Sample dilution summary

Information from the summary table in each workbook was directly imported into a master compilation of analytical results. The compilation could then be manipulated as desired to present the data in various ways. For example, the compilation could be searched for the number of apple samples that contained no detectable residues of any analyte or for the number of tomato samples that required dilution and reanalysis. 

Resonance Raman spectroscopy has been applied to studies of polyenes for the following reasons. The Raman spectrum of a sample can be obtained even at a dilute concentration by the enhancement of scattering intensity, when the excitation laser wavelength is within an electronic absorption band of the sample. Raman spectra can give information about the location of dipole forbidden transitions, vibronic activity and structures of electronically excited states. A brief summary of vibronic theory of resonance Raman scattering is described here. 

In summary, WSL uses 8 screened panellists, 60% dilution steps and, where possible, takes duplicate samples it is indicated that the corresponding 95% confidence limits are -33% to +49%. It should, of course, be remembered when comparing dilution values determined by the same set of panellists (e.g. to evaluate the % efficiency of odom control equipment on a particular day) that the standard error is somewhat reduced because the person to person variance need not be considered. 

In the WASTOXHAS procedure, ecotoxicity testing of leachate samples obtained at different liquid-to-solid ratios (or at different times of release) aims at measuring effects on species representing various levels of biological organization (see Section 5.4) as a function of dilution rate while controls without leachate are used as reference. In order to express results in a synthetic form, raw data obtained from concentration-response curves are transformed into a summary criterion corresponding to a specific measurement endpoint (e.g., EC5o, ECX, NOEC, LOEC, etc.) for each test (Fig. 3). 

In summary, available reports confirm that the cisplatin is not adversely affected by normal room irradiation for 24 hours or up to 72 hours, after dilution in 0.9% sodium chloride solution (36-38). The accelerated decomposition of cisplatin by UV-VIS radiation has been demonstrated by the studies of Cubbels et al. (39). Solutions exposed to UV-VIS radiation (300-35,000 lux) for two weeks, degraded more rapidly than solutions protected from radiation. The observed degradation rate constant, obtained from log concentration-time curves of these samples, was determined to be 0.385 per day = 6.5 hours). The manufacturer states that a cisplatin solution removed from its amber vial should be protected from UV-VIS radiation if it is not used within six hours, or if it is exposed to direct sunlight (Technical Information, Platinol, Bristol-Myers Squibb). 

When comparing luminescence intensities of various solutions, the absorbance (A) at the excitation wavelength (Aex) is important. Therefore, absorption spectra (or at least A Aex) should be measured for all samples. The absorbance at the excitation wavelength should be less than 0.1 (known as being optically dilute) in order to minimize the inner filter effect Differences in absorbance at the excitation wavelength between samples will affect luminescence intensity, so a correction is needed (see Results/Summary page). 

The concentration ranges covered by these methods are determined by the sensitivity of the instruments, the amount of sample taken for preparation and dilution volumes. The following is a brief summary of good practice in all oil analysis ... 

Summary of the Method. The sample is diluted approximately 1 1 with tetrahydrofuran and analyzed directly using a standard additions technique and a Varian-Techtron model 63 carbon rod atomizer. 

Summary of Method. The sample is diluted with tetrahydrofuran, and the metal in the solution is measured with an atomic absorption spectrophotometer equipped with a carbon rod atomizer (CRA-63). The... 

Summary of Method. The sample (1-10 g) is decomposed by heating with sulfuric acid. The resulting carbonaceous residue is ashed in a muffle furnace at 500°C. The ash is dissolved in dilute hydrochloric acid and... 

Trimmed and faced blocks are stained by immersion in a 10% solution of HgO in trifluor-oacetic acid for 10-60 min. Samples are washed in a dilute solution of trifluoroacetic acid followed by distilled water. Poly(phenylene oxide) (PPO) appears to have a higher mercury uptake than polystyrene in a bonded laminate of the two films [6]. Blends made by coextrusion of Kraton G and PPO show dispersed particles in a matrix. Kraton G is the lighter contrast polymer as it seems to take up less of the stain than the PPO. In summary, mercuric trifluoroacetate staining has been shown for several polymers where the dispersed phase particles are differentiated by this stain. The method has limited application. 

FIGURE 13.4 Quantitation of trace levels of copper in a sample of SRM orchard leaves using isotope dilution methodology. (From Multi-elemental Isotope Dilution Using the Elan ICP-MS Elemental Analyzer, ICP-MS Technical Summary TSMS-1, PerkinEhner Instruments, 1985.)... 

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