Hydrolysis analysis

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... 

Anticholinergics, such as atropine and oxyphenonium bromide, which are esters of carboxylic acids, were analysed in plasma and urine as pentafluorobenzyl esters [541,542], The method involves ion-pair extraction of the material under analysis, hydrolysis of esters and derivatization of the acid moiety. The minimal detectable amount was found to be 0.15 pg with the use of an ECD. 

Figure 35.3. End group analysis. Hydrolysis of methylated amylose. End unit of long molecule gives 2,3,4,6-tetra-O-methyl-D-glucose other units give 2,3,6-tri-O-methyl-D-glucose. ...

There are mainly two methods for chemical composition analysis hydrolysis method and MS method. Hydrolysis method is by adding ot-Cal to induce hydrolysis reaction and after the reaction is analyzed by HPLC MS is the direct detection of the product composition mass/charge ratio and can more accurately determine the composition of the product chemical components. 

The hemicellulosic fraction of the seed endosperm of groundnuts (Arachis hypogea) contains a (l- 4)- -D-gluco-D-mannan. The homogeneity of the polymer was confirmed by electrophoresis, sedimentation, and sugar analysis. Hydrolysis of the methylated polysaccharide yielded 2,3,4,6-tetra-O-methyl-D-glucose and -D-mannose, 2,3,6-tri-O-methyl-D-glucose, and 2,3,6-tri-O-methyl-D-mannose in the molar ratio 1.6 21.2 5.6, respectively. 

Hydrolysis of anthocyanins to yield anthocyanidins might be another important step during analysis. Hydrolysis is either accomplished by acidic hydrolysis of crude or purified extracts or by one-step extraction/hydrolysis protocols. 

Lipase Thermomyces insolens Fabric, fibers HPLC, dye assay, water absorption tests, gravimetric analysis Hydrolysis, increased hydrophilicity, improved dye uptake, weight loss [1, 62, 72, 101]... 

The amino add analysis of all peptide chains on the resins indicated a ratio of Pro Val 6.6 6.0 (calcd. 6 6). The peptides were then cleaved from the resin with 30% HBr in acetic acid and chromatogra phed on sephadex LH-20 in 0.001 M HCl. 335 mg dodecapeptide was isolated. Hydrolysis followed by quantitative amino acid analysis gave a ratio of Pro Val - 6.0 5.6 (calcd. 6 6). Cycll2ation in DMF with Woodward s reagent K (see scheme below) yielded after purification 138 mg of needles of the desired cyc-lododecapeptide with one equiv of acetic add. The compound yielded a yellow adduct with potassium picrate, and here an analytically more acceptable ratio Pro Val of 1.03 1.00 (calcd. 1 1) was found. The mass spectrum contained a molecular ion peak. No other spectral measurements (lack of ORD, NMR) have been reported. For a thirty-six step synthesis in which each step may cause side-reaaions the characterization of the final product should, of course, be more elaborate. 

This cleavage reaction is more often seen in structural analysis than in synthesis The substitution pattern around a dou ble bond is revealed by identifying the carbonyl containing compounds that make up the product Hydrolysis of the ozonide intermediate in the presence of zinc (reductive workup) permits aide hyde products to be isolated without further oxidation... 

A major advance was devised by Pehr Edman (University of Lund Sweden) that has become the standard method for N terminal residue analysis The Edman degrada tion IS based on the chemistry shown m Figure 27 12 A peptide reacts with phenyl iso thiocyanate to give a phenylthwcarbamoyl (PTC) denvative as shown m the first step This PTC derivative is then treated with an acid m an anhydrous medium (Edman used mtromethane saturated with hydrogen chloride) to cleave the amide bond between the N terminal ammo acid and the remainder of the peptide No other peptide bonds are cleaved m this step as amide bond hydrolysis requires water When the PTC derivative IS treated with acid m an anhydrous medium the sulfur atom of the C=S unit acts as... 

Many pharmaceutical compounds contain chromophores that make them suitable for analysis by UV/Vis absorption. Products that have been analyzed in this fashion include antibiotics, hormones, vitamins, and analgesics. One example of the use of UV absorption is in determining the purity of aspirin tablets, for which the active ingredient is acetylsalicylic acid. Salicylic acid, which is produced by the hydrolysis of acetylsalicylic acid, is an undesirable impurity in aspirin tablets, and should not be present at more than 0.01% w/w. Samples can be screened for unacceptable levels of salicylic acid by monitoring the absorbance at a wavelength of... 

Noncatalytic Reactions Chemical kinetic methods are not as common for the quantitative analysis of analytes in noncatalytic reactions. Because they lack the enhancement of reaction rate obtained when using a catalyst, noncatalytic methods generally are not used for the determination of analytes at low concentrations. Noncatalytic methods for analyzing inorganic analytes are usually based on a com-plexation reaction. One example was outlined in Example 13.4, in which the concentration of aluminum in serum was determined by the initial rate of formation of its complex with 2-hydroxy-1-naphthaldehyde p-methoxybenzoyl-hydrazone. ° The greatest number of noncatalytic methods, however, are for the quantitative analysis of organic analytes. For example, the insecticide methyl parathion has been determined by measuring its rate of hydrolysis in alkaline solutions. 

Ergonovine (100, R = NHCH(CH3)CH2 0H) was found to yield lysergic acid (100, R = OH) and (+)-2-aminopropanol on alkaline hydrolysis during the early analysis of its stmcture (66) and these two components can be recombined to regenerate the alkaloid. Salts of ergonovine with, for example, malic acid are apparently the dmgs of choice in the control and treatment of postpartum hemorrhage. 

Bromine ttifluoride is commercially available at a minimum purity of 98% (108). Free Br2 is maintained at less than 2%. Other minor impurities are HF and BrF. Free Br2 content estimates are based on color, with material containing less than 0.5% Br2 having a straw color, and ca 2% Br2 an amber-red color. Fluoride content can be obtained by controlled hydrolysis of a sample and standard analysis for fluorine content. Bromine ttifluoride is too high boiling and reactive for gas chromatographic analysis. It is shipped as a Hquid in steel cylinders in quantities of 91 kg or less. The cylinders are fitted with either a valve or plug to faciUtate insertion of a dip tube. Bromine ttifluoride is classified as an oxidizer and poison by DOT. 

Hexafluorophosphoric Acid. Hexafluorophosphoric acid (3) is present under ambient conditions only as an aqueous solution because the anhydrous acid dissociates rapidly to HF and PF at 25°C (56). The commercially available HPF is approximately 60% HPF based on PF analysis with HF, HPO2F2, HPO F, and H PO ia equiUbrium equivalent to about 11% additional HPF. The acid is a colorless Hquid which fumes considerably owiag to formation of an HF aerosol. Frequently, the commercially available acid has a dark honey color which is thought to be reduced phosphate species. This color can be removed by oxidation with a small amount of nitric acid. When the hexafluorophosphoric acid is diluted, it slowly hydrolyzes to the other fluorophosphoric acids and finally phosphoric acid. In concentrated solutions, the hexafluorophosphoric acid estabUshes equiUbrium with its hydrolysis products ia relatively low concentration. Hexafluorophosphoric acid hexahydrate [40209-76-5] 6 P 31.5°C, also forms (66). This... 

Table 4 lists the specifications set by Du Pont, the largest U.S. producer of DMF (4). Water in DMF is deterrnined either by Kad Fischer titration or by gas chromatography. The chromatographic method is more rehable at lower levels of water (<500 ppm) (4). DMF purity is deterrnined by gc. For specialized laboratory appHcations, conductivity measurements have been used as an indication of purity (27). DMF in water can be measured by refractive index, hydrolysis to DMA followed by titration of the Hberated amine, or, most conveniendy, by infrared analysis. A band at 1087 cm is used for the ir analysis. 

The ease of hydrolysis of metal alkoxides makes metal analysis a comparatively simple task. In many cases, the metal may be estimated by hydrolysis of a sample in a cmcible, and ignition to the metal oxide. Alternatively, the metal ion may be brought into solution by hydrolysis of a sample with dilute acid, followed by a standard analytical procedure for a solution of that particular metal. If the alcohol Hberated during the hydrolysis is likely to cause interference, it may be distilled from the solution by boiling. 

For the higher alkoxy groups, standard carbon and hydrogen analysis may be used, although careful sample preparation is required because of the ease of hydrolysis. Quantitative vapor-phase chromatography of alcohol Hberated during hydrolysis may also be used, but care must be taken in this case to ensure that hydrolysis is complete before the estimation is carried out. 

Methods have been developed for analysis or deterrnination of free amino acids in blood, food, and feedstocks (116). In proteins, the first step is hydrolysis, then separation if necessary, and finally, analysis of the amino acid mixture. 

Tolypomycins. The addition of small amounts of iron salts to the fermentation medium increases the production of tolypomycin Y (48) (7,203,204), the stmcture of which was arrived at by chemical degradation (205,206) and confirmed by x-ray crystallographic analysis (207) (Fig. 5). Mild acid hydrolysis of tolypomycin Y yields tolypomycinone [22356-23-6] (49, R = H), C27H42NO23, and tolyposamine [34174-76-0] C23H23NO2, (50). Further hydrolysis of tolypomycinone using acid yields tolyponone [24317-12-2] (51), which is also formed upon mild acid hydrolysis of rifamycia S. 

Complete basic hydrolysis, followed by the quantitative measurement of hydrogen formed, can be used to determine the number of Si—H and Si—Si bonds present in a particular compound. One molecule of H2 is Hberated for each Si—H and Si—Si bond present. The total siUcon content can be obtained from analysis of the resulting siUcate solution. 

In the determination of free formaldehyde in solution, eg, commercial reagents and pad bath formulation, the conditions of analysis allow hydrolysis of the /V-methy1o1 groups, usually between <1% and several percent. The NaOH formed is titrated with hydrochloric acid (82). Because of an incomplete reaction of sulfite with free formaldehyde, these low temperature methods (83) detect only 80—90% of the free formaldehyde present. Skill is important for correct results. 

At 25°C, pH 7.5, 1.5 ppm FAC, and 25 ppm cyanuric acid, the calculated HOCl concentration is only 0.01 ppm. Although the monochloroisocyanurate ion hydrolyzes to only a small extent, it serves as a reservoir of HOCl because of rapid hydrolysis. Indeed, this reaction is so fast that HClCy behaves like FAC in all wet methods of analysis. Furthermore, since HClCy absorbs uv only below 250 nm, which is filtered out of solar radiation by the earth s atmosphere, it is more resistant to decomposition than the photoactive C10 , which absorbs sunlight at 250—350 nm and represents the principal mode of chlorine loss in unstabilized pools (30). As Httie as 5 ppm of bromide ion prevents stabilization of FAC by cyanuric acid (23) (see also Cyanuric and ISOCYANURIC acids). 

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