离子选择性电极法测定溶液中B时去除Cl~-干扰的研究

讨论了用离子选择性电极法测定Br-时,不同浓度等级Cl-干扰状况及溴电极的电位响应能力变化情况。同时提出了应用Matlab建立线性回归方程测定Br-的方法,回归系数平方值R2 =1,回归方程与实验观测数据拟合理想。     

小麦粉中溴酸钾检测方法的比较

为了选择一种最适合小麦粉中溴酸钾的检测方法,分别对4种检测方法(滴定法、反滴定法、离子色谱法和液相色谱法)进行探讨,比较它们的原理、方法、精确度、检出限、回收率及稳定性等方面。结果表明,离子色谱法操作简单,灵敏度高,溴酸根离子的最低检出浓度为50μg/kg,标准曲线具有良好的线性关系,回收率达到92.5%,是溴酸钾检测定量的较好方法,适合广泛推广和应用。     

Influence of dietary phenolic acids on redox status of iron: Ferrous iron autoxidation and ferric iron reduction

We investigated the effect of dietary phenolic acids on the oxidation of Fe²⁺ caused by molecular oxygen. All phenolic acids bearing 3,4-dihydroxy (catechol) or 3,4,5-trihydroxy (galloyl) moiety formed chelates with ferric iron and significantly increased the rate of Fe²⁺ autoxidation. The carboxylate group and catechol substitution instead of galloyl moiety facilitated the ferrous ion oxidation more effectively. Caffeic acid and protocatechuic acid, the strongest accelerators of Fe²⁺ autoxidation, were able to facilitate autoxidation at concentrations lower than 1% of the initial amount of Fe²⁺. Therefore chelates of these catecholic acids with iron displayed ferroxidase-like activity. Conversely, when we started from ferric ions, catechols partially formed ferrous ions in the presence of ferrozine. Thus, catecholic acids formed stable chelates with iron, in which ferric ion is the dominant species, but the redox cycling of iron between Fe²⁺ and Fe³⁺ in chelates probably plays a crucial role in the catalysis of ferrous iron autoxidation. Interestingly, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid and vanillic (4-hydroxy-3-methoxybenzoic) acid protected ferrous ions from autoxidation as effectively as ascorbic acid and cysteine. These monophenolic acids, differently from ascorbic acid and cysteine, were not able to reduce ferric ions. Syringic (3,5-dimethoxy-4-hydroxybenzoic) acid did not alter the redox state of iron, only in a large excess over metal, syringic acid slightly inhibited ferrous ions autoxidation and partially reduced ferric ions. Therefore, the effects of syringic acid at high concentration were similar but much lower to those of ascorbic acid and cysteine. The biological importance of ferroxidase-like activity of polyphenols, especially the influence on iron absorption, is also discussed.     

低压离子排斥色谱法测定水样中的重碳酸盐

研究了低压离子排斥色谱电导检测碳酸氢根离子的新方法.考察了淋洗液浓度、流速、柱长对碳酸氢根保留时间的影响.确定最佳色谱条件为:1×10-5 mol/L硝酸为淋洗液,流速为0.45 mL/min,色谱柱柱长为75 mm.在此条件下,碳酸氢根的保留时间为5 min,检出限(S/N=3)为4.6 mg/L,连续11次测定峰高的相对标准偏差为2.26%.将方法用于自来水和矿泉水样品的分析,加标回收率在101.3%～107.8%之间.     

精梳棉/负离子粘胶纤维紧密纺细特纱的生产

负离子粘胶纤维强伸度低,纺纱与织造困难,从而阻碍了细特高密高档负离子功能性家纺产品的规模化生产.介绍了紧密纺精梳棉与负离子粘胶混纺细特纱的生产技术要点,包括原料选择、纺纱流程和工艺参数选择以及车间温湿度控制等,成纱各项性能指标可达Uster 2007公报25％水平,满足了市场对于高档负离子功能性家纺面料的规模化生产需求...     

XPS、AFM和ToF-SIMS的工作原理及在植物纤维表面分析中的应用

介绍了先进的表面分析仪器化学分析电子能谱(XPS)、原子力显微镜(AFM)、含飞行时间分析器的二次离子质谱仪(ToF-SIMS)的工作原理,回顾了近年来它们在植物纤维表面分析中的成功应用,综合利用XPS、AFM及ToF-SIMS方法,可分析和解决制浆造纸过程中的现象和问题。     

稀土元素 La 和 Ce 对小球藻生长的影响

本文以普通小球藻（Chlorella vulgaris）作为受试藻种,研究了硝酸镧和硝酸铈对其生长的影响,旨在探讨稀土化合物用于小球藻培养的方法和效果。具体实验包括：在藻类培养基中添加不同浓度的稀土硝酸盐,定时取样测定培养物光密度,绘制生长曲线并计算比生长速率（μ）,测定细胞密度最大时的干物质含量、叶绿素含量、类胡萝卜素含量以及可溶性糖含量。通过实验得出：10-3~10-6 mM的稀土元素在培养早期能够促进小球藻的细胞增殖,但随着培养时间延长促进作用减弱,比生长速率与对照组的差异逐渐缩小;10-3 mM La可将叶绿素a和b的含量分别提高24.46%和28.51%,10-4mM的Ce可将其分别提高50.76%和38.92%;此外,10-3mM La或Ce可分别将胞内可溶性糖含量提高13.83%和34.88%。上述研究表明：在藻类培养基中添加一定浓度的La或Ce,可以加快小球藻细 胞的早期增殖速度,缩短获得最大生物量的培养时间,同时还可提高叶绿素、类胡萝卜素以及可溶性糖的含量,但是两种稀土元素的效应浓度范围略有差异。     

Application of electrospray ionization ion trap/time-of-flight mass spectrometry for chemically-synthesized small RNAs

In this study, we have demonstrated an accurate and rapid small RNA analytical method with both sequence determination and detailed modification analysis by electrospray ionization-ion trap/time-of-flight mass spectrometry (ESI-IT/TOFMS). To develop this ideal method, we have examined the performance of ESI-IT/TOFMS using various chemically-synthesized model sequences of modified or unmodified microRNAs (miRNAs). The deconvoluted mass of a 22-nucleotide (nt) miRNA was obtained from a multiply charged precursor ion (MS(1)). The ion exhibited high mass accuracy (< 7 ppm) and high mass resolution (a value of m/Δm=10,000) and was therefore very useful in RNA composition assignment. The optimized MS(2) method using ion trap collision-induced dissociation, as well as automatic annotation analysis of product ions based on the accurate mass information, enabled the precise sequencing determination of intact miRNAs. Further, the detailed structural analysis of 3'-terminal modified nucleic acid in intact methylated miRNA was carried out using the MS(3) capability of the hybrid IT/TOFMS. The direct infusion method also provided a high throughput and good sensitivity because the analytical time and sample concentration needed in a series of experiments with reliable data were only 3 min and 100 nM, respectively. This study provides a novel approach for characterizing the intact chemically-synthesized small RNA without chemical and enzymatic digestions and would be widely applicable for the structural analysis of complicated modified small RNAs.     

Laboratory assessment of insecticidal effectiveness of natural zeolite and diatomaceous earth formulations against three stored-product beetle pests

The insecticidal effectiveness of two natural zeolite formulations (Minazel plus and Minazel), applied to wheat at selected rates of 0.25, 0.50 and 0.75 g/kg, and a diatomaceous earth formulation (DE) (Protect-It™), applied at the recommended rates of 0.15 g/kg for Sitophilus oryzae, 0.20 g/kg for Rhyzopertha dominica and 0.30 g/kg for Tribolium castaneum, were tested under laboratory conditions (24 ± 1 °C temperature and 45 ± 5% relative humidity). The highest adult mortality was observed after the longest exposure period of 21 days and 7 days of recovery, when all three zeolite dosage rates and the recommended DE dosage caused 97-100% mortality of S. oryzae and 94-100% of T. castaneum. On the other hand, 100% mortality was not achieved in any test variant involving R. dominica; the highest (about 92%) was detected for DE, while 52% and 79% mortality was achieved with the zeolites at the highest rate of 0.75 g/kg. Progeny reduction by >90% was achieved after 21 days of contact of all three beetle pests with DE-treated wheat, while the same level of reduction was achieved for S. oryzae and T. castaenum only after contact with the highest rate of the zeolite product, Minazel. Thus the two zeolite formulations are comparable to diatomaceous earth in controlling adult S. oryzae, R. dominica and T. castaneum, but only the Minazel formulation could effectively protect wheat from attack by S. oryzae or T. castaneum, and only with a higher rate of application than for the DE formulation.     

Toxic and behavioural effects of different modified diatomaceous earths on the German cockroach, Blattella germanica (L.) (Orthoptera: Blattellidae) under simulated field conditions

Defined populations of German cockroaches were observed after exposure to deposits (25 g/m²) of various modified and un-modified diatomaceous earth (DE) formulations by using a computer-aided device measuring motility, circadian rhythm, and mortality under defined environmental and climatic field-simulating conditions. In a humid climate (85% r.h.) with water and food offered ad libitum, complete population eradication could be achieved within 10 days with three out of seven DE formulations tested. Results revealed two basic factors affecting mortality: (a) formulations containing freshwater diatoms from Spain were significantly more effective than those originating from marine diatoms purchased from Fur Island, Denmark (P<0.0001), and (b) the higher the degree of coating with a silica-aerogel to increase oil-carrying capacity, the greater the efficacy (P<0.0001 to 0.07). Exposure to DEs resulted in complete disruption of the species-specific circadian rhythm of German cockroach populations with six out of seven DE formulations investigated. A remaining rudimentary circadian rhythm was found after exposure to one formulation. It is concluded that strongly hydrophobic formulations of DE can be used for effective cockroach control even in tropical environments, especially as part of a least-toxic Integrated Pest Management control strategy. Nevertheless, it remains unclear to what extent newly developed DEs, coated or formulated with different chemical compounds resulting in modified surface characteristics, could potentially produce adverse health effects to humans.