Chemical separation methods traditional

After matrix removal, samples can be measured using various techniques, such as AAS, AES, ICP, etc. Traditional chemical analysis methods, involving separation and gravimetric, titrimetric or polarographic determination of the elements, are being replaced by a wide selection of instrumental methods. 

The lanthanide group of elements (Table 11.7) is very difficult to separate by traditional methods because of their similar chemical properties. The techniques originally used, like the precious metals, included laborious multiple fractional recrystallizations and fractional precipitation, both of which required many recycle streams to achieve reasonably pure products. Such techniques were unable to cope with the demands for significant quantities of certain pure compounds required by the electronics industry hence, other separation methods were developed. Resin ion exchange was the first of these... 

Before anything else can be said about IEs, some rudimentary chemistry is needed. From a cookbook perspective, all explosives (be they military, commercial, or improvised) require the same chemical building blocks, which consist of a fuel and an oxidizer. Some explosives have the fuel and oxidizer as part of the same molecule, such as trinitrotoluene (TNT), and some explosives are comprised of mixtures of separate fuels and oxidizers, such as ammonium nitrate-fuel oil (ANFO). The oxidizer employed by the vast majority of explosives tends to be the NO2 (nitro) group. It is so predominant as an explosive ingredient that the primary focus of detection methods traditionally has been to look for nitro-derived properties. IEs tend to utilize a more diverse range of oxidizers. Table 3.1 gives a list of the numerous oxidizer possibilities. 

In chemical, petrochemical and related industries, separation processes are usually responsible for a major part of the production costs. In the separation of gas mixtures, adsorptive processes like Pressure Swing Adsorption (PSA) are being used by small and medium-sized industries, mainly because they have been found more efficient and economical than traditional separation methods. As part of her research project for a... 

Qualitative spectrochemical analysis requires only a very small sample. Frequently a complete qualitative analysis can be obtained from a 1-5 mg sample and a single exposure. All readily detectable elements can be observed from one spectrum of the sample. Qualitative analysis also is possible with samples difficult to handle by more traditional chemical methods for example, glasses, refractory materials, slags, minerals, etc., can be handled by reducing the sample to a fine powder. No chemical treatment or chemical separation is required. 

The analytical chemistry of alcoholic beverages, of which the determination of ethanol is only one facet, continues to develop. However, several methods of analysis for ethanol are available and tradition, government legal requirements, and convenience, taken together or separately, usually govern the choice of method. These methods include (1) distillation and specific gravity measurement, (2) gas-liquid chromatography, (3) IR spectrometry, (4) headspace techniques, (5) enzyme methods, (6) chemical (colorimetric) methods, and (7) refractometry. These methods are now considered in turn. 

While investigating interdependences between general physico-chemical properties of Uquid crystals and their separation ability, apart from traditional methods of physico-chemical investigations, methods of inverse gas chromatography are also used. ... 

Fast chemical isolation procedures to study the chemical and physical properties of short-lived radioactive nuclides have a long tradition and were applied as early as 1900 by Rutherford [1] to determine the half-life of Rn. A rapid development of fast chemical separation techniques [2-7] (see Ref. [5] for an in-depth review) occurred with the discovery of nuclear fission [8]. Indeed, the discovery of new elements up to Z = 101 was accomplished by chemical means [9]. Only from there on physical methods prevailed. Nevertheless, rapid gas-phase chemistry played an important role in the claim to discovery of Rf and Db [10]. As of today, the fastest chemical separation systems allow access to the study of a-particle emitting nuclides within less than 1 s as demonstrated by the investigation of Pa with a half-life of 0.85 s [11]. Reviews on rapid chemical methods for the identification and study of short-lived nuclides from heavy element synthesis can be found in [12-22]. 

These physical separation methods are often reinforced by chemical reactions, which are usually reversible. An elementary treatment of the role of chemical reactions in enhancing separation across a broad spectrum of phase equilibrium driven processes and membrane based processes has been included. The level of treatment in this book assumes familiarity with elementary principles of chemical engineering thermodynamics and traditional... 

However, compared with the traditional analytical methods, the adoption of chromatographic methods represented a signihcant improvement in pharmaceutical analysis. This was because chromatographic methods had the advantages of method specihcity, the ability to separate and detect low-level impurities. Specihcity is especially important for methods intended for early-phase drug development when the chemical and physical properties of the active pharmaceutical ingredient (API) are not fully understood and the synthetic processes are not fully developed. Therefore the assurance of safety in clinical trials of an API relies heavily on the ability of analytical methods to detect and quantitate unknown impurities that may pose safety concerns. This task was not easily performed or simply could not be carried out by classic wet chemistry methods. Therefore, slowly, HPLC and GC established their places as the mainstream analytical methods in pharmaceutical analysis. 

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