Phosphates, analysis of mixtures

Phenanthroline (o-phenan-throline), complex cation with nickel(II), 5 193n., 195 1-Phenylbiguanide complexes with eobalt(III), 6 71 Phosphate glasses, 3 88 Phosphates, analysis of mixtures of soluble, 3 91... 

The analytical utility of near-infrared spectroscopy can be demonstrated by an analysis of mixtures composed of glucose, lactate, urea, alanine, ascorbate, and triacetin in a pH 6.8 aqueous phosphate buffer.6 The chemical structures of these test compounds are presented in Figure 13.2. These components were selected to represent different classes of molecules expected in typical biological matrices. Glucose represents carbohydrates lactate represents small organic acids urea is a... 

Rubber compounds can contain a range of fillers such as silicates, sulphates, oxides, carbonates, phosphates, nitrates, titanium dioxide, barium sulphate and various clays. Analysis of mixtures of these additives is complicated and it is necessary to separate the constituents by dissolution in suitable inorganic solvents and/or filtration of insoluble substances such as silicates. The residues can be examined in several ways ... 

In order to determine the stereochemical course of the nonenzymic hydrolysis of cyclic nucleotides, and in particular to examine the role of pseudorotation, Gerlt and coworkers carried out a chiral phosphate analysis of the base-catalysed hydrolysis of cyclic deoxyadenosine monophosphate (Mehdi et al., 1983). In 0.2 m Ba(OH)2 at lOO C, cdAMP hydrolyses to a mixture of 3 dAMP and 5 dAMP. The position of label incorporation on hydrolysis in labelled water indicates P—O as opposed to C—O bond cleavage. The overall stereochemistry of hydrolysis was followed by recycliz-ing and analysing both the ring-opened products of ( O, 0) cdAMP hydrolysis (Scheme 31). 

This experiment uses the molybdenum-blue method to determine the concentration of phosphate in a phosphate/sodium chloride mixture. Elow-injection analysis is used to increase the speed of analysis, allowing students to... 

Analysis. Excellent reviews of phosphate analysis are available (28). SoHds characterization methods such as x-ray powder diffraction (xrd) and thermal gravimetric analysis (tga) are used for the identification of individual crystalline phosphates, either alone or in mixtures. These techniques, along with elemental analysis and phosphate species deterrnination, are used to identify unknown phosphates and their mixtures. Particle size analysis, surface area, microscopy, and other standard soHds characterizations are useful in relating soHds properties to performance. SoHd-state nmr is used with increasing frequency. 

Applications. The capabiHties of a gc/k/ms in separating and identifying components in complex mixtures is very high for a broad spectmm of analytical problems. One area where k information particularly complements ms data is in the differentiation of isomeric compounds. An example is in the analysis of tricresyl phosphates (TCPs) used as additives in a variety of products because of thek lubricating and antiwear characteristics (see Lubrication and lubricants). One important use of TCPs is in hydrauHc fluid where they tenaciously coat metal surfaces thereby reducing friction and wear. Tricresyl phosphate [1330-78-5] (7.2 21 exists in a variety of isomeric forms and the commercial product is a complex mixture of these isomers. 

The analysis of phosphates and phosphonates is a considerably complex task due to the great variety of possible molecular structures. Phosphorus-containing anionics are nearly always available as mixtures dependent on the kind of synthesis carried out. For analytical separation the total amount of phosphorus in the molecule has to be ascertained. Thus, the organic and inorganic phosphorus is transformed to orthophosphoric acid by oxidation. The fusion of the substance is performed by the addition of 2 ml of concentrated sulfuric acid to — 100 mg of the substance. The black residue is then oxidized by a mixture of nitric acid and perchloric acid. The resulting orthophosphate can be determined at 8000 K by atom emission spectroscopy. The thermally excited phosphorus atoms emit a characteristic line at a wavelength of 178.23 nm. The extensity of the radiation is used for quantitative determination of the phosphorus content. 

Figure 1. HPLC analysis of product progression during hydrolysis of 0.25 % polygalacturonate by PGII. Aliquots were withdrawn from the reaction mixture at timed intervals and reactions were stopped by raising the pH of the sample to pH 8.0 by mixing with 1 volume 25 mM Na-phosphate pH 9.5. Gl to G5 indicate the oligogalacturonates with corresponding degree of polymerization. The vertical axis shows the responce of the pulsed amperometric detector and the horizontal axis the elution time. Times of sampling are indicated above the trace.

Affinity chromatography and related techniques (e.g., thiol chromatography and IMAC) are widely used for preparative isolation because they enable a single protein or class of proteins to be selectively purified from very complex mixtures. They may be occasionally used as analytical tools. For example, protein A affinity chromatography has been used for quantitative analysis of immunoglobulins in ascites fluid.45 Information about surface-accessible histidine and phosphate groups may be obtained using IMAC. 

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