Dispersions of commercial casein and whey protein and laboratory-prepared soybean protein were studied in mixed dispersants of water with various aliphatic alcohols, methanol, ethanol, n-propanol and 2-propanol. Supernatant and protein sediments were separated by centrifugation in two steps: 1800 rpm 10 min, followed by centrifugation of the supernatant at 50000 rpm for 60 min (125000xg). A gel-like protein sediment obtained at low alcohol concentration by high-g centrifugation increased in amounts as a function of the alcohol concentration until it progressively transformed, with higher alcohol concentrations, into an opaque flock (precipitate), sedimenting at 1800 rpm. It was concluded that the sediment obtained by ultracentrifugation was a protein of increased density which was produced by partial and progressive dehydration and alcohol binding. The conversion of the sediment into a flock or precipitate is discussed in terms of the hydrophilic-lipophilic balance of the protein and of the polar-nonpolar character of the dispersant.

Methods are presented for investigating the site and form of growth of bacteria in model oil-in-water emulsions and in dairy cream. Following growth of the bacteria, the continuous aqueous phase is gelled using agarose and the oil phase removed using a mixture of chloroform and methanol. Using this method, the authors have found that Listeria monocytogenes, Salmonella typhimurium and Yersinia enterocolitica grow in the form of colonies in concentrated oil-in-water emulsions. Colonies of L. monocytogenes and Y. enterocolitica also form in artificially-inoculated fresh and tinned dairy cream. If information about the precise site of growth is not required, the authors have discovered that intact colonies can be liberated from the model emulsions by dissolving away the oil phase with chloroform: methanol.

A new, efficient, and sensitive cloud point methodology was developed for preconcentration of trace quantities of cobalt and nickel in water and food samples prior to their determination by flame atomic absorption spectrometry (FAAS). The metals react with 2-(benzothiazolylazo)-4-nitrophenol (BTANP) at pH 7.0 and micelle-mediated extraction using the nonionic surfactant Triton X-114 medium. The surfactant-rich phase was diluted with acidified methanol and the cobalt and nickel content was determined by FAAS. The optimum conditions (e.g. pH, reagent and surfactant concentrations, temperature and centrifugation times) were evaluated and optimized. The proposed CPE method showed linear calibration within the ranges 5.0–100 and 5.0–150 ng mL⁻¹ of cobalt and nickel, respectively, and the limits of detection of the method was 1.4 and 1.0 ng mL⁻¹ of cobalt and nickel, respectively. The interference effect of some cations and anions was also studied. The method was applied to the determination of both metals in water and food samples with a recovery from the spiked water samples in the range of 95–102%. The validation of the procedure was carried out by analysis of a certified reference material.

Herein, a novel Cu/CuFe₂O₄@iron-based metal-organic framework 88 A (Cu/CuFe₂O₄@MIL-88A(Fe)) was developed through a scalable hydrothermal strategy for the magnetic dispersive solid-phase extraction of chlorpyrifos and phosalone from water, fruit juice, and vegetable samples prior to corona discharge ion mobility spectrometry analysis. The resulting nanocomposite was characterized in detail, and thus the investigation indicated that the magnetic nanocomposite had good adsorption capacity, high surface area, dispersion, and superparamagnetic properties. In addition, the fabricated sorbent provided different interactions with the target analytes, (hydrogen bonding, hydrophobic contacts, and π-π stacking interactions) resulting in the improvement of extraction efficiency. The applied method based on Cu/CuFe₂O₄@ MIL-88A(Fe) was validated by investigating the affecting parameters, including the amount of magnetic nanocomposite (10.0 mg), sample pH (7.0), salt content (7.5 % w/v), extraction time (5 min), type of elution (150 μL of methanol), and desorption time (2 min). The linearity of the method was found to be in the range of 0.6–300.0 ng mL⁻¹ and 1.5–500.0 ng mL⁻¹, for chlorpyrifos and phosalone with the coefficient of determination of ≥0.9991. The limits of detections (LODs) of 0.2 and 0.5 ng mL⁻ ¹ were obtained for the determination of chlorpyrifos and phosalone, respectively. The relative standard deviation values (RSDs %) were calculated in the range of 4.4 %–6.1 % (intra-day, n = 5) and 6.3 %–8.0 % (inter-day, n = 3) for three days. Ultimately, the developed method was successfully applied for the extraction of the desired analytes from various spiked samples with acceptable recoveries (88.3–100.4 %).

We describe a nanosized Hg(II)-imprinted polymer that was prepared from methacrylic acid as functional monomer, ethyleneglycol dimethacrylate as cross-linker, 2,2′-azobisisobutyronitrile (AIBN) as radical initiator, 2, 2′-di pyrydyl amine as a specific ligand, and Hg (II) as the template ions by precipitation polymerization method in methanol as the progeny solvent. Batch adsorption experiments were carried out as a function of pH, Hg (II) imprinted polymer amount, adsorption and desorption time, volume, and concentration of eluent. The synthesized polymer particles were characterized physically and morphologically by using infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopic techniques. The maximum adsorption capacity of the ion-imprinted and non-imprinted sorbent was 27.96 and 7.89 mg g⁻¹, respectively. Under optimal conditions, the detection limit for mercury was 0.01 μg L⁻¹ and the relative standard deviation was 3.2 % (n = 6) at the 1.00 μg L⁻¹. The procedure was applied to determination of mercury in fish and water samples with satisfactory results.

In this paper, we describe ultrasonic assisted-dispersive solid phase extraction based on ion-imprinted polymer (UA-DSPE-IIP) nanoparticles for the selective extraction of lead ions. Ultrasound is a good and robust method to facilitate the extraction of the target ions in the sorption step and elution of the target ions in the desorption step. The ion-imprinted polymer nanoparticles used in the UA-DSPE-IIP were prepared by precipitation polymerization technique. The ion-imprinted polymer nanoparticles was synthesized using 2-vinylpyridine as a functional monomer, ethylene glycol dimethacrylate as the cross-linker, 2,2′- azobisisobutyronitrile as the initiator, 1,3,4-thiadiazole-2,5-dithiol as the ligand, methanol/dimethyl sulfoxide as the solvent, and lead as the template ion, through precipitation polymerization technique. The IIP nanoparticles were characterized by Fourier transformed infra-red spectroscopy (FTIR), thermogravimetric and differential thermal analysis (TGA/DTA), and scanning electron microscopy (SEM). Box-Behnken design (BBD) was used for optimization of sorption and desorption steps in UA-DSPE-IIP. In the sorption step: pH of solution, IIP amount (mg), sonication time (min) for sorption and in the desorption step: concentration of eluent (mol L⁻¹), volume of eluent (mL), and sonication time (s) for desorption was investigated and optimized by the Box-Behnken design. The optimum conditions for the method were pH of solution: 7.5, sonication time for sorption 7.5 min, IIP amount 24 mg, type and concentration of eluent HCl 1.4 mol L⁻¹, volume of eluent 2.1 mL, and sonication time for desorption 135 s. Under the optimized conditions, the limit of detection and relative standard deviation for the detection of lead ions by UA-DSPE-IIP was found to be 0.7 μg L⁻¹ and <4%, respectively.

Solvent-terminated dispersive liquid-liquid microextraction (ST-DLLME) as a simple, fast, and low-cost technique was developed for simultaneous extraction of Cd²⁺ and Cu²⁺ ions in aqueous solutions. Multiobjective evolutionary algorithm based on decomposition with the aid of artificial neural networks (ANN–MOEA/D) was used for the first time in chemistry, environment, and food sciences to optimize several independent variables affecting the extraction efficiency, including disperser volume and extraction solvent volume, pH, and salt addition. To perform the ST-DLLME operations, xylene, methanol, and dithizone were utilized as an extraction solvent, disperser solvent, and chelating agent, respectively. Non-dominated sorting genetic algorithm versions II and III (NSGA II and NSGA III) as multiobjective metaheuristic algorithms and in addition central composite design (CCD) were studied as comparable optimization methods. A comparison of results from these techniques revealed that ANN-MOEA/D model was the best optimization technique owing to its highest efficiency (97.6% for Cd²⁺ and 98.3% for Cu²⁺). Under optimal conditions obtained by ANN-MOEAD, the detection limit (S/N = 3), the quantitation limit(S/N = 10), and the linear range for Cu²⁺ were 0.05, 0.15, and 0.15–1000 μg L⁻¹, respectively, and for Cd²⁺ were 0.07, 0.21, and 0.21–750 μg L⁻¹, respectively. The real sample recoveries at a spiking level of 0.05, 0.1, and 0.3 mg L⁻¹ of Cu²⁺ and Cd²⁺ ions under the optimal conditions obtained by ANN–MOEA/D ranged from 94.8 to 105%.

Nano γ-alumina, with ultra-high specific surface area (387.2 m2 g-1), has been synthesized and used as a promising adsorbent material in solid-phase extraction. A simple, sensitive, and economic method was developed for speciation of inorganic antimony by slotted tube atom trapping flame atomic absorption spectrometry (STAT-FAAS) after flow injection on-line nano γ-alumina micro-column solid-phase extraction. In this method, Sb(III)-diethyldithiocarbamate (DDTC) complexes produced on-line from DDTC and Sb(III) were adsorbed by the synthesized γ-alumina nanoparticles in a micro-column, then eluted by 1.0 mol L-1 HNO3 in methanol, whereas Sb(V) remained in aqueous solution. The total inorganic Sb was determined by the same procedure after Sb(V) was reduced with thiourea. Under optimal conditions, the enrichment factor was 56.5 and the detection sensitivity was improved 40-fold for antimony by STAT-FAAS compared to conventional FAAS. The limit of detection was 6.0 ng L-1 for Sb(III) and 8.2 ng L-1 for Sb(V), respectively. The intra-day precision (RSDs, n = 11) were 2.8 % for Sb(III) and 3.5 % for Sb(V), respectively, and the inter-day precision (n = 3) were 7.1 % for Sb(III) and 8.4 % for Sb(V), respectively. The recoveries for the spiked samples were 93-107 %. The proposed method was applied to speciation of inorganic antimony in water and food samples successfully. ©Springer Science+Business Media New York 2012.