Octadecylamine, determination

FIG. 9 Silver nanoparticles capped by 4-carboxythiophenol electrostatically adsorbed to positively charged octadecylamine monolayers, (a) Mass uptake versus number of layers at subphase pH 12 and pH 9 the inset shows the contact angle of water versus the number of layers, (b) Absorbance spectra as a function of the number of layers transferred (left), with the inset showing the plasmon absorbance at 460 nm versus the number of layers. Thickness versus number of layers as determined by optical interferometry is shown on the right. (Reprinted with permission from Ref. 103. Copyright 1996 American Chemical Society.)... 

Hidalgo et al. [509] reported a method for the determination of molybdenum (VI) in natural waters based on differential pulse polarography. The catalytic wave caused by molybdenum (VI) in nitrate medium following preconcentration by coflotation on ferric hydroxide was measured. For seawater samples, hexadecyltrimethylammomum bromide with octadecylamine was used as the surfactant. The method was applied to molybdenum in the range 0.7-5.7 Xg/l. 

Cabezon et al. [662] simultaneously separated copper, cadmium, and cobalt from seawater by coflotation with octadecylamine and ferric hydroxide as collectors prior to analysis of these elements by flame atomic absorption spectrometry. The substrates were dissolved in an acidified mixture of ethanol, water, and methyl isobutyl ketone to increase the sensitivity of the determination of these elements by flame atomic absorption spectrophotometry. The results were compared with those of the usual ammonium pyrrolidine dithiocarbamate/methyl isobutyl ketone extraction method. While the mean recoveries were lower, they were nevertheless considered satisfactory. 

Hence a plot of cos B versus / /yi. should yield a straight line with an inclination given by the surface tension of the solid. Good and Girifalco used several liquids to verify this behavior. As an example they determined the surface tension of polytetrafluoroethylene and octadecylamine monolayers to be roughly 28 and 30 mN/m, respectively. 

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