Surfactants are important class of material used in latexes to impart stability at the
solid/liquid interface. Ionic surfactants and nonionic surfactants are known to provide electrostatic
and steric stabilisation. In this study, two surfactants having chain length of twelve
hydrocarbons were added to the natural rubber latex (NRL) respectively to determine its zeta
potential values, adsorption isotherm and rheological properties. Previous study has shown
that optimum stability was observed when the alkyl chain of surfactant contains twelve carbon
atoms. The zeta potential magnitude of NRL in the presence of sodium dodecyl sulphate
increased as the surfactant concentration increases, while polyoxyethylene dodecyl ether did
not show a significant change in zeta potential. The isotherms were of Langmuir Type 1, the
amount of surfactant adsorbed per unit area at the plateau region was 6.0 × 10−6 mol m−2
for sodium dodecyl sulphate and 2.1 × 10−6 mol m−2
for polyoxyethylene dodecyl ether.
The elastic modulus and relative viscosity of the NRL suspensions increased significantly
in the presence of sodium dodecyl sulphate and also with polyoxyethylene dodecyl ether as
compared to the NRL system due to stronger colloidal forces. The maximum packing volume
fractions of the NRL stabilised with sodium dodecyl sulphate and polyoxyethylene dodecyl
ether were found to be lower than NRL itself.
Para-arsanilic acid (p-ASA) has been widely used in the poultry industry to promote growth and prevent dysentery. It is excreted unchanged in the manure and released into non-target sites causing organoarsenic pollution risk to the environment and living system. Therefore, simple and effective analytical strategies are demanded for determining the samples that contain p-ASA. However, direct determination of both p-ASA and ortho-arsanilic acid (o-ASA) using differential pulse cathodic stripping voltammetry (DPCSV) gives the similar voltammograms that directly hamper the analysis used by the DPCSV technique. In this study, a method to determine and differentiate p-ASA from o-ASA via diazotization and coupling reaction of the amine groups followed by the direct DPCSV determination of diazo compounds is presented. The diazotization reaction carried out at pH 1.5 and 0 ± 1°C for 10 min showed two reduction peaks in DPCSV at-70 mV and -440 mV vs. Ag/AgCl (KCl 3 M). However, when the diazotization reaction was performed at pH 12.5 and 0 ± 1°C for 40 min, a coloured azo compound was produced and the DPCSV showed only one reduction peak that appeared at -600 mV vs. Ag/AgCl (3 M of KCl). The results of this study show that only p-ASA compound gave a reduction peak, whereas o-ASA compound did not give any peak. The detection limit of p-ASA was found to be 4 × 10(-8 )M. As a result, the proposed electro-analytical technique might be a good candidate to determine and differentiate the p-ASA present in the poultry and environmental samples.