Acetals procedures

The original procedure from which the Formalinethyl acetate centrifugal sedimentation technique was adapted was the Formalin-ether concentration method of Ritchie. Hie Formalin-ethyl acetate procedure avoids problems with the flammability and storage of ether. This procedure can be performed on specimens which have been fixed in Formalin for a time or on specimens with Formalin added during the processing. The procedure can also be performed on material fixed in MIF. 

Once a suitably polar plant extract is obtained, a preliminary cleanup is advantageous. The classical method of separating phenolics from plant extracts is to precipitate with lead acetate or extract into alkali or carbonate, followed by acidification. The lead acetate procedure is often unsatisfactory since some phenolics do not precipitate other compounds may coprecipitate and it is not always easy to remove the lead salts. 

In Chapter 10, the use of membranes for different applications are described. One of the possible membranes for hydrogen cleaning is an asymmetric membrane comprised of the dense end of a proton conduction perovskite such as BaCe0 95 Yb0 05O3 5 and a porous end to bring mechanical stability to the membrane. In this case, it is possible to take from the slurry, obtained by the acetate procedure, several drops to be released over a porous ceramic membrane, located in the spinning bar of a spin-coating machine. Thereafter, the assembly powder, thin film porous membrane is heated from room temperature up to 1573 K at a rate of 2K/min, kept at this temperature for 12 h, and then cooled at the same rate in order to get the perovskite end film over the porous membrane [50],... 

Polymer Unsaturation Analysis. Unsaturation is determined routinely by an iodine-mercuric acetate procedure (5). The result of this procedure, iodine number (cgrams of iodine/grams of polymer), was correlated to actual unsaturation by an infrared and an NMR study (4). The infrared study showed that the factor of 0.184 is needed to convert iodine number to % unsaturation. The NMR study showed that a factor of 0.196 is needed to convert iodine number to % unsaturation. [As an example, a piperylene-isobutylene copolymer with an iodine number of 20.7 would have unsaturation values of (20.7) (0.196) = 4.05 mole % (NMR) and (20.7) (0.184) = 3.82 mole % (infrared).]... 

Noyori s acetalization procedure and its variants have been used for the preparation of chiral cyclic acetals. The rigid 1,3-dioxolanes formed play an important role as temporary chiral auxiliaries in stereoselective reactions and as electrophilic reactants. ... 

In studies of polysaccharides structure, the alditol acetate procedure remains the most widely used GLC procedure. The advent of high-resolution glass capillary columns has allowed very efficient separations. Recent applications of these columns to alditol acetate separations have been described (55-57). The alditol acetate procedure requires reduction of the sugars with sodium borohydride. After removal of boric acid, the sample is acetylated by conventional means. Various polar stationary phases have been used in GLC separation of alditol acetates, in both packed and capillary columns. A low-polarity phase was used in a report ( ) which demonstrated the separation of trimethylsilylated alditols, and the neutral sugars in a hemicellulose sample were resolved. 

The aldose content of vegetable fibres has been determined by a modification of the alditol acetate procedure. ... 

A lot of interest in catecholamine metabolism has centred on their metabolic end-products 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) and 3-methoxy-4-hydroxyphenylethanol (MHPE). These compounds have been analysed most often as their TFA or PFP derivatives, with electron capture detection for sensitivity. Many different recipes have been published, all variants of the anhydride in ethyl acetate procedure, using different temperatures and reaction times. If 30 minutes at room temperature are sufficient [94], one does not need 40 minutes at 65 °C [95]. Pyridine is not recommended because it gives rise to interference, just as with acetic anhydride (see above). At the end of the reaction the mixture is evaporated to dryness with nitrogen, and the residue is taken up in ethyl acetate. These derivatives are susceptible to hydrolysis, and up to 2% of acetic anhydride may be included in the final solution to protect the derivatives against moisture. 

Simultaneous EC and ECL detection of amphetamines namely methamphet-amine, 3,4-methylenedioxyamphetamine, and 3,4-methylenedioxymethamphet-amine was performed employing CE. Eactors affecting the separation and detection performance, such as the detection potential, the pH value and concentration of the running buffer, the separation voltage, and the pH of the detection buffer, were explored. A liquid-liquid extraction with ethyl acetate procedure was... 

Peynaud (1937c) have applied the influence of pH on the hydrolysis of acetal as a method for the determination of the pH. The results for 26 samples by the acetal procedure averaged 3.19 and by the glass electrode 3.17. 

Method B described earlier). More than 100% of the methylmercury was recovered. When the acidified liver suspension containing mercuric ions was kept at room temperature overnight, the recovery increased. This indicated a synthesis of methylmercury ions from mercuric ions by the liver under the conditions used. Thus, this combined mercuric ion-cysteine acetate procedure for analysis of methylmercury could not be applied to liver. Some results obtained without addition of methylmercury compounds are seen in Table 15. 

For egg-yolk with low content of methylmercury the cysteine acetate procedure gave less than 90% recovery, (Method B described earlier). with the combined method using cysteine and mercuric ions the recovery of methylmercury salt decreased almost to zero. But for sediments in aquaria and sludge, which similarly could not be analysed by the original cysteine acetate modification, the combined method gave good results (Table 16). The combined cysteine/mercuric ion method was also applied to fish muscles with good recoveries. ... 

Follow cysteine acetate procedure only adding 2ml (10ml for 50g sample) of purified aqueous 5% mercuric chloride solution before the first extraction with benzene, (see Method A described earlier in this section). 

Rapid determination of methylmercury salt in liver. Follow cysteine acetate procedure only adding Ig of molybdic acid/lOg of sample to the liver suspension and shake for 30 seconds. Then add the sodium chloride, hydrochloric acid and benzene at once. Shake and centrifuge immediately. When preparing the calibration curve according to this procedure, add the methylmercury salt immediately beofre the first extraction with benzene. 

Follow cysteine acetate procedure using 50g of sample up to and including the transfer of 250ml of the first benzene extract to a separating funnel. Shake this extract with 4ml then two 3ml... 

Improved procedures for the preparation and g.c. analysis of peracetylated aldoses have been developed. Acetylation (AcjO-l-raethylimidazole) can be performed directly on acid hydrolysates, and factors influencing the ratios of isomers produced have been studied. This method was compared with the alditol acetate procedure for the quantitative analysis of four plant materials. G.l.c.-m.s. data have been reported for partially methylated and acetylated derivatives of L-gfycero-n-manno- and n-gfycero-D-manno-heptoses and -heptitols. ... 

Sodium kaolinite was a well-crystallized (98%) sample of Sigma Company, repeatedly washed with 1 M NaCl. The cation exchange capacity was 57 pmole g according to the silver-thiourea method [2], but 30 nmole g according to the ammonium acetate procedure [3]. The BET (Nj) area was 12 m g The aspect ratio (plate area/ edge area) of the particles is about 80 20%. 

This compound corresponds to the core oligosaccharide of Asn-linked glycoproteins and represents the most complex setting for which stereospecific 3-mannosylation has been achieved. The methoxybenzylidene-acetal procedure has also been implemented on a polymer support [119]. 

---