Glasses trace analysis

The main features of PC are low cost, need for small sample amount, high level of resolution, ease of detection and quantitation, simplicity of apparatus and use, difficult reproducibility (because of variation in fibres) and susceptibility to chemical attack. Identification of the separated components is facilitated by the reproducible Rj values. Detection methods in PC have been reviewed [368]. Fluorescence has been used for many years as a means of locating the components of a mixture separated by PC or TLC. However, also ATR-IR and SERS are useful. Preparative PC is unsuitable for trace analysis because filter paper inevitably contains contaminants (e.g. phthalate esters, plasticisers) [369]. For that purpose an acceptable substitute is glass-fibre paper [28]. 

Selection of digestion vessels the size of the digestion vessels depends on the sample volume. Standard vessels are 25, 40, SO, 100 and ISO ml glass. For extreme trace analysis, quartz and Teflon vessels are available. Vessels can also be supplied with dust covers and reflux extensions. 

Skarping G, Dalene M, Mathiasson L. 1988. Trace analysis of airborne 1,6-hexamethylenediisocyanate and the related aminoisoeyanate and diamine by glass capillary gas chromatography. J Chromatogr 435(3) 453-468. 

For the largest field of application for LA-ICP-MS - geological research - many different geological and glass standard reference materials are available. Using standard reference materials in LA-ICP-MS, analytical results for trace analysis in homogeneous samples can be obtained with an accuracy better than 10%, and a precision of 2-5% is also possible.25 If no suitable CRM... 

Figure 2-9 (a) Class A glass volumetric flask. [Courtesy A. H. Thomas Co., Philadelphia, PA.] (fc>) Class B polypropylene plastic volumetric flask for trace analysis. [Courtesy Fisher Scientific, Pittsburgh, PA.] Class A flasks meet tolerances of Table 2-3. Class B tolerances are twice as big as Class A tolerances, (c) Short-form volumetric flask with Teflon-lined screw cap fits in the analytical balance in Figure 2-3a. Teflon protects the cap from chemical attack. 

Trace analysis has its special hazards for the unwary. The most important of these are loss of material in the analytical process and contamination by outside sources. Everyone realizes that trace constituents can be lost from samples, but few are aware of the many ways in which this can occur. For example, phosphate has been observed to disappear mysteriously from water samples in polyethylene bottles (10). Nitric acid, used to clean plastic vials, has been observed to convert these surfaces to ion exchangers, which readily take up as much as 10 12 moles per sq. cm. of trace metals (16). Lead nitrate solutions unless made distinctly acidic, plate out much of the lead on the walls of glass bottles. While everyone realizes that formation of a precipitate is liable to carry out trace constituents either by adsorption or occlusion, it is not as well-known that vanishingly small amounts of precipitates—amounts likely to be overlooked on casual observation—may also do this. The fly-ash and soot, which seem to be inescapable components of city air,... 

Typically splitless injection is used for trace analysis by capillary GC. Splitless injections can exhibit problems with carryover, poor repeatability, and labile analytes. Penton (1991) reports improved results with the temperature-programmable injector. With a temperature-programmable injector, samples are injected into a glass insert at an injector temperature below the boiling point of the analysis solvent the injector temperature is then rapidly programmed to a higher value. Penton reported this technique offered greater ease of optimization and improved precision. 

Rijks, J. A., Drozd, J., and Novak, J. (1979). Versatile all-glass splitless sample introduction system for trace analysis by capillary gas chromatography. J. Chromatogr. 186, 167-181. 

Inorganic extractables/leachables would include metals and other trace elements such as silica, sodium, potassium, aluminum, calcium, and zinc associated with glass packaging systems. Analytical techniques for the trace analysis of these elements are well established and include inductively coupled plasma—atomic emission spectroscopy (ICP-AES), ICP-MS, graphite furnace atomic absorption spectroscopy (GFAAS), electron microprobe, and X-ray fluorescence. Applications of these techniques have been reviewed by Jenke. " An example of an extractables study for certain glass containers is presented by Borchert et al. ". ... 

In the past, the practice has been to take a sample from any depth in a large metal or (better) plastic container and then transfer the sample to another, usually plastic, container for subsequent analysis by appropriate analytical methods. Obviously, a metal container will contribute to the trace metal content of the sample, and even plastic containers will cause problems. Trace analysis studies have shown that plastic or glass sample containers can both absorb trace metal ions from the sample and/or contribute other metal ions to solution by surface dissolution 12, 13), Thus, the sample cannot be analyzed accurately because of the time-dependent effects on concentration which are related simply to the nature of the container and the conditions used to store the sample. 

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