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A method is described to measure changes in pressure inside a bottle during autoclaving without disturbing the integrity of the seal. Experiments showed that, in a perfectly sealed bottle, the pressure rose to a maximum of 58.2 psi absolute. If the rubber linear was unable to maintain the seal, air leaked slowly from the bottle both during the heating-up and the early sterilization period.
The stability constants for stannous fluoride complexes were determined by potentiostatic titration. The method involves incremental additions of fluoride wherein each addition is followed by titration with stannous such that there is no change in the electromotive force developed between the fluoride ion and the reference electrodes. The values obtained were beta1 equals 4 times 10-3, b2 equals 1.1 times 10-7, and b3 equals 1 times 10-9. The results of this work suggest that the potentiostatic method wound be useful for determining stability constants in complexation systems involving an ion for which a specific on electrode is available.
The published procedure for the synthesis of pyrrolidone-5-hydroxamic acid was improved. The acidity constant of the pyrrolidone-5-hydroxamic acid was determined as pKa = 8.65. In an aqueous solution of iron (III) ions, pyrrolidone-5-hydroxamic acid binds ferric ion, forming a mixture of mono-, bis-, and tris(pyrrolidone-5-hydroxamato)iron (III) complexes. These complexes were studied by potentiometric and spectrophotometric methods. The tris compound was isolated as dark orange-red crystals and identified according to elemental analysis and IR spectral data as C15H21FeN6O9.6H2O, having the magnetic moment of 5.67 B.M.
The binding of cupric ions to bovine serum albumin was investigated by using a cupric-ion-specific electrode. When using a modified form of the Scatchard equation, it was determined that there are at least two classes of binding sites on bovine serum albumin for cupric ions. One class has three binding sites of relatively strong affinity, with an average binding constant of 3.0 times 10(6). The other class has about 16 binding sites of relatively weak affinity, with an average binding constant of 2.0 times 10(4).
Apparent dissociation constants of organic acids were determined by potentiometric titration in the presence of cyclohexaamylose or cycloheptaamylose. The quantity deltapKa' = pKa' (cycloamylose)-pKa (water) was positive or zero for all carboxylic acids studied and negative or zero for all phenols. The term delta pKa' can be related to the cycloamylose concentration, K11alpha, and K11b, where K11a and K11b are 1:1 stability constants for complexes of the acid and the anion, respectively. From the dependen1a and K11b can be obtained. If deltapKa' not equal to 0, then K11a not equal to K11b; for carboxylic acids, K11a greater than or equal to K11b; for phenols, K11b greater than or equal to K11a. Because of variable pKa' shifts, it is possible to carry out differentiating titrations of some acid mixtures in cycloamylose solutions, whereas the same acids cannot be differentiated in water. If an acid is weakened by cycloamylose, its conjugate base is strengthened, and some carboxylate salts can be readily titrated in the presence of a cycloamylose.
A nonaqueous titrimetric method is proposed for determining the diastereomeric sulfates of quinine and quinidine. The sulfuric acid content of the alkaloid salts is precipitated, in the form of barium sulfate, with acetous barium acetate solution before the liberated alkaloid is titrated; the necessary calculations are provided. A favorable characteristic of the proposed procedure is the accuracy, speed, and ease of performance. The mean percent recoveries (p = 0.05) obtained with the proposed method for the sulfates of quinine and quinidine were 98.84 +/- 1.00 and 99.74 +/- 1.27, respectively, compared with 100.73 +/- 1.44 and 100.82 +/- 1.16, respectively, when the BP 1968 procedure was applied.
The microionization constants for two zwitterionic compounds were determined by incorporating two experimental techniques. These compounds have chromophoric changes dependent upon the solution pH. By combining the spectrophotometric measurements with potentiometric mmeasurements, all four microionization constants were calculated. The method used is completely general and is applicable to all diprotic compounds that exhibit this spectrophotometric behavior. The observed pKa's had differences of at most 1.2 units for either compound and were in the 1-4 range. A comparison of the results with each compound and similar compounds indicates that the values are resonable.
A series of N1-p-chlorophenyl-N5-alkylbiguanides were synthesized as potential inhibitors of dental plaque. Partition coefficients and pKa values were determined by standard methods. Biological activity was evaluated against Streptococcus mutans, a pure strain of plaque-forming bacteria. All compounds were compared to chlorhexidine acetate.
The initial aluminum hydroxide gel precipitate resulting from the reaction of aluminum chloride or aluminum sulfate with ammonium hydroxide is shown by potentiometric titration, chemical analysis, and the ratio of bound hydroxide to aluminum to fit a polymer model described previously. The formation of polynuclear hydroxyaluminum particles is treated as a stepwise process involving a deprotonation-dehydration mechanism, which results in the formation of six-membered rings; these rings may further coalesce by the same mechanism. The aluminum hydroxide gel precipitated from aluminum chloride can be represented by the formula Al(OH)2.55(Cl)0.45 and probably exists as a polymer of 10 fused six-membered rings. The aluminum hydroxide gel precipitated from aluminum sulfate can be represented by the formula Al(OH)2.30(SO4)0.35. This species probably exists as a polymer of three fused six-membered rings.
The effect of sorbitol on the aging of aluminum hydroxide gel, prepared by the reaction of aluminum chloride solution with strong ammonia solution to a final pH of 7.0, was studied by potentiometric titration, acid-consuming capacity, pH, hydroxide to aluminum ratio, chloride activity, X-ray diffraction, and IR spectroscopy. Gels containing sorbitol lost less than 10% of their acid-consuming capacity during a 6-month aging period compared with a loss of more than 60% for an identical gel without sorbitol. The mechanism by which sorbitol stabilizes the gel appears to be inhibition of the secondary polymerization reaction which takes place upon aging. Another polyhydroxy compound, quercetin, also stabilizes aluminum hydroxide gel.
Comparative antimicrobial activity of 3-chloro-2-oxazolidinone (I), 3-chloro-4-methyl-2-oxazolidinone (II), 3-chloro-4,4-dimethyl-2-oxazolidinone (III), and N-chlorosuccinimide (IV) was evaluated in aqueous buffers in the absence and presence of 5% horse serum. All four compounds had similar bactericidal activity in the absence of horse serum, but I and III had superior activity relative to IV when serum was present. Compound III was considerably more stable with respect ot loss of positive chlorine and bactericidal activity than I and II when stored in 0.1 M sodium dihydrogen phosphate buffered to pH 7.0 at 40 degrees. Thus, III is potentially the most useful bactericidal agent of those evaluated. The chlorine potentials of I, II, and III, the rate constants for transfer of positive chlorine from I and III to morpholine in aqueous solutions, and the hydrolytic stabilities of I and III with respect to loss of positive chlorine were evaluated. These data, together with previously calculated data for IV, are used to rationalize the observed bactericidal activities.
Polarographic and chronopotentiometric methods were applied to study the effects of the phenothiazine tranquilizers chlorpromazine hydrochloride and trifluoperazine hydrochloride on the electrochemical behavior of the flavin coenzymes flavin mononucleotide and flavin adenine dinucleotide. The effects of the drugs were measured mainly by decreases in the diffusion currents, id, developed in the polarographic experiments and by a similar decrease in the chronopotentiometric constant, ior1/2, in the chronopotentiometric experiments when the coenzymes were reduced in the presence of the added drugs. The observed interference with the redox properties of the coenzymes could conceivably be related to the reported ability of the drugs to inhibit respiration and produce their tranquilizing effect.
The interaction of various metal ions with anhydrotetracycline was investigated. A comparison of the UV-visible and fluorescence spectral characteristics of anhydrotetracycline and its metal-ion complexes with a number of modified anhydrotetracyclines in the presence of metal ions suggested that the C-11 oxygen was involved in metal-ion binding. Secondary binding was observed in the A-ring by circular dichroism when the primary site was blocked.
Overall stability constants of mono-, bis-, and tris(pyrrolidone-k-hydroxamato)iron(III) chelates were determined in aqueous solutions at 25 degrees as log beta1=1.49, log beta11=1.55, and log betaIII=0.21, respectively, where beta1=[Fe(C5H7O3N2)2+][H+]/[F=E3+][HC5H7O3N2], betaII=[Fe(C5H7O3N2)2+][H+]2/[Fe3+][hc5h7o3n2]2, and betaIII=[Fe(C5H7O3N2)3][H+]3/[Fe3+][HC5H7O3N2]3. Stability constants of all three chelates were determined potentiometrically in the 3.00-3.23 pH region. The stability constant of the mono chelate also was determined spectrophotometrically at 25 degrees as log beta1-1.52 by measuring absorbance at 500 nm (absorbance maximum), where the molar absorptivity was epsilon=1124 liters/(mole cm). Biological implications of hydroxamic acid-containing compounds are discussed.
The polarographic assays for cefamandole sodium and its formyl ester, cefamandole nafate, are described. Controlled potential coulometry is used as an absolute method for the assignment of purity of these compounds without the need for a reference material. The precision, accuracy, and selectivity of these assays were better than for the microbiological autoturbidimetric and automated iodometric assays. NMR, TLC, GC, and polarography are used to detect and quantitate likely impurities and degradation products.
A potentiometric nonaqueous titration procedure was developed for the quantitative determination of solasodine in fruits of the Solanum species. The steroid glycoalkaloids were extracted from freshly harvested fruits with 2% acetic acid and methanol. After hydrolysis, the common aglycone solasodine was extracted with benzene. An aliquot was mixed with an equal volume of acetone and titrated potentiometrically with 0.005 N perchloric acid in dioxane, using glass and silver electrodes for the determination.
A sensitive potentiometric monitoring method was developed that permits the continuous measurement of the disolution profiles of methyl vinyl ether-maleic anhydride-acid copolymers and salt derivatives. Three distinct rate periods were observed in the dissolution rate of the anhydride copolymer, expressed as percent anhydride dissolved, was independent of sample weight over the weight range studied. The acid form of the copolymer showed only one dissolution rate period, with dissolution being very rapid. The rapid initial pH decrease observed during the first stage of dissolution for a series of anhydride-acid copolymer powder samples correlated closely with the anhydride-acid ratio, permitting chemical characterization of the copolymer functionality simultaneously with the analysis of dissolution profiles. Similarly, the extent of copolymer alkaline salt conversion was inversely proportional to the initial maximum pH increase observed during the first stage of dissolution of these salts. Mechanisms of dissolution of copolymer powder materials are discussed and compared to the dissolution of compressed disks and films reported previously.
The kinetics of indomethacin were studied in the presence of the surfactants ethoxylated lanolin, polysorbate 80, and cetrimonium bromide under alkaline conditions at 30.3 degrees. The degradation followed apparent first-order kinetics. Plots of kobs versus surfactants; concentrations were curved with negative slopes for nonionic surfactants; but with the ionic surfactant, the plots showed a marked positive change in kobs as the surfactant concentration passed through the critical micelle concentration. Literature model systems adequately explained the data for nonionic surfactants but not for the ionic surfactant. A new set of equations was derived for each case using electrochemical potentials. The experimental data for all three surfactants fit the derived equations quite well.