Weights, classical analytical methods

Gravimetric analysis is one of classical analytical methods. It is based on chemical transformation of the sample using excess of a reagent to a substance, which is weighed after processing. The weight of the substance obtained serves as a base for calculation of amount of substance. 

The range of the (molecular) size of the analytes usually exceeds that which can be determined by classical laboratory analytical methods such as size exclusion chromatography, etc. [351]. Reports on investigated substances are widespread and cover applications such as the separation and characterization of proteins [450] and enzymes [240, 241], of viruses [132], the separation of human and animal cells [50, 51], the isolation of plasmid DNA [367], and the molecular weight and particle size distribution of polymers [216,217]. The approach is relatively new in biotechnology therefore, practical experiences are not yet abundant. Langwost et al. [229] have provided a comprehensive survey of various applications in bio-monitoring. 

Very useM hints about the analytical identity of polymer structures can be obtained from their dianges and for those of physical reference values as a result of chemical reactions. For this, there is a number of methods, mainly phyacal, for degradating the primary polymer structure The desired analytical standard is attained, however, only by the thermal and hydrolytic degradation procedures when one looks at it from a practical and economic point of view. The thermal procedures in particular have proved to be especially suitable for depol3mierisation of compounds of high molecular wei t to defined fragments of low molecular weight. Moreover it is usually possible to combine them with suitable chemical or physical techniques of identification. Classical hydrolytic methods, especially for breakdown of condensation and addition polymers, have maintained their role in the analysis of polymers. 

Fichtner and Giese [2] showed that the HPLC - MS method is an effective method for achieving a comprehensive analysis of elutable components (extractables) from polymeric materials. When applied correctly, it is superior to the classical HPLC-UV method and complemented the GC-MS method for the identification of thermally unstable, reactive and high molecular weight (M ) analytes (with M of about 100-4000 g/mol). The HPLC-MS method required fundamental and wide-ranging work to optimise the liquid chromatographic separation system and the ionisation conditions... 

The CLS method hinges on accurately modelling the calibration spectra as a weighted sum of the spectral contributions of the individual analytes. For this to work the concentrations of all the constituents in the calibration set have to be known. The implication is that constituents not of direct interest should be modelled as well and their concentrations should be under control in the calibration experiment. Unexpected constituents, physical interferents, non-linearities of the spectral responses or interaction between the various components all invalidate the simple additive, linear model underlying controlled calibration and classical least squares estimation. 

Wet methods are those that involve physical separation and classical chemical reaction stoichiometry, but no instrumentation beyond an analytical balance. Instrumental methods are those that involve additional high-tech electronic instrumentation, often complex hardware and software. Common analytical strategy operations include sampling, sampling preparation, data analysis, and calculations. Also, weight or volume data are required for almost all methods as part of the analysis method itself. 

J/n < 6,000). Often, no analytical data or structural characterization was provided. Room-temperature interfacial polycondensation methods were also investigated as a convenient alternative to classical polycondensations. Such methods were first reported for the preparation of polyamides and polyesters from the reaction of l,l -ferrocenyldi-carbonyl chloride with several diamines and diols. The synthesis of polyurethanes using this technique was also reported and involved the condensation of l,T-ferrocenedimethanol and l,T-bis(dihydroxyethyl)ferrocene with diisocyanates. Once again, however, these polymers possessed low molecular weights.The early research in these areas has been summarized and critically reviewed and will not be discussed further here. ... 

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