Functional groups, determination titration method

When the functionalized polymer contains acidic or basic groups, such as those in ion-exchange resins, the acid-base titration methods are the most suitable for functional group determination. Such methods are well-established (Helfferich, 1962), In one report (Schou et aL, 1975), the free amino group in an unblocked resin-peptide was determined by nonaque-ous titration with acid. Similarly, histidine incorporation could be deter-... 

A suitable functional group is assayed in the same sample. In general chemistry and many polymer applications, this is merely the titration of acid groups with a base, or vice versa. Note that only volumetric glassware and a method for end point determination are required to do this. 

The potentiometric titration was carried out in order to determine the functional groups present in the biomass surface. During the titration experiments, the C02-free condition was always maintained to avoid the influence of inorganic carbon on the solution pH. Detailed potentiometric titration procedure and estimation method of functional groups are available in the previous reports [4,6]. 

The other analytical methods necessary to control the typical specification given in Table 5 are, for the most part, common quality-control procedures. When a chemical analysis for purity is desired, acetylation or phthalation procedures are commonly employed. In these cases, the alcohol reacts with a measured volume of either acetic or phthalic anhydride in pyridine solution. The loss in titratable acidity in the anhydride solution is a direct measure of the hydroxyl groups reacting in the sample. These procedures are generally free from interference by other functional groups, but both are affected adversely by the presence of excessive water, as this depletes the anhydride reagent strength to a level below that necessary to ensure complete reaction with the alcohol. Both procedures can be adapted to a semimicro- or even microscale determination. 

The various latexes were characterized with respect to particle size and size distribution, surface charge and functional group density, and electrophoretic mobility behavior. As observed by transmission electron microscopy all latexes were found highly monodisperse with a uniformity ratio between 1.001 and 1.010, a property due to the short duration of the nucleation period involved in the various radical-initiated heterogeneous polymerization processes. The surface charge density was determined by a colorimetric titration method reported elsewhere [13]. 

The technique of titration calorimetry has been successfully used to determine the nature and abundances of a variety of acidic functional groups in proteins ( ). Several investigators have made rather limited efforts to use titration calorimetry to study humic substances, usually as a method to determine the cation exchange capacity or titratable acidity of humic substances (23, 24). Choppin and Kullberg ( ) have recently used titration calorimetry to determine the enthalpies of neutralization of acidic functional groups in humic substances and have combined that data with pH titration data to obtain AG, AH, and AS values... 

The pH of MCM-41 was measured with ASTM D 3838. About l.Og of dry MCM-41 was added to 20 ml of distilled water, and the suspension was shaken overnight to reach equilibrium. Then the sample was filtered, and pH of the solution was measured. The surface functional groups of the samples were determined by Boehm s titration method [13]. In the case of acid value, about l.Og of the sample was added to 100 ml of O.IN NaOH solution and the mixture was shaken for 24 h. Then the solution was filtered through a membrane filter and titrated with 0. IN HCI. Likewise, the base value was determined by converse titration. 

Karl Fischer Titration Moisture content of reference standards is commonly and accurately determined by Karl Fischer (KF) titration. KF titration determines total water content, including both the free water and water of hydration trapped in the crystal structure. Coulometric KF-titration is the most sensitive application of the method and is normally used for the small amounts of water found in reference standards. A volumetric technique is available for samples containing large amounts of water. Interference is a relatively common problem in KF titration and thus, due caution must be exercised in the interpretation of KF results. Reagents have been designed to cope with interfering functional groups.48-50... 

Titration The determination of assay values for reference standards, counter-ions, or impurities can often be independently determined via titration. While titration assays generally have less selectivity in comparison to chromatographic methods, the advantages of a broad spectrum of classical titration techniques that exist for organic functional groups is often overlooked. The methodologies include not only classical potentiometric acid/base titrations but also nonaqueous, redox, indirect, precipitation, and derivatization titrations.76-79... 

Neutralization titrations provide convenient methods for the direct or indirect determination of several organic functional groups. Brief descriptions of methods for the more common groups follow. 

Although all potentiometric methods of functional group analysis are inherently operational, the total acidity can be determined by the barium hydroxide method, if appropriate precautions are taken to remove all colored material from the reaction mixtures prior to the final titration. Any method that purportedly distinguishes between different classes of functional groups should be used with full awareness of the operational nature of the results that will be obtained. If potentiometric data are augmented with calorimetric andlor spectroscopic data, more accurate estimates of functional group concentrations may possibly be obtained. 

Due to the lack of suitable functional groups in steroid hormones, titrimetry has never played an important role in steroid hormone analysis. Of the several indirect methods, however, one is still widely used all pharmacopoeias contain methods for the determination of ethinyl steroids on the basis of the exchange of the acetylenic hydrogen for silver ions and the titration of the liberated acid with standard sodium hydroxide. 

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