Ammonium pyrrolidinedithiocarbamate-modified activated carbon micro-column extraction for the determination of As(III) in water by graphite furnace atomic absorption spectrometry

Ionic Liquid-Assisted DLLME and SPME for the Determination of Contaminants in Food Samples

Developing effective and green methods for food analysis and separation has become an urgent issue regarding the ever-increasing concern of food quality and safety. Ionic liquids (ILs) are a new chemical medium and soft functional material developed under the framework of green chemistry and possess many unique properties, such as low melting points, low-to-negligible vapor pressures, excellent solubility, structural designability and high thermal stability. Combining ILs with extraction techniques not only takes advantage of ILs but also overcomes the disadvantages of traditional extraction methods. This subject has attracted intensive research efforts recently. Here, we present a brief review of the current research status and latest developments regarding the application of IL-assisted microextraction, including dispersive liquid–liquid microextraction (DLLME) and solid-phase microextraction (SPME), in food analysis and separation. The practical applications of ILs in determining toxic and harmful substances in food specimens with quite different natures are summarized and discussed. The critical function of ILs and the advantages of IL-based microextraction techniques over conventional extraction techniques are discussed in detail. Additionally, the recovery of ILs using different approaches is also presented to comply with green analytical chemistry requirements.

A new method for highly efficient separation and determination of arsenic species in natural water using silica modified with polyamines

A simple and highly efficient method for the determination of highly toxic arsenic species using non-covalently aminated silica is proposed. The polyamines including poly(hexamethyleneguanidine), poly(4,9-dioxadodecane-1,12-guanidine), hexadimethrine, and poly(diallyldimethylammonium) were tested as silica modifiers. The prepared adsorbents allow effective preconcentration of anionic species of arsenic from aqueous solutions. It was found that As(V) can be quantitatively extracted from solutions at pH 4.5-7.0 by the anion exchange mechanism in less than 5 min, while neutral at this pH As(III) was not adsorbed at these conditions. A reaction with 2,3-dimercapto-1-propanesulphonic acid, which resulted in the formation of the negatively charged complex of As(III) with adsorbents was used for its quantitative extraction from solutions with a pH of 3.5-6.5. A system of two cartridges filled with poly(diallyldimethylammonium) modified silica and the on-line reaction of As(III) with 2,3-dimercapto-1-propanesulphonic acid proceeding between the cartridges was used for separate preconcentration and determination of As(V) and As(III) at pH 5. The proposed method was used for four-year monitoring of natural water pollution by arsenic in the area of residence of the indigenous peoples of Tyva Republic (Russia).

High efficiency of calcined anionic clay to remove the chromate anions CrO42-from polluted water

Calcined anionic clay based on zinc and aluminum was used to remove the pollutant CrO42- from wastewater. This adsorbent material derived from layered double hydroxide (LDH) was chosen for its higher adsorption capacity, its affinity for most pollutants, and its non-toxicity. The kinetic study suggesting a high affinity between the pollutant and calcined LDH (CLDH). The pollutant is retained in multilayer and follows the Freundlich model. Thermodynamic study indicates a physical interaction. The elimination reaches 100% with a retention capacity of 3333 mg/g. After cycles of regeneration and in comparison with other adsorbents, CLDH has proven its efficiency and high performances to remove CrO42- anions.

Application of Sodium Dodecyl Sulfate/Activated Carbon onto the Preconcentration of Cadmium Ions in Solid-Phase Extraction Flow System

In the present study, activated carbon (AC) surface modified with sodium dodecyl sulfate (SDS), written as SDS/AC, was applied as an adsorbent for preconcentration and determination of trace amount of cadmium ions in environmental sample waters. The SDS modification on AC was performed at the same time, while cadmium ions were concentrated in the flow system as solid-phase extraction. After the separation and preconcentration steps, cadmium retained on SDS/AC was eluted with HNO3 and was subsequently determined by flame atomic absorption spectrometry (FAAS). The analytical parameters that influence the quantitative determination of trace cadmium, such as SDS concentration, pH and volume of sample solution, eluent conditions, and interference, were optimized. At the optimum conditions, the general matrix elements had little interference on the proposed procedure. The detection limits was 17 ng·L−1, and the relative standard deviation (RSD) for 12 experiments at 10 µg·L−1 cadmium solutions was 2.8%. The developed method was applied into the analysis of environmental samples spiked cadmium.

Speciation and determination of inorganic arsenic species in water and biological samples by ultrasound assisted-dispersive-micro-solid phase extraction on carboxylated nanoporous graphene coupled with flow injection-hydride generation atomic absorption spectrometry

In this paper, carboxylated nanoporous graphene as a nanoadsorbent was evaluated in two types of ultrasound assisted-dispersive micro-solid phase extraction for speciation of trace As(v) and As(iii) ions in natural water and human biological samples.

Adsorption of Hexavalent Chromium from Aqueous Solution Using Chemically Activated Carbon Prepared from Locally Available Waste of Bamboo (Oxytenanthera abyssinica)

This study reports on the adsorption of Hexavalent Chromium from aqueous solutions using activated carbon prepared from bamboo (Oxytenanthera abyssinica) waste by KOH activation heating in an electrical furnace at 1073 K for 3 hrs. Batch adsorption experiments were also carried out as a function of pH, contact time, initial concentration of the adsorbate, adsorbent dosage, and temperature of the solution. Kinetic studies of the data showed that the adsorption follows the pseudo-second-order kinetic model. Thermodynamic parameters showed that adsorption on the surface of BWAC was feasible, spontaneous in nature, and exothermic between temperatures of 298 and 318 K. The equilibrium data better fitted the Freundlich isotherm model for studying the adsorption behavior of Hexavalent Chromium by BWAC. IR spectrum for loaded and unloaded BWAC was obtained using FT-IR spectrophotometer. Adsorption efficiency and capacity of Hexavalent Chromium were found to be 98.28% at pH 2 and 59.23 mg/g at 300 K.

Synthesis of a novel chelating resin and its use for selective separation and preconcentration of some trace metals in water samples

A new chelating resin, poly[N-(4-bromophenyl)-2-methacrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid-co-divinylbenzene], was synthesized and characterized. The resin was used for selective separation, preconcentration and determination of Cu(II), Ni(II), Co(II), Cd(II), Pb(II), Mn(II) and Fe(III) ions in water samples by flame atomic absorption spectrometry. Effects of pH, concentration and volume of elution solution, sample flow rate, sample volume and interfering ions (Na(+), K(+), Ca(2+), Mg(2+), Fe(3+), Mn(2+), Al(3+), Zn(2+), Pb(2+), Cu(2+), Ni(2+), Cd(2+), Cl(-) and SO(4)(2-)) on the recovery of the analytes were investigated. The sorption capacity of the resin was 25.6, 19.8, 32.1, 41.3, 38.9, 13.9 and 18.3 mg g(-1) for Cu(II), Ni(II), Co(II), Cd(II), Pb(II), Mn(II) and Fe(III), respectively. A high preconcentration factor, 100, and low relative standard deviation, <or=2.5% (n=7) values were obtained. The detection limits (microg L(-1)) were 0.57 for Cu(II), 0.37 for Ni(II), 0.24 for Co(II), 0.09 for Cd(II), 1.6 for Pb(II), 0.19 for Mn(II) and 0.72 for Fe(III). The method was validated by analysing fortified lake water (TMDA-54.4, a trace element fortified calibration standard) and spiked water samples. The method was applied to the determination of the analytes in tap and lake water samples.