X-ray imaging of various biological samples using a phase-contrast hard X-ray microscope

In this study, we visualized the internal structures of various bio-samples and found the optimum conditions of test samples for the 7 keV hard X-ray microscope of the Pohang light source. From the captured X-ray images, we could observe the intercellular and intracellular structures of dehydrated human cells and mouse tumor tissues without using any staining materials in a spatial resolution better than 100 nm. The metastasized lung tissue, which was several tens of micrometers in thickness, was found to be very well suited to this hard X-ray microscope system, because it is nearly impossible to observe such a nontransparent and thick sample with a high spatial resolution better than 100 nm using any microscopes such as a soft X-ray microscope, an optical microscope, or an electron microscope.     

Quantitative elemental X-ray imaging of frozen-hydrated biological samples

It is shown that quantitative X-ray imaging of planed, frozen-hydrated, biological bulk samples that have not been etched is possible. X-ray imaging represents a better alternative to static beam (selected area) analysis of fractured frozen-hydrated samples. This procedure avoids the undesirable necessity of etching planed frozen-hydrated samples to provide an interpretable electron image. Qualitative oxygen and carbon X-ray images, which can be acquired in a short time, can be used for distinguishing morphological features and remove the requirement for electron images. In test samples of frozen-hydrated albumin, containing salts, analyses by X-ray images compared well with static beam (selected area) analyses from the same samples. An example of an analysis of frozen-hydrated insect Malpighian tubules is given in which the response to ouabain treatment was analysed. In this example X-ray imaging showed that ouabain resulted in a significant increase in cytoplasmic and luminal Na and a significant decrease in cytoplasmic and luminal K. X-ray imaging also showed that there was a significant increase in cellular water content. The presence of a potassium gradient in soybean root nodules was also demonstrated. The use of standard deviation images for processing low count images increases analytical precision but results in underestimates of the true concentrations.     

The possibilities of a mass spectrometer equipped with a Llewellyn inlet system in the analysis of air and water samples

The design of a multimembrane inlet system, in which the method proposed by Llewellyn for enriching gases (through the addition of volatile organic components and certain other gases) for purposes of chromatography/mass spectrometry is described. A mechanism that enables one to obtain an enrichment effect of 10⁶ for a considerable group of compounds in the process of analyzing air and water samples, supplied to the mass spectrometer through the proposed inlet system, is considered. The results are given from the experimental verification of the inlet system operating as part of a portable magnetic mass spectrometer.Translated from Pribory i Tekhnika Eksperimenta, No. 1, 2005, pp. 101–104.Original Russian Text Copyright © 2004 by Kogan, Victorova, Victorov.     

Mapping the intake of different elements in vegetal tissues by dual-energy X-ray imaging at DaPhine synchrotron light source

This article reports on the first utilization of the soft X-ray beamline at the DaPhine synchrotron light source for mapping the intake of different elements in plant tissues. As a test, the method of dual-energy X-ray microradiography was applied to the investigation of the natural sulfur content in dried leaf and root samples. Our ultimate goal was to monitor the pollutant lead and its intake, which was added in controlled doses to the hydroponic medium of laboratory-controlled samples of vegetal species. The results obtained by the nondestructive X-ray radiographic analysis are compared to the values of concentrations determined by a standard chemical analysis utilizing atomic absorption spectroscopy. From this comparison the validity of the X-ray detection of heavy metals in biological samples has been confirmed. The superposition of the dual energy results on the simple planar radiography shows the representation of the pollutant intake directly on the sample structures. It should be pointed out that this method, developed here for plant root and leaves could be applied to any biological sample of interest, but the preparation and observation conditions necessitate different strategies according to the type of sample under analysis.     

Progress in quantitative X-ray microanalysis of frozen-hydrated bulk biological samples

The analysis of bulk frozen-hydrated biological samples has developed now to a level where practical application of the technique is possible. Provided the sample is carefully coated with a conductive metal, the development of a space charge capable of causing a significant distortion of the electron diffusion volume does not seem to occur, and analytical resolution can be conveniently held to approximately 2 μm (both depth and lateral resolution). Two valid quantitative methods are available, and two methods of determining dry weight fractions are also available. An area where further research could lead to improvement in analysis of frozen-hydrated bulk samples is in the investigation of fracturing methods. If fracture planes that were flat and reproducible could be easily obtained, some of the difficulties of analysing frozen-hydrated bulk samples would be considerably reduced.     

Energy-dispersive X-ray microanalysis of aqueous biologic samples on bulk supports

The present investigation describes a modification of the liquid droplet technique that allows for the quantitative elemental analysis of small volumes (< 100 picoliters) of aqueous biologic samples using a scanning transmission electron microscope (Philips 400 HTG-STEM) equipped with an EDAX energy dispersive detector. Aliquots of samples and standards were micropipetted onto solid beryllium supports under paraffin oil. The oil was washed with organic solvents and the samples frozen and freeze-dried. The samples were excited in a Philips 400-HTG-STEM by scanning a 1-μm, 20-kV electron beam over the surface of the droplets, and the X-ray spectra were collected. Measured X-ray intensities in characteristic peaks were found to be linearly related to the concentration of various elements in the sample. This work demonstrates the feasibility of performing quantitative elemental analysis of minute samples and cells in a scanning transmission electron microscope equipped with an energy dispersive X-ray detector.     

Personal-computer-based system for electron beam X-ray microanalysis of biological samples

A system based on a personal computer has been developed which provides a relatively inexpensive way to equip an electron microscopy laboratory for quantitative elemental analyses of cryosectioned biological samples. This system demonstrates the feasibility of making an X-ray analyser from a personal computer, together with commercially available hardware and software components. Hardware and software have been assembled to drive the beam in a scanning electron microscope, collect and analyse X-ray spectra, and save, retrieve, and analyse data. Our software provides a menu-controlled user interface to direct spectra acquisition and analysis. Spot analyses, video images, and quantitative elemental images may be obtained and results transferred in ASCII format to other computers. Wet weight, as well as dry weight, concentrations are calculated, if measurements were made of areas of the hydrated sample before it was freeze-dried. Grey-level copies of video and quantitative elemental images may be made on a laser printer.     

高温氧化法测定高盐样品中总有机碳的含量

本文介绍一种测定氯化钠和碳酸钠水溶液中总有机碳的新方法,步骤简单快速,3min即可完成一个样品的测定。经过加标回收实验,回收率为92%,证明测定结果准确可靠,可广泛应用于环境检测和医药行业。     

手动注射进样高温分解法测定汽油中的氧含量

对CHN-O-RAPID元素分析仪的进样部件作了改装，使仪器可以手动注射进样，采用手动注射进样高温分解法测定了新标准汽油中的氧含量，分析结果偏差符合ATSM D 5622方法的要求。     

气相色谱法测定岩石样品中的水含量

研究建立了一种使用高分辨弹性毛细柱+TCD气相色谱仪快速检测岩石样品中的水含量的方法,该方法通过使用无水乙醇密闭加热超声对岩石样品中的水萃取,用毛细色谱柱对混合物进行分离,在TCD检测器中检测,采用外标法进行定量。该方法具有需用岩石量少、检测周期短、准确度高、重复性好等特点。使用该方法建立的标准曲线,其相关系数都达0.999以上,检测岩石样品中水含量的相对标准偏差达0.1%以上,可以满足研究的需要。     

Sequential quantitative X-ray elemental imaging of frozen-hydrated and freeze-dried biological bulk samples in the SEM

Planed frozen-hydrated (FH) bulk biological samples of chicken retina were analysed by X-ray elemental imaging in a scanning electron microscope and reanalysed after freeze-drying in the microscope column. Sequential elemental imaging of the same bulk sample in this way provides improved information on element distributions. There was no evidence of element redistribution during the freeze-drying process. Quantitative elemental images were obtained and interpreted to deduce relative and absolute element concentrations in different regions of the retina. Water concentrations were determined from the difference in oxygen concentrations at 15 kV and 5 kV in FH and freeze-dried (FD) samples, respectively. Two accelerating voltages were used to maintain similar X-ray excitation volumes. Water concentrations were also estimated by relating measured oxygen concentration in FH samples to the concentration of oxygen in solutions of a generalized protein in water and by comparing concentrations of phosphorous or sulphur in the FH and FD states.     

Some theoretical considerations on X-ray microanalysis in the environmental or variable pressure scanning electron microscope

This paper presents a new correction procedure for quantitative x-ray microanalysis in the environmental or variable pressure scanning electron microscope (SEM). This method is based on a plot of the measured intensity as a function of the fraction of nonscattered beam intensity, f_p. The theory predicts that the plot should be linear and the corrected intensity is given for f_p = 1. The advantage is that such a plot is valid for any measured pressures, which is not the case with the usual pressure correction methods. To use this method, a simple equation is derived to compute f_p. Other variations of this correction procedure are also presented. Comparison with measurements performed by Mansfield (1999) show the great consistency of this method.     

荧光分析法测定铁精粉中高钛量

介绍了X射线荧光光谱测定铁精粉中高钛量,在没有高钛铁精粉标准物质的情况下,通过自制高钛量铁精粉试样,添加到工作曲线上扩大上限范围来校正曲线,使铁精粉中钛量校正曲线线性范围增宽,线性准确,满足了铁精粉中0.00％～5.00％钛含量测量范围内的分析需求.     

能量色散X射线荧光分析法测定石油焦硫含量的研究

通过二次标样法建立了测定石油焦硫含量的能量色散X射线荧光（EDXRF）分析法,与传统的管式炉法相比,该方法具有测定速度快,重复性好,准确度高的优点,为此建立了相应的企业标准,以便在生产中应用。同时考察了样品的粒度、装样深度及水分对测定结果的影响。     

X射线荧光法快速测定蒙脱石(固态)中的铝含量

本文介绍采用X射线荧光法测定蒙脱石中铝含量的方法及相关条件,并对测量结果精度进行分析。本方法具有样品前期处理简单、干扰因素小,且快速、准确等特点。     

Skirting: a limitation for the performance of X-ray microanalysis in the variable pressure or environmental scanning electron microscope

The variable pressure or environmental scanning electron microscope (VP-SEM; ESEM) has become the microscope of choice for many scientists and technologists. Hence, the development of robust methods for X-ray microanalysis, limited by skirting, has become critical. In this paper, two pressure variation correction methods (Doehne and Gauvin) are compared. Both of these methods appear to be effective; the results were found to be well within 10% of the values obtained at 0 Pa. The Doehne method is dependent on an empirical factor (D), therefore the accuracy of the results will depend on the accuracy of this value. Also the Doehne method is compromised by the nonlinearity of the response with pressure. The Gauvin method is more user-friendly and more precise when considering the total range of pressure.     

X荧光光谱法测定银矿石中的主次元素

采用粉末压片制样,通过顺序扫描型波长色散X荧光光谱仪快速测定内蒙古自治区银矿石中的Ag、Ga、S、Cu、Pb、Zn等主次元素,通过对方法的仪器条件进行对比,最终确定最佳条件。对国家标准物质测定结果的精密度进行讨论,方法测定数据令人满意。     

变量优选在纺织品棉含量近红外分析中的应用

为实现用较少的变量建立适当的模型,以准确预测未知棉涤样品的棉含量,用NIRFlex N-500近红外光谱仪采集297个棉涤样品的光谱,用蒙特卡罗无信息变量消除法(MC-UVE)对变量进行筛选,偏最小二乘法(PLS)建立棉含量的定标模型,根据各个模型所用的样品数、交叉验证均方根误差(RMSECV)、预测集均方根误差(RMSEP)和预测相关系数(r)评价定标模型的精度和稳定性。结果表明:通过上述数据预处理方法进行变量筛选后,用PLS建立的校正模型不仅使数据的运算量大幅度降低,还能很好地预测未知样品的棉含量,使得基于近红外光谱的棉涤样品中棉含量的定量分析方法进一步简化。     

高频加热-红外线吸收法测定石灰石样品中硫含量

石灰石样品熔融时分解产生的氧化钙对硫有很强的吸附能力,而且极容易吸水。分析用坩埚主要成分是二氧化硅和三氧化二铝,而且表面有粗糙的微孔容易吸附空气中的二氧化碳和水汽。本文采用高频加热方式燃烧石灰石样品,红外线吸收法测定硫含量,确定了仪器分析的最佳条件、坩埚与样品的预处理方法、合理的称样质量、适宜的助熔剂与加入方式。通过对不同石灰石标准样品分别进行测定,测定结果与标准值基本一致,相对标准偏差(RSD,n=10)小于3.50%,实验结果表明,本方法测定结果准确可靠,有效解决了样品和坩埚因为吸附作用影响硫含量分析结果不稳定的问题。