Surface-active Organic Compounds Research Articles

The hygroscopic characteristics of aerosol with surface-active organic compounds

The hygroscopic characteristics of aerosol with surface-active organic compounds

Determination of antibilharzial antimony compounds by direct current, differential pulse, square-wave and alternating current anodic stripping voltammetry

A simple, rapid and sensitive method has been developed for the determination of Sb(III) in five antimonial antibilharzial drugs using anodic stripping voltammetry. The method is based on the reduction of Sb(III) on the HMDE, followed by a selected mode of oxidative sweep, i.e. direct current, differential pulse, square-wave or first harmonic alternating current sweep, using 2 mol/L HCl as a supporting electrolyte. Voltammograms for various sample concentrations in the range 3–47 ppb Sb(III) were recorded and the respective calibration graphs constructed. To overcome the expected effect of adsorption of surface active organic compounds on the mercury drop, the standard addition technique of Sb2O3 solution was applied to calculate the recoveries of all the tested antimonials. The method gave reproducible results within 2% and the limit of detection for all measurement modes was 3 ppb. SW and AC modes seem to achieve lower detection limits than the other two modes. The four modes proved to be of equal accuracy and precision.

Cathodic stripping voltammetry of glutathione in natural waters

The electrochemistry of metal–glutathione complexes at a hanging mercury drop electrode was investigated and a procedure was optimized to determine glutathione in natural waters using cathodic stripping voltammetry (CSV). Adsorption of complexes of mercury(I) and copper(I) with glutathione can be utilized to preconcentrate the glutathione on the electrode prior to a voltammetric scan. The greatest sensitivity was obtained when the voltammetric scan was preceded by adsorptive deposition of a 1:1 complex of copper(I) with glutathione in the presence of added copper(II). The reduction current of the copper(II) in the adsorbed glutathione complex was utilized to quantify the concentration of glutathione in solution. The sensitivity of the CSV determination of glutathione in sea-water was high at pH 5 and 8.5 with optimum copper concentrations of 1 and 0.2 µmol l–1, respectively. Adsorption was carried out at –0.225 V at pH 5 and –0.250 V at pH 8.5. The limit of detection was 1.2 nmol l–1 of glutathione at pH 8.5 using a deposition time of 60 s. Interference by surface-active organic compounds in samples from the Mersey estuary was minimized by passing the samples through a Sep-Pak C18 cartridge; interference by copper complexing compounds was minimized by omitting the addition of copper to the sample. A preliminary study of the Mersey estuary using the proposed procedure indicated the presence of glutathione at levels between 20 and 300 nmol l–1; the glutathione behaved conservatively at salinities between 23 and 33 [of the practical salinity scale (psu)], decreasing with increasing salinity.

Surface pressure and wave-damping effects of surface-active organic compounds on seawater

The surface pressure vs concentration and area per molecule curves for monolayers of stearic acid, palmitic acid, oleic acid, palmitoleic acid, triolein, and cholesterol were determined on a clean artificial seawater surface using a modified Langmuir trough. The effectiveness of each compound at wave damping was then estimated mathematically using equations derived by Dorrestein [(1951) General linearized theory of the effect of surface films on water ripples. Proc. Amster. Aca. Sci. 54, 260–350]. We conclude from these analyses that compounds forming highly expanded monolayers on seawater are more effective at damping capillary and short gravity waves (<6 cm wavelength) and generally require lower surface concentrations for this effect than materials forming highly condensed monolayers. Maximal variations in wave amplitude attenuation by different materials are predicted for wavelengths between 2 and 6 cm. All six materials are predicted to cause some wave damping at wavelengths less than 20 cm. However, between 6 and 20 cm waves, a rapid transition occurs which makes the condensed monolayers more effective at damping the longer wavelengths.

Determination of titanium in sea water using adsorptive cathodic stripping voltammetry

A procedure is presented for determining titanium dissolved in sea water and fresh water using cathodic stripping voltammetry preceded by adsorptive collection of its mandelic acid complexes. The optimized conditions include a pH of 3.3, a mandelic acid concentration of 4 mM and an adsorption potential of −0.15 V. The peak potential is −0.9 V. Differential pulse modulation is used, with a pulse rate of 10 s −1 and a scan rate of 20 mV s −1. The limit of detection is 0.03 nM Ti when a 10-min adsorption time is used. The sensitivity is higher for fresh water than sea water owing to interfering Ti complexation by fluoride in sea water. Interference caused by surface-active organic compounds, which lower the sensitivity owing to adsorption on the mercury electrode, is removed by UV photolysis of the sample prior to the analysis. The method was tested by determining Ti in samples from the North Sea and the Indian Ocean.

Determination of tin in sea water by adsorptive cathodic stripping voltammetry

Total dissolved tin in estuarine waters is determined by cathodic stripping voltammetry with adsorptive collection of complexes of tin (II) with tropolone. The optimized conditions include a deposition potential at −0.8 V and a re-oxidation potential of −0.4 V from which the potential change is initiated in a negative direction. A complicated preconcentration step, involving adsorption of the complex, amalgamation, re-oxidation, re-adsorption and measurement of the reduction current of the adsorbed complexes, is required to eliminate interference from molybdenum which is present in sea water at a level 3–4 decades higher than that of tin. The optimum reagent concentration is 40 μM tropolone and the optimum pH is 2.1. Samples are UV-photolysed prior to analysis in order to remove interfering surface-active organic compounds, simultaneously converting organotin compounds to inorganic tin. The limit of detection is 5 pM tin using a 10-min stirred deposition prior to the scan. Relative standard deviations were 3% ( n=6) for the determination of 30 pM Sn and 0.8% for 1 nM tributyltin ( n=5) in sea water.

Surface chemistry of carbonaceous gold ores, II. Effects of organic additives on gold adsorption from cyanide solution

The effects of model surface active organic compounds (dodecylamine (DDA), tricaprylylmethylammonium chloride (Aliquat 336), sodium dodecylsulfate (SDS) and dinonylnaphthalenesulfonic acid (HDNNS)) on gold adsorption by Prestea (Ghana) carbonaceous gold ore were investigated with the aid of adsorption and electrophoretic mobility experiments. The influence of SDS on the uptake of gold by the carbon extract obtained from the ore was also studied. The results indicate that gold uptake in aqueous cyanide solution is enhanced markedly by Aliquat 336 and slightly by DDA or SDS, while HDNNS has a strong opposite effect. Gold loading was also reduced by 37% when pretreatment with hexane was used. The influence of the additives on gold uptake is interpreted in terms of coulombic and hydrophobic interactions between the surfactants and the solid surface, competition between the organic reagents and the aurocyanide complex for interfacial sites, as well as electrostatic and chemical interactions between the adsorbed additives and the aurocyanide complex.

The inhibitory effect of some surface active organic compounds on the electrooxidation of strongly adsorbed species derived from HCOOH on polycrystalline platinum

The effect of dimethylsulphoxide (DMSO), acetonitrile (AN) and acetone (AC) on the adsorption and oxidation of formic acid on platinum electrodes was studied using radiometric and potentiodynamic methods. It was found that formic acid is not adsorbed on the electrode surface previously covered with DMSO, AN or AC. The oxidation of chemisorbed species derived from HCOOH in the presence of DMSO and AN is inhibited because of lowering of the surface concentration of adsorbed water which is an oxidant in the process. The catalytic effect of acetonitrile on the direct oxidation of formic acid on the platinum electrode was higher on smooth than on rough surfaces. The effect was not observed in the presence of DMSO and AC.

The inhibitory effect of some surface active organic compounds on the electrooxidation of strongly adsorbed species derived from HCOOH on polycrystalline platinum

The effect of dimethylsulphoxide (DMSO), acetonitrile (AN) and acetone (AC) on the adsorption and oxidation of formic acid on platinum electrodes was studied using radiometric and potentiodynamic methods. It was found that formic acid is not adsorbed on the electrode surface previously covered with DMSO, AN or AC. The oxidation of chemisorbed species derived from HCOOH in the presence of DMSO and AN is inhibited because of lowering of the surface concentration of adsorbed water which is an oxidant in the process. The catalytic effect of acetonitrile on the direct oxidation of formic acid on the platinum electrode was higher on smooth than on rough surfaces. The effect was not observed in the presence of DMSO and AC.

Effect of the components of the precipitation bath in viscose manufacture on the corrosion of type 06KhN28MDT alloy

The effect of the components of the working precipitation bath on the corrosion process of EI-943 alloy has been established. The most aggressive component is hydrogen sulfide. Surface-active agents and organic compounds, on the contrary, retard the rate of corrosion. In carrying out further studies, an investigation of the effect of the components of the WPB on highly alloyed nickel-base alloys is of definite interest, and also a study of the action of various surface-active agents.

The sea as a source of atmospheric phosphorus

The geochemical fractionation of phosphorus on the drop produced by bubbles bursting in seawater has been studied using a field sampling system called the Bubble Interfacial Microlayer Sampler (BIMS). The droplets from bursting bubbles were collected on filter samples in Narragansett Bay, Rhode Island during the summer of 1975. Phosphorus was found to be fractionated by the bubble-bursting process. The enrichment factor ranged from 4 to 170. Enrichment was found to increase with decreasing phosphorus concentration at 20 cm depth while it decreases with increasing wind velocity. Enrichment was independent of bubbling depth. Together these facts suggest that the sea-surface microlayer is the source of the phosphorus on the ejected drops. Organic phosphorus on the filter samples was found to be enriched relative to surface-water phosphorus by factors of 100–200, while reactive phosphorus was enriched by factors of only 6–8. This suggests that surface-active organic phosphorus compounds are the source phosphorus in the microlayer. The organic phosphorus content of samples of atmospheric particulates collected over the phosphate-rich upwelling waters near the Peru coast was found to correlate significantly with sea-salt sodium. Enrichments calculated using the average phosphorus concentration of the surface water in this area agree well with the results of the BIMS study. Thus it appears that phosphorus fractionation does occur in nature and may be important in supplying this nutrient to some coastal regions of the world.

Effect of inorganic ions and surface active organic compounds on the adherence of oral streptococci

A reduction in the adherence of oral streptococci was observed after topical application of aluminum ions to standardized dentin test pieces whereas pyrophosphate and tripolyphosphate seemed to inhibit the adherence after incorporation in the incubation solution. A pronounced effect was recorded after topical application of surfactants with the positively charged primary amino group as end group. Hydrofluorides of several such aliphatic amines effectively reduced the number of colony-forming units washed off from the test pieces. Also the free base of hexadecylamine showed a similar effect. Inhibition of adherence was also obtained with long chain esters of lysine, with an optimum at 16 carbon atoms in the alcohol group. These compounds have the advantage of being built up from molecules known to the body.

Surface active organic material in the marine atmosphere

Constituents of the marine atmosphere were collected on shallow trays exposed to onshore winds on the windward coast of the Island of Oahu. Upon addition of distilled water to the trays the collected materials formed organic monomolecular films on the water surface, and the curves for film pressure versus area for these films were determined at the field site. The monolayer studies indicated the presence of weakly surface-active organic compounds and hydrocarbons as well as strongly adsorbed, highly polar species. Simultaneous collections of oceanic particulate matter were made with a high-volume air sampler with glass fiber filters. The organic material was extracted from the filters with chloroform and analyzed for specific fatty acids by gas chromatography. The ratios of the quantities of the principal fatty acids found in the air samples were similar to previously reported fatty acid ratios from sea surface samples collected at the air-sea interface. It was concluded that the ocean appears to be a major source of airborne maritime organic matter. The implications of these data to sea fog and haze stabilization are discussed.

Electrocapillary investigations of highly surface-active organic compounds by drop-time measurements

Electrocapillary investigations of highly surface-active organic compounds by drop-time measurements