Sample preparation liquid-solid

Sample Preparation Liquid Samples, Extracts, and Solutions of Solids... 

Figure 9. Partial H NMR spectrum of 13 LiN03 at 213 K. Top sample prepared by solid-liquid extraction using freshly opened CDC13. Bottom sample prepared with water-saturated CDCI3. (Reprinted with permission from ref. 32. Copyright 2004 American Chemical Society.)...

Solid Phase Microextraction Out of the many sample preparation methods, solid phase microextraction (SPME) is one of the most frequently used. SPME is used for the determination of VOCs in liquid, gas, and solid samples. The great advantage of the method is that it combines, in one stage, the isolation and enrichment of compounds, and completely eliminates the need for organic solvents. 

The laser vaporization approach allows the use of even the most refractory target materials. The source configuration used in Fig. 1 involves a target rod that is rotated and translated in a continuous screw motion to expose fresh metal to the laser beam. This has been found necessary to provide acceptable pulse-to-pulse reproducibility. Target rods of refractory metals, semiconductors, carbon, polyethylene, alumina, and alloys have all been vaporized successfully to make clusters in many laboratories. For some materials a disk target is preferred due to the ease in sample preparation. Molecular solids, liquids, and solutions could also be used, though care must be taken to consider the additional complex plasma chemistry one is likely to encounter. 

Infrared Sample Preparation Liquid Samples Solid Samples... 

One more trend that is worth mentioning is the miniaturization of sample preparation techniques. Solid phase microextraction is one good example of where very small samples are consumed and very small extracts are produced. Solid phase extractions can also be scaled down by reducing the bed volume or by use of coated membranes. Likewise liquid-liquid extractions can be scaled down conserving both sample and solvent. 

The injector is an interface that achieves reproducible and accurate transfer of a sample volume between the system operator and the chromatographic column in a front (band) as narrow as possible. Usually, for analysis by high-performance liquid chromatography (HPLC), samples are prepared in a liquid state (as a solution in an appropriate solvent or mixture of solvents, obtained as a result of sample preparation of solid or liquid samples). For practical reasons (avoiding column overloading), even for analytes in a liquid state under ambient conditions, dilution in appropriate solvents is more often used. 

The most important sample preparation methods for chromatographic analyses (including ion chromatography), taking into consideration the sample form (liquid, solid or gaseous) are ... 

Another advantage of this technique is the simplicity of samples preparation. The solid samples can be extracted in a deuterated solvent while liquid or freeze-dried extracts are often prepared by adding 5-10 % of deuterated solvent D2O [1,6]. 

Is the polymer matrix as claimed Infra-red analysis is a good technique for this determination. IR spectra can be obtained quickly with minimum sample preparation. Liquids and films can be run directly. The dust from filing a solid sample can be ground with potassium bromide (KBr) and a pellet pressed for analysis. Is the additive readily apparent in the spectrum ... 

The main problems with field analysis are sample preparation for solids and lack of sensitivity for liquids. One option for converting solid matrices (rock, soil, concrete etc.) into solution is to utilise equipment for the preparation of XRF bead samples. Portable versions are available commercially and use lithimn borate fusion at 1000°C to solubilise siliceous and other refractory matrices in a single step, rather than repeated extraction with aggressive and toxic reagents, such as hydrofluoric and/or perchloric acids. The beads can be analysed non-destructively for major components by portable XRF and then dissolved for alpha spectrometry or HazWAC, as required. 

Atomization The most important difference between a spectrophotometer for atomic absorption and one for molecular absorption is the need to convert the analyte into a free atom. The process of converting an analyte in solid, liquid, or solution form to a free gaseous atom is called atomization. In most cases the sample containing the analyte undergoes some form of sample preparation that leaves the analyte in an organic or aqueous solution. For this reason, only the introduction of solution samples is considered in this text. Two general methods of atomization are used flame atomization and electrothermal atomization. A few elements are atomized using other methods. 

Bulk density is easily measured from the volume occupied by the bulk solid and is a strong func tion of sample preparation. True density is measured by standard techniques using liquid or gas picnometry Apparent (agglomerate) density is difficult to measure directly. Hink-ley et al. [Int. ]. Min. Proc., 41, 53-69 (1994)] describe a method for measuring the apparent density of wet granules by kerosene displacement. Agglomerate density may also be inferred from direcl measurement of true density and porosity using Eq. (20-42). 

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). 

Raman spectroscopy is a very convenient technique for the identification of crystalline or molecular phases, for obtaining structural information on noncrystalline solids, for identifying molecular species in aqueous solutions, and for characterizing solid—liquid interfaces. Backscattering geometries, especially with microfocus instruments, allow films, coatings, and surfaces to be easily measured. Ambient atmospheres can be used and no special sample preparation is needed. 

The sample preparation discussed will not include the addition of standards for quantitative analysis as this subject will be dealt with in the chapter on quantitative analysis. Samples can arrive for LC analyses as solids, liquids or a mixture of both and, therefore, the three possibilities must be considered separately. Furthermore, the... 

Liquid samples might appear to be easier to prepare for LC analysis than solids, particularly if the compounds of interest are present in high concentration. In some cases this may be true and the first example given below requires virtually no sample preparation whatever. The second example, however, requires more involved treatment and when analyzing protein mixtures, the procedure can become very complex indeed involving extraction, centrifugation and fractional precipitation on reversed phases. In general, however, liquid samples become more difficult to prepare when the substances are present at very low concentrations. 

FIGURE 6.20 Sample application using preparative circular planar chromatographic device (the black zones symbolize the applied sample) (a) liquid phase sample application, (b) solid phase application into the center hole of the plate, (c) solid phase sample application into a scrapped channel. (From Botz, L., Nyiredy, Sz., and Sticher, O., J. Planar Chromatogr. 3, 401-406, 1990. With permission.)... 

The need to understand the fate of pesticides in the environment has necessitated the development of analytical methods for the determination of residues in environmental media. Adoption of methods utilizing instrumentation such as gas chro-matography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS), liquid chromatography/tandem mass spectrometry (LC/MS/MS), or enzyme-linked immunosorbent assay (ELISA) has allowed the detection of minute amounts of pesticides and their degradation products in environmental samples. Sample preparation techniques such as solid-phase extraction (SPE), accelerated solvent extraction (ASE), or solid-phase microextraction (SPME) have also been important in the development of more reliable and sensitive analytical methods. 

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