Specimen requirements

Quantitative Electron-Probe Microanalysis. (V. D. Scott and G. Love, eds.) John Wiley Sons, New York, 1983. Taken from a short course on the electron microprobe for scientists working in the field. A thorough discussion of EDS and WDS is given, including experimental conditions and specimen requirements. The ZAF correction factors are treated extensively, and statistics, computer programs and Monte Carlo methods are explained in detail. Generally, a very useftd book. 

The ratio of Cam/Ccr can be determined on a random urine sample and thus avoids the time, labor, and errors involved in collecting the timed urine specimen required for the urinary amylase determination. 

Population Residue Levels to be Detected. The number of individual specimens required per composite was determined by the MDL values for the different compounds addressed by the broad scan analyses. As indicated previously, a universal MDL of 10 ng was considered to be appropriate for the compounds of interest. The number of individual specimens per composite was chosen so that there was a high probability that an injection drawn from the extract of the composited sample contained an analyte level exceeding 10 ng for each compound in which the population residue levels exceed the stated levels that were of Interest to be detected. The population residue levels of Interest correspond to concentrations expected to be toxic to humans yet are not chosen to be too small to require a very large number of specimens per composite. 

The number of specimens required per composite was the minimum value of N satisfying Equation 1 for all compounds addressed by the broad scan analyses. One constraint on the value of N was that the total mass of the composited sample could not exceed sample preparation and extraction constraints (approximately 30 gram). To actually determine the value of N it was noted that the value of N satisfying Equation 1 depends on the assumed distribution of population residue levels. Various lognormal distributions (i.e. values of the mean and standard deviation) were therefore investigated to determine how N varies with these parameters. 

Listed below are specimen requirements, reagents, and the procedures used for sample preparation. 

The specimen requirements are the same as for the Berry spot test. 

NOTE Preparation of specimens requires that dimensions be measured precisely. It is assumed that the dimensions of the compressed specimen are small with respect to the dimensions of the contacting surfaces (plates) to ensure that the sample remains in contact with the plates. Occasionally, it is desirable to compress a sample in its natural state (i.e., no specimen cutting). 

The order in which the treatments were to be applied was programmed into the computer, and the apparatus then operated unattended until it was time to insert a fresh data recording disc disc or to change the specimens. A complete series of treatments on a group of three specimens required about 6 weeks. 

The ASTM D 897 tensile button test is widely used to measure the tensile strength of a butt joint made with cylindrical specimens (Fig. 20.3). The tensile strength of this bond is defined as the maximum tensile load per unit area required to break the bond (measured in pounds per squre inch). The cross-sectional bond area is usually specified to be equal to 1 in.2. The specimen is loaded by means of two grips that are designed to keep the loads axially in line. The tensile test specimen requires considerable machining to ensure parallel surfaces. 

Some specimens required either longer exposure times or greater concentrations of fluorescent dye to incorporate it throughout the hair. In only a Korean hair sample was uniform rhodamine staining throughout the hair shaft not achieved. 

The equations cited above are for an ideal semi-infinite plate, with no boundary effects. Application to real specimens requires calibration factors, so that the fracture toughness of Eq. (11-51), at the critical point is given by ... 

As previously indicated, the determination of a drug concentrations in plasma specimens requires the construction of a calibration response curve. This curve is often constructed as a straight line from the measured peak response ratios (y,) plotted against their respective calibrator concentrations (x,). The drug concentration in a specimen or the apparent (back-calculated) calibrator concentration is obtained from a rearrangement of theequation for the calibration line (without error) x,- = (y,- — b)/m. An example of a calibration curve with back-calculated concentrations is given the first four columns of Table 10. 

Conventional approaches to microbiological examination of specimens require that they be cultured to assess the total numbers of specific groups of microorganisms or to determine the presence or absence of particular named species. The majority of samples taken for examination contain mixtures of different species, so simple plating onto an agar surface may fail to detect an organism that is present at < 2% of the total viable population. Various enrichment culture techniques may therefore be deployed to detect trace numbers of particular pathogens, prior to confirmatory identification. 

Several medications, including anticholinesterases such as pyridostigmine bromide, are toxic to mice, but can be dialyzed from samples before testing. To avoid interfering with the mouse bioassay, a list of the patient s medications should accompany any diagnostic samples sent. All specimens require refrigeration at 4°C (37). 

Specimen requirements (i.e., conditions for collection, specimen volume requirements, the necessity for anticoagulants and preservatives, and necessary storage conditions)... 

Repeated freezing and thawing of specimens may cause deterioration of many proteins and should be avoided. The minimum amount of specimen required is generally loop, . 

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