Sample application solid samples

In the event that extraction is not useful or feasible, total dissolution of a sample may be required. Total dissolution involves the proper choice of solvent—one that will indeed dissolve the total sample. For solid samples, this will usually involve the use of water or acid-water mixtures, sometimes fairly concentrated acid solutions. For this reason, it is useful to summarize the application of water and the most common laboratory acids ... 

Theoretical and applied aspects of microwave heating, as well as the advantages of its application are discussed for the individual analytical processes and also for the sample preparation procedures. Special attention is paid to the various preconcentration techniques, in part, sorption and extraction. Improvement of microwave-assisted solution preconcentration is shown on the example of separation of noble metals from matrix components by complexing sorbents. Advantages of microwave-assisted extraction and principles of choice of appropriate solvent are considered for the extraction of organic contaminants from solutions and solid samples by alcohols and room-temperature ionic liquids (RTILs). 

Rutherford back-scattering spectroscopy (RBS) is one of the most frequently used techniques for quantitative analysis of composition, thickness, and depth profiles of thin solid films or solid samples near the surface region. It has been in use since the nineteen-sixties and has since evolved into a major materials-characterization technique. The number and range of applications are enormous. Because of its quantitative feature, RBS often serves as a standard for other techniques. 

So far powerful lasers with picosecond to nanosecond pulse duration have usually been used for the ablation of material from a solid sample. The very first results from application of the lasers with femtosecond pulse duration were published only quite recently. The ablation thresholds vary within a pretty wide interval of laser fluences of 0.1-10 J cm , depending on the type of a sample, the wavelength of the laser, and the pulse duration. Different advanced laser systems have been tested for LA ... 

For the application of flame spectroscopic methods the sample must be prepared in the form of a suitable solution unless it is already presented in this form exceptionally, solid samples can be handled directly in some of the non-flame techniques (Section 21.6). 

FIGURE 5.16 Template scheme (top view) for solid phase sample application (SPSA) and process of performance (cross section of steps a to e) 1 — base of the device, 2 — glass plate, 3 — adsorbent layer, 4 — sample, 5 — top of the device, 6 — plunger to compress. Step a Template placed onto the preparative plate Step b Marking by means of a thin needle Step c Scraped out channel on the preparative plate Step d Filling in of the prepared mixture of sample and deactivated adsorbent Step e Compression by means of a plunger. (From Botz, L., Nyiredy, Sz., and Sticher, O., J. Planar Chromatogr, 3, 10-14, 1990. With permission.)... 

This mode of chromatogram development is, in principle, almost identical with continuous development. The only feature that varies is the length of the developing path. In short bed-continuous development (SB/CD), this path is very short, typically equal to several centimeters [23-25]. This is the reason why this mode is preferentially applied for analytical separations. However, a similar technique is applied for zonal sample application and online extraction of solid samples, which are described in the following text. 

Rossbach M, Ostapczuk P, Emons H (1998) Microhomogeneity of candidate reference materials Comparison of solid sampling Zeeman-AAS with INAA. Fresenius J Anal Chem 360 380-383. Rossbach M, Stoeppler M (1987) Use of CRMs as mutual calibration materials and control of synthetic multielement standards as used in INAA. J Radioanal Nud Chem Artides 113 217-223. Sargent M (1995) Development and application of a protocol for quality assurance of trace analysis. Anal Proc 32 71-76. 

Supercritical fluid extraction (SFE) is generally used for the extraction of selected analytes from solid sample matrices, but applications have been reported for aqueous samples. In one study, recoveries of 87-100% were obtained for simazine, propazine, and trietazine at the 0.05 ug mL concentration level using methanol-modified CO2 (10%, v/v) to extract the analytes, previously preconcentrated on a C-18 Empore extraction disk. The analysis was performed using LC/UV detection. Freeze-dried water samples were subjected to SFE for atrazine and simazine, and the optimum recoveries were obtained using the mildest conditions studied (50 °C, 20 MPa, and 30 mL of CO2). In some cases when using LEE and LC analysis, co-extracted humic substances created interference for the more polar metabolites when compared with SFE for the preparation of the same water sample. ... 

Numerous applications of SEE were published during the 1980s soon after the availability of commercial instrumentation. Supercritical fluids (SFs) have useful characteristics for the extraction of trace analytes from solid samples, most notably... 

Solid-phase sorbents are also used in a technique known as matrix solid-phase dispersion (MSPD). MSPD is a patented process first reported in 1989 for conducting the simultaneous disruption and extraction of solid and semi-solid samples. The technique is rapid and requires low volumes (ca. 10 mL) of solvents. One problem that has hindered further progress in pesticide residues analysis is the high ratio of sorbent to sample, typically 0.5-2 g of sorbent per 0.5 g of sample. This limits the sample size and creates problems with representative sub-sampling. It permits complete fractionation of the sample matrix components and also the ability to elute selectively a single compound or class of compounds from the same sample. Excellent reviews of the practical and theoretical aspects of MSPD " and applications in food analysis were presented by Barker.Torres et reported the use of MSPD for the... 

Automated devices have been introduced for the three main steps of the chromatographic process, namely sample application, chromatogram development and evaluation. Appropriate sample application, i.e. its deposition on the plate as a small start zone, without damage to the solid-phase layer, is critical to the success of TLC. Sample application modes include spotting with the help... 

Applications The potential of a variety of direct solid sampling methods for in-polymer additive analysis by GC has been reviewed and critically evaluated, in particular, static and dynamic headspace, solid-phase microextraction and thermal desorption [33]. It has been reported that many more products were identified after SPME-GC-MS than after DHS-GC-MS [35], Off-line use of an amino SPE cartridge for sample cleanup and enrichment, followed by TLC, has allowed detection of 11 synthetic colours in beverage products at sub-ppm level [36], SFE-TLC was also used for the analysis of a vitamin oil mixture [16]. 

Table 8.23 Applications of direct solid sampling in ETAAS...

Different analytical procedures have been developed for direct atomic spectrometry of solids applicable to inorganic and organic materials in the form of powders, granulate, fibres, foils or sheets. For sample introduction without prior dissolution, a sample can also be suspended in a suitable solvent. Slurry techniques have not been used in relation to polymer/additive analysis. The required amount of sample taken for analysis typically ranges from 0.1 to 10 mg for analyte concentrations in the ppm and ppb range. In direct solid sampling method development, the mass of sample to be used is determined by the sensitivity of the available analytical lines. Physical methods are direct and relative instrumental methods, subjected to matrix-dependent physical and nonspectral interferences. Standard reference samples may be used to compensate for systematic errors. The minimum difficulties cause INAA, SNMS, XRF (for thin samples), TXRF and PIXE. 

---