Sampling, automation

Hot splitless WCOT 0.5 ppm (FID) without preconcentration Lower injection temperature than split Trace analysis Handles dirty samples Automation Flash vaporisation Optimisation required (splitless time, oven temperature, solvent) Limited number of solvents ( solvent effect ) Thermal degradation possible Discrimination possible Poor direct quantification Unsuitable for very polar substances... 

SFE-GC-MS is particularly useful for (semi)volatile analysis of thermo-labile compounds, which degrade at the higher temperatures used for HS-GC-MS. Vreuls et al. [303] have reported in-vial liquid-liquid extraction with subsequent large-volume on-column injection into GC-MS for the determination of organics in water samples. Automated in-vial LLE-GC-MS requires no sample preparation steps such as filtration or solvent evaporation. On-line SPE-GC-MS has been reported [304], Smart et al. [305] used thermal extraction-gas chromatography-ion trap mass spectrometry (TE-GC-MS) for direct analysis of TLC spots. Scraped-off material was gradually heated, and the analytes were thermally extracted. This thermal desorption method is milder than laser desorption, and allows analysis without extensive decomposition. 

The photo-oxidation of dissolved organic carbon in batch procedures [56, 57] requires long reaction times, because of the thickness of the sample. Automated, continuous procedures, where the sample is irradiated by a medium pressure mercury lamp [30,57] brought great improvement and are utilised in several commercial instruments. 

Automatic instruments are usually reflection-type instruments that measure the deflection of a beam of light as it passes from one medium, into the sample and then is reflected back to a detector. The angle at which the light beam exits the medium is related to the refractive index of the sample. Automated instruments are calibrated with standard substances of precisely known refractive index prior to use. 

Refinement approaches lead to a decreased cycle time via the faster and more efficient analysis of samples. Automation is an obvious and desirable goal to speed up the analysis, optimize the measurement, and coordinate diverse tasks. A tremendous emphasis is placed on aspects of analysis such as sample preparation and data processing and data management. Once considered to be peripheral to the actual analysis, these activities have become important elements of high throughput analysis. 

Soxhlet extraction and automated Soxhlet extraction are described in this section. Soxhlet extraction was named after Baron Yon Soxhlet, who introduced this method in the mid-nineteenth century. It had been the most widely used method until modern extraction techniques were developed in the 1980s. Today, Soxhlet is still a benchmark method for the extraction of semivolatile organics from solid samples. Automated Soxhlet extraction (Soxtec being its commercial name) offers a faster alternative to Soxhlet, with comparable extraction efficiency and lower solvent consumption. 

The introduction of membranes in the field of sample preparation contributes to minimal organic solvent use, minimal contamination and exposure to toxic or dangerous samples, automation, and effective cleanup and analyte isolation. 

For analysis of free compounds, the headspace analysis with a multiphase fiber is even more interesting and less time-consuming. This approach can replace the majority of the quantification of free compounds measured by SPE techniques, considering also the possibility of the sampling automation using a GC-MS system which can be coupled to a statistical treatment of fragments abundance (Kinton et al., 2003 Cozzolino et al., 2006). Moreover, HS-SPME/GC-MS is a very effective and efficient method to analyze specific compounds present in trace levels at about ppt level, because they can be better and selectively enriched in the headspace. This method is employed nowadays to quantify some important and peculiar sensory compounds such as ethyl and vinylphenols, pyrazines, cork off-flavour substances (TCA, etc.) and other contaminants such as geosmine (Riu et al., 2002 Chatonnet et al., 2006) and, as shown below, sulphur volatiles. 

It is especially important to perform calibration experiments with plasma or other high-viscosity samples. Automated procedures that include on-line gravimetric and density determinations have been reported [68,69], Not all workstations provide the same level of tuning of liquid-class parameters. Some vendors offer multivariate analysis packages that help users set up the appropriate Uquid-class experiments and then use statistical approaches such as design of experiment (DOE) to guide the determination of optimal liquidhandling parameters [70]. 

Headspace is useful for the trace analysis of compounds having a high affinity for the fiber phase and that can be enriched in the HS of the sample. The use of a multiphase fiber is a very interesting and low time-consuming approach. It also considers the possibility of sampling automation using a GC/MS system coupled with a statistical method for treatment of fragment abundance (Kinton et al., 2003 Cozzolino et al.,2006). 

Following the measurement, the beads are washed from the cell, which is then cleaned and made ready for the next sample. Automated instruments for clinical diagnostics, capable of handling multiple samples without operator intervention, are available. 

Microscopy. Characterization of particulate from suspensions using microscopic methods is an effective method for establishing the size distribution of the particles and also their composition. Using properly prepared samples, automated image analysis techniques can be used that significantly reduce data collection times. Although the size distribution and composition of the suspended particles are important, the real strength of microscopic methods is the ability to observe particles in suspension and to determine how they interact and associate. There is little difference in microscopic methods applied to solids in suspension or to oil droplets in suspension (emulsions). As a result, the bulk of this discussion is borrowed from a similar chapter on emulsion characterization found in reference 19. 

Sampling Automation. In the terminology given in the first part of the chapter, instruments that emulate manual sample handling and processing without the use of control loops are automatic (mechanized), but not automated. Among the automatic functions are ... 

For voltammetric study of the total antioxidant activity of the samples automated voltammetric analyzer Analyzer of TAA (Ltd. Polyant Tomsk, Russia) was used. As supporting electrolyte the 10 ml of phosphate buffer (pH = 6.76) with known initial concentration of molecular oxygen was used [7]. The electrochemical cell (V = 20 ml) was connected to the analyzer and consisted of a working MFE, a silver-silver chloride reference electrode with KCl saturated (Ag AgCl KCl J and a silver-silver chloride auxiliary electrode. The investigated samples (10-500 ml) were added in cell. 

See also Building Materials. Ceramics. Sample Handling Comminution of Samples Automated Sample Preparation. X-Ray Fluorescence and Emission ... 

For voltammetric study of the total antioxidant activity of the samples automated voltammetric analyzer Analyzer of TAA (Ltd. Polyant Tomsk, Russia) was used. As supporting electrolyte the 10 ml of phosphate buffer (pH = 6.76) with... 

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