Paints elemental analysis

Samples which cannot be frozen or which do not need to be frozen, such as soils intended for elemental analysis, plastics, paints or any other samples where both the matrix and the analyte are non-volatile and stable at ambient temperatures, are usually stored at 0 to 5°C. It may not even be necessary to refrigerate the sample, as many are stable at room temperature. 

Using forensic photography as a precursor to any sample acquisition forms the foundation of the protocol, and allows purposive sampling. EDS should be performed to establish which elements to expect before attempting any quantitative elemental analysis such as ICP-OES/MS. Before working with actual artifacts, a set of replicated materials must be used and a successful trial run using the planned methods of analysis whether ICP-OES/MS, GC-MS or any others, must be achieved, so the methods of preparation can be adjusted properly. To facilitate this, appropriate materials must be replicated, which might mean that plants or minerals must be collected, and dyed or painted comparative standards must be created, so the unknown can be compared to the known. For many of the Old World dye plants these standards already exist. However, for North American dye plants comparative collections are in the early phases and subsequent analysis of colorant constituents have not yet been conducted (68,69). 

The potential of ultrasonic extraction for field-based extractions has been put into use in the industrial hygiene and environmental single-element analysis of, for example, lead from glass fibre filter ambient air samples [13,14] or from lead-based paint, urban dust and river sediment [15] hexavalent chromium from coal fly ash and paint chips [16] and strontium from river sediment [17]. Ultrasonic extraction has also proved effective as a prior step in multi-element determinations of heavy metals. 

Deconinck, I., Latkoczy, C., Guenther, D. et al. (2006) Capabilities of laser ablation-induc-tively coupled plasma mass spectrometry for (trace) element analysis of car paints for forensic purposes. J Anal Atom Spectrom, 21 (3), 279-287. 

X-ray fluorescence (XRF) spectroscopy is useful for qualitative elemental analysis of paint samples. It does not require dissolution of the sample and can be applied to dry films. When an energy-dispersive instrument is employed, XRF provides rapid information on the presence of elements of atomic number higher than or equal to 12 (e.g., above magnesium). However, from a quantitative point of view, the sensitivity, accuracy, and reproducibility of XRF measurements is lower than that of flame, electrothermal, or plasma atomic spectrometry. 

With LA, MC-ICP-MS isotope ratio measurements can be performed in just a few minutes per sample as compared with the several hours per sample required for TIMS analysis. In addition, LA-MC-ICP-MS can yield spatially resolved isotope ratio characterization. Thus, provenance studies of ceramic paints, glazes, and slips in situ by LA-MC-ICP-MS measurement of lead and/or other isotope ratios are obvious areas for future development. Hints of the potential of this approach are highlighted in a recent study by Huntley [74], which showed that interaction on different spatial scales can be detected via elemental analysis of paste together with lead isotope analysis of glaze paints on Zuni glazed wares. 

Most paints do not usually display as much diversity in chemistry, color, and layer structure as do automotive ones. Therefore, a wider variety of analytical instruments are often used to characterize them. Along with microscopy and IR spectroscopy, other methods frequently used are pyrolysis GC/MS and inorganic elemental analysis by X-ray spectroscopy in the SEM. X-ray diffraction is also of use in the identification of crystalline pigments and fillers. 

Speakman and his colleagues describe the application of inductively coupled plasma mass spectrometry (ICP-MS) to the elemental analysis of obsidian, chert, pottery and painted and glazed surfaces. Only a very small area is affected in the laser ablation sampling, usually 1000 pm by 1000 pm by 30 pm. Their method is virtually nondestructive since the ablated area is not visible to the naked eye. Because ICP-MS has a lower detection limit than other... 

Duncan et al. (1990) have noted the use of brass powders as metallic pigments on Japanese artefacts. Metallic bronze of a grey colour has recently been found on three paintings o f Pemgino, one from the National Gallery, London and two in Florence elemental analysis showed this alloy to contain a ratio of tin to copper of 1 2 which in dry ground powder form appears grey. 

A 68 element ICP-MS scan was performed on one dried white-colored paint sample. The chemical elements scanned for during the ICP analysis and the detection limits are provided in Table 5. Approximately 0.5 g of each sample was prepared by an acid digestion technique prior to conducting the ICP-MS analysis. Shown in Table 6 are the quantified ICP-MS results for the sample. Elements scanned for but not detected are either not present in the sample or may be present below the detection limit. 

Neutron activation analysis is an attractive method in many trace element problems, or where the total amount of sample is limited. Many geochemical studies of trace constituents and semi-conductor developments have used the technique, whilst in recent years pollution investigations have provided a new focus. In forensic science small flakes of paint, single hairs and a variety of other small samples have been analysed and identified by activation analysis. In recent years activation analysis has lost further ground to ICP-MS which provides more comprehensive information and is more readily operated. Sensitivity is also comparable in many cases. 

The high sensitivity of modem instrumental techniques such as ICP-MS (Chapter 9) means that in many cases only small samples (typically, a hundred milligrams or less) need be taken for destructive analysis. However, this also means that the amounts of some individual elements may be very low, and problems of contamination can be significant. Common external contaminants include A1 from deodorants, Pb from paint or car exhausts, Zn from skin particles (and therefore from dust), and Na from sweat. The levels of contamination for each batch of samples will be revealed by the sample... 

Results For the St. Louis data, the target transformation analysis results for the fine fraction without July Uth and 5th are given in table 6. The presence of a motor vehicle source, a sulfur source, a soil or flyash source, a titanium source, and a zinc source are indicated. The sulfur, titanium and zinc factors were determined from the simple initial test vectors for those elements. The concentration of sulfur was not related to any other elements and represents a secondary sulfate aerosol resulting from the conversion of primary sulfur oxide emissions. Titanium was found to be associated with sulfur, calcium, iron, and barium. Rheingrover ( jt) identified the source of titanium as a paint-pigment factory located to the south of station 112. The zinc factor, associated with the elements chlorine, potassium, iron and lead, is attributed to refuse incinerator emissions. This factor could also represent particles from zinc and/or lead smelters, though a high chlorine concentration is usually associated with particles from refuse incinerators ( ). The sulfur concentration in the refined sulfate factor is consistent with that of ammonium sulfate. The calculated lead concentration in the motor vehicle factor of ten percent and a lead to bromine ratio of about 0.28 are typical of values reported in the literature (25). The concentration of lead in... 

The use of activation analysis in criminal investigations (forensic activation analysis) is also well established. The basic idea here is to match the trace-element distributions found in bullets, paint, oil, and so on found at the scene of a crime with the trace-element distributions in objects found with criminal suspects. Such identification is rapid and nondestructive (allowing the actual evidence to be presented in court). Moreover, the probability of its correctness can be ascertained quantitatively. Other prominent examples of the use of forensic activation analysis involve confirmation of the notion that Napoleon was poisoned (by finding significant amounts of arsenic in hair from his head) and the finding that the activation analysis of the wipe samples taken from a suspect s hand can reveal not only if he or she has fired a gun recently but also the type of gun and ammunition used. 

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