Pretreatment techniques

Type of su ension Particle size range Time required to settle 

In addition to fister settling, a destabilised stem will generally possess enhanced fihration characteristics. These inqrrovements follow fiom the increased possibility of particulate colfisions, with the production of clusters or floes of partides. The clusters have a greater effective diameter. Thus fiom the Stokes relation h  

The process of destabilisation is known as coagulation [La Mer and Healey, 1963] the chemicals used to produce destabilisation are termed primary coagulents, which act to reduce the rqrulsive potential of the surfiice charges. The overall result is a relatively small cluster 

Cationic Polyacrymide, Partially Substituted Quaternary Ammonium Group  

The reduction in filtration reastance, referred to above, may also be achieved by adding a certain amount of fi-ee-filtering particles to the feed sn ension. Filter aids are natura% 

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The apphed pretreatment techniques were digestion with a combination of acids in the pressurized or atmospheric mode, programmed dry ashing, microwave digestion and irradiation with thermal neutrons. The analytical methods of final determination, at least four different for each element, covered all modern plasma techniques, various AAS modes, voltammetry, instrumental and radiochemical neutron activation analysis and isotope dilution MS. Each participating laboratory was requested to make a minimum of five independent rephcate determinations of each element on at least two different bottles on different days. Moreover, a series of different steps was undertaken in order to ensure that no substantial systematic errors were left undetected. 

In the separation of biomolecules, sample preparation almost always involves the use of one or more pretreatment techniques. With high-performance liquid chromatography (HPLC), no one sample preparation technique can be appHed to all biological samples. Several techiques may be used to prepare the sample for injection. For example, complex samples require some form of preffactionation before analysis, samples that are too dilute for detection require concentration before analysis, samples in an inappropriate or incompatible solvent require buffer exchange before analysis, and samples that contain particulates require filtration before injection into the analytical instrument. 

There are numerous metal pretreatment techniques that can be used in addition to solvent degreasing. To obtain metal/polymer systems which exhibit strong initial adhesion it is usually sufficient to wash the metal with a solvent followed by an acid etch or sandblasting technique to remove any weak oxide layers and roughen the surface simultaneously. 

A major aspect of an SLS process may be conditioning of the slurry to improve its filterability. Table 11.4 summarizes common pretreatment techniques, and Table 11.5 lists a number of flocculants and their applications. Some discussion of pretreatment is in Section 11.3. 

The stable free radicals in coal can adversely affect the 13C signal intensity. However, the quantitative reliability of the method can be greatly improved by prior treatment of coal with chemicals such as samarium(II) iodide (Stock et al., 1988) to selectively reduce the organic free radicals. Thus, this potential error that has influenced the quantitative aspects of the method can be reduced by the use of a novel pretreatment technique as well as an appropriate standard for measurement of chemical shifts. 

Bagheri, H. and A. Salemi. 2006. Headspace solvent microextraction as a simple and highly sensitive sample pretreatment technique for ultra trace determination of geosmin in aquatic media. J. Sep. Sci. 29 57-65. 

Huehmer, R. and Henthorne, L. (2006) Advances in RO pretreatment techniques innovations and applications of sea-water and marginal water desalination. IDS 8th Annual Conference Technion, Haifa. 

Pretreatment techniques and technologies can be categorized into four (4) general types ... 

Appropriate pretreatment techniques and/or technologies for a given RO application needs to be selected based on the quality of the influent water to be treated by RO. Some water, such as well water with low concentrations of iron and manganese, may require very little, if any, pretreatment, while other water, such as river or lake water, may require extensive pretreatment using sequenced techniques and technologies. 

Table 8.1 Mechanical RO pretreatment techniques and species that these techniques address.

Table 8.7 Chemical RO pretreatment techniques and the species each technique treat.

During the ensuing five years, a number of pitches were developed as carbon fiber precursors through use of various pretreatment techniques (4-9). We explored four basic pretreatment processes, sometimes in combination (a) polymerization and/or... 

Hydtylainen, T. Critical evaluation of sample pretreatment techniques. Anal. Bioanal. Chem. 

The issues of nonconventional pollutants is an evolving subject and related primarily to oleochemicals. Parameters involved include various chlorinated organics, heavy metals, and phenols. Each must be addressed on its merits. Solutions involve a variety of pretreatment techniques and occasionally result in a source control solution such as a product being discontinued. 

Liu J-F, Liang X, Jiang G-B, Cai Y-Q, Zhou Q-X, and Liu G-G. High performance hquid chromatography determination of 4-nonylphenol, 4-rert-octylphenol, and their short ethoxyl chain polyethoxylates in water samples using a microporous membrane hquid-hquid extraction sample pretreatment technique. J. Sep. Sci. 2003 26 823-828. 

The primary aim of this book is to provide readers interested in solid sample pretreatment with an overview of available techniques for development of this step of the analytical process. The title of the book is intended to reflect that it is mainly concerned with the dissolution or removal of target analytes from solid samples. Once they have selected the technique most closely fitting their intended purpose, readers can obtain a deeper knowledge about the technique of choice in the specialized literature — in fact, providing a thorough description of each of the wide variety of sample pretreatment techniques available at present was obviously outside the scope of a book like this. In fact, only those aspects that can be illustrated with reasonable concision are dealt with specifically in it. For identical reasons, the book does not touch on the subsequent steps of the analytical process. The authors therefore assume that the reader will be acquainted with the general principles of chromatography in its different variants, as well as with those of commonplace molecular optical and electroanalytical techniques, and atomic and mass spectrometries. 

This chapter is not meant to be a short course in LC. Some aspects of LC, important in relation to combined liquid chromatography-mass spectrometry (LC-MS), are discussed, e.g., column types and miniaturization, phase systems and separation mechanisms, and detection characteristics. In addition, important sample pretreatment techniques are discussed. Special attention is paid to new developments in LC and sample pretreatment. 

The term sample preparation may refer to the various stages of the analysis procedure, as shown in Fig. 1. An ideal sample pretreatment technique should have the following characteristics ... 

At present elements in coal can be determined with acceptable accuracy and precision with proper choice of analytical procedure and sample pretreatment technique. Multielement standards and numerous consensus samples are now readily... 

Destructive methods the determination of the amount of a substance in a material usually leads to the destruction of the test sample. This is realised by pretreatment techniques such as acid digestion, fusion, extractions etc. to bring the test sample into a liquid or other simple form compatible with the final determination technique or instrument. Nearly all modern methods of measurements, e.g. spectrometry, require sample pretreatment procedures. 

Twenty three laboratories from eleven European countries participated in the certification campaign (see section 6.6.4). Table 6.16 summarises the different techniques of final determination used by these laboratories. Pretreatment techniques were digestions with combination of acids including HCIO4 and HF, in a pressurised or atmospheric mode, Kjeldahl pretreatment, programmed dry ashing and oxygen combustion. Other methods hardly used any pretreatment (e.g. INAA). 

Table 7.1 summarises the different techniques of final determination used pretreatment techniques were based on digestion with combination of acids in pressurised or atmospheric mode, programmed dry ashing, combustion and irradiation with thermal neutrons. A detailed description of the methods is given in the certification report [1]. 

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