DMSO Water Content

DMSO and water form a solution with nonideal behavior, meaning that the properties of the solution are not predicted from the properties of the individual components adjusted for the molar ratios of the components. The strong H-bonding interaction between water and DMSO is nonideal and is the primary driver for the very hygroscopic behavior of DMSO. Even short exposure of DMSO to humid air results in significant water uptake. Water and DMSO nonideal behavior results in an increase in viscosity on mixing due to the extensive H-bond network. 

---

Fischer titration may not be reliable for water concentration determination in the presence of highly hygroscopic electrolytes, e.g., LiCl/DMAc [119]. This conclusion has been also verified for TBAF/DMSO, by adding known amounts of water to the solvent system, followed by determination of the water content by Karl-Fischer titration. Whereas the added water ranged from 0.23 to 1.19 mol H, that determined by titration ranged from 0.21 to... 

Figure 2. Computed kinetics of water loss from mouse ova cooled at 1 °C to 32 °C/min in 1M DMSO. The curve labeled EQ shows the water content that ova have to maintain to remain in equilibrium with extracellular ice. If ova or embryos contain more than equilibrium amounts of water when they cool to below -30 °C, they will undergo intracellular freezing. Usually such freezing is lethal, but if the quantity of ice is small, some internally frozen cells can be rescued by rapid warming. (From Mazur, 1990.)...

SF1PP is relatively insoluble in aqueous environments and must be dissolved in an organic solvent prior to addition to a reaction medium. Suggested solvents include dioxane and DMSO that are low in water content to avoid hydrolysis of the NHS ester. 

If the water content is driven off (usually by heating to 350 °C in a vacuum), the dehydrated zeolite becomes an avid absorber of small molecules, especially water. The size of the molecules that can be absorbed is limited by the zeolite pore diameter, which is different for different zeolites (Table 7.1) a given zeolite (e.g., zeolite 3A) can be a highly selective absorber of, say, small amounts of water from dimethyl sulfoxide (DMSO) solvent. For this reason, dehydrated zeolites are often called molecular sieves. 

Solvent and concentration effects on keto-enol tautomerization have been investigated in DMSO-water mixtures and aqueous micellar solutions, for 2-acetylcyclo-hexanone and 2-acetyl-1-tetralone.286 Dramatic rate increases aboves 60% DMSO content have been explained in terms of solvent structure solvent polarity alone cannot rationalize the effect. 

The carboxymethylation of cellulose with sodium chloroacetate in an aqueous system generally showed that the 2-OH group was more reactive than the 6-OH group, whereas the 3-OH was the least reactive. A low water content medium resulted in a relatively more uniform reactivity than a high water content reaction [202]. Similarly, carboxymethylation in a nonaqueous system (SO2-DEA-DMSO) [79] resulted in a more uniform reaction and a higher reactivity of the 6-OH group as compared to an aqueous reaction. Interestingly, carboxymethylation with sodium iodoacetate substantially enhanced the reactivity of the 3-OH, which was found to be most reactive under this condition. 

The redox properties of tetraphenylporphyrin have been studied in dimethyl sulfoxide (DMSO) and more polar water/DMSO mixtures. Increasing solvent polarity [i.e. inereasing water content) shifts the reduction potentials to more positive values and makes the reduetion step more favourable, since a better solvated anion is formed from a neutral speeies [291]. 

Salt, solvent, and substituent effects in the alkaline hydrolysis (and alkoxide-promoted decomposition) of phosphonium compounds have been reviewed. The rate of alkaline hydrolysis of tetraphenylphosphonium chloride in DMSO-water mixtures increases by as much as 10 -fold as the DMSO content is increased, due to desolvation of the reactant ions. ... 

Increasing water content and formation of crystalline material are two synergistic causes for decreased solubility in DMSO after freeze-thaw cycles. Storage of DMSO stocks at low temperatnre is a good strategy if stability is an issne, bnt it is not a wise practice if solubility is an issne. Lipinski recommends storing DMSO stock solutions at room temperatnre for short term use to minimize solnbility effects (Lipinski, 2004b). 

Use 90% DMSO/Water Consistent water content, volume and concentration Fast access as liquid Favor drug-Uke properties Instability for certain compounds... 

Site-directed functionalization of CD-PEI was achieved with fcr/-butylphenyl ester 41 which contains a precursor of 1,5,9-triazacyclododecane (TC).By taking advantage of the recognition of tert-butylphenyl moiety by CD, PEI was acylated with 41 in 9% (v/v) DMSO-water. After a few additional steps of modification, PEI derivative 42 which contains both the metal (Cu(II), Ni(Il), or Zn(II)) complex of TC and CD cavity was prepared. The content of CD and TC in 42 was 1.2 residue mol%. The primary and the secondary amino groups of 42 were blocked by acetylation. In a separate preparation, TC was attached to PEI randomly by... 

The Novartis approach of storing stocks solutions at 2 mM concentration in a 90 10 DM SO water mixture (15,17) provides a critical advantage for the HTCP system. With the addition of 10% water to DMSO, the freezing point of the mixture drops from 18 to below 4°C. This freezing point depression avoids the potential for repeated freeze/thaw cycles which could impact the solubility of some compounds. Since no melting step is required, sample access is rapid. At a storage temperature of 4°C and a relative humidity of 15-20% the water content of a 90 10 DMSO water mixture is close to equilibrium so that very little further water is absorbed from the atmosphere. 

DMSO is a very good solvent. Around 90 % of the compounds that end up in a library will dissolve in DMSO. In chloroform or acetone, the figure is only 70 %. Although it is easy to understand the choice for DMSO, not until quite recently was there any concern as to what DMSO might actually do to the compounds. It is not an inert solvent. DMSO is not only mildly reactive but absorbs large amounts of water when exposed to normal air. This became a problem when aware of the problems associated with stability in DMSO solution, companies started to store daughter plates at low temperatures (down to -20°C) only to find large increases in the water content from repeated freeze-thaw cycles. 

High boiling solvents such as DMF, DMAc, DMSO, NMP and the glycols do not have aqueous azeotropes and are easy to separate from water by distillation both at atmospheric and reduced pressures. The hold-up in conventional industrial batch distillation equipment can make very low water contents hard to achieve and taking distillate from a side stream some way down the column maybe desirable. 

A new spectrophotometric procedure was elaborated by Khalaf and Rimpler [Kh 80] for the determination of the water content of basic solvents (e.g., pyridine, DMSO, DMFA) based on the reaction of 5-isothiocyanato-l,3-dioxo-2-p-tolyl-2,3-dihydro-lH-benz(de)isochinoline with water. The reaction results in the formation of the 5-amino product of this reagent, causing the appearance of a new absorption band in the vicinity of 430 nm wavelength. The intensity of this new band was shown to be in linear correlation with the water content of the sample between 0.3-0.02 vol%. The reproducibility was found to be + 2.2%. 

Table 1 shows that the water content in a DMSO mobile phase varies from zero to 40%. It is advantageous to use a mobile phase that is a good solvent for starch. Jackson studied the solubility of com starches in a mixture of DMSO and water and found that maximum solubility was obtained when DMSO with 10% water was used (16). Solubility dropped sharply in pure DMSO. DMSO with 0.03 M NaNOj has been used as the mobile phase for many years in the author s laboratory (28,29). Table 2 shows the results of a study of the solubility of waxy com granules, com granules, and enzyme-degraded waxy com in DMSO and 0.03 M NaNOj and in DMSO, 10% water, and 0.03 M NaNOj. The solutions were heated at 80°C for 54 h and then analyzed by SEC. The peak areas were used as measurements of the solubility of starches in the two solvent systems. The results indicate that both solvents are about equal in dissolving starch samples. 

---