Solid sampling, direct

There are advantages to direct solid sampling. Sample preparation is less time consuming and less prone to contamination, and the analysis of microsamples is more straightforward. However, calibration may be more difficult than with solution samples, requiring standards that are matched more closely to the sample. Precision is typically 5% to 10% because of sample inhomogeneity and variations in the sample vaporization step. 

A suitable method to determine the degree of homogeneity of an element in a material is by repetitive analysis of a large number of small soUd ahquots by direct solid sample analysis. As shown in Figure 4.3, there is a functional relationship between the sample mass used for analysis and the standard deviation of repetitive analysis. 

ScHRON W, Liebmann A, Nimmereall G 2000) Direct solid sample analysis of sediment, soils, rocks and advanced ceramics by ETV-ICP-AES and GF-AAS. Fresenius J Anal Chem 366 79-88. 

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]. 

Nondestructive radiation techniques can be used, whereby the sample is probed as it is being produced or delivered. However, the sample material is not always the appropriate shape or size, and therefore has to be cut, melted, pressed or milled. These handling procedures introduce similar problems to those mentioned before, including that of sample homogeneity. This problem arises from the fact that, in practice, only small portions of the material can be irradiated. Typical nondestructive analytical techniques are XRF, NAA and PIXE microdestructive methods are arc and spark source techniques, glow discharge and various laser ablation/desorption-based methods. On the other hand, direct solid sampling techniques are also not without problems. Most suffer from matrix effects. There are several methods in use to correct for or overcome matrix effects ... 

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

Table 8.34 Requirements of an ideal direct solid sampling method for elemental analysis...

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. 

Direct solid sample analysis is still mostly a subsidiary method, confined to specific analytical tasks, rather than truly complementary to traditional analysis via solutions. Solid sampling is not standard in routine... 

Direct solid sampling (bulk metal, thin film, compacted powder, solution residues)... 

Nimmerfall G, Schron W (2001) Direct solid sample analysis of geological samples with SS-GF-AAS and use of 3D calibration. Fresenius J Anal Chem 370 760... 

LA-ICP mass spectrometry is becoming the method of the choice for trace and isotope analysis of solid samples and is already the most important laser induced technique in inorganic mass spectrometry due to the advantage of direct solid sampling by focused laser irradiation on the sample surface and its ability to provide microscale information. 

Regarding FAAS, only a study by Flores et al. [74] employed PLS to quantify Cd in marine and river sediments measured by direct solid sampling FAAS. 

Figure 21-9 Direct solid sampling showing end view of furnace.

M. Hornung and V. Krivan, Determination of Trace Impurities in Tungsten by Direct Solid Sampling Using a Transversely Heated Graphite Tube. Anal. Chem. 1998, 70, 3444. 

U. Schaffer and V. Krivan, Analysis of High Purity Graphite and Silicon Carbide by Direct Solid Sampling Electrothermal Atomic Absorption Spectrometry, Fresenius J. Anal. Chem. 2001,371, 859 R. Nowka and... 

Mixed Gas Plasmas. Water loading can be reduced by a desolvation system (condenser or membrane separator) only if the vast majority of the water can be removed. One way to eliminate the introduction of water into the plasma during measurement of the analyte signals is with electrothermal vaporization, laser ablation, or other direct solid sampling techniques. Mixed gas plasmas,... 

Figure 4.8 shows an example for this mode of correction applied for the determination of Pb in pig kidney reference material, using direct solid sample analysis. The three-dimensional plot in Figure 4.8a shows that a strong molecular absorption with pronounced fine structure appears short after the atomic absorption signal. Figure 4.8b shows the time-integrated absorbance spectrum of PO,... 

Figure 4.8. Least-squares BC for molecular spectra with rotational fine structure determination of Pb in the BCR 186 Pig Kidney CRM at 217.001 nm using HR-CS ET AAS and direct solid sample analysis (a) absorbance over time and wavelength after correction for continuous absorption (b) reference spectrum absorbance over wavelength integrated over time for NH4H2P04 (the dotted line represents the center pixel) (c) absorbance over time and wavelength after subtraction of the reference spectrum using least-squares BC.

Figure 4.17. Three-dimensional graph for Cr in the NIST 8415 Whole Egg Powder SRM in the vicinity of the 357.87 nm line pyrolysis temperature 700°C, atomization temperature 2500°C direct solid sampling analysis.

Figure 4.19. Determination of Pb in biological reference materials in the vicinity of the 217.001 nm line pyrolysis temperature 700°C, atomization temperature 1700°C Ru permanent modifier direct solid sampling analysis (a) wavelength integrated over time for the NIST 8414 Bovine Muscle SRM (b) wavelength integrated over time for NIST 8415 Whole Egg Powder (c) absorbance over time for Whole Egg Powder, recorded at selected pixels in the vicinity of the analytical line.

Figure 4.20. Three-dimensional graphs for Se in the BCR 186 Pig Kidney CRM pyrolysis temperature 800°C, atomization temperature 2000°C Ir permanent modifier direct solid sampling analysis (a) in the vicinity of the 196.026 nm line (b) in the vicinity of the 203.985 nm line.

Metal Content. Calcium, sodium, and boron contents of paper samples were determined by using a direct solid-sampling technique in conjunction with flameless atomic absorption spectroscopy (20,24). A Varian Techtron AA-6 spectrophotometer was employed with a model 90 carbon rod atomizer. In addition to the direct solid-sampling technique, calcium content was also determined by digesting samples with concentrated hydrochloric acid for 30 min. 

The most salient features of laboratory-built atomizers for direct solid sampling are as follows ... 

LIMITS OF DETECTION (LoD) OBTAINED IN DIRECT SOLID SAMPLING ETA-AAS AND COMPARISON WITH THOSE REPORTED FOR OTHER METHODS USED FOR THE ANALYSIS OF TITANIUM... 

CONTENTS OF TRACE IMPURITIES AS DETERMINED IN NIOBIUM PENTOXIDE BY DIRECT SOLID SAMPLING ETA-AAS AND COMPARISON WITH THE RESULTS OBTAINED BY SLURRY SAMPLING ETA-AAS (SIS-ETA-AAS) AND SOLUTION ETA-AAS (SoI-ETA-AAS)... 

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