Specimen preparation

After the specimen rod is prepared, it is mounted in its holder so that it will lie accurately along the rotation axis of the camera when the specimen holder is rotated. This adjustment is made by viewing the specimen through a short-focus lens or low-power microscope temporarily inserted into the camera in place of the beam-stop tube the specimen holder is then adjusted so that the specimen does not appear to wobble when the holder is rotated. Rotation of the specimen during the exposure is common practice but not an intrinsic part of the powder method its only purpose is to produce continuous, rather than spotty, diffraction lines by increasing the number of powder particles in reflecting positions. 

To begin with, we obviously require specimens which are chemically pure, i. e., contain no other component than the polymer species. This may 

The primary dimensional requirement on a polymer sample is that it be sufficiently thin. (It is possible to obtain reflection spectra of polymers [Robinson and Price (187, 188)], in which case thin specimens are not required, but the use of this technique has thus far not proven to be as fruitful as transmission spectra, and we will not consider it here.) In the NaCl prism region (roughly 650 to 3500 cm-1) specimens as thin as 0.002 mm may be required in order to avoid essentially 100% absorption at some band peaks. The average thickness required in this region for most bands is usually about 0.02 mm. Thicknesses about ten times larger are optimum for frequencies above 3500 cm 1 (the overtone and combination region) and below 650 cm-1 (the far infrared region). Samples areas down to 1 by 3 mm are usable [Wood (247)], and even smaller if a microspectrometer is employed [Blout (76)]. 

The most convenient and effective method for preparing a tip specimen is by electrochemical polishing of a piece of thin wire of 0.05-0.2 mm diameter. Usually the methods developed for electropolishing thin film specimens in transmission electron microscopes are also applicable for polishing field ion microscope tips.7 In Table 3.1 some of the commonly used emitter polishing solutions and conditions for the polishing are listed for various materials.8 

For chemically reactive metals such as Fe, Ni, Mo and W, etc., tip polishing is in general very simple. As shown in Fig. 3.5, a beaker is filled with three quarters of the recommended polishing solution. A piece of thin wire is mounted on a mechanical manipulator so that the wire can be dipped into the solution to a desirable depth, and can also be lifted out of the solution. Usually a section of about 5 to 8 mm should be immersed in the solution. A counter-electrode, either a piece of Pt foil or simply a piece of tungsten wire, can be a loop or simply a straight piece of foil or wire. It is essential that the tip specimen wire is held in the vertical position so that the convection of the solution during the polishing can be 

Carbon (graphite) Heat in oxidizing flame Same as molybdenum  

Silicon Cone. HN03(45%) +.48% HF(42%) + CH3COOH(13%) Dip into solution 

For noble metals such as Pt, Ir, Rh, Ru and their alloys, a molten salt tip polishing method is found to be most effective. The recommended salt mixture is put into a crucible of Pt or more simply of Fe to about three quarters capacity. The salt mixture is melted with a gas burner and the tip polishing can then proceed as before. The crucible can be used as the counter electrode. Usually one finds the best result by keeping the salt just near its melting point, which is around 400 to 500 °C. 

A detailed account of methods of AP specimen preparation has been given by Miller and Smith (1989) to which reference may be made if necessary. 

A typical blank is about 10 mm long and 0.25 mm square or circular in cross-section, produced from bulk material by standard forming methods. Starting material in the form of thin ribbons or surface layers would require coating the desired region with a photoresist film, then writing a suitable pattern followed by etching away the unwanted material. 

In the case of more difficult specimens, focussed ion beam milling may be employed in their preparation, and discussed in Section 1.7. 

ASTM D2094-69-00 Standard practice for preparation of bar and rod specimens for adhesion tests. 

Only a few methods for urinary catecholamines have been published that do not require preextraction prior to analysis. These methods minimized sample preparation by making use of different precolumn derivatization procedures. The selection of a suitable method for sample preparation prior to analysis by HPLC depends on a number of factors, such as the biological source, the type of column used and the selectivity of the detection method. In cases where the analyte concentration is very low and the analyte is present in a complex matrix (urine or plasma) with interfering compounds, an exhaustive pretreatment may be unavoidable. Sample pretreatment is also essential to ensure the sensitivity and specificity of the assay and protect the analytical column from contamination. 

Eiquid- or solid-phase extraction methods have been adopted for the isolation of catecholamines and their metabolites from urine samples. The liquid extraction system is ordinarily based on the formation of a complex, in alkaline medium, between diphenylborate and the diol group in the catecholamines. However, the liquid extraction methods reported in the literature are relatively tedious and often involved multiple extraction steps.For the more widely used solid-phase extraction methods, catecholamines may be selectively isolated from the urine sample by adsorption with activated alumina, phenylboronic acid or cation-exchange resins. All the specimen preparative procedures are specific for the free catecholamines, i.e. the extracted catecholamines do not include the conjugated fraction. 

The procedure for extraction of catecholamines with activated alumina was developed by Anton and Sayre, and has subsequently been used in a number of studies. Alumina extraction has not been popular, although automated purification with alumina microcolumns was studied closely by Tsuchiya et al. The sample preparation scheme includes increasing the pH of the alumina to 8.5 and vigorous shaking of the sample with the alumina, resulting in adsorption of the catecholamines by attraction of the hydroxyl groups of the catechol nucleus. The alumina can then be washed with water or buffer, and finally the catecholamines are eluted with acid, such as 0.3 m acetic acid. Since catecholamines are 

They reported several studies that evaluated 

In general, minimal sample handling offers many advantages and if the HPLC-conditions are well chosen for a particular analytical problem, very crude samples can often be analyzed without off-line manipulation. Assays involving direct injection of the specimen may eliminate the necessity for an internal standard if recoveries are high and reproducible. In some cases of catecholamine analysis, the compounds may also be injected directly for 

Small wood chips are employed in UV microscopic measurements. If partially delignified wood is to be studied, care must be taken to conduct the delignifica-tion in such a manner that the fibers are not dispersed before the specimen is embedded. In the quantitative analysis of lignin, the wood chips should be solvent-extracted to remove extraneous materials. For Larix leptolepis, Imagawa and Fukazawa (1978) recommend sequential extraction with n-hexane at room temperature for 5 days, alcohol-benzene (1 2, v/v) in a Soxhlet extractor for 48 h, and acetone-water (1 1, v/v) at room temperature for 4 days. 

After the extraction, the chips are embedded in a suitable resin using a capsule or a rubber bed. Embedding media commonly used for electron microscopy are also suitable for UV microscopy. However, the well-known Epon 812 formulation of Luft (1961) shows increasing absorbance at lower wavelengths (Wood and Goring 1973, Boutelje and Jonsson 1980). Instead, the following formulation is recommended for low absorbance  

The clotting of blood in specimen collection tubes, their subsequent centrifugation, and the transfer of serum to secondary tubes require time to complete. When performed manually, it has been known to cause delays in the preparation of a specimen for analysis. Consequently, to eliminate the problems associated with specimen preparation, systems are being developed to automate this process. The following developments are noteworthy. 

When an assay system has been designed to analyze whole blood samples, specimen preparation time is essentially eliminated. Automated or semiautomated ion-selective electrodes, which measure ion activity in whole blood rather than ion concentration, have been incorporated into automated systems to provide certain test results within minutes of the drawing of a specimen. This approach is now commonly used for assaying electrolytes and some other common analytes. Another approach involves either manual or automated application of whole blood to dry reagent films and visual or instrumental observation of a quantitative change. This approach is exemplified by the Reflotron Plus. 

Several manufacturers have developed fully automated specimen preparation systems. These systems are described later in the chapter. 

The microstructure of a material can only be viewed in a light microscope after a specimen has been properly prepared. Metallurgists have developed extensive techniques and accumulated knowledge of metal specimen preparations for over a century. In principle, we can use these techniques to examine not only metallic materials but also ceramics and polymers in practice, certain modifications are needed and a certain degree of caution must be exercised. The main steps of specimen preparation for light microscopy include the following. 

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Interpretable high-resolution structural infomiation (e.g. preservation of dimensions, or correlation of the stmctiiral detail with a physiologically or biochemically controlled state) is therefore obtained exclusively from samples in which life has been stopped very quickly and with a sufficiently high time resolution for the cellular dynamics [19]. Modem concepts for specimen preparation therefore try to avoid traditional, chemical... 

The infonuation that can be extracted from inorganic samples depends mainly on tlie electron beam/specimen interaction and instrumental parameters [1], in contrast to organic and biological materials, where it depends strongly on specimen preparation. 

Muiier M and Moor H 1984 Cryofixation of thick specimens by high pressure freezing The Science of Bioiogicai Specimen Preparation ed J-P Revei, T Barnard and G H Haggis (O Hare, iL SEM, AMF 60666) pp 131-8... 

Testing—includes test specimen preparation, bond durabiHty tests, and stmctural performance tests. It should be noted that formaldehyde emission tests of phenoHc bonded products such as stmctural plywood are not required because emissions are normally about 0.02—.03 pl/L (ppm), weU below the previously noted safe level of 0.10 p.L/L (ppm). 

Microscopists in every technical field use the microscope to characterize, compare, and identify a wide variety of substances, eg, protozoa, bacteria, vimses, and plant and animal tissue, as well as minerals, building materials, ceramics, metals, abrasives, pigments, foods, dmgs, explosives, fibers, hairs, and even single atoms. In addition, microscopists help to solve production and process problems, control quaUty, and handle trouble-shooting problems and customer complaints. Microscopists also do basic research in instmmentation, new techniques, specimen preparation, and appHcations of microscopy. The areas of appHcation include forensic trace evidence, contamination analysis, art conservation and authentication, and asbestos control, among others. 

Transmission electron microscopy is very widely used by biologists as well as materials scientists. The advantage of being able to resolve 0.2 nm outweighs the disadvantages of TEM. The disadvantages include the inabiUty of the common 100-kV electron beam to penetrate more than a few tenths of a micrometer (a 1000-kV beam, rarely used, penetrates specimens about 10 times thicker). Specimen preparation for the TEM is difficult because of the... 

Tests using a constant stress (constant load) normally by direct tension have been described in ISO 6252 (262). This test takes the specimen to failure, or a minimum time without failure, and frequently has a flaw (drilled hole or notch) to act as a stress concentrator to target the area of failure. This type of testing, as well as the constant strain techniques, requires careful control of specimen preparation and test conditions to achieve consistent results (263,264). 

K. C. Thompson-Russell and J. W. Edington. Electron Microscope Specimen Preparation Techniques in Materials Science. Monographs in Practical Electron Microscopy, No. 5- Philips Technical Library, Eindhoven Delaware, 1977. 

Specimen Preparation for Transmission Electron Microscopy I. (J. C. Brav-man, R. M. Anderson, and M. L. McDonald, eds.) Volume 115 in MRS symposium proceedings series, 1988. 

In addition to cleanliness (contamination effects), surface morpholt and the alteration of composition during specimen preparation can cause serious artifacts in microanalysis. In some older instruments, the microscope itself produces undesirable high-energy X rays that excite the entire specimen, making difficult the accurate quantitation of locally changing composition. Artifacts also are observed in the EDS X-ray spectrum itself (see the article on EDS). 

S. Amelincks, D. van Dyck, J. van Landuyt, G. van Tendeloo (eds.) Electron Microscopy Principles and Fundamentals,VCH Verlagsgesellschaft mbH, Weinheim 1997. 2-178 R. M. Anderson, S. D. Walck (eds.) Specimen Preparation for Transmission Electron Microscopy of Materials IV, Materials Research Society, Pittsbrrrgh 1997. 

Fig. 33. High resolution C(ls) XPS spectra obtained from (A) silver and (B) polymer fracture surfaces of specimens prepared by curing the polyamic acid of PMDA/4-BDAF against polished silver substrates. Reproduced hy permission of the American Chemical Society from Ref. [391.

ASTM El078, Standard guide for procedures for specimen preparation, mounting, and analysis in auger electron spectroscopy. X-ray photoelectron spectroscopy, and secondary ion mass spectrometry. ASTM, West Conshohocken, PA. 

These latter curves are particularly important when they are obtained experimentally because they are less time consuming and require less specimen preparation than creep curves. Isochronous graphs at several time intervals can also be used to build up creep curves and indicate areas where the main experimental creep programme could be most profitably concentrated. They are also popular as evaluations of deformational behaviour because the data presentation is similar to the conventional tensile test data referred to in Section 2.3. It is interesting to note that the isochronous test method only differs from that of a conventional incremental loading tensile test in that (a) the presence of creep is recognised, and (b) the memory which the material has for its stress history is accounted for by the recovery periods. 

A specimen obtained by tbe reduction of limonene tetrabromide by Godlewski and Eoshanowitsch had a specific rotation + 125° 36 which is practically equal to an observed rotation of + 106° 30, thus confirming the purity of the specimens prepared by fractional distillation. 

Linalol is not particularly easy to purify, as it yields practically no crystalline compounds suitable for purification purposes. The characters of the various specimens prepared therefore vary, especially in regard to their optical rotation. The following figures, for example, have been recorded for linalol with a laevo-rotation —... 

The above values apply to natural dihydrocarveol from caraway oil. A specimen prepared by the reduction of carvone had a specific gravity 0-927 at 20° and refractive index 1-48168. i (r.ii4.j... 

Baker and Smith have isolated an aldehyde from the oils of Eucalyptus hemiphloia and Eucalyptus bractata, of the formula C,oH,gO, which they have named cryptal. Two specimens prepared from the former oil had the following characters —... 

Hitzig et al. have produced a simplified model of the aluminium oxide layer(s) to explain impedance data of specimens prepared under different layer formation and sealing conditionsThe model also gives consideration to the formation of active and passive pits in the oxide layer. Shaw et al. have shown that it is possible to electrochemically incorporate molybdenum into the passive film which, as previously noted, improves the pitting resistance. 

Brammar, 1. S. and Dewey, M. A. P., Specimen Preparation for Electron Metallography. Blackwell, Oxford (1966)... 

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