Preliminary sample handling

PROTOCOLS FOR CORROSION FILM ANALYSIS 2.1. Preliminary Sample Handling 

On the other hand, samples from industrial failure have inevitably come in contact with an oxidizing atmosphere and probably been subjected to other interference such conditions must be accepted as a fact of life. However, to compensate for this, the analyst must attempt to play the role of detective, piecing together as many as possible of the events surrounding the failure. Some questions that might be a.sked are concerned with (a) details of the chemical environment surrounding the specimen at the time of the failure, (b) any changes in those conditions which have occurred recently, (c) the method of manufacture 

Sometimes the analyst is asked about protocols for taking additional samples from the failed component (or even the reference). Whenever possible samples should be cut by methods in which neither heat nor fluids contaminate the surface to be analyzed. Cutting methods of choice therefore include hacksaws and heavy-duty metal shears. Where use of these is impractical, torch cuts should be as far as possible from the failed area and water, not oil,. should be used as a lubricant with cutting saws. Samples from failures can normally be stored under air in closed containers. 

Many corrosion specimens from either of the origins described above may contain a plethora of chemical elements when subjected to surface or microanalysis. Some of these could be considered to be contaminants because they arose from processes having little or nothing to do with the corrosion. For example, the internal walls of high-pressure autoclaves are ready sources of cross-contaminants from previous experiments, particularly alkaline and heavy elements. Similar elements precipitate in many industrial heat transport circuits from sources as varied as valve packing to water treatment columns. In the case of the controlled experiment, it is best to remove the source of the contamination and then repeat the run. No such option is available with most failure specimens. 

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Some conditions are required for Eq. 7 to be valid Areas and weights must be expressed in the same unit system both for analysis and calibration because precision and accuracy of this method only depend on the precision and accmacy of weighings, they depend neither on the precision and accuracy of the dilutions nor on the injected volume (unlike the external standard method). It requires no preliminary determination of the proportionality coefficients. However, if some points of the sample handling are fully corrected by the use of an internal standard, other difficulties still remain. ... 

To determine the effect on the skin and on the cholinesterase activity of the blood of persons engaged in handling the Vaporizers, 10 volunteers were selected for investigation six men and four women. Before they handled the Vaporizer, blood was drawn by venipuncture from each subject, and the cholinesterase activity of the plasma and erythrocytes was determined. Two of the volunteers were used in a preliminary trial, one in handling the Vaporizer for 30 minutes, and the other by having the Vaporizer fixed to the volar aspect of the forearm for 30 minutes. Another sample of blood was drawn 24 hours after the experimental procedures (Table I). 

For preparation of the aggregated polynucleotide-MBSA complex, it is convenient to use the polynucleotide at a concentration of about 200-500 /ig/ml. A stock solution of 10 mg of MBSA per milliliter in water is prepared the powdered or lyophilized MBSA does not dissolve readily in saline. An amount of MBSA equal to the total weight of the polynucleotide is added to the annealed polymer. A white precipitate should be visible after the MBSA is added. It is an easily handled fine suspension with most polymers, but fibrous strands may be formed with samples of very high molecular weight. Preliminary mechanical homogenization or soni-cation usually reduces such polymers to a size that will form a manageable suspension with the MBSA. 

Once the appropriate dose has been established, the entire batch of wine can be treated. It is essential that it should be in the same oxidation-reduction state as the sample used for the preliminary trial. Treatment should therefore take place shortly after the test and the wine must not be handled in the meantime. If the wine to be treated is kept in several containers, separate trials must be carried out for each one. 

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