Water solubility determination described

The purified tetraethyl pyrophosphate is a colorless, odorless, water-soluble, hygroscopic liquid (24, 4 )- It possesses a very high acute toxicity (28), exceeding that of parathion, and is rapidly absorbed through the skin. There is no spray-residue problem, however, for tetraethyl pyrophosphate hydrolyzes even in the absence of alkali to nontoxic diethyl phosphoric acid. Hall and Jacobson (24) and Toy (47) have measured its rate of hydrolysis, which is a first-order reaction. Its half-life at 25° C. is 6.8 hours and at 38° C. is 3.3 hours. Coates (10) determined the over-all velocity constant at 25° C. k = 160 [OH-] + 1.6 X 10 3 min.-1 Toy (47) has described an elegant method for preparing this ester as well as other tetraalkyl pyrophosphates, based upon the controlled hydrolysis of 2 moles of dialkyl chlorophosphate ... 

Trans oxidative addition of CH3I to [Ir(acac)(cod)] affords the structurally determined complex [Ir(acac)(cod)(CH3)1].241 The reaction of [(Npet)2Ir]Cl, Npet = o-(diphenylphosphino)benzylide-nejethylamino, with tetrachloro-o-quinone yields the structurally characterized product (135).242 The synthesis and characterization of the water-soluble complex (136) have been described.243... 

McFarland et al. recently [1] published the results of studies carried out on 22 crystalline compounds. Their water solubilities were determined using pSOL [21], an automated instrument employing the pH-metric method described by Avdeef and coworkers [22]. This technique assures that it is the thermodynamic equilibrium solubility that is measured. While only ionizable compounds can be determined by this method, their solubilities are expressed as the molarity of the unionized molecular species, the intrinsic solubility, SQ. This avoids confusion about a compound s overall solubility dependence on pH. Thus, S0, is analogous to P, the octanol/water partition coefficient in both situations, the ionized species are implicitly factored out. In order to use pSOL, one must have knowledge of the various pKas involved therefore, in principle, one can compute the total solubility of a compound over an entire pH range. However, the intrinsic solubility will be our focus here. There was one zwitterionic compound in this dataset. To obtain best results, this compound was formulated as the zwitterion rather than the neutral form in the HYBOT [23] calculations. 

According to the synthetic strategy just described, a series of water-soluble carbosi-lane dendrimers were made, bearing peripheral galabiose trimers interspaced by 29 A, adjusted to the binding-site distances (Fig. 75).432 The binding affinity to SLT-I and SLT-II B subunits were determined by Scatchard plot analysis. Hexavalent compound 610 showed KD values of 1.3 and 1.6 /M for SLT-I and SLT-II,... 

Some years later, Miller and others (1996) described a modified TEAC assay that is able to determine the antioxidant activity of carotenoids. In the improved version, ABTS,+, the oxidant, is generated by oxidation of 2,2 -azinobis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS2 ) with manganese dioxide. A similar approach was described by Re and others (1999) in which ABTS was oxidized with potassium persulfate (Fig. 10.2), this version of the TEAC assay is applicable to both water soluble and lipophilic antioxidants (Re and others 1999 Pellegrini and others 1999). 

Gel electrophoretic patterns of water-soluble proteins in the five peanut flours were determined as previously described (2) and show considerable differences in protein character (Figure 2). In... 

Hermann (2000) described a rapid automated method involving generation of a known amount of free radicals and the detection of the excess by photochemiluminescence. Test kits are available for determination of total water-soluble antioxidants, fat-soluble antioxidants and ascorbic acid. A luminometric method was developed for the determination of antioxidative activity and was subsequently applied to anthocyanin and betalaine colour concentrates (Kuchta et al., 1999). The method involved quantification of the interruption in luminescence from the hydrogen peroxide-horse radish peroxidase-luminol system in the presence of antioxidants. 

Some of the properties of polymers derived from (NPC12)W and alanine152 and from arylamines153 have been described. The former are water-soluble and have potential medical applications. Molar refraction and volume data on NP(NHC6-H4R-p)2n (R = H, Me, OMe, or Cl) have been determined.154... 

In the experiments described by Pays et al. [44], the double globules were composed of dodecane and the surfactants used were sorbitan monooleate (SMO), which is oil soluble, and the water-soluble SDS. The concentrations of both surfactants were fixed and the initial internal droplet volume fraction was varied between 5% and 35%. The coalescence frequency was determined from a simple experiment in which the globule surface was totally saturated by the water droplets. For... 

As the quantity of water-soluble constituents in the various hido powders varies greatly, it is always necessary, before using a hide powder for tannin determinations, to determine the quantity of soluble constituents by a blank test according to the method described here. 

Perfetti et al. (131) described a method for the determination of ethoxyquin in milk. Milk solids were precipitated by adding acetonitrile, and the water-acetonitrile supernatant was washed with hexane to remove fat. The addition of NaCl caused the water-acetonitrile solution to separate into an aqueous phase and an acetonitrile phase, thus separating ethoxyquin from most water-soluble impurities. A large volume of water was then added to the acetonitrile layer, and ethoxyquin was partitioned into hexane and removed at reduced pressure. The residue was dissolved in the mobile phase and analyzed on a 250-mm X 4.6-mm-ID. Ultrasphere ODS column using fluorescence detection with excitation of 230 nm, and emission of 418 nm, respectively. A mixture of water and acetonitrile with a diethylamine-acetic acid buffer was the mobile phase. Recoveries from milk samples fortified at 1, 5, and 10 ng/g averaged 78%, with a coefficient of variation of 5.0%. Low concentrations (less than 1 ng/g) of apparent ethoxyquin were detected in commercial milk samples analyzed by this method. 

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