Paints reference materials

Figure 9.2 PCA score plot of amino acidic profiles obtained in the GC/MS analysis of samples from the collection of paint reference materials of Opificio delle Pietre Dure (+), containing egg, casein and animal glue as binders, and of samples from the OL17bis series (x ) from the Leonetto Tintori Collection [ 10]...

Because of the risk of lead poisoning, the exposure of children to lead-based paint is a significant public health concern. The first step in the quantitative analysis of lead in dried paint chips is to dissolve the sample. Corl evaluated several dissolution techniques. " In this study, samples of paint were collected and pulverized with a Pyrex mortar and pestle. Replicate portions of the powdered paint were then taken for analysis. Results for an unknown paint sample and for a standard reference material, in which dissolution was accomplished by a 4-6-h digestion with HNO3 on a hot plate, are shown in the following table. 

The %w/w lead in a lead-based paint Standard Reference Material and in unknown paint chips is determined by atomic absorption using external standards. 

Elaboration of the method for the identification of colour compounds by RPLC MS should comprise four steps (1) spectral characterization of reference materials (standards) and subsequent optimization of detection parameters, as well as those of their chromatographic separation (2) analysis of natural dyestuffs used as colouring materials in historical objects (3) analysis of model samples (dyed fibres, paintings) prepared according to old recipes (4) application of the acquired knowledge to identification of colourants present in historical objects. 

A number of methods are used to reduce and prevent corrosion. The most common method is to paint iron materials so that the metals are protected from water and oxygen. Alloying iron with other metals is also a common means to reduce corrosion. Stainless steel is an alloy of iron, chromium, nickel, and several other metals. Iron may also be protected by coating it with another metal. Galvanizing refers to applying a coating of zinc to protect the underlying metal. Additionally, because it is a more active metal, zinc oxidizes rather than iron. 

Traces are identified by determining their chemical composition and certain physicochemical properties, and comparison with reference material (database) or comparative material collected from the suspect. Criminalistic laboratories create extensive databases on the physical features and production of glass, paints, papers, fabrics and other materials, as well as collecting thousands of samples for comparison purposes. 

Processing of research results leads to determination of the following conclusion if as a result of conducted comparative physicochemical analyses, the properties and chemical composition of material forming the evidence trace are found to be consistent with those of the reference material, then, on this basis, the materials could have a common origin. This means, in the case of analysis of samples of paint, glass, plastic and fibres, that they could have constituted a single entity before... 

The obtained analytical data allow a conclusion to be drawn about whether the compared paint samples could have originated from the same coat of paint or not. If the reference material (i.e. from the suspect) is not available, only establishment of the kind of paint and the type of paint coat is possible. In the case of automobile paints, it is also possible to find the model of car involved in an accident. Eor this purpose, analytical data are compared with a database containing information about the type of paint coatings (layering, chemical composition of each layer) used in various types and models of vehicles in Europe. Such a collection has existed in Europe since 1995 and is updated every year with information on new products. Experts from many criminalistic laboratories have participated in its creation. Comparison with such a database provides information about the make and model of the vehicle involved in the incident and its year of production. It is thus helpful in identifying the perpetrator s vehicle. It should be emphasised that identifying the make and year of production of a vehicle on the basis of a paint database only applies to vehicles with a factory-new coat of paint. 

Standard Reference Material (SRM) 1597 obtained from the National Institute of Standards and Technology, was tested in an assay of tumor initiation in female SENCAR mice (Marston et al. 2001). SRM 1597 is a mixture derived from a medium crude coke oven coal tar dissolved in toluene. Certified values have been published for selected PAH components of this mixture including B[a]P. Dibenzo[a,l]pyrene (DB[a,l]P) is not a component of SRM 1597. SRM 1597 (1 mg per 125 pL, which contains 10.4 pg B[a]P) was painted onto the shaved skin of 6-7-week-old mice over a period of 2 weeks (the number of applications was not reported) and in some cases, treatment with SRM 1597 was followed 5 minutes later with B[a]P or DB[a,l]P). The treatment groups were as follows 10 mice with 200 pL toluene as a control 30 mice with 1 mg SRM 1597 35 mice with 200 nm (50.4 pg) B[a]P in 100 pL toluene 35 mice with 1 mg SRM 1597 plus 200 nm (50.4 pg) B[a]P in 100 pL toluene 35 mice with 2 nmol (0.6 pg) DB[a,l]P and 35 mice with 1 mg SRM 1597 plus 2 nmol DB[a,l]P. Two weeks after initiation, twice-weekly promotion was begun with 12-0-tetradecanoyl-phorbol-13-acetate (TPA) at... 

A hole is bored in the substrate prior to applying the paint coating. The hole is plugged with a nonwetting material such as Teflon. This will permit easy removal of the plug after the substrate has been painted. Refer to Figure 11.9. 

The American Society for Testing Materials (ASTM) has provided validated procedures for quantification of lead in various types of paint samples. ASTM E 1645 prescribes preparation of paint lead chips for analysis while methods ASTM E 1613, ASTM E 1775, and ASTM PS 88 are directed to measurements of lead. The NIST has made paint standard reference materials (SRM) available for calibration and validation of lead paint measurement methodologies. SRM 2579 is available as a paint film while SRM 2589 consists of paint samples collected from interiors of various homes and prepared as a homogeneous powder, 100,000 ppm (10%) lead, with >99% of the particles being <100 pm in size. 

Relatively few studies have been made on the feasibility of quantitative FAB analysis. Riley et al. [217] have described a quantification procedure to monitor the paint additive Tinuvin 770 in two coating systems (acrylic melamine and a hydroxy ester melamine). Tinuvin 770 proved to be well suited for FAB analysis in coating extracts on glycerol basis using an internal standardisation procedure. Lay et al. [218] have developed a FAB-MS method for the quantitative analysis of plasticisers (DEHP, including any isomeric dioctyl phthalates) in baby PVC pacifiers that does not require sample extraction, clean-up, or chromatographic separation. A reference material, didecylphthalate (DDP), was added to a solution of the PVC sample in THF as an internal standard. Quantitation was based on the relative... 

Description of normal stress measurements on a practical but complex material, paint, is available (150). More recent pubHcations (151—154) give the results of investigations of normal stress differences for a variety of materials. These papers and their references form a useful introduction to the measurement of normal stress differences. 

Corrosion resistance should also be considered with particular reference to the ambient environment. Painting schemes, coating materials and other protective skins (along with the substrate bonding method) should all be reviewed against the prevailing conditions. 

Organic materials Corrosive vapours are sometimes emitted by organic materials used either in packaging or in the manufactured article, and may be troublesome in confined spaces. Some woods, particularly unseasoned oak and sweet chestnut, produce acetic acid (see Section 18.10), and certain polymers used in paints, adhesives and plastics may liberate such corrosive vapours as formic acid and hydrogen sulphide . It may be necessary to carry out exposure trials, particularly where materials capable of liberating formaldehyde or formic acid are involved. Most corrosion problems of this kind can be prevented by using desiccants, and in many cases they are confined to imperfectly cured materials. For an excellent review see Reference 9. 

Metal atoms can be incorporated into polymers using two approaches. For probing new reactions between metal atoms and polymers a small-scale spectroscopic approach, sometimes referred to as the Fluid Matrix Technique (11), is used. The coreactant polymer matrix, containing on the order of 0.5 fll of polymer, is preformed on an optical surface. In the case of viscous fluids such as 2 the material is painted on the substrate and held at temperatures ranging typically from 200 to 270 K. The temperature is chosen to maintain low volatility but retain mobility. Under high vacuum [10 6 torr]... 

The resins are substances derived mostly from vegetable sources some have been used as binders in the preparation of paints and varnishes, others as incense burned in ritual ceremonies, and a few, such as amber, have been used on their own, as semiprecious stones. It should be noted, however, that since the midtwentieth century the term resin has acquired a new meaning that of a synthetic pliable "plastic" material that can be shaped, mostly when hot. Synthetic resins are used mainly for packaging and for making textile fibers and automobile parts. In the discussion that follows the term resin is used to refer only to resins of natural origin (Serpico and White 2000a Parry 1918). 

Organic polymers are sometimes referred to as plastics (although, this should be confined to thermoplastic polymers), macromolecules or resins, though the latter is often used to describe raw polymeric material awaiting fabrication. Many polymers are used in various forms that are not associated with normal plastic materials. These include paints and coatings, elastomers (rubbers), adhesives, sealants (caulks), surfactants and also their use in various industrial applications, e.g., ion-exchange resins, membranes. 

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