Solubility and stability

Oxazines can form salts with strong acids. The salts vary with regard to their solubility and stability. Some of the hydrochlorides are hydrolyzed by water. Some less common salts are known e.g., dichromates and ferrocyanates, " chloroplatinates and chloroaurates. Sometimes the picrates can also be used to identify the 1,3-oxazine derivatives. " In some instances a special procedure is required to form the picrates, as the heterocyclic ring can open under the action of picric acid. " ... 

Solubility and stability of coelenterazine. Coelenterazine is very poorly soluble in neutral aqueous buffer solutions, and the solutions are unstable in air. It can be easily dissolved in water in the presence of alkali, but the resulting solution is extremely unstable under aerobic conditions. Coelenterazine is soluble in methanol, and the solution is relatively stable. The stability is enhanced by the addition of a trace of HCl. A methanolic solution of coelenterazine can be stored for several days at — 20°C, and a methanolic solution containing 1-2 mM HCl can be stored for several months at — 70°C under aerobic conditions without significant oxidation. In many other organic solvents, coelenterazine is less stable, and spontaneously auto-oxidized at significant rates. In dimethylformamide and DMSO, it is rapidly decomposed accompanied by the emission of chemiluminescence. e-Coelenterazines are generally less stable than coelenterazines. 

A series of corresponding ergoline and ergolene derivatives was synthesized. The ergotamine derivative showed an interesting antihypertensive activity. Unfortunately, the substance has very poor solubility and stability and therefore the further pharmacological evaluation was stopped (ref. 25). 

Solubilities and stabilities of calcium phosphates in natural waters have been described (735), as have the nucleation and growth of calcium phosphate from solution (736). Several species have long been known to inhibit the precipitation of calcium phosphates, for example carbohydrates (646) and statherin, the tyrosine-rich peptide which occurs in saliva (737). The role of... 

Hexamethylcyclotrigermathiane (22) and hexamethylcyclotristannathiane (23) also react easily with Et3P=CHMe, which enabled us to obtain the first betaines with the thiolate center in the germanium (24) and tin (25) series (Scheme 12).60,61 Both betaines are solid finely crystalline white substances, whose solubility and stability in the solid state and in solutions are similar to those of the silicon analog 20n. 

It is also possible to isolate bis(carbene) complexes involving the heavier alkaline earth metals. Thus, the reaction of two equivalents of 4 (R = Me or (Bu, R = H) with calcium, strontium and barium bis(trimethylsilyl)amides [M N(SiMe3)2 2(thf)2] (M = Ca, Sr, Ba) resulted in the displacement of two thf molecules to afford the corresponding biscarbene species, 19 (19). The solubilities and stabilities of these complexes were found to decrease from calcium to barium. 

Bischoff, J. L., J. A. Fitzpatrick and R. J. Rosenbauer, 1993, The solubility and stabilization of ikaite (CaC03 6H2O) from 0 °C to 25 °C, environmental and paleoclimatic implications for thinalite tufa. Journal of Geology 101, 21-33. 

At the same time, while working out such combinations, one should solve a number of problems - compatibility, solubility, and stability of various ingredients in a combination. 

In the enantiotropic case the relative solubility and stability changes at a specific transition temperature where the two solubility curves cross. A given polymorph may be more soluble (less stable) above the transition point, but less soluble below and vice versa, Figure 4. An example of this relationship is the Form C and A or B relationships for Cimetidine in the case study. 

As the next step, suitable sample conditions have to be found which maximize the protein s solubility and stability in order to prepare samples that are stable for several weeks, allowing the spectroscopist to collect all necessary spectra without having to prepare a new sample after each experiment. In particular, if aggregation has been detected, solution conditions have to be screened to produce a monodispersed protein solution. The most elegant way to screen many different solution conditions with a minimum amount of protein is the use of either the microdialysis button [9] or the microdrop screen [10, 11]. In these screens, small amounts (1-5 pL) of concentrated protein solutions are... 

The required high concentration of ligands limits the number of compounds that can be tested simultaneously, since the total amount of ligands is normally limited for reasons of solubility and stability of the protein. 

The design of an effective CE separation system is highly facilitated by previous knowledge of some physicochemical parameters of analyses, such as ionic charge, molecular mass, solubility and stability. Generally, the best separation of small charged species can be achieved by CZE, while MEKC can be employed for the separation of small uncharged analyses. 

Quaternary ammonium periodates, prepared either from periodic acid and the quaternary ammonium hydroxide [21, 22] or by metathesis from sodium periodate and a quaternary ammonium salt [e.g. 23-25], have been used for a range of oxidations at stoichiometric levels in two-phase systems [21-33], The tetra-n-butyl-ammonium and hexadecyltrimethylammonium salts are both highly soluble in organic solvents (considerably less so in water), whereas benzyltriethylammonium periodate has a lower solubility and stability than either salt. 

HRP substrates (Sred) can be selected to give products that can be monitored easily by colorimetric, fiuorometric or chemiluminescent methods. A popular choice in colorimetric assays is 3,3, 5,5 -tetrameth-ylbenzidine (TMB), a colorless substance that gives a blue product (Sox) on oxidation. Important considerations when choosing suitable substrates are cost, safety, sensitivity, solubility, and stability. It is sometimes necessary to use a substrate that gives an insoluble colored product, for example, in histochemical staining or membrane-bound immunoassays. 

The metal-donor bonds are predominantly ionic and become more labile for calcium, strontium, and barium compared to beryllium and magnesium. The solubility and stability of the complexes decrease from calcium to barium. The 1 1 adducts of NHCs with BH3 or BF3 (28 and 29) are thermally stable and can be sublimed without decomposition. This is in sharp contrast to the properties of conventional carbenes, which rely on a pronounced metal-to-ligand back donation and are, thus, not suited to forming adducts with electron-poor fragments such as... 

Developing an isolation approach is an activity that is frequently overlooked or addressed as an afterthought. However, solubility and stability data may dictate the development of a chromatographic method that requires the elaboration of the isolation, that is, it is more complicated than a simple evaporation of the mobile phase. The development of the chromatographic process should be linked to and interactively codeveloped with the isolation. Ideally, the isolated impurity sample should not contain other compounds or artifacts, such as solvents, mobile-phase additives or particulate matter from the preparative chromatography, as they may interfere with the structure elucidation effort or adversely affect the stability of the impurity during the isolation process. Therefore, it is preferable to avoid or minimize the use of mobile-phase additives. However, should this prove to be impossible, the additive used should be easy to remove. The judicious choice of mobile phase in the HPLC process increases the ability to recover the compound of interest without or with minimum degradation. The most common... 

Solubility diagrams have nearly always been calculated using solubility and stability constants. Experimental determination of the solubility of iron oxides as a function of pH has been concerned predominately with ferrihydrite. Lengweiler et al. 

What are the pA a value(s), partition coefficients, solubilities and stability of a drug substance under development ... 

Boiling Points, Melting Points, Solubility, and Stability. 4.2 Chromatographic Behavior. 4.3 Aromaticity. 4.4 Tautomerism... 

Boiling Points, Melting Points, Solubility, and Stability... 

It is an ethyl ether derivative of dihydroartemisinin in sterile arachis oil. A racemic mixture of a, P-artether (30 70 ratio) has greater solubility and stability than artemisinin and is more cost-effective. 

The product is a very pale yellow to cream-colored solid. It is hygroscopic and is soluble in liquid ammonia, with limited solubility and stability in acetonitrile, dimethyl sulfoxide, and dimethylformamide. Water or moisture from the air leads to disproportionation, and so the product must be stored under anhydrous... 

Local anesthetics are weak bases and are usually made available clinically as salts to increase solubility and stability. In the body, they exist either as the uncharged base or as a cation. The relative proportions of these two forms is governed by their pKa and the pH of the body fluids according to the Henderson-Hasselbalch equation ... 

The activated phenols are C-0 coupled each other. The dimer thus formed is activated by a similar mechanism, and polymerization occurs. The effects of the amine ligand (L) are to improve the solubility and stability of the Cu ion, to affect the stability of the substrate-coordinated complex, and to control the redox potential of the Cu ion. The Cu-complex catalyst not only enhances the rate of polymerization, but it also has an important effect on the coupling reaction. 

The compound [ Ce(N(SiMe3)2)3 2(p-ri r 2-O2)] (25) had limited solubility and stability in a hydrocarbon solution and hence reliable NMR or Raman solution spectra were not obtained. 

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