Distribution of pesticides in n-hexane/water and n-hexane/acetonitrile systems and estimation of possibilities of their extraction isolation and preconcentration from various matrices

Distribution of 150 most widely used pesticides of different chemical classes (amides, anilinopirimidines, aromatics, benzenesulfonates, carbamates, dicarboximides, organophosphorus compounds, phenyl esters, phenylureas, pyrazoles, pyrethroids, pyrimidines, strobilurins, sulfamides, triazines, triazoles, etc.) in n-hexane/water and n-hexane/acetonitrile systems was investigated at 25 °C. Distribution constants of pesticides (P) have been calculated as ratio of pesticide concentration in n-hexane to its concentration in water or acetonitrile phase. HPLC and GC methods were used for pesticides determination in phases. It was found that the overwhelming majority of pesticides are hydrophobic, i.e. in n-hexane/water system Lg P ? 0, and the difference in Lg P values can reach 9.1 units. Replacement of water for acetonitrile leads to dramatic fall of Lg P values reaching 9.5 units. The majority of Lg P values in this case are negative and their differences is strongly leveled in comparison with a hexane/water system. Thus, maximal difference in pesticides Lg P values for n-hexane/acetonitrile system is 3.2 units. It is shown that n-hexane can be used for selective and efficient extraction and preconcentration of pesticides from water matrices. On the other hand, acetonitrile is effective for the isolation and preconcentration of pesticides from hydrocarbon and vegetable oil matrices. The distribution constants described in the paper may be effectively used for the estimation of possibilities of extraction isolation, preconcentration and separation of pesticides.     

Determination of erythromycins in fermentation broth using liquid phase extraction with back extraction combined with high performance liquid chromatography

Liquid phase extraction with back extraction (LPE-BE) combined with high performance liquid chromatography-diode array detection (HPLC-DAD) was applied for the extraction and determination of erythromycin A, B and C in fermentation broths. According to this procedure, the fermentation broth with the adjustment pH at a fixed value of 10 was first mixed with organic solvent (V_broth/V_org = 1.0). After shaking, the mixture was separated into two phases by microfuging at 13,000 rpm for 15 min. Then back extraction was performed into the acidic aqueous phase with pH 5.0 (V_org/V_aq = 1.0). After centrifugation at 3000, the two phases were separated and 50 μL of the acidic aqueous phase was injected into the HPLC. The effects of different variables such as the nature of extraction solvent and the pH of samples and buffer were investigated. At the most appropriate conditions, dynamic linear ranges of 0.5–8, 0.1–0.9 and 0.1–0.9 mg mL⁻¹ and limits of detection of 0.03, 0.003 and 0.002 mg mL⁻¹ were obtained for erythromycin A, B and C, respectively. Relative standard deviations (RSDs) of the proposed method were less than 9.5%. The mean recoveries were 99.5%. The proposed method is simple and sensitive with highly clean-up effect and it can be used for monitoring the progress of erythromycin fermentation.     

Extraction and preconcentration of tylosin from milk samples through functionalized TiO2 nanoparticles reinforced with a hollow fiber membrane as a novel solid/liquid‐phase microextraction technique

The aim of this study was to introduce a novel, simple, and highly sensitive preparation method for determination of tylosin in different milk samples. In the so‐called functionalized TiO₂ hollow fiber solid/liquid‐phase microextraction method, the acceptor phase is functionalized TiO₂ nanoparticles that are dispersed in the organic solvent and held in the pores and lumen of a porous polypropylene hollow fiber membrane. An effective functionalization of TiO₂ nanoparticles has been done in the presence of aqueous H₂O₂ and a mild acidic ambient under UV irradiation. This novel extraction method showed excellent extraction efficiency and a high enrichment factor (540.2) in comparison with conventional hollow fiber liquid‐phase microextraction. All the experiments were monitored at λ_max = 284 nm using a simple double beam UV‐visible spectrophotometer. A Taguchi orthogonal array experimental design with an OA₁₆ (4⁵) matrix was employed to optimize the factors affecting the efficiency of hollow fiber solid/liquid‐phase microextraction such as pH, stirring rate, salt addition, extraction time, and the volume of donor phase. This developed method was successfully applied for the separation and determination of tylosin in milk samples with a linear concentration range of 0.51–7000 μg/L (r² = 0.991) and 0.21 μg/L as the limit of detection.     

中空纤维膜液相微萃取-高效液相色谱联用技术测定尿液中痕量己烯雌酚

采用中空纤维液相微萃取与高效液相色谱联用技术测定了尿液样品中的痕量己烯雌酚;考察了样品相酸度、中间相种类、接收相浓度、搅拌速度、萃取时间等对液-液-液三相微萃取效率的影响,进而确定了最佳萃取条件.结果表明,当样品相pH为2.5,中间相为甲苯,接收相为3μL 0.25mol/L氢氧化钠溶液,搅拌速度为800r/min,萃取时间为50min时,萃取效率最佳.在最佳萃取条件下,样品的回收率为76.4%,相对标准偏差为3.8%.     

Recent progress in microporous polymers from thermally rearranged polymers and polymers of intrinsic microporosity for membrane gas separation: Pushing performance limits and revisiting trade-off lines

Polymers are promising materials for gas separation membranes. However, the trade-off relationship between gas permeability and selectivity remains an obstacle for achieving polymer membranes that exhibit high gas permeation with desirable separation efficiency. Improving polymer microporosity is of interest in gas separation membranes to enhance gas transport behavior. Polymer modifications by (a) incorporating intrinsically microporous units and/or (b) increasing chain rigidity can enhance microporosity in conventional polymer membrane materials such as polyimides. These strategies are adopted for new classes of microporous polymers, thermally rearranged (TR) polymers, and polymers with intrinsic microporosity (PIMs), to maximize gas transport properties. Their outstanding gas separation performances have redefined the traditional trade-off lines. This review aims to explore the advances in microporous polymers for gas separation applications. The approaches on TR polymers and PIMs to enhance their microporosity are listed, and their developments are evaluated in the context of revisiting performance limits for industrially relevant gas separation applications.     

Extraction of cadmium from aqueous solutions by emulsion liquid membrane (ELM) using three different carriers dissolved in a 70:30 ratio of sunflower oil to kerosene

This study explores the use of novel green emulation liquid membranes (GELMs) for the simultaneous extraction and stripping of Cd (II) from aqueous solutions. A solute is transported through the membrane due to the presence of the carrier and then concentrated in the internal phase. Soybean, sunflower, corn, and canola oils were used to form green substitutes to petroleum-based organic diluents for use as GELMs. Bis-(2-ethylhexyl) phosphate (D2EHPA), tri-butyl- phosphate (TBP), and trioctylamine (TOA) were the extractants, span 80 was the emulsifier, and HCl or H₂SO₄ was used as the stripping agent. The best conditions for maximum extraction efficiency (98.68%), stripping efficiency (97.14%), and lowest membrane breakage (0.9%) were achieved using a mixture of sunflower oil and kerosene in the ratio of 70:30. The other optimum values of the variables were: 2% (v/v) Span 80, 10 min emulsification time, 12700 rpm emulsification speed, 400 rpm of agitation speed, 5% (v/v) D2EHPA, an external phase pH was 3.5, an internal phase of 0.25 M HCl, and 5:1 of the treat ratio (external phase to emulsion) at 10 min contact time. The synthesized membrane was reused eight times, with approximately the same efficiency and no significant breakage during the first seven cycles.