Hydrolysis methods

Determination of iron as iron (III) oxide by initial formation of basic iron (III) formate Discussion. The precipitation of iron as iron(III) hydroxide by ammonia solution yields a gelatinous precipitate which is rather difficult to wash and to filter. Iron(III) can, however, be precipitated from homogeneous solution as a dense basic formate by the urea hydrolysis method. The precipitate obtained is more readily filtered and washed and adsorbs fewer impurities than that formed by other hydrolytic procedures. Ignition yields iron(III) oxide. 

An elegant alternative to the simple hydrolysis method is to use precursors already containing several of the required siloxane linkages. Thus, T8ReR 2... 

Yamada, H., Moriya, H., and Tsugita, A., Development of an acid hydrolysis method with high recoveries of tryptophan and cysteine for microquantities of protein, Anal. Biochem., 198, 1, 1991. 

Shutes A, Der CJ (2005) Real-time in vitro measurements of GTP hydrolysis. Methods 37 183-189... 

It is worth noting that the partide sizes of samples prepared by the urea hydrolysis method are larger than other LDHs. Such a finding can be rationalized by considering the slow hydrolysis of urea [61], since it can be classified as a very weak Bronsted base (pfCb= 13.8). Its hydrolysis mechanism consists of the formation of ammonium cyanate as the rate-determining step, followed by fast hydrolysis of the cyanate to ammonium carbonate ... 

Similar procedures adopted for the synthesis of TS-1 (the mixed alkoxide method, dissolved titanium method, pre-hydrolysis method, wetness impregnation method, and promoter induced synthesis method) were also used for the synthesis of TS-2. Tetrabutylammonium hydroxide (TBAOH) instead of TPAOH was used as the template (6,7,305-308). 

Ti-ZSM-48 was prepared by the dissolved titanium method using fumed silica (Cabosil), TBOT, H202, and diaminooctane (309-310). Ti-ZSM-48 was also prepared using hexamethonium hydroxide base and by the pre-hydrolysis method (311). 

Last but not least of the liquid calorimetric media are aqueous solutions used in the hydrolysis of simple and complex fluorides. Stepwise replacement of F by OH occurs, and mixed products are not unusual. Thus the BFj ion hydrolyzes to species BF (OH)l and one has to ensure that the same product composition is formed in the auxiliary heat experiments (99). The problem is accentuated when polynuclear species form, as the equilibration can be slow. The inconsistencies in the heats of alkaline hydrolysis of MoF6 and WFe found by various authors and of the enthalpy of SbF5—derived by assuming SbF5 and Sb205 dissolved in 10 M HF produced the same species in solution—illustrate the difficulties. It is as well to confirm enthalpies of higher valent fluorides obtained by hydrolysis by alternative nonaqueous methods, especially since uncertainty in the Afl (Fderived enthalpy. The advantage of hydrolysis methods, apart from the simplicity of technique, is that the heats are small and one can tolerate... 

It is obvious that acid hydrolysis methods leave a number of unsolved problems and many minor disagreements to be ironed out. In general, however, the available results suggest that the natural celluloses consist chiefly of crystalline material which is only slowly eroded by acids. The non-crystalline fraction appears to be relatively more susceptible to hydrolysis than the crystalline fraction and to have a greater capacity to absorb moisture. In other words, the non-crystalline fraction is probably more reactive than the crystalline material, as Mark14 has suggested. In this connection the fact should not be overlooked that the surface layer of the crystallites is probably amorphous and hence relatively more reactive than the underlying layers. 

The reverse Claisen reaction is common, especially with cyclic P-ketoesters, such as one gets from the Dieckmann reaction (see Section 10.8). If one only wants to hydrolyse the ester, it thus becomes necessary to use the rather less effective acid-catalysed hydrolysis method (see Section 7.9.2). 

In the formation of metal (hydrous) oxides, hydrolyzed metal ions are the primary constituent species. In the "forced hydrolysis" method, the latter are generated by deproionation of the coordinated water of the hydrated cation at elevated temperatures, according to ... 

Additional factors that may affect the reliability of the chemical scoring methods lie with the inherent difficulties of amino acid analysis. The analytical procedure for amino acid analysis can affect both the recovery and reliable quantitation of amino acids. Proteins must first be hydrolyzed to amino acids before analysis. Hydrolysis methods affect the amino acid recovery. Cystine, methionine, tryptophan, threonine, serine, and tyrosinecan bedestroyed during hydrolysis. Valine and isoleucine are released slowly and may not be completely... 

Amino acid analysis is fraught with literally dozens of pitfalls. For novel protein ingredients, those that have undergone chemical modification, or ones that have been subjected to high heat, conventional methods for protein hydrolysis may or may not be effective. It may be necessary to evaluate different hydrolysis methods to determine which provides the best recovery. 

Quantitative results for different foods using the hydrolysis method need to be treated with caution. Hydrolysis conditions should be adjusted based on the knowledge of a crude soy food extract—i.e., the range of isoflavone con-... 

B Penke, R. Ferenczi, K Kovacs. A new acid hydrolysis method for determining tryptophan in peptides and proteins. Anal Biochem 60 45-50, 1974. 

CW Gehrke, PR Rexroad, RM Schisla, JS Absheer, RW Zumwalt. Quantitative analysis of cystine, methionine, lysine and nine other amino acids by a single oxidation-4 hour hydrolysis method. J Assoc Off Anal Chem 70 171-174, 1987. 

The data obtained for yield and fluorine content (Table III) are more in accordance with an addition compound than with a monoester. Therefore, formation of such a compound containing one molecule of TFA per sugar unit during the treatment of polysaccharides with TFA is very probable. On the other hand, this result means for the hydrolysis method that after evaporating the TFA, the hydrolysate should be treated with water to decompose the addition compound. 

For avoiding high losses in pentoses, another, more moderate hydrolysis method for lignin-containing material was developed. The method is proposed only if arabinose, xylose, galactose, and rhamnose are of interest. In this case, the material is swollen in 100% TFA and boiled with 20% TFA. The result of such a moderate hydrolysis, compared with that of an intensive hydrolysis, is demonstrated in Figure 7. It can be seen that after careful hydrolysis the areas of the peaks of rhamnose... 

---