Selective separation of essential phenolic compounds from olive oil mill wastewater using a bulk liquid membrane

Olive oil mill wastewater (OMWW) is very rich in phenolic compounds especially the key compounds of caffeic acid (CA), hydroxytyrosol (HTY), and tyrosol (TY). Therefore, the development of new and effective analytical and industrial methods for the separation and concentration of these valuable compounds has attracted great attention in the last decades. In this study, a selective transport and separation method for CA, HTY, and TY from OMWW samples, obtained from different olive orchards, using a new bulk liquid membrane (BLM) procedure was developed. Various factors influencing the transport efficiency such as pH of the source and receiving phases, nature and volume of the organic membrane, stirring rate, and transport time were investigated and optimized. Under optimal experimental conditions, the transport efficiencies of CA, HTY, and TY from the OMWW samples of 90.1 %, 28.4 %, and 34.9 % were obtained, respectively. Relative standard deviations (RSDs, n = 7) were found to be 4.1 %, 3.8 %, and 3.0 % and the limits of detection (LODs) obtained were 0.001 mg L^?1, 0.011 mg L^?1, and 0.008 mg L^?1, for CA, HTY, and TY, respectively.     

Experimental and computational study on the aqueous acidity constants of some new aminobenzoic acid compounds

The acidity constants of three new aminobenzoic acid derivatives were determined using potentiometric and spectrophotometric methods in 0.10 M aqueous potassium nitrate solution as supporting electrolyte. The potentiometric data and UV–Vis absorption spectra of solutions were recorded in the course of their pH-metric titration with a standard base solution. The protolytic equilibrium constants, concentration distribution diagrams and number of components involved have been calculated. The relative pK_a values for three acids were also calculated using ab initio quantum mechanical method at the HF/6-31G** level of theory in combination with CPCM continuum solvation method. The influence of substituents on the ionization constants of the studied molecular structures was investigated. The satisfactory agreement between the experimentally derived and theoretically calculated pK_a values provides solid support for the acid–base reactions proposed in this work.     

Spherical agarose-coated magnetic nanoparticles functionalized with a new salen for magnetic solid-phase extraction of uranyl ion

The authors describe a method for magnetic solid phase extraction of uranyl ions from water samples. It is based on the use of spherical agarose-coated magnetic nanoparticles along with magnetic field agitation. The salen type Schiff base N,N’-bis(4-hydroxysalicylidene)-1,2-phenylenediamine was synthesized from resorcinol in two steps and characterized by infrared and nucleic magnetic resonance spectroscopies. The particles were then activated by an epichlorohydrin method and functionalized with the Schiff base which acts as a selective ligand for the extraction of UO₂(II). Following preconcentration and elution with HCl, the ions were quantified by spectrophotometry using Arsenazo III as the indicator. The effects of pH value, ionic strength and amount of the adsorbent on the extraction of UO₂(II) were optimized by a multivariate central composite design method. Six replicate analyses under optimized conditions resulted in a recovery of 96.6 % with a relative standard deviation of 3.4 % for UO₂(II). The detection limit of the method (at a signal-to-noise ratio of 3σ) is 10 μg L￣¹. The method was successfully applied to the determination of UO₂(II) in spiked water samples.

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Graphical Abstract Spherical agarose-coated magnetic nanoparticles (SACMNPs) were prepared in the presence of Span 85 (a nonionic surfactant) and functionalized by a salen type Schiff base for magnetic solid-phase extraction of uranyl ion

     

Ultrasensitive direct determination of BTEX in polluted soils using a simple and novel pressure-controlled solid-phase microextraction setup

A pressure-controlled headspace solid-phase microextraction (PC-HS-SPME) setup was developed, by reconsidering the strengths and weaknesses points of the similar reported systems. The new setup was coupled with gas chromatography–flame ionization detection (GC–FID) for direct analysis of benzene, toluene, ethylbenzene and xylene (BTEX) in contaminated soils, without any sample preparation step. The important experimental factors, affecting the performance of the method, including volumes of extraction and vacuum vials, type of SPME fiber, extraction time and temperature, moisture content of the sample, and sonication time were studied and optimized. Under the optimal conditions, good linearity of the calibration curves (R² > 0.997) was obtained in the concentration range of 0.1–20,000 ng g^?1. The limits of detections were found to be 0.001–0.08 ng g^?1. The relative standard deviations, for six repetitive analyses of 100 ng g^?1 BTEX, were obtained to be 5.7–12.3%. The PC-HS-SPME–GC–FID procedure was successfully applied for the extraction and determination of BTEX in the polluted soil samples.     

Cooling-Assisted Headspace Hollow Fiber-Based Liquid-Phase Microextraction Setup for Direct Determination of PAHs in Solid Samples by Using Volatile Solvents

To reinforce the extraction efficiency of the liquid- and solid-phase microextraction methods, different cooling-assisted setups have been employed, most of which are complicated, expensive, tedious, and do not show good performances due to indirect transfer of cold to the extraction phase. In this research, a simple, low-cost and effective cooling-assisted headspace hollow fiber-based liquid-phase microextraction (CA-HS-HF-LPME) device was fabricated and evaluated, which is able to directly cool down the extraction phase in different modes of LPME. It was coupled to GC-FID and utilized for the direct determination of PAHs in contaminated soil samples using volatile organic solvents. Different effective experimental variables including type and volume of extraction solvent, extraction time and temperature, and temperature of the cooled organic solvent were evaluated and optimized. Under the optimized experimental conditions (e.g., organic extracting solvent: 3 µL of acetone; extraction time: 20 min; extraction temperature: 90 °C; and temperature of cooled organic drop: −25 °C), good linearity of calibration curves (R ² > 0.99) was obtained in a concentration range of 1–10,000 ng g⁻¹. The limits of detection (LODs) were obtained over the range of 0.01–0.1 ng g⁻¹. The relative standard deviations (RSD%, n = 6) of 0.1 µg g⁻¹ PAHs were found to be 4.7–10.1 %. The CA-HS-HF-LPME-GC-FID method was successfully used for the direct determination of PAHs in contaminated soil and plant samples, with no sample manipulation. The results were in agreement with those obtained by a validated ultrasound-assisted solvent extraction (UA-SE) method.

     

Study of the Essential Oil Composition of Cumin Seeds by an Amino Ethyl-Functionalized Nanoporous SPME Fiber

An ultrasound assisted SPME method with a new nanoporous SBA-15 fiber functionalized with 3-[bis(2-hydroxyethyl)amino]propyl-triethoxysilane was successfully applied to the study of the essential oil composition of cumin (Cuminum cyminum L.) seeds. The sample was irradiated by ultrasound radiation and its volatile components were collected by the fiber from the sample headspace and directly injected into a GC-MS injection port for analysis. A simplex method was used for optimization of four different parameters affecting the efficiency of the extraction. Under the optimized conditions (i.e. sample weight, 0.6 g; temperature, 70 °C; sonication time, 12 min and extraction time, 28 min), the number of components identified by the proposed method and their amounts were identical to those of a hydrodistillation technique. The extraction efficiency of the SBA-15 fiber was superior to a PDMS commercial fiber. The major components identified were p-menta-1,3-dien-7-al, cuminaldehyde, γ-terpinene and p-cymene, respectively. The proposed method was applied to a comparative study of the essential oil composition of cumin in three different climate conditions of the Lorestan province in Iran. The results indicated that the essential oils in the temperate and tropical locations were 94.0 and 85.6% of the cold region, respectively.     

Preparation of a Novel Agarose-Salen Adsorbent,and its Use for Efficient Column Preconcentration and Flame AAS Determination of Lead in Water

A cross-linked agarose (Novarose) support was chemically modified with a novel salen-type Schiffs base; 2,2-[1,2-ethandiyl bis(nitrilimethylidyne)] bis(orthocresol) and was used to develop an efficient, simple and low-cost method for matrix separation and preconcentration of lead in water. The binding capacity of the adsorbent, packed in a 6.5mm i.d. glass column, was tested for different metal ions, and a capacity of 4973 (±95) µg per mL of packed adsorbent for triplicate measurements was obtained for lead at pH 6.0.The effects of pH, ionic strength, buffer concentration, sample volume, eluent concentration and volume, and matrix ions on the column recovery of Pb²⁺ were carefully studied. Quantitative recoveries were obtained for the analyte in a pH range of 5.5 to 7.0. Enrichment volumes up to 300mL and ionic strengths up to 0.5molL^–1 had no significant effect on the recovery of Pb²⁺. The method also tolerated relatively high concentrations of matrix ions such as Ca²⁺, Mg²⁺, Fe³⁺, Cu²⁺, Zn²⁺, Mg²⁺ and Cd²⁺ with no considerable effect on the analytes signal. A few mL of 0.4molL^–1 hydrochloric acid was sufficient for quantitative elution of the analyte from a 0.5mL column before its flame AAS determination. Preconcentration factors up to 60 and a detection limit of 2.5µgL^–1 were obtained for the method. The precision, expressed as relative standard deviation, was 2.9% (at 100µgL^–1) calculated from six replicate measurements. The method was successfully applied to the determination of Pb²⁺ in some river and spiked river water samples with good precision.     

Flow injection spectrophotometric determination of trace amounts of selenium

A simple, rapid and sensitive flow injection spectrophotometric method for determination of selenium (0.005-1.5 mug ml(-1)) is described. The method is based on the catalytic effect of Se(IV) on the reduction reaction of thionine (TN) with sulphide ion, monitored spectrophotometrically at 598 nm. The detection limit is 5 ng ml(-1) the relative standard deviation for eight replicate measurements is 1.1% for 1 mug ml(-1) of selenium. The sampling rate is 25-30 samples h(-1). The procedure was applied successfully to the determination of selenium in real samples.     

Selective preconcentration of ultra trace copper(II) using octadecyl silica membrane disks modified by a recently synthesized glyoxime derivative

A new simple and reliable method has been developed to selectively separate and concentrate ultra trace amounts of copper ion in aqueous samples for subsequent measurement by atomic absorption spectrometry (AAS). The Cu²⁺ ions are adsorbed selectively and quantitatively during passage of aqueous solutions through octadecyl silica membrane disks modified with bis(2-hydroxyphenylamino) glyoxime. The retained copper ions then stripped from the disk with a minimal amount of 0.2 M nitric acid solution as eluent, and determined by AAS. The proposed method permitted large enrichment factors of about 100 or higher.The limit of detection of the proposed method is 0.004 ng ml⁻¹. The maximum capacity of the membrane disks modified with 25 mg of ligand was found to be 280±32 μg of copper(II). The effects of various cationic interferences on the percent recovery of copper in binary mixtures were studied.The method was successfully applied to the recovery and determination of copper in several water samples.     

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2016–2018)

One of the most cited limitations of capillary and microchip electrophoresis is the poor sensitivity. This review continues to update this series of biannual reviews, first published in Electrophoresis in 2007, on developments in the field of online/in‐line concentration methods in capillaries and microchips, covering the period July 2016–June 2018. It includes developments in the field of stacking, covering all methods from field‐amplified sample stacking and large‐volume sample stacking, through to isotachophoresis, dynamic pH junction, and sweeping. Attention is also given to online or in‐line extraction methods that have been used for electrophoresis.