Solid immobilized reagents

Unloaded silica does not recover HPA from aqueous solution. The surface of silica gel modified with quarternary ammonium salts (QAS) gets anion-exchange properties. The aim of the work is the elaboration of solid-phase reagents on the base of ion associate of HPA with QAS immobilized onto silica surface for the determination of phosphoms and organic reductants. Heterocyclic (safranine and lucigenine) and aliphatic (trinonyloctadecyl ammonium iodide and tetradecyl ammonium nitrate) compounds have been examined as QAS. 

Brombenztiazo (BBT) is known to be one of the best reagents for extraction-photometric determination of cadmium(II). The reagent also fonus complexes with Co(II), Cu(II), Fe(II), Ni(II), Zn(II). The aim of this work was to develop a solid-phase reagent on the base of BBT immobilized on silica gel for sorption-spectroscopic and visual test determination of Cadmium, and also for soi ption-atomic-adsoi ption determination of total heavy metals contents in natural waters. 

In the present work, the technique of XO and MTB immobilization onto silica gel in the form of its complexes with Fe(III) and Bi(III) respectively were found. The acid - base and chemical-analytical characteristics of solid-phase reagents were examined. The optimal conditions of quantitative recovery of Pb(II) and Zn(II) from diluted solutions, such as acidity of aqueous phase, the mass of the sorbents, the volume of solutions and the time of equilibrium reaching, were found. The methods of and F" detenuination were based on a competitive reactions of Zr(IV) with immobilized MTB and or F". Optimal conditions of 0,0 and F" determination in solution using SG, modified ion associates QAS-MTB (pH = 1,5, = 5-10 mol/1). 

The packed bed reactor is particularly lu ul for reactions involving solid-phase reagents such as cati Psts, immobilized enzymes,and metallic reducing agents [641,642,646,647,658]. Since solutions are added in this isase, there are no... 

In addition to the sensors dealt with in Section 3.3.1.1, which could equally have been included in this Section as they use consumable immobilized reagents and regenerable fluorophores, Frei et al. developed a sensor for HPLC determinations based on the solid-state detection cell depicted in Fig. 3.38.B, where they immobilized 1-bromonaphthalene for measuring phosphorescence quenchers. Experiments demonstrated the sensor s usefulness for determining nitrate with a detection limit of ca. 10" M and an RSD of 4% for an analyte concentration of M. However, the scope of application of this sensor to chromatographically separated anions is rather narrow owing to the low sensitivity of the quenched phosphorescence detection for iodide and other halides [268]. 

The role of bifunctional (tagged) reagents in the transformations described above is similar to that of polymer-immobilized reagents. However, they exhibit more reliable reaction kinetics because they react in the solution phase. Moreover, manipulation of these reagents is more easily automated since transfer of solutions is much easier than transfer of solids. 

MW protocols for oxidation-reduction reactions using immobilized reagents on solid supports have been extensively explored. The oxidation of sulfides to sulfoxides and sulfones was also developed under MW irradiation with good... 

The second large reaction database is Chemical Abstracts from the American Chemical Society, accessed most often via the Scifinder interface. It basically suffers from the same limitations as mentioned above. The main advantage of Scifinder for combinatorial chemists is the ability to also search for keywords. Thus, a search for a specific reaction type combined with keywords such as solid phase or immobilized reagent often leads to useful literature citations. 

Since the discovery of solid phase peptide synthesis in 1963 [4], the venerable polystyrene resin has remained the cornerstone of combinatorial chemistry over the years and continues to be utilized as the primary mode of support for immobilizing reagents and scavengers. This section briefly outlines the latest developments of resin-based scavengers. 

This chapter is divided in five sections. The first one highlights the potential of immobilizing a natural product core structure on solid phase to facilitate its diversification into a library of analogues. The next three sections cover the de novo synthesis of natural products using solid phase synthesis, immobilized reagents or isolation tags respectively. Finally, the last section reviews six landmark libraries based on natural products or natural product motifs. 

Immobilized phase transfer eatalyst (Q+X ) I Solid inorganie reagent (M+Y )... 

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