Sampling preliminary tests

VI.4 PRELIMINARY TESTS ON THE SEMIMICRO SCALE In most cases samples submitted for analysis are solid. The preliminary tests 1-8 described in this section are to be carried out on solid samples. If the sample is liquid (e.g. a solution), these tests can be omitted, though tests 3-8, with little modifications, might be useful even for such samples. Preliminary tests to be carried out with liquid samples are described under test 9. 

Pyrolysis and reforming of several types of common plastics (polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polyurethane, and polycarbonate) were studied qualitatively, using a micro-reactor interfaced with a MBMS. Each type of plastic pyrolyzed at 550-750°C. This was followed by steam reforming of vapors in a fixed bed of C-11 NK catalyst at 750-800°C. The composition of the product gas (mass spectrum) was observed for different values of the steam-to-carbon mtio and space velocity that changed depending on the size of plastic samples. Preliminary tests showed that at process conditions similar to those used for reforming natural gas, polymers were almost completely converted to hydrogen and carbon oxides. 

Preliminary Test Operation of the unit shoiild be set at the test protocol conditions. A preliminaiy set of samples should be taken to identify problems with instruments, measurements, and sample locations. This preliminaiy set of measurements should also be an yzed in the same manner that the full-test results will be analyzed to ensure that the measurements wiU lead to the desired results. Modifications to the test protocol can be made prior to exerting the effort and resources necessary for the complete test. 

In order to reduce sampling errors, during the preliminary tests, in the sampling process, the slurry was sampled with a device, consisting of a rigid tube, 3cm in diameter and 3m in height, into which a plasticcoated steel cable was placed, to which a rubber sphere, 6cm in diameter was anchored. The sphere closes the lower end of the tube itself. 

Several preliminary tests have been carried out to date. These have been used to set up the experimental system, the plan of analytical deter minations and method of sampling. They were followed by two complete cycles of tests, one in the Feb.—May period and the other in the Jul.—Oct. period of the same year. A third cycle is currently under way. 

Preliminary tests indicated that the distribution of inorganics within a particle could be a function of the rate at which the lignite sample was dried. Rapid drying rates resulted in a concentration of inorganics in the central zone of a particle, whereas slow drying rates resulted in a concentration at the outer perimeter of the particle. 

The sample collected from the crystaUizer was diluted with filtered electrolyte (2.0 wt% aqueous NaCl) and decanted to separate the fines from the coarse crystals. The dilution and decantation were repeated 5-7 times till 200 ml of the decanted sample was obtained. Preliminary tests by hoh (8) have shown tiiat these repeated decantantions were sufficient to recover at least 95% of the fines present in the original sample. Both the fine and coarse fractions were then analysed with the Coulter Counter using a 50 p.m orifice tube for the former and a 280 im orifice tube for the latter. By adjusting the Coulter Counter s settings, a set of particle number counts at different sizes (successive sizes differing by a factor of 21/3) was made for each of the 2 orifice tubes used. 

DCP were subjected to two types of preliminary tests— capacity tests and desorption efficiency tests. On the basis of these tests, a sorbent material was tentatively selected for each analyte the selection was confirmed only after the overall sampling and analysis method was validated. 

The sorbent materials that performed best in the capacity and desorption efficiency tests were investigated further with respect to the stability of the sorbed analyte. Preliminary tests of analyte stability were conducted by a procedure similar to that in the desorption efficiency tests the procedure differed in that samples were stored 7 d prior to analysis rather than Id. To be acceptable, a sorbent material had to exhibit no statistically significant loss of analyte at the 0.05 significance level by a two-tailed t test. 

Storage Stability. It must be shown that no greater than 10% loss occurs in samples stored for seven days under ambient conditions. This will ensure ample time to ship the samples from the field to the laboratory. Preliminary tests may be performed on spiked samples, but the final testing must be done with samples collected from test air, since distribution of the analyte on the sorbent is different for spiked samples. 

Preliminary Testing Data Any data generated during the developmental and clinical trial phases of the drug may be useful to determine the expected manufacturing process variability. The process variability is an important factor to define the sampling plan to be used in the stability study. 

Our preliminary testing with duodenal smooth muscle produced variable results. In three of the mice tested, 15 to 20 second contractions were recorded, but in two, this result could not be reproduced. This may have been due to problems with the measuring equipment. At times, the muscle was visibly contracting, yet produced no tracing. Also, a larger sample size is necessary for statistical analysis. 

However, care must be exercised in using molecular sieves for drying organic liquids. Appreciable amounts of impurities were formed when samples of acetone, 1,1,1-trichloroethane and methyl-r-butyl ether were dried in the liquid phase by contact with molecular sieves 4A (Connett Lab.Practice 21 545 1972). Other, less reactive types of sieves may be more suitable but, in general, it seems desirable to make a preliminary test to establish that no unwanted reaction takes place. For the principles of synthesis and identification see R. Szostak Molecular Sieves, Chapman Hall, London 1988, and for structure, synthesis and properties see R.Szostak Handbook of Molecular Sieves, Chapman Hall 1992. 

Because the objective of the protocol was not only to get a quantitative elemental analysis, but also to keep the sample size as small as possible, EDS must be considered as preliminary test for elemental analysis by ICP-MS or ICP-OES, thus allowing for the chemical composition of die material to dictate what must be done next... 

Preliminary tests with samples of vitreous silica, quartz, cristobalite, and tridymite not treated with NaOH showed an effect which for quartz was previously described (7, 13) repeated tests on the same sample did not reproduce the dissolution pattern but gave reduced values. The example in Figure 8 shows three of four repeated runs on the same cristobalite sample. Although the surface area remained constant, the concentration increase with time was always slower than in the preceding... 

Preliminary test method increment (sample) collection, processing, and analysis... 

Preliminary testing of the unpurified polyxanthate dispersant mentioned earlier, during the selective flocculation of three high sulfur coals, is described here. The coal samples used for the study were Kentucky No. 9, Meigs Creek, and Ohio No. 6. The coal... 

Equilibrium Dialysis The ED is performed for five test concentrations (0.01, 0.05, 0.1, 1 and 10 pg/mL) for each of the test plasma samples against PBS. At each concentration, four cells, each containing 1 ml of spiked plasma and PBS, are prepared for each plasma type. After the time to reach the equilibrium (e.g. 4 hr), which was determined in the preliminary test, the dialysis is stopped. Aliquots of 200 pL plasma sample or PBS buffer are taken from each cell. To determine the concentration bound in plasma (Cb) or the free or unbound fraction (cu) in the buffer the samples are analyzed by LC/MS-MS of LSC. The analytical method... 

Invert Sugar Conduct a preliminary test to ascertain the volume of water to be added to the 20 mL of Standardized Fehling s Solution to obtain a final total volume of 75 mL when the endpoint of the titration is reached. The invert sugar content of the Sample Solution should be between 250 and 400 mg per 100 mL so that a titer between 25 and 40 mL is needed to achieve the endpoint. Calculate the amount of water to be added to the Mixed Fehling s Solution as the difference... 

Subjects were not allowed to eat or drink anything else during the test period. Samples of plasma were collected after a 12-hour fast and hourly for 4 hours postdose. Plasma samples were analyzed for manganese content using graphite furnace atomic absorption spectrophotometry (Friedman, et al., J. Hutr. In press.) Consecutive tests in the same subjects were separated by a minimum of 14 days, since preliminary testing indicated no residual effect of the manganese dose after this time interval. 

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