Potassium freeze-dried

The pH of the mixture was adjusted to 7.5 by adding a saturated sodium bicarbonate solution. After being washed twice with diethyl ether, the reaction solution was acidified to pH 2 with dilute hydrochloric acid and extracted with ether. The ether solution containing the free penicillin was washed twice with water and then extracted with 50 ml of N potassium bicarbonate solution. After freeze drying of the obtained neutral solution, the potassium salt of o-azidobenzylpenicillin was obtained as a slightly colored powder (11.2 grams, 54% yield) with a purity of 55% as determined by the hydroxylamine method (the potassium salt of penicillin G being used as a standard). 

Preparation of luciferase. Organisms were freeze-dried, powdered, and washed with ethyl acetate to destroy the majority of catalase activity. The washed residue was extracted with 50 mM potassium phosphate buffer, pH 6. The extract was fractionated by ammonium... 

Maher [130] has described a procedure for the determination of total arsenic in sediments. Arsenic is converted into arsine using a zinc reductor column, as shown in Fig. 12.8. The evolved arsine is trapped in a potassium iodide-iodine solution and other arsenic determined spectrophotometrically as an arsenomolybdenum blue complex. The detection limit is 0.024pg and the coefficient of variation is 5.1% at the 0.1 pg level. The method is free from interferences by other elements at levels normally encountered in sediments. In this method the sediments were freeze-dried and ground (to less than 200pm) before analysis. 

In the presence of freeze-dried potassium fluoride, perfluoro-2-methylpent-2-ene reacts with activated methylene compounds to yield pyrans (81MI22400). The fluoride ion abstracts a proton from the methylene group and subsequent condensation of the carbanion with the perfluoroalkene affords a dienone (19) which ring closes to the pyran (20 Scheme 3). In the case of pentane-2,4-dione a divinyl ether (21) is also formed. This product is considered to arise from reaction of the alkene at the oxygen of the enolate ion. 

Clavulanic acid may be extracted from the culture medium. Normally the cells of the Streptomyces clavuligerus are first removed from culture medium by filtration or centrifugation. Then clavulanic acid is extracted into an organic solvent, for example, n-butanol or ethyl acetate, or n-butyl acetate, or methyl isobutyl ketone. Then n-butanol fraction are treated with new aqueous phase using potassium hydrogen carbonate and then this aqueous phase is washed with n-butanol. This aqueous extract, after separation of the phases, is concentrated under reduced pressure. Freeze-drying at -20°C may also be... 

A solution of potassium cyanate (11 mg) in water (1.36 ml) was added portionwise during 1 hour to a solution of the above hydrazide (118 mg) in a 20 1 v/v mixture of water and acetic acid (10 ml). The mixture was freeze-dried and the residue was purified by reverse-phase column chromatography (Dynamax 60 ANG, C18, 1 inch diameter) using a gradient of 10% to 40% by volume of acetonitrile in water containing 0.1% trifluoroacetic acid. There was thus obtained goserelin (100 mg, 25% yield overall), the structure of which was confirmed by mass spectroscopy. 

A 250-ml round-bottomed flask was charged with 2,4,6-trimethylphenol (44.1 mmol), 4-fluoro-benzonitrile (44.1 mmol), potassium carbonate (52.8 mmol), and a mixture of 100 ml NMP and 60 ml of toluene and then heated to 140°C for 8 hours. The mixture was filtered, the filtrate poured into 5% hydrochloric acid, and the organic and aqueous layers separated. The organic layer was diluted with CH2CI2 and concentrated. After the light brown oily residue was freeze-dried, the product was isolated in 97% yield. 

For less activated aromatic systems (those without a nitro substituent), the halogcn-ex-changc reaction has been investigated with potassium fluoride in a variety of polar aprotic solvents in the presence or absence of a catalyst (see Table 13). Many different types of catalysts have been investigated these include crown ethers, quaternary ammonium salts, 3,164 pjjos-phonium salts, aminophosphonium salts, compounds containing a phosphorus and an amino function, and inorganic fluorides of boron, aluminum, tin, phosphorus, titanium and zirconium. Different forms of potassium fluoride have been used these include spray-dried potassium fluoride, freeze-dried potassium fluoride, potassium fluoride recryslal-lized from methanol, and potassium fluoride dispersed on caleium fluoride. ... 

The approved variations [14] in the Karl Fischer method include volumetric titration methods to either a visual (excess iodine or addition of an indicator) or volta-metric endpoint detection method. The visual or voltametric endpoint methods usually require 30-40 mg of sample for analysis for freeze-dried biological products containing from 1.0% to 3.0% residual moisture. Coulometric Karl Fischer instruments generate the iodine from potassium iodide for water titration at the electrodes. Only 10-20 mg of freeze-dried sample is required for accurate analysis. 

Oguchi, T. Yamashita, J. Yonemochi, E. Yamamoto, K. Nakai, Y. Effects of saccharides on the decomposition of cephalothin sodium and benzylpenicillin potassium in freeze-dried preparations. Chem. Pharm. Bull. 1992, 40, 1061-1063. 

Freeze-dried serum provides no advantage over serum frozen at -30°C in the determination of species such as glucose, urea, nitrogen, sodium, potassium, total protein and... 

Mathews and his coworkers 8 described an unusual behavior for samples of freeze-dried potassium benzylpenicillin and potassium phenoxymethyl penicillin. These samples absorbed moisture from the air up to a maximum content of 7-14 per cent. Then the samples suddenly contracted in volume and began to lose weight until they had returned to their original weight. 

They conclude the abrupt change at the point of maximum moisture content is a spontaneous crystallization of substantially amorphous material. At 120°,a freeze-dried sample of potassium benzylpenicillin decomposed within 16 hours. After exposure to air, it was stable for 96 hours at this temperature,as was a control sample crystallized from aqueous-butanol. The heat of solution of the freeze-dried sample... 

The exclusively stereospecific and sterically sensitive ring expansion of isomeric vinylcyclopro-panes 21 to cyclopentenes 22 was detected in the desilylation of 21 with freeze-dried potassium fluoride. ... 

Monophasic Ln x MnOs (Ln = La, Nd) perovskites with high surface areas (8-27 m /g) were synthesised at mild conditions by the freeze-drying method, and were found to be active for the catalytic combustion of ethane at low temperatures (573 to 648 K). As a general troid, the substitution of the rare earth cation by potassium decreased the intrinsic activity, reduced the reaction order in oxygen and, for the more substituted samples (x>0.10), it increased the selectivity to ethene. It was found that the rare earth cation also influenced the catafytic activity of the substituted perovskites. These effects were analysed in terms of structural modifications induced by the introduction of potassium in the perovskites. 

As the Halex reaction using alkaline fluorides is carried out in an heterogeneous system, the influence of the physical state of the solids must be taken into account. Several pre-treatments of potassium fluoride have been proposed to improve its performances which are evidently linked to the area of the solid surface. Spray-drying (refs. 68, 69) and freeze-drying (ref. 70) are now considered as more activating treatments of KF than calcination. Very recently, however, slow recrystallisation in methanol has been claimed to deliver a potassium fluoride which is even more effective than the spray-dried one (ref. 41). Some comparisons are given on Figure 8, Table 24 and Pictures 1 and 2. 

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