Inhibition by cardiolipins of platelet-activating factor-induced rabbit platelet activation

Evidence is presented that cardiolipin, a naturally occurring phospholipid, inhibits the aggregatory effect of platelet-activating factor (paf) on rabbit plateletsin vitro. Bovine heart cardiolipin was shown to inhibit the aggregation of washed rabbit platelets induced by 1×10⁻¹⁰ M and 2×10⁻¹⁰ M paf with IC₅₀ values (doses for half-maximal inhibition) of 8.4±0.8×10⁻⁷ M and 2.6±0.6×10⁻⁶ M, respectively. Phosphonocardiolipin was also able to inhibit platelet aggregation induced by 1× 10⁻¹⁰ M paf with an IC₅₀ value of 3±1×10⁻⁷M. Both compounds, in concentrations up to 1×10⁻⁵ M, were unable to aggregate washed rabbit platelets and failed to inhibit the aggregation induced by 0.9 and 1.8 μM adenosine diphosphate or 0.2–1.0 μM arrchidonic acid. By contrast, the acetylated derivative of cardiolipin exerted an aggregatory effect on aspirin-treated rabbit platelets in the presence of creatine phosphate/creatine phosphokinase. This aggregation was inhibited by the specific paf antagonists BN 52021 and WEB 2086. Also, platelets treated with acetyl-cardiolipin were insensitive to the aggregatory effect of paf. Phosphatidic acid, phosphatidylglycerol,bis(dipalmitoylglycero)phosphate and their phosphono analogues were totally inactive. Similar data were obtained when platelet-rich plasma was used instead of washed rabbit platelets. Our results support the hypothesis that the effect of cardiolipin is mediated through specific paf receptors that act on the rabbit platelet membrane.     

Simple Determination of Deoxycholic and Ursodeoxycholic Acids by Phenolphthalein-β-Cyclodextrin Inclusion Complex

An expeditious colorimetric methodology for the determination of the deoxycholic acid (DCA) and of the ursodeoxycholic acid (UDCA) in pharmaceutical formulations is reported. The method is based on their competitive complexation reaction with a color indicator to form β-cyclodextrin-inclusion complexes. Several pH color indicators were tested, but phenolphthalein (PHP) showed the best interaction with the β-cyclodextrin (β-CD) with an inclusion yield higher than 95%. The best concentrations of β-cyclodextrin to form inclusion complexes were 1.24 × 10⁻³ and 6.2 × 10⁻⁴ M at pH 9.5 and 10.5. Statistical analysis of the results showed that the pH had a significant effect on the DCA determination and that high β-CD-PHP inclusion complex concentrations had a significant negative effect on the UDCA determination (p < 0.05). The limit of detection and limit of quantification were 3.94 × 10⁻⁵ and 1.31 × 10⁻⁴ M for DCA (range: 6.1 × 10⁻⁶–3.13 × 10⁻³ M), 4.08 × 10⁻⁵  and 1.36 × 10⁻⁴ M for UDCA (range: 6.05 × 10⁻⁶–3.88 × 10⁻⁴ M). This simple and cheap method showed high stability and feasible instrumentation.     

Preparation of voltammetric biosensor for tryptophan using multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) were grown by chemical vapor deposition. The effect of the composition of carbon paste electrode on its voltammograms was evaluated in basic solution with 5.0×10⁻⁵ M tryptophan (Trp). It was found that addition of MWCNTs to the carbon paste would generate the peak current of Trp because of its catalytic effect on the redox process. The pH strongly affects the peak potential of Trp. The best analytical response was obtained at pH 13.0. The anodic peak currents were proportional to Trp concentrations in the range of 1.0×10⁻⁹−1.0×10⁻⁴ M under the optimized experimental conditions. The detection limit was 2.2×10⁻¹⁰ M. The effect of potential scan rate on the peak potential and peak current of tryptophan was investigated. The correlation of the peak currents against v^1/2 (v is the scan rate) is linear, which is very similar to a diffusion-controlled process. The proposed biosensor was applied to the determination of Trp in pharmaceuticals formulations successfully.     

Platelet activating factor induced respiratory mucosal damage

Human sinus mucosal specimens from eight normal individuals were exposed to platelet activating factor (PAF) at concentrations ranging from 10⁻⁶ M to 10⁻¹¹ M in a humidified CO₂ chamber at 37°C. The mucosal surface of the specimens was recorded on video tapes and magnified 2,500 times on a 19-inch television (TV) monitor. Ciliary activity of each ciliated cell was photoelectrically measured on the TV monitor in real time. PAF induced mucosal damage which resulted in a coarse profile including ciliostasis and exfoliation of epithelial cells. The length of the incubation period in which the initial coarse profile occurred on the mucosal surface inversely correlated with the concentration of exposed PAF ranging from 10⁻⁶ M to 10⁻¹⁰ M with r=−0.712 (p<2×10⁻⁴). Both the control medium and 10⁻⁸ M lysoPAF showed no effect on ciliary activity or mucosal surface alteration even after 24 hr of exposure. Significant ciliary inhibition was noted after 6 hr of exposure to PAF at concentrations of 10⁻⁸ M and 10⁻¹⁰ M (p<0.05). After 10 hr of exposure, significant ciliary inhibition (p<0.01) was noted at all concentrations. Inhibition occurred in a time- and dose-dependent manner. The length of the incubation period in which initial ciliostatis occurred and the level of PAF concentration showed an inverse correlation with r=−0.918 (p<10⁻⁶). These results indicate that PAF is cytotoxic to human respiratory mucosa. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Effects of quenching mechanisms of carotenoids on the photosensitized oxidation of soybean oil

The effects of 0, 1.0 × 10”⁻⁵, 2.5 × 10⁻⁵, and 5.0 × 10⁻⁵ M β-apo-8'-carotenal, β-carotene, and canthaxanthin on the photooxidation of soybean oil in methylene chloride containing 3.3 × 10⁻⁹ M chlorophyll b were studied by measuring peroxide values and conjugated diene content. β-Apo-8'-carotenal, β-carotene, and canthaxanthin contain 10,11, and 13 conjugated double bonds, respectively. The peroxide values and conjugated diene contents of oils containing the carotenoids were significantly lower (P<0.05) than those of control oil containing no carotenoid. As the number of conjugated double bonds of the carotenoids increased, the peroxide values of soybean oils decreased significantly (P<0.05). The quenching mechanisms and kinetics of the carotenoids in the photosensitized oxidation of soybean oil were studied by measuring peroxide values. The steady-state kinetics study showed that carotenoids quenched singlet oxygen to reduce chlorophyll-sensitized photooxidation of soybean oil. The singlet-oxygen quenching rate constants ofβ- apo-8'-carotenal, β-carotene, and canthaxanthin were 3.06 × 10⁹, 4.60 × 10⁹, and 1.12 × 10¹⁰ M⁻¹sec⁻¹, respectively.     

Homogeneous electrocatalytic oxidation of <Emphasis Type="SmallCaps">d</Emphasis>-penicillamine with ferrocyanide at a carbon paste electrode: application to voltammetric determination

The electrooxidation of d-penicillamine (d-PA) was studied in the presence of ferrocyanide as a homogeneous mediator at the surface of a carbon paste electrode in aqueous media using cyclic voltammetry (CV) and chronoamperometry. Under optimum pH in CV the oxidation of d-PA occurs at a potential about 380 mV less positive than that in the absence of ferrocyanide. The catalytic oxidation peak current was dependent on the d-PA concentration and a linear calibration curve was obtained in the ranges 4.0 × 10⁻⁵–2.0 × 10⁻³ M and 8.0 × 10⁻⁶–1.8 × 10⁻⁴ M of d-PA with CV and differential pulse voltammetry (DPV) methods, respectively. The detection limits (3σ) were determined as 1.9 × 10⁻⁵ and 3.2 × 10⁻⁶ M by CV and DPV methods. This method was also used for the determination of d-PA in pharmaceutical preparations by the standard addition method.     

Arachidonic acid autoxidation in an aqueous media effect of α-tocopherol,cysteine and nucleic acids

The autoxidation of arachidonic acid dispersed in aqueous media was evaluated simultaneously with and without different agents, e.g., α-tocopherol at different concentrations, cysteine, DNA and RNA. The autoxidation rate of arachidonic acid was evaluated by quantitative gas liquid chromatography (GLC) determination of the unoxidized acid and by spectrophotometric measurement of conjugated dienes. α-Tocopherol exhibited a prooxidant activity at concentrations of 1.25 × 10⁻⁴ M and 1.25 × 10⁻⁵ M and a weak antioxidant activity at a concentration of 1.25 × 10⁻⁶ M. Cysteine showed antioxidant activity and greatly reduced the prooxidant activity of α-tocopherol. DNA and RNA had no effect in either case. α-Tocopherol oxidation was followed by high pressure liquid chromatography (HPLC). The prooxidant effect was accompanied by a rapid oxidation of α-tocopherol, except in the presence of cysteine, which prevented the oxidation of α-tocopherol.     

Diffusivity of bacteria

The effects of motility and aggregation on the diffusion coefficient for bacteria were studied in an aqueous system. The effects of cell concentrations, capillary tube sizes, and dilution rates on the diffusion coefficient were examined. In general, motile cells can diffuse about 1000 times faster than non-motile cells.Pseudomonas aeruginosa, a motile cell, andKlebsiella pneumoniae, a non-motile cell, were used for this research. Diffusion coefficients were measured by the capillary tube assay developed by Adler [1969]. From this procedure the diffusion coefficient ofPseudomonas aeruginosa was 2.1×10⁻⁵ (standard deviation: 1.0× 10⁻⁵) cm²/s and that ofKlebsiella pneumoniae was 0.9×10⁻⁵ (standard deviation : 0.5 × 10⁻⁵) cm²/s. The diffusion coefficient ofPseudomonas aeruginosa was about 2.3 times higher than that ofKlebsiella pneumoniae. The Stokes-Einstein equation could not be used for estimating the diffusion coefficients forKlebsiella pneumoniae andPseudomonas aeruginosa. The experimental value for the diffusion coefficient ofKlebsiella pneumoniae was about 2000 times higher than that (4.5×10⁻⁹ cm₂/s) obtained from the Stokes-Einstein equation. This discrepancy was due to the aggregation ofKlebsiella pneumoniae.     

A hydroxylamine electrochemical sensor based on electrodeposition of platinum nanoclusters on choline film modified glassy carbon electrode

A sensitive hydroxylamine sensor was developed based on electrodeposition of Pt nanoclusters on choline film modified glassy carbon electrode (nano-Pt/Ch/GCE). The properties of the composites were characterized by field emission scanning electron microscope, X-ray photoelectron spectroscopy, powder X-ray diffraction, and electrochemical investigations. The designed nano-Pt/Ch/GCE showed a high sensing performance for hydroxylamine in a wide concentration ranges of 5.0 × 10⁻⁷–1.1 × 10⁻³ M and 1.1 × 10⁻³–19 × 10⁻³ M. The detection limit was 0.07 μM (s/n = 3). The proposed electrode presented excellent operational and storage stability for the determination of hydroxylamine. Moreover, the sensor showed good sensitivity, selectivity, and reproducibility properties. All the results indicated the designed sensor had a good potential application in the determination of hydroxylamine.     

Electrocatalytic oxidation of glutathione at carbon paste electrode modified with 2,7-<Emphasis Type="Italic">bis</Emphasis> (ferrocenyl ethyl) fluoren-9-one: application as a voltammetric sensor

Electrooxidation of glutathione (GSH) was studied at the surface of 2,7-bis (ferrocenyl ethyl) fluoren-9-one modified carbon paste electrode (2,7-BFEFMCPE). Cyclic voltammetry (CV), double potential-step chronoamperometry, and differential pulse voltammetry (DPV) were used to investigate the suitability of this ferrocene derivative as a mediator for the electrocatalytic oxidation of GSH in aqueous solutions with various pH. Results showed that pH 7.00 is the most suitable pH for this purpose. At the optimum pH, the oxidation of GSH at the surface of this modified electrode occurs at a potential of about 0.410 V versus Ag|AgCl|KCl_sat. The kinetic parameters such as electron transfer coefficient, α = 0.61, and rate constant for the chemical reaction between GSH and redox site in 2,7-BFEFMCPE, k _h = 1.73 × 10³ cm³ mol⁻¹ s⁻¹, were also determined using electrochemical approaches. Also, the apparent diffusion coefficient, D _app, for GSH was found to be 5.0 × 10⁻⁵ cm² s⁻¹ in aqueous buffered solution. The electrocatalytic oxidation peak current of GSH showed a linear dependence on the glutathione concentration, and linear calibration curves were obtained in the ranges of 5.2 × 10⁻⁵ M to 4.1 × 10⁻³ M and 9.2 × 10⁻⁷ M to 1.1 × 10⁻⁵ M with cyclic voltammetry and differential pulse voltammetry methods, respectively. The detection limits (3σ) were determined as 1.4 × 10⁻⁵ M and 5.1 × 10⁻⁷ M for the CV and DPV methods, respectively. This method was also examined as a selective, simple, and precise new method for voltammetric determination of GSH in real sample such as hemolysed erythrocyte.     

An Effective Amperometric Biosensor Based on Gold Nanoelectrode Arrays

A sensitive amperometric biosensor based on gold nanoelectrode array (NEA) was investigated. The gold nanoelectrode array was fabricated by template-assisted electrodeposition on general electrodes, which shows an ordered well-defined 3D structure of nanowires. The sensitivity of the gold NEA to hydrogen peroxide is 37 times higher than that of the conventional electrode. The linear range of the platinum NEA toward H₂O₂ is from 1 × 10⁻⁶ to 1 × 10⁻² M, covering four orders of magnitudes with detection limit of 1 × 10⁻⁷ M and a single noise ratio (S/N) of four. The enzyme electrode exhibits an excellent response performance to glucose with linear range from 1 × 10⁻⁵ to 1 × 10⁻² M and a fast response time within 8 s. The Michaelis–Menten constant km and the maximum current density i _max of the enzyme electrode were 4.97 mM and 84.60 μA cm⁻², respectively. This special nanoelectrode may find potential application in other biosensors based on amperometric signals.     

Simultaneous determination of dopamine and uric acid on nafion/sodium dodecylbenzenesulfonate composite film modified glassy carbon electrode

A novel electrochemical sensor has been constructed by using a glassy carbon electrode (GCE) coated with nafion/sodium dodecylbenzenesulfonate (SDBS). Differential pulse voltammetry (DPV) was used to study the electrochemical behaviors of dopamine (DA) and uric acid (UA). An optimum of 5 mM SDBS together with 0.05 wt% of nafion was used to improve the resolution and the determination sensitivity successfully. In 0.1 M phosphate buffer solution (pH 6.5), the modified electrode exhibited high electrocatalytical activity toward the oxidation of DA and UA with obvious reduction of overpotential. Compared with bare GCE, the modified electrode resolved the voltammetric response of DA and UA into two well-defined voltammetric peaks by DPV, which can be used for simultaneous determination of these species in mixture. The peak currents obtained from DPV were linearly related to the concentrations of DA and UA in the ranges of 4.0 × 10⁻⁷–8.0 × 10⁻⁵ M and 4.0 × 10⁻⁶–8.0 × 10⁻⁴ M, respectively. The detection limit of DA and UA (signal-to-noise ration was 3) were 5.0 × 10⁻⁸ and 4.0 × 10⁻⁷ M, respectively.     

Biological response of guinea pig peritoneal macrophages to platelet-activating factor

We investigated the effects of platelet-activating factor (PAF) on guinea pig peritoneal macrophages. Specific and high-affinity binding sites for PAF were detected on guinea pig peritoneal macrophages. Scatchard analysis of PAF binding revealed high affinity binding sites (7.9×10⁴/cell) with a dissociation constant of 2.3×10⁻¹⁰ M. When treated with 10⁻⁹−10⁻⁵ M PAF, guinea pig peritoneal macrophages released hydrogen peroxide into the medium in a time-dependent manner. The release reaction upon stimulation with 10⁻⁵ M PAF reached a plateau within 30 min and the extent of release was twice as high as that when stimulated byN-formyl-L-methionyl-leucyl-L-phenylalanine (fMLP; 2 μM)-treated cells. Neither lysoPAF nor the PAF enantiomer was effective. PAF-induced H₂O₂ release was inhibited specifically by PAF antagonists, suggesting that PAF activated macrophages through binding to specific sites. Lysosomal enzyme (N-acetyl-β-D-glucosaminidase) was released from guinea pig peritoneal macrophages upon treatment with 10⁻⁵ M PAF for 60 min. Guinea pig peritoneal macrophages were treated with PAF for 8 hr and the conditioned medium was examined for cytokines. The medium exhibited cytocidal activity against mouse fibroblast L929 cells [tumor necrosis factor (TNF) activity], and this activity was comparable to that detected after treatment of cells with the bacterial lipopolysaccharide (LPS). Furthermore, the same conditioned medium also showed colony-stimulating factor (CSF) activity. Generation of these cytokines was stereospecific. Our findings suggest that PAF is a unique macrophage activator that potentiates both respiratory burst/lysosomal enzyme release (early-phase response) and monokine production/glucose consumption (late-phase response). Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Pathogenesis of oleic acid-induced lung injury in the rat: Distribution of oleic acid during injury and early endothelial cell changes

Oleic acid-induced lung injury, a well-described laboratory model for acute pulmonary injury in the rat and other species, causes morphologic and cellular changes similar to human adult respiratory distress syndrome (ARDS). Experiments were performed to test the hypothesis that the initial event of oleic acid lung injury is damage of the pulmonary vascular endothelium by oleic acid, with subsequent pulmonary damage and inflammation. Oleic acid levels were followed in the lung and other tissues by measuring accumulation of¹⁴C-oleic acid; the direct effects of oleic acid and other fatty acids on rat endothelial cells, alveolar type II cells, and hepatocytes in culture were determined. Lung tissue from treated rats was also examined by light and electron microscopy for evidence of endothelial cell damage. At 30 min after injury, oleic acid reached high concentrations in lung tissue as demonstrated by presence of radiolabel (3.24×10⁻⁶ moles per gram of tissue), with counts in the lung nearly an order of magnitude greater than in any other organ measured. Oleic acid was present in the lung mostly as free fatty acid (85%), and was also present in the alveolar fluid supernatans, rather than being cell-associated (1.7×10⁻⁷ moles vs. 1.1×10⁻⁸ moles at 30 min). Oleic acid was toxic to endothelial cells after one minute of exposure at concentrations of 5×10⁻⁴M and above. Electron microscopy showed endothelial cell changes as early as 10 min after induction of injuryin vivo, including the presence of endothelial cell blebbing. The results of these studies suggest that the initial event in oleic acid lung injury is damage to the pulmonary vascular endothelial cell.     

Development of a new biosensor for mediatorless voltammetric determination of hydrogen peroxide and its application in milk samples

A new biosensor for the voltammetric detection of hydrogen peroxide was developed based on immobilization of catalase on a clinoptilolite modified carbon paste electrode using bovine serum albumin and glutaraldehyde. The biosensor response was evaluated according to electrode composition, reaction time, solution pH and temperature. The voltammetric signals were linearly in proportion to H₂O₂ concentration in the range 5.0 × 10⁻⁶–1.0 × 10⁻³ M with a correlation coefficient of 0.9975. The detection limit is 8.0 × 10⁻⁷ M and the relative standard deviation for 4.0 × 10⁻⁴ M hydrogen peroxide was 1.83% (n = 6). The biosensor exhibited high sensitivity, and it was determined that it could be used for more than 2 months. In addition, the biosensor was successfully applied for the determination of hydrogen peroxide in milk samples.     

Kinetic model of asymmetric reduction of 3-oxo-3-phenylpropionic acid ethyl ester using <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> CGMCC No.2266

The kinetic model of asymmetric reduction of 3-oxo-3-phenylpropionic acid ethyl ester using Saccharomyces cerevisiae CGMCC No.2266 with 10% glucose as co-substrate to realize the regeneration of NADPH was established. The effect factors on reduction, the type and the content of co-substrate and coenzyme, and the changes of the substrate and product content vs. time during the reaction process were investigated. The results indicate that 10% glucose can increase the reaction conversion from 23.0% to 98.4% and NADPH is reducer. The reduction process conforms with sequence mechanisms. The model parameters are as follows: v _m =5.0×10⁻⁴ mol·L⁻¹·h⁻¹, k₁=1.5×10⁻⁶ mol·L⁻¹·h⁻¹, k₂=3.0×10⁻³ mol·L⁻¹·h⁻¹. The kinetic model is in good agreement with the experimental data.     

The role of calcium in the regulation of prostacyclin synthesis by porcine aortic endothelial cells

Both bradykinin (EC₅₀=8 ng/ml) and the ionophore A23187 (EC₅₀=3×10⁻⁷ M) potently stimulated arachidonate release and prostaglandin synthesis in porcine aortic endothelial cells. The response to each was completely dependent on extracellular Ca²⁺ (EC₅₀=3×10⁻⁷ M); no role for intracellular Ca²⁺ was noted. The rapid Ca²⁺ influx prompted by either activator was consistent with the time course for arachidonate release. Whereas the arachidonate released in response to bradykinin was trasient, that released in response to A23187 was more prolonged, and paralleled a continued influx of Ca²⁺. Ca²⁺ entry elicited by bradykinin was mediated by channels which could not be blocked by verapamil. When Mn²⁺ was substituted for Ca²⁺, no stimulation of prostacyclin synthesis was seen in response to A23187; however, the bradykinin response was unaffected. The mechanism of these effects was studied using doses of bradykinin or A23187 which resulted in increases in Ca²⁺ influx and prostacyclin synthesis of similar magnitude for each agonist. Under these conditions, trifluoperazine blocked elevated prostacyclin synthesis (ID₅₀=5–6×10⁻⁶ M for each agonist). Trifluoperazine sulfoxide, however, was much less active. Pimozide inhibited bradykinin-stimulated prostacyclin synthesis at low doses (ID₅₀=3×10⁻⁶ M). Trifluoperazine was much less effective against high doses of A23187 (4×10⁻⁶ M). These data suggest that arachidonate release and prostacyclin synthesis are dependent on influx of extracellular calcium and subsequent activation of a Ca²⁺-dependent phospholipase by a calmodulin-mediated mechanism.     

Surface hydrophobicity alteration of fractionated paraffin wax, crude by-product polyolefin wax and their blend

The surface compositions of crude by-product polyolefin wax (wax K) from a naphtha cracking unit, fractionated commercial paraffin wax (wax J) and their blend (wax M) were compared, under various conditions, by using FT-IR. Then a practical criterion was theoretically derived by back-of-the-envelope-calculation to estimate the diffusivity for the surface enrichment of hydrophilic functional groups. The hydrophobicity in terms of chemical structure and functional groups was altered by changing the environment as well as by blending wax K with wax J. The surface properties of wax J and wax M turned out more hydrophobic than that of wax K within the experimental period of water-submerged condition, even though the structure and functional groups on the surfaces of all waxes under ambient atmospheric condition are extremely similar. Thus the blend of wax M behaved unlike wax K but similarly to wax J in terms of alteration of hydrophobicity. Such values of diffusivity as 1.35×10⁻¹¹ cm²/s and 1.96×10⁻¹¹ cm²/s are established for wax J and wax M, respectively, under 1 day water-submerged condition. Furthermore, under 1 week water-submerged condition, the values of their diffusivity for wax J, wax K and wax M are estimated as 3.06×10⁻¹² cm²/s, 7.23×10⁻¹¹ cm²/s and 1.50×10⁻¹¹ cm²/s, respectively. The obtained values of diffusivity are consistent, in terms of the order of magnitude, with the value of diffusion coefficient of 5.75×10⁻¹¹ cm²/s obtained, using a very complicated empirical-formula, by Chen et al. for the investigation of surface-modifier enrichment. Thus, the suggested criterion may be very useful and practically applied to clarify the process of surface enrichment from general polymer-blends.     

Anodic behaviour of fulvestrant and its voltammetric determination in pharmaceuticals and human serum on highly boron-doped diamond electrode using differential pulse adsorptive stripping voltammetry

The electrochemical oxidation of fulvestrant was made on highly boron-doped diamond electrode using differential pulse adsorptive stripping voltammetry. The highest current intensities were obtained by applying +1.10 V during 150 s for boron-doped diamond electrode. For boron-doped diamond electrode, linear responses were obtained for the concentrations between 1 × 10⁻⁶ and 8 × 10⁻⁵ M in standard samples and between 1 × 10⁻⁶ and 4 × 10⁻⁵ M in serum samples. The repeatability of the method was 0.55 RSD% for differential pulse adsorptive stripping voltammetry. The analytical values of the method are demonstrated by quantitative determination of fulvestrant in pharmaceutical formulations and human serum, without the need for separation or complex sample preparation, since there was no interference from the excipients and endogenous substances. Selectivity, reproducibility, and accuracy of the developed methods were demonstrated by recovery studies.     

The hydrolysis of soap solutions. II. The solubilities of higher fatty acids

Summary The solubilities of capric, lauric, myristic, palmitic, and stearic acids in water at 25° and 50°C. were determined by use of conductivity measurements. Correction was made for carbon dioxide; and total solubilities, together with the concentration of dissociated and of undissociated acid were calculated. Their solubilities range from 359×10⁻⁶ M for capric acid to 2.1×10⁻⁶ M for stearic acid at 25°C. The solulility of laric and myristic is approximately doubled by an increase of temperature from 25° to 50°C., that of capric, palmitic, and stearic acids increases by 25 to 40%.