenol by in-situ electrochemically generated oxidant

A novel in-situ electrochemical oxidation method was applied to the degradation of wastewater containing chlorophenol. Under oxygen sparging, the strong oxidant, hydrogen dioxide, could be in-situ generated through the reduction of oxygen on the surface of the cathode. The removal rate ofchlorophenol could be increased 149% when oxygen was induced in the electrochemical cell. The promotion factor was estimated to be about 82.63% according to the pseudo-first-order reaction rate constant (min-1). Important operating parameters such as current density, sparged oxygen rate were investigated.Higher sparged oxygen rate could improve the degradation of chlorophenol. To make full use of oxygen, however, sparged oxygen rate of 0.05 m3/h was adopted in this work. Oxidation-reduction potential could remarkably affect the generation of hydrogen peroxide. It was found that the removal rate of chlorophenol was not in direct proportion to the applied current density. The optimum current density was 3.5 mA/cm2 when initial chlorophenol concentration was 100 mg/L and sparged oxygen rate was 0.05 m3/h.     

顶空气相色谱法测定化妆品中甲醇

本文采用顶空气相色谱法测定化妆品中甲醇的含量。用氢火焰离子化检测器检测，化妆品中甲醇的最低检测浓度为1．5mg／kg，在样品中加标量分别为20mg和40mg时，回收率为91．9％-95．2％，依本法取两份样品分别测6次，变异系数为1．6％-2．8％。     

Carnosine and taurine contents in individual fibres of human vastus lateralis muscle

Analysis of ATPase characterized type I and type II fibres from biopsy samples of the vastus lateralis muscle of four male subjects showed a selective distribution of carnosine and free taurine similar to that observed in other species. The mean carnosine concentration was twice as high in type II compared with type I muscle fibres (23.2 +/- 17.8 and 10.5 +/- 7.6 mmol . kg -1 dry weight, respectively), while taurine was four times higher in type I compared with type II muscle fibres (39.2 +/- 17.8 and 9.6 +/- 2.6 mmol . kg -1 dw, respectively). Overlap in the concentration of carnosine or taurine between fibre types occurred only once in one subject. There was no overlap between fibre types in the ratio of carnosine to taurine. Higher carnosine concentrations in type II fibres will result in a greater contribution to the buffering of H+ arising from anaerobic metabolism. The contribution in a type II fibre with the highest carnosine content was estimated to equal 28% of that from other sources.     

A quantum chemistry study on reaction mechanisms of SO2 with O3 and H2O2

Reaction mechanisms of SO2 with O3 and H2O2 were investigated using quantum chemistry ab initio methods. Structures of all reactants, products, and transition states were optimized at the B3LYP/6-311G＋（3df,2p） level, and energy calculations were made at the G2M level. SO2 reactions with O3 and H2O2 occurred by O-abstraction and OH-abstraction by SO2, respectively, at length forming SO3＋O2 （3Eg） and H2SO4. For SO2＋O3 reactions the barrier height was predicted to be 9.68 kcal/mol with a rate constant of 3.61 × 10^-23 cm^3/（molecule.s） at 300 K, which is below the experimental upper limit. The rate constant predicted for this reaction accords well with the one provided by National Institute for Standards and Technology （NIST） in 250-500 K. For SO2＋H2O2 reactions the barrier height was predicted to be 62.39 kcal/mol with a rate constant of 2.48× 10^-61 cm^3/（molecule.s） at 300 K.     

Hydrogen transfer reduction of ketones using formic acid as a hydrogen donor under hydrothermal conditions

The hydrothermal experiments with ketones and formic acid showed that the hydrogen transfer reduction of ketones can be conducted using formic acid as a hydride donor in the presence of NaOH at 300 ℃. The yield of alcohols was considerably higher at a much lower ratio of hydrogen source to ketones than the traditional Meerwein-Ponndorf-Verley （MPV） reduction, reaching 60% for isopropanol from acetone and 70% for lactic acid from pyruvic acid. Water molecules may act as a catalyst in the hydrogen transfer reduction of ketones under hydrothermal conditions.     

Oxidative stress and antioxidant status in cervical cancer patients

Cervical cancer (CaCx) is a global public health problem as it is the second most common cancer leading to the death of women worldwide. Many references revealed that the low levels of antioxidants induce the generation of free radicals leading to DNA damage and further mutations. In the present study attempt have been made to evaluate the levels of serum Lipid peroxide, Nitric Oxide (NO^.) Erythrocytic—Superoxide Dismutase (RBC-SOD), Vitamin-C, serum Copper (Cu) and serum Zinc (Zn). 120 patients were divided in 4 groups according to the increasing CaCx stages i.e. stage I, II, III & IV respectively. All the patients were around the age group of 25–65 years. 30 healthy women between the same age group were treated as controls. Highly significant increased values of MDA, NO^. and Cu were observed (p<0.001) whereas the activity of RBC-SOD, levels of Vitamin-C and Zn were significantly decreased in CaCx patients as compared with healthy controls (p<0.001). Cu/Zn ratio was found to be altered in CaCx patients. From our findings it can be concluded that the oxidative stress is induced among CaCx patients, which inturn increases the risk of CaCx.