Sample preparation solubilization

Solubilizing all or part of a sample matrix by contacting with liquids is one of the most widely used sample preparation techniques for gases, vapors, liquids or solids. Additional selectivity is possible by distributing the sample between pairs of immiscible liquids in which the analyte and its matrix have different solubilities. Equipment requirements are generally very simple for solvent extraction techniques. Table 8.2 [4,10], and solutions are easy to manipulate, convenient to inject into chromatographic instruments, and even small volumes of liquids can be measured accurately. Solids can be recovered from volatile solvents by evaporation. Since relatively large solvent volumes are used in most extraction procedures, solvent impurities, contaminants, etc., are always a common cause for concern [65,66]. 

One inherent property of peptides that interact with membranes is that self-association or even aggregation will interfere with solubilization by organic solvents or micelles. The preparation, purification and sample preparation of extremely hydrophobic (often transmembrane) peptides is nontrivial and has been addressed by only a few papers [74—79]. 

The chemical or physical form of trace metals in water is often of interest. The form in which a specific element is present will often influence is toxic effects. For instance the chemical state of chromium affects its toxicity i.e., Cr+6 is more carcino genic than Cr+3, Kopp (48) has described the various forms in which metals may he present. The categories include dissolved metals, suspended metals, total metals, extractable metals and organometallics. In addition, Kopp describes sample preparation requirements for each category. Gihhs (20) has also studied metal species in river water. It should be obvious that the desired analytical result has to he considered beforehand. For example, if dissolved metal concentrations were desired and normal acid preservation performed, suspended metals could possibly be solubilized to a large extent. Both Hamilton (25) and Robertson (81) have shown vast differences between acidified and non-acidified samples. Many other publications have dealt with this subject (16, 37, 80, 30). 

Procedures of the sample preparation are enough trivial now with the exception of producing of CgoFWS. This was produced without using of any solubilizers and chemical modification [4], The method is based on transferring of fullerene from organic solution into the aqueous phase with the help of ultrasonic treatment [6]. The highest concentration of the solution used in present experiments was 400 pM/1. 

LPS samples preparation Dissolve 10 p.g of LPS samples in 10 (xL distilled water, and mix with 10 (xL of freshly prepared 2 x solubilization buffer. Incubate the sample in boiling bath for 5 min. Load the samples to the wells of the prepared gel. 

Both solution samples and spiked filter samples containing Cr (III) and Cr (VI) as Cr y were prepared. Samples were solubilized using both a nitric acid and a nitric-perchloric acid digestion. 

In this chapter, the description of applications highlights the selection of the instrumentation used as well as the alkaline solubilization sample preparation (often the most critical part of a complete analytical method). The main characteristics of the suspension sample introduction method are also emphasized. A brief discussion on subgroups of these methods, identibed by the atomic spectrometric instrumental approach, is bnally presented. 

The entire sample must be soluble to be separated. If it is not, sample preparation can be performed to remove insoluble endogenous sample components. If the solute is not soluble, the appropriate additives must be used to solubilize it. So long as wavelengths less than 220 nm are not required, 6 M urea is an excellent solvent. Both ionic and nonionic surfactants are also useful in this regard. Acetate buffers provide better solubility compared to phosphate buffers. These approaches maintain a totally aqueous system, which is most robust. Organic solvents are often used in CE, but migration time precision is usually worse compared to aqueous systems. 

This chapter gives an overview of decomposition methods and recent developments and applications of the decomposition of different materials. Other sample preparation methods, such as chemical extraction and leaching, solubilization with bases, enzymatic decomposition, thermal decomposition, and anodic oxidation, are beyond the scope of this contribution and are not discussed. 

Fig. 3. Time-course of solubilization of elastin from three bovine tissues (Golte et al., 1962). The elastin samples (prepared by autoclaving) were suspended in 0.5 N NaOH and maintained at 25°C with gentle rocking. The amino acid composition of the samples is given in Table I. Key O = elastin from bovine ear cartilage A elastin from bovine aorta X = elastin from bovine ligamentum nuchae.

Analysis of Particles by Atomic Absorption Spectrometry. Various methods of sample preparation were attempted to solubilize the... 

Finally, sample preparation is expedited due to the solubilization capability of micellar media, avoiding laborious steps to separate the matrix, previously performed to sample injection. All these features have allowed the development of multiple applications that are highly competitive against conventional RPLC. 

Analytical pyrolysis has a number of characteristics that can make it a very powerful tool in the study of polymers and composite materials. The technique usually requires little sample and can be set with very low limits of detection for a number of analytes. For Py-GC/MS the identification capability of volatile pyrolysate components is exceptionally good. A range of information can be obtained using this technique, including results for polymer identification, polymer structure, thermal properties of polymers, identification of polymer additives, and for the generation of potentially harmful small molecules from polymer decomposition. In most cases of analysis of a polymer or composite material, the technique does not require any sample preparation, not even solubilization of the sample, which may be a difficult task for the type of materials analyzed. The analysis can be easily automated and does not require expensive instrumentation (beyond the cost of the instrument used for pyrolysate analysis). 

Sample Preparation of Foam and Water Samples and Humic Substances Isolation. All foam and water samples were filtered through 0.45- Lim silver filter using stainless-steel filtration units. Silver filtration of Como Creek and Suwannee River foam samples resulted in build up of a brown extract on the filter paper, which was readily solubilized in 0.1 N sodium hydroxide. This extract was refiltered through silver filters as a sodium hydroxide solution. This fraction was believed to be colloidal in nature and was treated as a separate humic fraction, called the "foam-extract" fraction. A part of the filtered foam was freeze dried directly and considered "raw" foam. Fulvic and humic acids were isolated from foam and stream-water samples via the XAD-8 adsorption technique developed by Thurman and Malcolm (77), freeze dried, and weighed. To obtain a sufficient mass of humic substances, each entire sample was used for one extraction. As multiple samples were not extracted, calculation of the error associated with humic substances isolation cannot be made, and the contributions of humic substances to the DOC content must be regarded as estimates. 

Finally, contamination of sample spectra can also occur by cross-contamination during sample preparation and by carryover of residual analyte from a sample analyzed earlier in the run.172 173 Essentially, any component of the assay that is reused for each sample or batch of samples can be a source of cross-contamination or carryover. These include, for example, evaporators, pipettors, automated liquid handlers, recycled sample vials, and LC and GC autosamplers. Care needs to be taken in the selection of appropriate wash solvents that will readily solubilize the sample and analytes. This will usually be a combination of high percentage of organic solvents that may include a volatile acidic or basic modifier (e.g., formic acid or aqueous ammonia). Failure to properly wash all sample components from a chromatographic column can result in late eluting components appearing in the next, or later, analytical runs. 

Generically, sample preparation in bottom-up proteomics involves the solubilization of proteins from the biological source, protein fractionation, subsequent enzymatic digestion of the proteins, and separation of the resulting peptides. Unique enrichment techniques can be applied in many of these preparatory steps (Figure 5). 

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