The research presented in this paper investigates the adsorption of cation surfactantsscetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC)sonto magnetic nanoparticles and the application of this mixed hemimicelles solidphase extraction (SPE) method for the preconcentration of several typical phenolic compoundssbisphenol A (BPA), 4-tertoctylphenol (4-OP), and 4-n-nonylphenol (4-NP)sfrom environmental water samples. In this novel SPE method, the charged surfactants CTAB and CPC form mixed hemimicelles on Fe 3 O 4 nanoparticles (Fe 3 O 4 NPs), which causes retention of analytes by strong hydrophobic and electrostatic interactions. The SPE method combines the advantages of mixed hemimicelles and magnetic nanoparticles. In order to provide guidelines for the mixed hemimicelles SPE method development, surfactant adsorption isotherms and -potential isotherms were also investigated. The main factors affecting the adsolubilization of analytes, such as the amount of Fe 3 O 4 NPs and surfactants, the type of surfactants, the solution pH, the sample loading volume, and the desorption conditions, were investigated and optimized. A concentration factor of 800 was achieved by the extraction of 800 mL of several environmental water samples using this SPE method. Under the selected conditions, detection limits obtained for BPA, 4-OP, and 4-NP were 12, 29, 34 ng/L, respectively. The accuracy of the method was evaluated by recovery measurements on spiked samples, and good recoveries (68-104%) with low relative standard deviations from 2 to 7% were achieved. The advantages of this new SPE method include high extraction yields, high breakthrough volumes, short analysis times, and easy preparation of sorbents. To the best of our knowledge, this is the first time that a mixed hemimicelles SPE method based on magnetic separation and nanoparticles has been used for the pretreatment of environmental water samples.

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Being suspected to have carcinogenic and estrogenic properties, the determination of phthalate esters in various environmental samples is very important for environmental risk assessment. In the present paper, a new solid-phase extraction system for HPLC determination of di-ethyl-phthalate, di-n-propyl-phthalate, di-iso-butyl-phthalate, and di-cyclohexyl-phthalate was developed. The four analytes were quantitatively adsorbed on multi-walled carbon nanotubes packed cartridge, then the analytes were quantitatively desorbed with acetonitrile, finally the analytes in acetonitrile eluate were determined by HPLC. Parameters influencing the extraction efficiency such as volume of sample solutions and eluent volume, were examined. Under the optimized conditions, detection limits of 0.18-0.86 ng ml −1 were achieved for four phthalate esters. The proposed method had been used to determine the four phthalate esters in tap water, river water, and sea water samples. No phthalate esters were found in the river water and sea water samples. For the case of tap water sample, di-ethyl-phthalate, di-n-propyl-phthalate, and di-cyclohexyl-phthalate were not found, only 2.0 ng ml −1 of di-iso-butyl-phthalate was found. The accuracy of the proposed method was tested by recovery measurements on spiked samples, the recoveries of 80.3-104.5% were obtained in most cases.

Ionic liquid mixed hemimicelles-based solid-phase extraction for the preconcentration of five phthalates in environmental water sample was investigated in this paper. A comparative study on the use of room temperature ionic liquids (RTILs) 1-hexyl-3-methylimidazolium bromide ([C 6 mim]Br) and 1-dodecyl-3-methylimidazolium bromide ([C 12 mim]Br)-coated silica as sorbents was presented. Owing to having bigger adsorption amounts for analytes [C 12 mim], Br-coated silica was selected as SPE material and the five analytes di-ethyl-phthalate (DEP), di-n-propyl-phthalate (DnPP), di-n-butyl-phthalate (DnBP), di-cyclohexyl-phthalate (DcHP) and di-(2-ethylhexyl)-phthalate (DEHP) can be quantitatively extracted under optimal conditions. The analytes retained on the cartridge were desorbed completely with 3 mL methanol (pH 2). Predominant factors influencing the extraction efficiency, such as RTILs concentration, pH value, ionic strength and breakthrough volume were discussed. The proposed method had been applied to determining the five phthalates in four environmental water samples and concentration factor of 600 was achieved easily. Detection limits obtained ranged between 0.12 and 0.17 g/L. The accuracy of this method was evaluated by recovery measurement on spiked samples, and good recovery results (85-107%) with relative standard deviation (R.S.D.) of below 6% were achieved.

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