复合流动分析法测定环境水样中的总磷

应用FSIV型流动分析仪,采用在线紫外／过硫酸盐消解、复合流动分析法对环境水样中的总磷进行测定。通过试验,确定了最佳测定条件,对方法的灵敏度、准确度和精密度进行了测试,测定的方法检出限为0．006mg／L,相对标准偏差（P,3D）为1．2％～6．5％,回收率为9;3．5％～107％。该方法测定结果与标准法测定结果无显著性差异,可以用于测定环境水样中的总磷。     

连续流动分析法测定地表水中的总磷研究

使用Skalar SAN++型连续流动分析仪测定地表水中的总磷。在水样中加入过硫酸钾溶液,经过110℃高温高压和UV消解器消解,将水体中存在的各形态的磷消解成正磷酸盐,正磷酸盐在酸性条件和酒石酸锑钾的存在下,与四水合钼酸铵反应生成磷钼黄,随后用抗坏血酸将其还原成磷钼蓝[1],于波长880nm处测量吸光度。实验结果表明,在0～2mg/L的线性区间内,方法的精密度和准确度较高,检出限为0.001mg/L。每一个样品从消解到分析只需要3min左右即可完成,同时准确度、精密度满足分析要求,非常适合目前任务量下大批量地表水样的分析。     

连续流动分析法测定环境水样中痕量亚硝酸盐

建立连续流动分析法测定环境水样中亚硝酸盐的方法。研究表明,该方法的线性范围为1.0～200μg/L,检出限1.69μg/L(n=11),回收率在97.16%～101.52%间,方法精密度为1.2%和0.7%。方法具有分析速度快、准确度和精密度高、操作简单等一系列优点,是监测环境水体中亚硝酸盐的理想方法。     

连续流动分析测定环境水样中的挥发酚

建立用Smartchem140全自动化学分析仪测定环境水样中的挥发酚的方法,方法具有良好的线性相关性和重复性,回收率为99.8%～103.8%,方法简便实用,用于环境样品分析,所得结果令人满意。     

连续流动分析法在线监测环境水样中的总氰

本文选用连续流动分析技术,水样通过紫外消解器和在线蒸馏系统,快速测定环境水样中的总氰化物。结果表明:在0～272.0μg/L范围内,体系吸光度值与总氰浓度呈良好的线性关系(r~2>0.9999);检出限0.6μg/L(n=21),方法精密度为0.66%～1.82%;实际样品加标回收率为93.4%～108.8%;方法应用于环境标准样品GSBZ 50018-90中总氰的检测,测量值与标准值相符。该方法具有分析速度快、准确度和精密度高等一系列优点,是监测环境水体总氰化物的理想方法。     

两种型号连续流动分析仪对地表水中总磷测定的比较研究

选取环保系统内较常用的两种型号连续流动分析仪AA3型和SKALAR SAN++型对地表水中总磷进行了测定。本文对仪器结构、准确度、精密度及检出限方面进行了比对。实验结果显示：这两种型号连续流动分析仪测定结果都能满足水体中总磷的监测技术要求,均能较好地应用于实际样品的测定。     

在线消解流动注射光度法测定水中的总磷

使用自行研制的全自动流动注射分析仪,采用在线消解流动注射法测定水中的总磷.方法的检出限为0.008mg/LP;线性范围为0.1-5mg/LP,线性相关系数r为0.9998;其相对标准偏差为0.69%;实际水样的加标回收率为93%-111%;样品测定频率为14样/小时.本方法快速、简便、灵敏度较高,线性范围、精密度和准确度均符合国家标准.     

总磷测定方法中样品显色时间的探讨

氯化亚锡还原法和钼酸铵分光光度法是测定水中总磷的两种主要监测方法，本文通过试验分析得出两种方法的最佳显色时间分别是15—30分钟和10—30分钟，且钼酸铵分光光度法的显色较稳定等结论。     

分段流动分析法测定水中的氨氮

使用FS-Ⅳ型流动化学分析仪测定地表水中的氨氮。方法检出限0.002mg/L,以氨氮计检测限0.002mg/L,适用范围0.01-25.0mg/L,精密度准确度高,能够满足大批量水样分析的需要。     

Measurements of the electrical parameters for different water samples

The resistance and capacitance values of the water samples are measured by using two different cell probes (length 10 cm and 5 cm) and a measuring module. Measured conductivities for the different water samples are compared where the lowest conductivity is obtained for the distilled water (3.28 μS/cm) and the highest value is for the boiled water 325.91 μS/cm. Using the measured series resistance values, and by knowing the frequency (1 kHz), the imaginary part of permittivity value is also determined. The imaginary part of the permittivity for the distilled water with the long cell probe is about 0.524 × 10⁻⁷ F/m (for the short probe is 0.523 × 10⁻⁷ F/m) while for the boiled water sample is the highest value of 53.58 × 10⁻⁷ F/m (for the short probe is 51.87 × 10⁻⁷ F/m). Imaginary part of the permittivity factor for the given samples from measurements with the long and short probes are compared.     

Recent progress in freeze-fracturing of high-pressure frozen samples

Pancreatic tissue, bacteria and lipid vesicles were high‐pressure frozen and freeze‐fractured. In addition to the normal holder, a new type of high‐pressure freezing holder was used that is particularly suitable for suspensions. This holder can take up an EM grid that has been dipped in the suspension and clamped in between two low‐mass copper platelets, as used for propane‐jet freezing. Both the standard and the new suspension holder allowed us to make cryo‐fractures without visible ice crystal damage. High‐pressure frozen rat pancreas tissue samples were cryo‐fractured and cryo‐sectioned with a new type diamond knife in the microtome of a freeze‐etching device. The bulk fracture faces and blockfaces were investigated in the frozen‐hydrated state by use of a cryo‐stage in an in‐lens SEM. Additional structures can be made visible by controlled sublimation of ice (‘etching’), leading to a better understanding of the three‐dimensional organization of organelles, such as the endoplasmic reticulum. With this approach, relevant biological structures can be investigated with a few nanometre resolution in a near life‐like state, preventing the artefacts associated with conventional fixation techniques.     

Measurement of d-spacing of crystalline samples with SAXS

A method for measuring the d-spacing on scale of nanometers of a crystalline sample with a standard small angle X-ray scattering (SAXS) setup by moving either the sample or detector, instead of directly measuring sample-to-detector distance is presented. The formulae of the d-spacing and its errors are derived. The error variation is analyzed in detail by simulation. The effectiveness of the method is further verified by the experiments on a standard sample.     

贵阳市集中饮用水源中总有机碳和无机碳的测定

总有机碳是表示水体中有机物含量的参数,本文通过测定贵阳市集中饮用水源及各支流水质的总有机碳值和无机碳值,反映了贵阳市集中饮用水的有机污染况状,为保护和治理饮用水源地提供了数据支持。     

Determination of drugs and drug‐like compounds in different samples with direct analysis in real time mass spectrometry

Direct analysis in real time (DART), a relatively new ionization source for mass spectrometry, ionizes small‐molecule components from different kinds of samples without any sample preparation and chromatographic separation. The current paper reviews the published data available on the determination of drugs and drug‐like compounds in different matrices with DART‐MS, including identification and quantitation issues. Parameters that affect ionization efficiency and mass spectra composition are also discussed. © 2011 Wiley Periodicals, Inc., Mass Spec Rev 30:875–883, 2011     

Freeze-substitution protocols for improved visualization of membranes in high-pressure frozen samples

Specimen preparation methods based on high‐pressure freezing and freeze‐substitution have enabled significant advances in the quality of morphological preservation of biological samples for electron microscopy. However, visualization of a subset of cellular membranes, particularly the endoplasmic reticulum and cis Golgi, is often impaired by a lack of contrast. By contrast, some efforts to increase membrane staining may lead to excessively granular staining. No one freeze‐substitution method has emerged that both overcomes these limitations and is suitable for all types of analysis. However, one or more of the following protocols, perhaps with minor modifica‐tions, should yield satisfactory results in most cases. Freeze‐substitution in glutaraldehyde and uranyl acetate in acetone, followed by embedding in Lowicryl HM20, generates samples suitable for both immunolocalization and high‐resolution structural studies. Membranes are typically lightly stained but very well defined. Initial freeze‐substitution in tannic acid and glutaraldehyde in acetone prior to exposure to osmium tetroxide significantly enhanced contrast on mammalian cellular membranes. Finally, initial trials indicate that freeze‐substitution in potassium permanganate in acetone can provide strong contrast on endoplasmic reticulum and Golgi as well as other membranes. The tendency of permanganate to degrade cytoskeletal elements and other proteins when employed in aqueous solutions at room temperature is apparently curtailed when it is used as a freeze‐substitution reagent.     

The measurement of water distribution in frozen specimens

There are three techniques to measure local water fractions in the cryomicroscope. First, water content may be measured by a direct analysis of oxygen in bulk samples using a windowless detector. Secondly, mass thickness may be estimated in frozen-hydrated, then frozen-dried sections. This technique offers unrivalled spatial resolution, especially if the radiation dose in the frozen-hydrated state is kept low by the use of electron scattering techniques instead of an X-ray microanalytical background determination. External water content standards can be used instead of frozen-hydrated sections and the whole analysis can even be performed exclusively on frozen-dried sections at room temperature. Thirdly, local water fractions can be evaluated from X-ray microanalytical measurements of element concentrations per mass in the frozen-hydrated and frozen-dried state. Corrections necessary for the other techniques cancel out. However, the high radiation dose required for a fully quantitative analysis excludes the use of these methods in thin or ultrathin sections.     

水样中CODcr与TOC的关系

化学需氧量（CODcr）和总有机碳（TOC）是反映水体受有机物质污染程度的重要指标。以株洲市四个污水处理厂水样为研究对象,对水样的TOC与CODcr进行测定,将得到的数值进行统计分析,得出二者具有一定的线性关系,对今后CODcr的应急监测具有很好的指导作用。     

Fabrication of ordered aerogel samples with different densities

A method is described that allows the synthesis of denser samples of a nematically ordered aerogel from commercial Nafen with the effective density of 72 mg/cm³. The method is based on the drying of Nafen pre-immersed in a liquid (water, ethanol, pentane, or liquid nitrogen). The density of the final product is measured as a function of the surface-tension coefficient of the liquid filling the sample.     

Freeze substitution of high-pressure frozen samples: the visibility of biological membranes is improved when the substitution medium contains water

Biological membranes are often poorly visible with the electron microscope after high‐pressure freezing and freeze‐substitution. The water content of the sample and of the substitution medium is one factor among others that strongly influences membrane visibility. In order to investigate this effect, high‐pressure frozen yeast cells, rat‐pancreas tissue and arthropod tissue were freeze‐substituted with and without adding water to the substitution medium. The visibility of the biological membranes was generally improved if the substitution medium contained 1–5% water. The effect was especially pronounced in yeast cells, where membrane visibility was poor after freeze‐substitution with water‐free medium but good after addition of 5% water to the substitution medium.