On the theory of polarographic maxima

The theory of polarographic maxima is presented taking into account the interaction of momentum transport, the electrostatic potential field, the adsorption—desorption and the faradaic processes. Several earlier results are generalised. The systems approach employed here is also extended to quasi-linear situations.     

On the rate maxima observed in the acid-hydrolysis of some alkylhydroxamic acids

Rate maxima seen in the acid-hydrolysis of 2,2-dimethyl- and phenylacetohydroxamic acids are discussed in terms of acid-base equilibria, transition state formation and the different acidity functions that control these steps.     

Synthesis of the sulfonated condensed polynuclear aromatic (S-COPNA) resins as strong protonic acids

The mixture (PXG/PR=1.00) of pyrene (PR) and p-xylylene glycol (1,4-benzenedimethanol) (PXG) in the presence of 5 wt % of p-toluenesulfonic acid (TsOH) was heated at 140 °C for 45 min under nitrogen to give the highly viscous condensed polynuclear aromatic (COPNA) resin. It was converted into an infusible and insoluble solid by further heating at 300 °C for 1 h. The obtained material was treated with fuming sulfuric acid at 80 °C for 15 h under nitrogen to give the sulfonated COPNA resin. The similar acidic resin was prepared by the reaction of phenanthrene or naphthalene with PXG in the presence of TsOH followed by sulfonation. The performance of the sulfonated polymers as the strong protonic acids was evaluated.     

Adsorption properties of alumina modified by stearic and oleic acids

Two sets of alumina samples were prepared, one chemically modified by stearic acid and the other by oleic acid, with modifier concentrations within 0.1–4.0 groups/nm². The adsorption of nitrogen, water, and benzene vapors, as well as Acid Orange dye (from aqueous solution), was studied as a function of modifier concentration. In the highest concentration (2.7 groups/nm²), stearate generates a dense surface monolayer, which is hardly accessible to the penetration of molecules of the test compounds. Alumina with stearate concentrations of about one-half the monolayer coverage is the most active adsorbent of organic ions from aqueous solutions. Alumina with the limiting oleate concentration adsorbs a large benzene volume (three times the specific pore volume of the support), because oleate exists on the surface in a liquid state.     

Solubilities of palmitic and stearic fatty acids in supercritical carbon dioxide

The solubilities of two fatty acids, namely hexadecanoic acid (palmitic acid) and octadecanoic acid (stearic acid) in supercritical carbon dioxide (SCCO₂), were determined at T = (328 and 338) K from 12.8 MPa to 22.6 MPa. Three models, namely a thermodynamic model based on the Peng–Robinson equation of state with Kwak and Mansoori mixing rules, a model based on dilute solution theory proposed by Mendez-Santiago and Teja and a new reformulated Chrastil equation model, were used to correlate the solubilities. In all the models, the correlation constants are temperature independent. All the models successfully correlated the experimental results for the solubilities of hexadecanoic acid within 3%.     

High-performance liquid chromatographic analysis of free palmitic and stearic acids in cerebrospinal fluid

A relatively simple method for extraction of free fatty acids from cerebrospinal fluid with aminopropyl bonded-phase columns, and the estimation of palmitic acid (C16:0) and stearic acid (C18:0) concentrations by high-performance liquid chromatographic analysis is described. The values of C16:0 and C18:0 in patients with non-neurological disorders lie within a narrow range, with a mean (+/- S.D.) of 4.02 +/- 0.33 micrograms/ml for C16:0 and 2.72 +/- 0.39 micrograms/ml for C18:0.     

Effect of UVA radiation on membrane fluidity and radical decay in human fibroblasts as detected by spin labeled stearic acids

The ultraviolet A (UVA) radiation component of sunlight (320-400 nm) has been shown to be a source of oxidative stress to cells via generation of reactive oxygen species. We report here some consequences of the UVA irradiation on cell membranes detected by electron paramagnetic resonance (EPR) spectroscopy. Paramagnetic nitroxide derivatives of stearic acid bearing the monitoring group at different depths in the hydrocarbon chain were incorporated into human fibroblasts membranes to analyze two main characteristics: kinetics of the nitroxide reduction and membrane fluidity. These two characteristics were compared for control and UVA-irradiated (0-250 kJ/m(2)) cells. The term relative redox capacity (RRC) was introduced to characterize and to compare free radical reduction measured by EPR with some well-known viability/clonogenicity tests. Our results showed that UVA-irradiation produces a more rigid membrane structure, especially at higher doses. Furthermore, we found that trends agree in survival measured by neutral red (NR), trypan blue (TB), and clonogenic efficiency compared with RRC values measured by EPR for low and medium exposure doses. Above 100 kJ/m(2), differences between these tests were observed. Antioxidant effect was modeled by alpha-tocopherol-acetate treatment of the cells before UVA irradiation. While NR, TB and clonogenicity tests showed protection at the highest UVA doses (>100 kJ/m(2)), results obtained with EPR measurements, both membrane fluidity and kinetics, or using MTT test did not exhibit this protective effect.     

Optimization of conditions for synthesizing sulfonated hydrazides of benzoic and benzenesulfonic acids

The kinetic relationships of arenesulfonation of benzoic and benzenesulfonic acid hydrazides were studied. Based on the data obtained, the conditions for synthesizing these products were optimized. The synthesis can be performed using aqueous-organic solvents containing 2-propanol, 1,4-dioxane, or tetrahydrofuran as nonaqueous component. The thermal stability of benzenesulfohydrazide and its sulfonation product was compared on the basis of data of gas chromatography–mass spectrometry. The fragmentation pathways of the reactants and target product, sulfonated benzenesulfohydrazide, were suggested.     

Retention prediction and hydrophobicity estimation of weak acidic compounds by reversed-phase liquid chromatography using acetic and perchloric acids as ion suppressors

Simple acids are usually applied to suppress the ionization of weakly ionizable acidic analytes in reversed-phase liquid chromatography. The purpose of this study is to investigate the retention behavior of various weak acidic compounds (monoprotic, diprotic, triprotic, and tetraprotic acids) using acetic or perchloric acid as ion suppressor in a binary hydroorganic mobile phase. The apparent n-octanol–water partition coefficient (K _ow ″) was proposed to calibrate the n-octanol–water partition coefficient (K _ow) of weak acidic compound. LogK _ow ″ was found to have a better linear correlation with logk _w, the logarithm of the retention factor obtained by extrapolating to neat aqueous fraction of the mobile phase, for all weakly ionizable acidic compounds. This straightforward relationship offers a potential medium for direct measurement of K _ow data of weak acidic analytes and can be used to predict retention behavior of these compounds in the ion suppression reversed-phase liquid chromatographic mode.     

Effect of ammonium ions on the polarographic behavior of nitriles and amides of some pyridinecarboxylic acids

The character of the polarographic reduction of picolinonitrile, nicotinonitrile, isonicotinonitrile, isocinchomeronic acid dinitrile, picolinamide, and nicotinamide on a dropping mercury electrode with a buffer-solution base electrolyte in the presence of ammonium ions depends on the concentration of the ammonium ions, which interact with the ring nitrogen.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 353–355, March, 1973.