Analysis, laboratory paint

Polymeric materials then, whether natural (such as cellulose, resins, and proteins) or synthetic (such as polyolefins, nylons, and acrylics), behave in reproducible ways when exposed to pyrolysis temperatures. This permits the use of pyrolysis as a sample preparation technique to allow the analysis of complex materials using routine laboratory instruments. Pyrolytic devices may now be interfaced easily to gas chromatographs, mass spectrometers, and FT-IR spectrometers, extending their use to solid, opaque, and multicomponent materials. Laboratories have long made use of pyrolysis for the analysis of paint flakes, textile fibers, and natural and synthetic rubber and adhesives. The list of applications has been expanded to include documents, artwork, biological materials, antiquities, and other complex systems that may be analyzed with or without the separation of various layers and components involved. 

An essential part of this research was accurate assessment of indices of body lead burden PbB concentration was the key predictor variable studied. Measurements of PbB levels, as well as lead in house paint and house dust, were done by the Heavy Metals Analysis Laboratory, Department of Pathology, UNC-Chapel Hill. 

Optical Techniques. The most important tool in a museum laboratory is the low power stereomicroscope. This instmment, usually used at magnifications of 3—50 x, has enough depth of field to be useful for the study of surface phenomena on many types of objects without the need for removal and preparation of a sample. The information thus obtained can relate to toohnarks and manufacturing techniques, wear patterns, the stmcture of corrosion, artificial patination techniques, the stmcture of paint layers, or previous restorations. Any art object coming into a museum laboratory is examined by this microscope (see Microscopy Surface and interface analysis). 

The relatively low entry level instrumentation cost and the relatively simple experimental methods associated with GARField - both comparable to a standard bench-top relaxation analysis spectrometer as commonly used by the food industry, for example, for water/fat ratio determinations - offer potential advantages to the industrial based user. Indeed, the overwhelming majority of the applications development work described here has been carried out in collaboration with major multi-national industrial corporations such as ICI Paints, Unilever and Uniqema, with industry sponsored research laboratories and associations such as Traetek, and with a range of small-medium sized enterprises. 

Chromatographic procedures applied to the identification of proteinaceous paint binders tend to be rather detailed consisting of multiple analytical steps ranging from solvent extractions, chromatography clean up, hydrolysis, derivatisation reactions, and measurement to data analysis. Knowledge of the error introduced at each step is necessary to minimise cumulative uncertainty. Reliable results are consequently obtained when laboratory and field blanks are carefully characterised. Additionally, due to the small amounts of analyte and the high sensitivity of the analysis, the instrument itself must be routinely calibrated with amino acid standards along with measurements of certified reference proteins. All of these factors must be taken into account because many times there is only one chance to take the measurement. 

When round robin tests were performed to test the reproducibility of these standard procedures, large coefficients of variation between laboratories were obtained for tin-free paints (78-80% and 24-32% for the ISO and ASTM methods respectively Haslbeck and Holm, 2005). These discrepancies have multiple sources such as the analytical method (Haslbeck and Holm (2005) report 4-54% deviations when different laboratories measuring samples of known concentration), the sea water conditions both in the holding tank and the measuring tank (Haslbeck and Holm, 2005), the sample preparation for analysis... 

Most of our understanding of the marine chemistry of trace metals rests on research done since 1970. Prior to this, the accuracy of concentration measurements was limited by lack of instrumental sensitivity and contamination problems. The latter is a consequence of the ubiquitous presence of metal in the hulls of research vessels, paint, hydrowires, sampling bottles, and laboratories. To surmount these problems, ultra-clean sampling and analysis techniques have been developed. New methods such as anodic stripping voltammetry are providing a means by which concentration measurements can be made directly in seawater and pore waters. Most other methods require the laborious isolation of the trace metals from the sample prior to analysis to eliminate interferences caused by the highly concentrated major ions. 

Polymer films of approximately 1000 microns wet film thickness were laid down with a bar applicator on PTFE coated glass panels and the solvent allowed to evaporate at ambient temperature for a standard period of seven days. A typical plot of solvent weight loss with time is shown in Figure 2. The thickness of the wet film was dictated by the need to have adequate mechanical strength in the dry films in order that they might be suitable for subsequent mechanical test procedures. Dry film thicknesses were approximately 300 microns as measured by micrometer. The dried polymer films were examined by dynamic mechanical thermal analysis (DMTA) (Polymer Laboratories Ltd.). Typical DMTA data for a polymer and paint are... 

Mr. Ali Hosni has academic background in chemistry and geology and about 36 years working experience with the industry. Furthermore, Mr. Hosni has long experience in chemical analysis and quality control laboratories of a Iron and Steel industry, Paint... 

Figure 8. The Henry Francis du Pont Winterthur Museums analytical laboratory setup for the analysis of pigments on painted silk. (Courtesy of The Henry Francis du Pont Winterthur Museum.)...

Initially, Wolkoff et al. (1991) developed a testing protocol for the FLEC cell. Later, a Nordtest method for laboratory measurements was approved (Nordtest, 1995). This Nordtest method mainly deals with the FLEC as a testing device for the determination of VOCs at standard climate and using adsorbent tubes intended for analysis by GC. Trade standards describing materials sampling etc. have been developed for specific products like paints (SVEFF, 1997) and flooring materials (GBR 1992a, GBR... 

For urine analysis sample aliquots are diluted 1 1 with distilled water before application to the AAS stabilized temperature platform (Leung and Henderson, 1982). Fecal analysis require considerably more complicated preparation steps than serum or urine. The procedure developed in the author s laboratory (Brown et al., manuscript in preparation) is summarized as follows Frozen specimens are thawed and distilled water is added (1 mL per 2 g feces) and the sample is homogenized in a sealed container on a paint shaker. A 10 mL aliquot is ashed at 550°C in a muffle furnace, dissolved in dilute HNO3 snd analyzed by GF-AAS. 

The Administrator shall establish protocols, criteria, and minimum performance standards for laboratory analysis of lead in paint films, soil, and dust. Within 2 years after October 28,1992, the Administrator, in consultation with the Secretary of Health and Human Services, shall establish a program to certify laboratories as qualified to test substances for lead content unless the Administrator determines, by the date specified in this paragraph, that effective voluntary accreditation programs are in place and operating on a nationwide basis at the time of such determination. To be certified imder such program, a laboratory shall, at a minimum, demonstrate an abihty to test substances accurately for lead content... 

This might help to explain why forensic analysts invest a lot of time in the identification or qualitative stage of the analysis. It is not uncommon to find forensic laboratories performing a three-tier assessment of potential controlled substances. This will involve a presumptive test, followed by a chromatographic separation and finally a mass spectral identification. Many of the analyses performed in the forensic environment are focused on what is present in the sample, rather than how much is there. Another example of this might be a paint examination, where it is important to assess the components present in relation to their chemical composition and also layer structure. Toxicological analysis, on the other hand, does require both a qualitative and quantitative assessment of what is present in the sample. 

Any item or debris suspected of containing accelerant residue should be collected in a tightly sealed, clean, and previously unused paint can, a special evidence bag, or a clean glass jar to prevent further evaporation. The container should be of size similar to the amount of debris but should be no more than three-fourths full, leaving sufficient headspace volume for subsequent laboratory analysis. Care should be taken to avoid contamination as this will compromise the value of the evidence. The container should be labeled with the investigator s name as well as the date, department, location, area from which the sample was taken, case numbei and description of the item or contents. The chain of custody must be maintained if the evidence is to be used in court. 

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