Starches dissolution

Wilpiszewska, K.S.A.T. Ionic liquids Media for starch dissolution, plasticization and modification. Carbohydr. Polym. 2011, 86 (2), 424-428. 

Ghdants are needed to faciUtate the flow of granulation from the hopper. Lubricants ensure the release of the compressed mass from the punch surfaces and the release/ejection of the tablet from the die. Combinations of siUcas, com starch, talc (qv), magnesium stearate, and high molecular weight poly(ethylene glycols) are used. Most lubricants are hydrophobic and may slow down disintegration and dmg dissolution. 

Starch nitrated by Brown and Miliar (Ref 10) by dissolution in nitric acid and subsequent precipitation with the help of sulphuric acid, was stabilized by washing in ether and chloroform... 

Fig. 11 Effect of particle size of phenacetin on dissolution of drug from granules containing starch and gelatin. Q, particle size 0.11-0.15mm A, particle size 0.15-0.21 mm , particle size 0.21-0.30mm , particle size 0.30-0.50mm , particle size 0.50-0.71 mm. (From Ref. 17.).

Fig. 17 Effect of starch content of granules on dissolution rate of salicylic acid contained in compressed tablets. Q, 5% . 10% x, 20% starch in granules. (From Ref. 22.).

DS Desai, BA Rubitski, SA Varia, AW Newman. Physical interactions of magnesium stearate with starch-derived disintegrants and their effects on capsule and tablet dissolution. Int J Pharm 91 217-226, 1993. 

Desizing by chemical decomposition is applicable to starch-based sizes. Since starch and its hydrophilic derivatives are soluble in water, it might be assumed that a simple alkaline rinse with surfactant would be sufficient to effect removal from the fibre. As is also the case with some other size polymers, however, once the starch solution has dried to a film on the fibre surface it is much more difficult to effect rehydration and dissolution. Thus controlled chemical degradation is required to disintegrate and solubilise the size film without damaging the cellulosic fibre. Enzymatic, oxidative and hydrolytic degradation methods can be used. 

Not all modified starches are suitable for removal by aqueous dissolution alone. Such modifications of natural starches are carried out to reduce solution viscosity, to improve adhesion and ostensibly to enhance aqueous solubility. Commercial brands vary [169], however, from readily soluble types to those of limited solubility. Indeed, some may be as difficult to dissolve as potato starch if they have been overdried. It is thus very important to be sure of the properties of any modified starch present. If there are any doubts about aqueous dissolution, desizing should be carried out by enzymatic or oxidative treatment. Even if the size polymer is sufficiently soluble, it is important to ensure that the washing-off range is adequate. Whilst the above comments relate to modified starches, other size polymers such as poly(vinyl acetate/alcohol) and acrylic acid copolymers vary from brand to brand with regard to ease of dissolution. 

The labile nature of the components necessitates that, for fundamental investigations, the starch should preferably be extracted from its botanical source, in the laboratory, under the mildest possible conditions.26 Industrial samples of unknown origin and treatment should not be used. The characterization of the starch would appear to entail (1) dissolution of the granule without degradation, (2) fractionation without degradation, (3) complete analysis of the finer details of structure of the separated components (including the possibilities of intermediate structures between the extremes of amylose and amylopectin), and (4) the estimation of the size, shape, and molecular-weight distribution of these fractions. 

Soluble oil metal-working fluids, 1 22 Soluble oils, 15 240 Soluble silicates, 22 451-452 dissolution of, 22 455-456 history and applications of, 22 452 Soluble starch synthases, 12 492 Soluble titanium glycolate complexes, 25 87 Solute clearances... 

While the cuprous cyanide solution is warmed gently (to 60°-70°) on the water bath, a solution of p-tolyldiazonium chloride is prepared as follows Heat 20 g. of p-toluidine with a mixture of 50 g. of concentrated hydrochloric acid and 150 c.c. of water until dissolution is complete. Immerse the solution in ice-water and stir vigorously with a glass rod so that the toluidine hydrochloride separates as far as possible in a microcrystalline form. Then cool the mixture in ice and diazotise with a solution of 16 g. of sodium nitrite in 80 c.c. of water, added until the nitrous acid test with potassium iodide-starch paper persists. The diazonium chloride solution so obtained is poured during the course of about ten minutes into the warm cuprous cyanide solution, which is meanwhile shaken frequently. After the diazo-solution has been added the reaction mixture is heated under an air condenser on the water bath fox a further quarter of an hour, and then the toluic nitrile is separated by distillation with steam (fume chamber, HCN ). The nitrile (which passes over as a yellowish oil) is extracted from the distillate with ether, the p-cresol produced as a by-product is removed by shaking the ethereal extract twice with 2 A-sodium hydroxide solution, the ether is evaporated,... 

Procedure Weigh accurately 0.15 g of mephenesin and dissolve in 50 ml of DW into a 250 ml iodine-flask. Add to it 25.0 ml of 0.1 N potassium bromate solution and 10.0 g of powdered potassium bromide. After the dissolution of KBr, add 10 ml of hydrochloric acid, insert the moistened stopper, and after 10 seconds add 10 ml of potassium iodide solution. Titrate with 0.1 N sodium thiosulphate using starch solution as indicator. Each ml of 0.1 N potassium bromate is equivalent to 0.00911 g of C10H,4O3. 

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