ABSTRACT
Cloud point extraction(CPE) utilizing a cationic surfactant, tricaprylmethylammonium chloride(Aliquat 336), was carried out to separate and concentrate bisphenol A(BPA) from aqueous media. Cloud point phase separation of Aliquat 336 at room temperature(about 25 ℃) was induced by the addition of Na_2SO_4. The parameters affecting extraction efficiency, such as concentrations of Aliquat-336 and Na_2SO_4, pH, and equilibration time were evaluated. The results showed that the extraction efficiency was practically constant in the studied range of Aliquat 336, co-solvent(methanol), pH and dissolved organic matters. At the operational CPE conditions, distribution constant, K_D, of the distribution of BPA between the surfactant-rich and aqueous phases of the CPE system was estimated to be 10~4. Coupled to liquid chromatography with UV detection, the CPE method offered a detection limit of 0.34 μg/L in distilled water and recovery of BPA ranged from 90% to 108.6% with a sample volume of 50 mL in three matrices studied. The high extraction efficiency might be due to combination of ion-pair, hydrophobic effects and cation-π interaction, based on the micelles' size distribution and zeta potential analysis.
ABSTRACT
Objective To develop a new method for the determination of trace silver in water by flame atomic absorption(FAAS) after cloud point extraction.Methods Diethyldithiophosphate(DDTP) and triton X-114 were respectively used as the chelating agent and surfactant.The effects of experimental conditions such as acidity,concentration of chelating agent,surfactant and methanol,equilibration temperature and time,interference ion on cloud point extraction were investigated.Results Under the optimum condition,0.5 ml of 0.1 mol/L DDTP solution,0.5 ml of 50 g/L Triton X-114 and 5 ml of 1 mol/L hydrochloric acid were added and the volume was made up to 50 ml.The mixture was heated in a thermostatic bath at 40 ℃ for 15 min,the linear range of determination for silver was 0-100 ng/ml,the equation of linear regression was A = 0.005 8cAg+ 0.001 6,r = 0.999.The detection limit was 0.83 ng/ml,the recovery rate was in the range of 97%-105%,and the relative standard deviation was 3.1%(n=11) for 20 ng/ml Ag.There was no significant interference for silver solution containing 5 000 times of K+,Na+,Ca2,Mg2,NO3,SO4 + +-2-and Cl-,1 000 times of Al3+ and Zn2+,500 times of Fe2+ and Mn2+,100 times of Pb2+ and Cu2+.Conclusion The method is rapid,accurate,simple and applicable to the determination of trace silver in water samples.
ABSTRACT
Objective To develop a new method for the determination of trace manganese in water by flame atomic absorption after cloud point extraction. Methods The effect of experimental conditions such as pH value and concentration of reagents and equilibration temperature on cloud point extraction and determination sensitivity was discussed. The chemical variables affecting the separation phase and extraction recovery were optimized. Results Under the optimum conditions, pre-concentration of only 50 ml of sample in the presence of 0.05% Triton X-114 presented a detection limit of 0.28 ?g/L(3?) for manganese. The enhancement factor was 65 for manganese. The relative standard deviation was 2.17%. The calibration graph using the pre-concentration system for manganese was linear with a correlation coefficient of 0.999 at levels near the detection limits up to at least 120 ?g/L. The recovery rates were 98.0%-101.5%. Conclusion The method is rapid, accurate, simple and is suitable for determination of trace manganese in water samples.