Losses organic samples

After heating, the sample turned bulklike with black color, and EDX data showed that the residues contained S in addition to a large amount of I and Ag. X-ray diffraction patterns of the residues gave the main diffraction peaks of Agl, indicating that the residues were mainly Agl crystallite. Total mass losses of samples 1-VI obtained from TGA lie between the total organics content and total mass amount of C + H + O in the samples from the elemental analysis, for which the data are tabulated in Table 4.4.4. The difference may be caused by the residual S in the particle surface. This result supports that heating mainly resulted in the decomposition of organics in the powders. 

SIMPLICITY. No complicated equipment is needed for the implementation of solid adsorbents to accumulate organic compounds from water. The procedure is identical to gravity flow adsorption chromatography used for decades by many chemists to remove extraneous material from liquid samples in a process called sample cleanup. The simplicity of this procedure with the reduced sample manipulations minimizes solute losses and sample contamination. 

Once again, a literature review must be done to determine which acid to use as an internal standard. The internal standard will be used to calculate the percent recovery, which quantitates organic acid losses during sample preparation. 

Pankow, J.M. 1990. Minimization of volatilization losses during sampling and analysis of volatile organic compounds in water. In Significance and Treatment of Volatile Organic Compounds in Water Supplies. Ram, N.M., Christman, R.F., and Cantor, K.P., Eds., Chapter 5, pp. 73-86. Lewis Publishers, Inc., Chelsea, MI. 

Sample Fischer Assay Litres/Tonne Oil % Water % Char % Gas + Losses % Organic Carbon in Char % Oil Yield (% of Fischer Assay)... 

The simplest method of decomposing an organic sample prior to determining the cations it contains is to heat the sample over a flame in an open dish or crucible until all carbonaceous material has been oxidized to carbon dioxide. Red heat is often required to complete the oxidation. Analysis of the nonvolatile components follows dissolution of the residual solid. Unfortunately, there is always substantial uncertainty about the completeness of recovery of supposedly nonvolatile elements from a dry-ashed sample. Some losses probably result fiom the entrainment of finely divided particulate matter in the convection currents around the crucible. In addition, volatile metallic compounds may be lost during the ignition. For example, copper, iron, and vanadium are appreciably volatilized when samples containing porphyrin compounds are ashed. 

Electroorganic oxidation reactions were monitored on electrodes that were fully immersed in the electrolyte. The organic reactants were directly added to the electrolyte. In some of these experiments, the electrodes described above were used. In other experiments, non-Teflon-bonded catalyts were used by employing a specially constructed Teflon cell. The sample was placed in this cell between a piece of gold foil and a piece of gold screen. The gold screen served as the current collector. An outer layer of Celgard microporous film, placed over the screen, was used to prevent loss of sample into the solution. Additional experimental details may be found in reference (3). 

The temperature of samples taken at different locations in the packed bed was sometimes as high as 393 K, so a certain amount of methanol vapour was flashed off and consequently the measured molar concentrations of the organic compounds were higher than in the reactor. On the basis of Eq. 1 and 2 we still obtain the correct hydrogen conversions, automatically compensated for the evaporation loss during sampling. 

Serious cadmium losses have been reported when organic samples were ignited and ashed by the dry-ash method (12), This was confirmed during work of the Project. A sample of spiked crude oil was ignited to a carbonaceous residue, and the carbon was burned off in a muffle furnace after the residue was wetted with a few drops of sulfuric acid. The inorganic ash was solubilized with dilute hydrochloric acid and then was analyzed by flame atomic absorption. Recovery of added cadmium averaged 78%. 

Selenium has been reported to be completely lost from organic samples when subjected to dry ashing techniques (11). As part of the Trace Metals Project, ashing studies were carried out which confirmed the loss for dry ashing of petroleum matrices. When ashing aids such as sulfur or magnesium oxide were used, some selenium was retained in the ash, but the recovery was not complete. 

All of the sample collection methods suffer from inlet losses, as the reactive organic peracids and peroxides tend to decompose on unconditioned surfaces. Aerosols deposited in samphng hnes can also react with the peroxides, with subsequent loss of sample. For this reason, sample lines must be kept clean and as short as possible. A surfaceless intake scmbber has been designed to avoid surface loss. This system minimizes surface contact of the sample by eliminating all surfaces at the intake. 

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