Plastic sample containers

If volatile organic materials are present in the sample, plastic sample containers cannot be used. Many small organic molecules are able to diffuse through plastics. If the sample container is not tightly sealed, the volatiles may... 

Where the plastic sample contains both a major organic additive and a filler, it is necessary to pyrolyse the extracted portion of the sample and then record an infrared spectrum of the collected pyrolysis condensates. Providing that an extensive database of pyrolysate spectra is available (234), this method is very successful in identifying generic polymer types and polymer blends. In the case of blends, it is also possible to express the results semi-quantitatively if the appropriate standards are available. 

The principal uses of PCTFE plastics remain in the areas of aeronautical and space, electrical/electronics, cryogenic, chemical, and medical instmmentation industries. AppHcations include chemically resistant electrical insulation and components cryogenic seals, gaskets, valve seats (56,57) and liners instmment parts for medical and chemical equipment (58), and medical packaging fiber optic appHcations (see Fiber optics) seals for the petrochemical /oil industry and electrodes, sample containers, and column packing in analytical chemistry and equipment (59). 

The following experimental details apply both to the determination of tungsten with bromine as internal standard, and to the experiments of Table 7-2. The solutions filled a 3-ml container made by sectioning a 10-ml beaker. To prevent" evaporation and to maintain a fixed distance between x-ray tube window and sample surface, the beaker-section was covered with Mylar film, 0.0025 cm thick, placed in a plastic sample holder and pressed firmly against the sample drawer. The Mylar film attenuated the x-rays uniformly enough so as not to affect the precision of the results. 

For the hybridization, samples with deposited DNA were placed in plastic envelopes containing 2 mL of the hybridization buffer (10 mM Tris-HCl, pH 7.6,1 mM EDTA, 0.5% SDS). Twenty mL of the boiled probe was added to the same envelope. The envelopes were then sealed and placed into the water thermostat at 60°C, with stirring overnight. After the hybridization, the samples were strongly washed with distilled water for 10 min, dried, and measured. Cold hybridization was performed at room temperature. 

Plant material should be added to a disk mill (grain or seed matrices) or a vertical batch processor (all other matrices). Add an equal portion of pelletized dry ice to the sample (vertical processor only). Macerate the plant sample (or sample + dry ice) until a homogeneous mixture is obtained. Store the homogenized mixture in doubled plastic bags at —20 5°C. For samples containing dry ice, allow the open bag to stand in the freezer overnight to allow the dry ice to sublime prior to sealing the bag. 

The cloth dosimeter from the California roller technique consisted of placing a 15.2-cm x 61.0-cm piece of cotton cloth on treated turf, covering the cloth with plastic, and rolling over it with a 25-lb roller. The cloth was then placed in a sample container, which was put in a cooler and transported to the laboratory. The dosimeter was then extracted with hexane. An aliquot of... 

Changes in the distribution of organic compounds in a seawater sample can be due to physical, chemical, or biological factors. As a physical factor, we might consider the absorption of surface-active materials on the walls of the sample container. While this effect cannot be eliminated it can be minimised by the use of the largest convenient sample bottle, and the avoidance of plastic (especially Teflon) containers. Another possible method of eliminating this source of error would be to draw the sample directly into the container in which the analytical reaction is to be run. 

The important influence that sample container materials can have on seawater sample composition is illustrated next by two examples one concerning the storage of metal solutions in glass and plastic bottles, the other concerning the storage of solutions of phthalic acid esters and polychlorinated biphenyls in glass and plastic. 

An early study referred to the determination of traces of gold in ores by absorbing this element on the surface of foamed plastic [23], The sample containing the gold traces was first dissolved by a HC1-HN03 mixed solution and a piece of foamed plastic was then placed therein. After vibration for 30 min. on a vibrator, the solid material was removed, washed with tap water, and placed in a CL cell. A 2-mL volume of 1.0 mmol/L EDTA was added to the cell and the lid was closed then 2 mL of 0.01 mmol/L luminol solution was injected into... 

Of the tin additives studied, the anhydrous and hydrated zinc stannates, ZnSnO and ZnSn(OH), respectively, are considerably more effective flame-retardant synergists with the bromine present in the plastic than 8-stannic acid (Figure 1). In line with this observation, oxidic tin-zinc systems have previously been found to exhibit superior flame-retardant properties to tin oxides alone (19-22). In addition, ZnSnO, gives higher values of 01 than Sb20, incorporation levels studied, and, in fact, the 1% ZnSnO - containing plastics outperform samples containing 2% Sb O,. 

The plastics industry uses P.R.57 1 primarily wherever performance in application is a minor concern, especially with respect to lightfastness. In plasticized PVC, for instance, transparent coloration (0.1% pigment) of P.R.57 1 equal only step 2 on the Blue Scale, while samples containing TiOz never score higher than step 3. The exact value depends on the standard depth of shade and on the pigment concentration. P.R.57 1 is not suitable for use in concentrations below approximately 0.03%. 

The primary area of application for P.R.247 is in plastics, in which it produces medium to bluish, brilliant and opaque shades of red. Its tinctorial strength is moderate. 0.28% pigment is needed, for instance, to formulate 1/3 SD HDPE samples containing 1 % TiOz. Such samples equal step 6-7 on the Blue Scale for hghtfastness. 

The plastics industry uses P.O.36 to color PVC. 1/3 to 1/25 SD plasticized PVC samples containing 5% Ti02 equal step 8 and step 7, respectively, for lightfastness,... 

P.Br.23 shows excellent heat stability in polyolefins. 1/3 SD samples containing 1 % TiOz, as well as transparent colorations at 1/3 SD in HDPE are stable to exposure to 300°C for 5 minutes. In injection molding, P.Br.23 considerably affects the shrinkage of the plastic at 220°C, an effect which diminishes with increasing temperature (Sec. 1.8.3.2). 

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