Samples paint

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 water concentration in the paint and in the paint film has been determined using a Mitsubishi moisture meter. The anode cell was filled with Karl-Flscher reagent and the cathode cell with a mixture of pyridine, formamlde and Karl-Flscher reagent (70/30/6Z (v/v)). Paint samples were injected directly into the cathode solution. 

Unpigmented paint samples were brushed onto a potassium bromide crystal or polyethylene sheet (paint film thickness about 5 microns) and stored at controlled relative humidity using saturated salt solutions in closed vessels or a climate controlled room. 

As indicated in Section 6.2.2, DI-CIMS suffers from poor reproducibility. For nonvolatile additives that do not evaporate up to 350 °C, direct quantitative analysis by thermal desorption is not possible. The method depends on polymer formulation standards that are reliably mixed. Wilcken and Geissler [264] described rapid quality control of l- xg paint samples by means of temperature-programmable DI-EIMS with PCA evaluation. 

As microwave sample preparation has evolved, standard microwave procedures have been developed and approved by numerous standard methods organisations (ASTM, AOAC International, EPA, etc.), see ref. [64]. Examples are standard test methods for carbon black/ash content (ASTM Method D 1506-97), lead analysis in direct paint samples (ASTM Method E 1645-94), etc. Table 8.15 shows some microwave ashing references (detection weight). A French AFNOR method utilises the atmospheric pressure single-mode microwave method as an alternative sample preparation procedure for Kjeldahl nitrogen determination [84], The performance of a microwave-assisted decomposition for rapid determination of glass fibre content in plastics for QC has been described [85]. 

ASTM. 1998c. ASTM E 1645. Standard practice for the preparation of dried paint samples for subsequent lead analysis by atomic spectrometry. American Society for Testing and Materials. 

Figure 11 shows the ATR-FTIR spectrum acquired from the surface of the white-colored paint sample after the paint had been dried. Figure 12 shows the closest spectral library database matches obtained Figure 13 compares the spectrum of the surface of the white-colored paint sample with that of a reference library spectrum of a vinyl toluene-modified alkyd. The binder from the dried... 

Figure 11 ATR-FTIR spectrum of the dried white-colored paint sample. 

Figure 12 FTIR spectral library database matches to the spectrum shown in Figure 9 obtained from the dried white-colored paint sample.

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. 

Table 6 ICP-MS results for the white-colored paint sample...

Table 7 shows the calculated weight percent of calcium carbonate and titanium dioxide in the white-colored paint sample. These levels are based on the calcium and titanium levels shown in Table 6. Calcium carbonate was evident by the FTIR spectrum acquired from the dried paint sample, shown in Figure 13. (Flad it been available, Raman spectroscopy, which gives ready access to the low wavenumber region, could have been used to confirm the presence (and polymorphic form) of titanium dioxide [4].) Given the white color of the paint, it is likely that the titanium present was present as titanium dioxide, and this was assumed in the calculations. The calculated weight percentage of calcium carbonate in the dried paint is 21.7 wt%, and 12.6 wt% in the paint containing the solvents. The titanium dioxide levels were calculated to be 30.6 and 17.7 wt% in the dried and solvent-containing paint sample, respectively.

In conclusion, the paint sample was comprised of 63.3 wt% solids (polymers and fillers) and 36.7 wt% solvent. The solids were likely comprised of calcium carbonate and titanium dioxide at 12.6 and 17.7 wt%, respectively, of the total sample including solvent. The calcium carbonate and titanium dioxide were calculated based on the measured levels of calcium and titanium from the ICP analysis. Not counting the calcium and titanium levels there is 4.9 wt% of additional metals present. Based on the calcium carbonate level and titanium dioxide level along with the remaining percentage of metals present, 34.9 wt% of the total sample is accounted for. Therefore, the maximum level of alkyd in the sample is 28.4 wt%. TGA is recommended in order to quantify the level of alkyd and total level of mineral fillers in the dried paint sample. 

The solvents encompass 36.7 wt% of the paint sample. The solvent appears to be consistent with a mixture of a VM P naphtha with toluene. Toluene is the major constituent. 

The experimental set-up used for the micro-LIBS measurements on the painted sample is sketched in Figure 1. 

M.P. Colombini, S. Francesconi, R. Fuoco, F. Modugno, Characterisation of proteinaceous binders and drying oils in wall painting samples by GC MS, Journal of Chromatography A, 846, 101 (1999). 

Figure 5.17 GALDI mass spectra of (a) Japan wax and (b) a dark blue paint sample from Jean Francois Raffaelli Le defile devant la maison de Victor Hugo pour ses 80 ans (1902, Musee Victor Hugo, Paris) [59], Both spectra are dominated by tripalmitin (m/z 830) and higher homologues (see Table 5.8)...

In the analysis of paint samples, a stepwise extraction of the various lipid and resinous components has been proposed [33] which uses isooctane, methanol, chloroform/methanol (7 3) and methanol/oxalic acid (10%). The last extraction releases FAs from the metal soaps. 

In the case of paint samples where lipids are often admixed with proteinaceous binders, in some cases acidic hydrolysis is proposed to simultaneously hydrolyse proteins and triglycerides in the same step [35,36], although in acidic conditions the hydrolysis of triglycerides is not quantitative. 

The analysis of paint samples represents a peculiar case, in which the identification of lipids is made virtually possible by the fact that the range of used materials is limited to drying oils (linseed, poppy seed, walnut, tung), egg yolk, and beeswax. Safflower oil (from... 

Lipids are generally identified in paint samples by evaluating characteristic ratio values of FA amounts and comparing them with naturally or artificially aged reference paint layers. Molar or weight contents are obtained after quantification based on calibration curves. 

High amounts of a,co-dicarboxylic acids (mainly suberic, azelaic and sebacic) in a paint sample are indicative of the presence of an aged drying oil. This is because dicarboxylic acids, of which azelaic is the most abundant, are produced during the auto-oxidation of the polyunsaturated acylic chain present in drying oils. 

The ratio between the amounts of azelaic and palmitic acids (A/P) is a parameter for differentiating drying oils from egg lipids in paint samples because the amount of dicarboxylic acid formed in the ageing of egg lipids is considerably less than it is in drying oils. Values of A/P >1 indicate a drying oil, values of A/P <0.3 are typical of egg lipids,... 

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