Headspace Extraction of Chlorobenzenes from Water Using Electrospun Nanofibers Fabricated with Calix[4]arene-Doped Polyurethane-Polysulfone.

Chlorobenzenes (CBs) are persistent and potentially have a carcinogenic effect on mammals. Thus, the determination of CBs is essential for human health. Hence, in this study, novel polyurethane−polysulfone/calix[4]arene (PU-PSU/calix[4]arene) nanofibers were synthesized using an electrospinning approach over in-situ coating on a stainless-steel wire. The nanosorbent was comprehensively characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) techniques. The SEM analysis depicted the nanofiber's unique morphology and size distribution in the range of 50−200 nm. To determine the levels of 1,2,4-trichlorobenzene, 1,2,3-trichlorobenzene, and 1,2,3,4-tetrachlorobenzene in water samples, freshly prepared nanosorbent was employed using headspace-solid phase microextraction (HS-SPME) in combination with gas chromatography micro electron capture detector (GC-µECD). Other calixarenes, such as sulfonated calix[4]arene, p-tert-calixarene, and calix[6]arene were also examined, and among the fabricated sorbents, the PU−PSU/calix[4]arene showed the highest efficiency. The key variables of the procedure, including ionic strength, extraction temperature, extraction duration, and desorption conditions were examined. Under optimal conditions, the LOD (0.1−1.0 pg mL−1), the LDR (0.4−1000 pg mL−1), and the R2 > 0.990 were determined. Additionally, the repeatability from fiber to fiber and the intra-day and inter-day reproducibility were determined to be 1.4−6.0, 4.7−10.1, and 0.9−9.7%, respectively. The nanofiber adsorption capacity was found to be 670−720 pg/g for CBs at an initial concentration of 400 pg mL−1. A satisfactory recovery of 80−106% was attained when the suggested method's application for detecting chlorobenzenes (CBs) in tap water, river water, sewage water, and industrial water was assessed.

Synthesis of new Zn-decorated metal-organic frameworks for enhanced removal of carcinogenic textile dye: equilibrium and kinetic modeling studies.

This paper describes the synthesis and characterization of Zn2+ decorated (adipic and terephthalic acid as linkers) piperazine-based metal-organic framework (P-MOFs) and their extraction behavior toward the Chicago sky blue (CSB) dye. The formation of Zn2+-decorated P-MOFs was confirmed by FT-IR spectroscopy, energy-dispersive spectroscopy, X-ray diffraction, BET surface area analysis and TGA. Adsorption behavior of the synthesized P-MOFs was explored through solid-phase adsorption (batch method) prior to UV-Vis spectrophotometric determination. Adsorption parameters, including adsorbent dosage, pH of solution, dye concentration, and time, were optimized. Excellent percentage removal of 94% and 95% for AP-Zn-MOF and TP-Zn-MOF, respectively, was achieved at pH 7.5. Kinetics studies indicated that the synthesized adsorbents AP-Zn-MOF and TP-Zn-MOF followed the pseudo-second-order rate model with R2 value 0.9989. The Freundlich isotherm with high R2 value as compared to Langmuir isotherm indicated that CSB adsorption for the synthesized MOFs follows multilayer adsorption.

Green sporopollenin supported cyanocalixarene based magnetic adsorbent for pesticides removal from water: Kinetic and equilibrium studies.

In this study, magnetic sporopollenin supported cyanocalixarene (MSP-CyCalix) nanocomposite was synthesized and introduced as an adsorbent material for the removal of pesticides from aqueous media. MSP-CyCalix was characterized by different analytical techniques FTIR, SEM, EDX, BET, VSMand TEM. Chlorpyrifos and hexaconazole pesticides were chosen as model analytes solutions for testing the adsorption efficiency of MSP-CyCalix adsorbent. The adsorption results showed that the incorporated cyano functional groups significantly increased the chemical reactivity and adsorption capacity for pesticides. To obtain the highest possible performance, experimental parameters such as pH, salt, dosage and time were optimized. Adsorption kinetics and isotherms models showed that pesticide adsorption process was well fitted with the pseudo-second-order and Langmuir models with a maximum adsorption capacity of 13.88 mg g-1 and 12.34 mg g-1 and a removal efficiency of >90% for both pesticides. Lastly, MSP-CyCalix maintained a removal efficiency of >80% for ten cycles and 60% after the eleventh cycles of usage. The results proved that MSP-CyCalix nanocomposite can be used as an efficient adsorbent for the removal of pesticide residues from water.

Nitrile-calixarene grafted magnetic graphene oxide for removal of arsenic from aqueous media: Isotherm, kinetic and thermodynamic studies.

A novel adsorbent was developed based on nitrile functionalized calix [4]arene grafted onto magnetic graphene oxide (N-Calix-MGO) for remediation of arsenic (III) ions from aqueous media. The nanocomposite was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The effective parameters on adsorption efficiency such as pH, adsorbent dosage, contact time, initial concentration, and temperature were studied. The adsorption process was provided with a high removal efficiency up to (90%) at pH 6 which followed by IUPAC Type II pattern. The mathematical models of kinetics and isotherm validated the experimental process. The adsorption kinetic is followed pseudo-first-order model with R2 > 0.9. The adsorption equilibrium was well fitted on the Freundlich model (R2 ∼ 0.96) as compared Langmuir model (R2 ∼ 0.75). Hence, the Freundlich model suggested a multilayer sorption pattern with a physisorption mechanism for arsenic (III) uptake ono developed nanocomposite with a sorption capacity of 67 mg/g for arsenic. The Gibbs free energy (ΔG° < -20 kJ/mol) showed As(III) uptake ono N-Calix-MGO nanocomposite was the physical adsorption mechanism.

Sonodecoration of magnetic phosphonated-functionalized sporopollenin as a novel green nanocomposite for stir bar sorptive dispersive microextraction of melamine in milk and milk-based food products.

The novel green magnetic phosphonated-functionalized sporopollenin nanocomposite (MPSP-nanocomposite) was synthetized and used for stir bar sorptive dispersive microextraction (SBSDME) of melamine in milk and milk-based food products. TEM, SEM-EDX, FT-IR, VSM techniques were applied for characterization of MPSP-nanocomposite. The influential parameters including pH, extraction time, stirring rate, elution solvent type and volume, sample volume, desorption time, and ionic strength were studied and at optimum conditions, the linear range of 1-500 (µg L-1), the LOD (S/N = 3) of 0.30 (µg L-1), and the LOQ (S/N = 10) of 0.95 (µg L-1) were achieved. The intra-day precision values (RSD (%), n = 7) of 3.5% for the melamine concentration of 25 (µg L-1). The relative recoveries of 95.8% to 99.6% were acquired for the real samples which confirmed that the proposed method could be successfully utilized in complex matrixes with high matrix effects.

Conversion of waste frying oil into biodiesel using recoverable nanocatalyst based on magnetic graphene oxide supported ternary mixed metal oxide nanoparticles.

The magnetic graphene oxide (GO) supported with heterogeneous ternary mixed metal oxide (MMO) was used as nanocatalyst to enhance the conversion of waste frying oil (WFO) triglycerides to biodiesel via esterification process. In this regard, acidic MGO was modified with three basic metal cations of cerium, zirconium, and strontium oxides to produce heterogeneous MGO@MMO nanocatalyst. The nanocatalyst was characterized by FESEM, TEM, EDX and FTIR. The influence of different parameters such as catalyst material ratio, methanol to oil ratio, contact time, and reaction temperature was studied. Based on the results of effecting parameters, the MGO@MMO nanocatalyst converted WFO to biodiesel with a yield 94%, a reaction time of 90 min, methanol to oil ratio (8:1), and a temperature of 60 °C. Esterification mechanism indicated the MGO@MMO nanocatalyst having both binary Brønsted acid-base sites that increased the conversion yields as compared to MGO and MMO at low temperatures.

Equilibrium, kinetic and thermodynamic study of pesticides removal from water using novel glucamine-calix[4]arene functionalized magnetic graphene oxide.

A novel nanocomposite of MGO-NGC, composed of magnetic Fe3O4 nanoparticles (M), graphene oxide (GO), and N-methyl-d-glucamine functionalized calix[4]arene (NGC), was synthesized and applied as an effective adsorbent for the removal of two selected pesticides, namely hexaconazole and chlorpyrifos from water samples. The adsorbent was characterized by FTIR, SEM, EDX, TEM, and XRD. The main parameters affecting the adsorption process such as adsorbent dosage, pH of sample solution, salt effect, pesticide concentration, and adsorption time were investigated. The data from kinetic studies fitted well to the pseudo-second order kinetic model with R2 > 0.99. Among the isotherm models of Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich, the Langmuir isotherm fitted well to the adsorption process and demonstrated the monolayer adsorption pattern of the pesticides. Moreover, high adsorption capacities of 78.74 and 93.46 mg g-1 were obtained for chlorpyrifos and hexaconazole, respectively. Thermodynamic and free energy data indicated the physisorption mechanism for the adsorption process. The new adsorbent can be employed as an efficient, environment friendly, and highly reusable alternative for the removal of chlorinated pesticides from aqueous media.

Fabrication of calixarene-grafted magnetic nanocomposite for the effective removal of lead(II) from aqueous solution.

Magnetic nanocomposites adorned with calixarene were successfully prepared by immobilizing diethanolamine functionalized p-tert-butylcalix[4]arene (DEA-Calix) onto silica-coated magnetic nanoparticles (MNPs). The synthesis, surface morphology, purity, elemental composition and thermal stability of newly prepared nanocomposites were analyzed using FT-IR spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), X-ray diffractometer (XRD), thermal gravimetric analysis (TGA) and vibrating sample magnetometer (VSM). Magnetic solid-phase adsorption (MSPA) was employed to explore the adsorption behavior of DEA-Calix-MNPs towards Pb(II) from water samples prior to its flame atomic absorption spectrometric analysis. The essential analytical factors governing the adsorption efficiency such as solution pH, mass of adsorbent, concentration and contact time have been investigated and optimized. The results depict that DEA-Calix-MNPs has excellent adsorption efficiency 97% (at pH 5.5) with high adsorption capacity of 51.81 mg g-1 for Pb(II) adsorption. Additionally, kinetic and equilibrium studies suggested that Pb(II) adsorption process follows a pseudo-second-order model and Langmuir isotherms, respectively. Real sample analysis also confirmed field applicability of the new DEA-Calix-MNPs adsorbent.

New sporopollenin-based ß-cyclodextrin functionalized magnetic hybrid adsorbent for magnetic solid-phase extraction of nonsteroidal anti-inflammatory drugs from water samples.

A magnetic solid-phase extraction (MSPE) procedure on the newly synthesized magnetic ß-cyclodextrin functionalized with toluene diisocyanate (TDI) as a linker and further modified with bio-polymeric spores of sporopollenin (MSp-TDI-ßCD), was developed for the extraction of nonsteroidal anti-inflammatory drugs (NSAIDs), namely, indoprofen (INP), ketoprofen (KTP), ibuprofen (IBP) and fenoprofen (FNP) from water samples prior to their HPLC-DAD determination. The newly synthesized MSp-TDI-ßCD was comprehensibly characterized using FT-IR, XRD, SEM-EDX, BET and VSM analyses. The separation of selected NSAIDs on MSp-TDI-ßCD from aqueous solution was simply achieved by applying an external magnetic field via a permanent magnet. The MSPE parameters affecting extraction performance, i.e. sorbent dosage, sample volume, extraction and desorption time, type of organic eluent and volume and solution pH were investigated and optimized. The proposed method showed linear range between 0.5 and 500 ng ml-1, low limit of detection at S/N = 3 (0.16-0.37 ng ml-1) and limit of quantification at S/N = 10 (0.53-1.22 ng ml-1). The inter-day (n = 15) and intra-day (n = 5) precision for the proposed methods given by relative standard deviation (RSD%) was in the range of 2.5-4.0 and 2.1-5.5, respectively. The extraction recoveries of NSAIDs from environmental samples (tap, drinking and river water) ranged from 92.5% to 123.6%, with satisfactory precision (RSD% less than 12.4%).

Fabrication of calixarene-grafted bio-polymeric magnetic composites for magnetic solid phase extraction of non-steroidal anti-inflammatory drugs in water samples.

Calixarene framework functionalized bio-polymeric magnetic composites (MSp-TDI-calix) were synthesized and utilized as magnetic solid-phase extraction (MSPE) sorbent for the extraction of non-steroidal anti-inflammatory drugs (NSAIDs), namely indoprofen (INP), ketoprofen (KTP), ibuprofen (IBP) and fenoprofen (FNP), from environmental water samples. MSp-TDI-calix was characterized by FT-IR, XRD, FESEM, EDX, VSM and BET analysis, and the results were compared with Sp-TDI and Sp-TDI-calix. To maximize the extraction performance of MSp-TDI-calix decisive MSPE affective parameters such as sorbent amount, extraction time, sample volume, type of organic eluent, volume of organic eluent, desorption time and pH were comprehensively optimized prior to HPLC-DAD determination. The analytical validity of the proposed MSPE method was evaluated under optimized conditions and the following figures of merit were acquired: linearity with good determination coefficient (R2 ≥ 0.991) over the concentration range of 0.5-500 µg/L, limits of detection (LODs) ranged from 0.06-0.26 µg/L and limits of quantitation (LOQ) between 0.20-0.89 µg/L. Excellent reproducibility and repeatability under harsh environment with inter-day and intra-day relative standard deviations were obtained in the range of 2.5-3.2% and 2.4-3.9% respectively. The proposed method was successfully applied for analysis of NSAIDs in tap water, drinking water and river water with recovery efficiency ranging from 88.1-115.8% with %RSD of 1.6-4.6%.

Magnetic graphene sol-gel hybrid as clean-up adsorbent for acrylamide analysis in food samples prior to GC-MS.

Graphene (G) modified with magnetite (Fe3O4) and sol-gel hybrid tetraethoxysilane-methyltrimethoxysilane (TEOS-MTMOS) was used as a clean-up adsorbent in magnetic solid phase extraction (MSPE) for direct determination of acrylamide in various food samples prior to gas chromatography-mass spectrometry analysis. Good linearity (R2=0.9990) was achieved for all samples using matrix-matched calibration. The limit of detection (LOD=3×SD/m) obtained was 0.061-2.89µgkg-1 for the studied food samples. Native acrylamide was found to be highest in fried potato with bright-fleshed (900.81µgkg-1) and lowest in toasted bread (5.02µgkg-1). High acrylamide relative recovery (RR=82.7-105.2%) of acrylamide was obtained for spiked (5 and 50µgkg-1) food samples. The Fe3O4@G-TEOS-MTMOS is reusable up to 7 times as a clean-up adsorbent with good recovery (>85%). The presence of native acrylamide was confirmed by mass analysis at m/z=71 ([C3H5NO]+) and m/z=55 ([C3H3O]+).

Magnetic sporopollenin-cyanopropyltriethoxysilane-dispersive micro-solid phase extraction coupled with high performance liquid chromatography for the determination of selected non-steroidal anti-inflammatory drugs in water samples.

A facile dispersive-micro-solid phase extraction (D-µ-SPE) method coupled with HPLC for the analysis of selected non-steroidal anti-inflammatory drugs (NSAIDs) in water samples was developed using a newly prepared magnetic sporopollenin-cyanopropyltriethoxysilane (MS-CNPrTEOS) sorbent. Sporopollenin homogenous microparticles of Lycopodium clavatum spores possessed accessible functional groups that facilitated surface modification. Simple modification was performed by functionalization with 3-cyanopropyltriethoxysilane (CNPrTEOS) and magnetite was introduced onto the biopolymer to simplify the extraction process. MS-CNPrTEOS was identified by infrared spectrometrywhile the morphology and the magnetic property were confirmed by scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM), respectively. To maximize the extraction performance of ketoprofen, ibuprofen, diclofenac and mefenamic acid using the proposed MS-CNPrTEOS, important D-µ-SPE parameters were comprehensively optimized. The optimum extraction conditions were sorbent amount, 40 mg; extraction time, 5 min; desorption time; 5 min; sample volume, 15 mL; sample pH 2.0; and salt addition, 2.5% (w/v). The feasibility of the developed method was evaluated using spiked tap water, lake water, river water and waste water samples. Results showed that ketoprofen and ibuprofen were linear in the range of 1.0-1000 µg L-1 whilst diclofenac and mefenamic acid were linear in the range 0.8-500 µg L-1. The results also showed good detection limits for the studied NSAIDs in the range of 0.21-0.51 µg L-1 and good recoveries for spiked water samples in the range of 85.1-106.4%. The MS-CNPrTEOS proved a promising dispersive sorbent and applicable to facile and rapid assay of NSAIDs in water samples.

Synthesis of piperazine functionalized magnetic sporopollenin: a new organic-inorganic hybrid material for the removal of lead(II) and arsenic(III) from aqueous solution.

The present work describes the successful functionalization/magnetization of bio-polymeric spores of Lycopodium clavatum (sporopollenin) with 1-(2-hydroxyethyl) piperazine. Analytical techniques, i.e., Fourier transform infrared (FT-IR), field emission scanning electron microscope (FESEM), energy-dispersive X-ray spectroscopy (EDS), and vibrating sample magnetometer (VSM), were used to confirm the formation of 1-(2-hydroxyethyl) piperazine-functionalized magnetic sporopollenin (MNPs-Sp-HEP). The proposed adsorbent (MNPs-Sp-HEP) was used for the removal of noxious Pb(II) and As(III) metal ions from aqueous media through a batch-wise method. Different experimental parameters were optimized for the effective removal of selected noxious metal ions. Maximum adsorption capacity (q m ) 13.36 and 69.85 mg g-1 for Pb(II) and As(III), respectively, were obtained. Thermodynamic parameters such as free energy (ΔG°), entropy (ΔS°), and enthalpy (ΔH°) were also studied from the adsorption results and were used to elaborate the mechanism of their confiscation. The obtained results indicated that newly adsorbent can be successfully applied for the decontamination of noxious Pb(II) and As(III) from the aqueous environment.

Magnetic graphene coated inorganic-organic hybrid nanocomposite for enhanced preconcentration of selected pesticides in tomato and grape.

The new magnetic graphene based hybrid silica-N-[3-(trimethoxysilyl)propyl]ethylenediamine (MG@SiO2-TMSPED) nanocomposite was synthesized via sol-gel process, and used as an effective adsorbent in magnetic solid phase extraction (MSPE) of three selected pesticides followed by gas chromatography micro-electron capture detection (GC-µECD). The adsorbent was characterized using Fourier transform-infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDXS) techniques. The analytical validity of the developed method was evaluated under optimized conditions and the following figures of merit were obtained: linearity, 1-20µgkg-1 with good determination coefficients (R2=0.995-0.999); limits of detection (LODs), 0.23-0.30µgkg-1 (3×SD/m, n=3); and limits of quantitation (LOQ), 0.76-1.0µgkg-1 (10×SD/m, n=3). The precision (RSD%) of the proposed MSPE method was studied based on intra-day (3.43-8.83%, n=3) and inter-day (6.68-8.37%, n=12) precisions. Finally, the adsorbent was applied to determination of pesticides in tomato and grape samples and good recoveries were obtained in the range from 82 to 113% (RSDs 5.1-8.1%, n=3).

Novel Palm Fatty Acid Functionalized Magnetite Nanoparticles for Magnetic Solid-Phase Extraction of Trace Polycyclic Aromatic Hydrocarbons from Environmental Samples.

A novel adsorbent, palm fatty acid coated magnetic Fe3O4 nanoparticles (MNP-FA) was successfully synthesized with immobilization of the palm fatty acid onto the surface of MNPs. The successful synthesis of MNP-FA was further confirmed by X-Ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and Energy dispersive X-Ray spectroscopy (EDX) analyses and water contact angle (WCA) measurement. This newly synthesized MNP-FA was applied as magnetic solid phase extraction (MSPE) adsorbent for the enrichment of polycyclic aromatic hydrocarbons (PAHs), namely fluoranthene (FLT), pyrene (Pyr), chrysene (Cry) and benzo(a)pyrene (BaP) from environmental samples prior to High Performance Liquid Chromatography- Diode Array Detector (HPLC-DAD) analysis. The MSPE method was optimized by several parameters such as amount of sorbent, desorption solvent, volume of desorption solvent, extraction time, desorption time, pH and sample volume. Under the optimized conditions, MSPE method provided a low detection limit (LOD) for FLT, Pyr, Cry and BaP in the range of 0.01-0.05 ng mL-1. The PAHs recoveries of the spiked leachate samples ranged from 98.5% to 113.8% with the RSDs (n = 5) ranging from 3.5% to 12.2%, while for the spiked sludge samples, the recoveries ranged from 81.1% to 119.3% with the RSDs (n = 5) ranging from 3.1% to 13.6%. The recyclability study revealed that MNP-FA has excellent reusability up to five times. Chromatrographic analysis demonstrated the suitability of MNP-FA as MSPE adsorbent for the efficient extraction of PAHs from environmental samples.

New magnetic graphene-based inorganic-organic sol-gel hybrid nanocomposite for simultaneous analysis of polar and non-polar organophosphorus pesticides from water samples using solid-phase extraction.

A new graphene-based tetraethoxysilane-methyltrimethoxysilane sol-gel hybrid magnetic nanocomposite (Fe3O4@G-TEOS-MTMOS) was synthesised, characterized and successfully applied in magnetic solid-phase extraction (MSPE) for simultaneous analysis of polar and non-polar organophosphorus pesticides from several water samples. The Fe3O4@G-TEOS-MTMOS nanocomposite was characterized using Fourier transform-infrared spectroscopy, energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy and X-ray diffraction. Separation, determination and quantification were achieved using gas chromatography coupled with micro electron capture detector. Adsorption capacity of the sorbent was calculated using Langmuir equation. MSPE was linear in the range 100-1000 pg mL-1 for phosphamidon and dimethoate, and 10-100 pg mL-1 for chlorpyrifos and diazinon, with limit of detection (S/N = 3) of 19.8, 23.7, 1.4 and 2.9 pg mL-1 for phosphamidon, dimethoate, diazinon and chlorpyrifos, respectively. The LODs obtained is well below the maximum residual level (100 pg mL-1) as set by European Union for pesticides in drinking water. Acceptable precision (%RSD) was achieved for intra-day (1.3-8.7%, n = 3) and inter-day (7.6-17.8%, n = 15) analyses. Fe3O4@G-TEOS-MTMOS showed high adsorption capacity (54.4-76.3 mg g-1) for the selected OPPs. No pesticide residues were detected in the water samples analysed. Excellent extraction recoveries (83-105%) were obtained for the spiked OPPs from tap, river, lake and sea water samples. The newly synthesised Fe3O4@G-TEOS-MTMOS showed high potential as adsorbent for OPPs analysis.

New chrysin-functionalized silica-core shell magnetic nanoparticles for the magnetic solid phase extraction of copper ions from water samples.

This study describes the synthesis, characterization and application of a new chrysin-based silica core-shell magnetic nanoparticles (Fe3O4@SiO2-N-chrysin) as an adsorbent for the preconcentration of Cu(II) from aqueous environment. The morphology, thermal stability and magnetic property of Fe3O4@SiO2-N-chrysin were analyzed using FTIR, FESEM, TEM, XRD, thermal analysis and VSM. The extraction efficiency of Fe3O4@SiO2-N-chrysin was analyzed using the batch wise method with flame atomic absorption spectrometry. Parameters such as the pH, the sample volume, the adsorption-desorption time, the concentration of the desorption solvent, the desorption volume, the interference effects and the regeneration of the adsorbent were optimized. It was determined that Cu(II) adsorption is highly pH-dependent, and a high recovery (98%) was achieved at a pH 6. The limit of detection (S/N=3), the limit of quantification (S/N=10), the preconcentration factor and the relative standard deviation for Cu(II) extraction were 0.3 ng mL(-1), 1 ng mL(-1), 100 and 1.9% (concentration=30 ng mL(-1), n=7), respectively. Excellent relative recoveries of 97-104% (%RSD<3.12) were achieved from samples from a spiked river, a lake and tap water. The MSPE method was also validated using certified reference materials SLRS-5 with good recovery (92.53%).

Preconcentration and determination of lead and cadmium levels in blood samples of adolescent workers consuming smokeless tobacco products in Pakistan.

The present study was aimed to evaluate the cadmium (Cd) and lead (Pb) levels in the blood samples of adolescent boys, chewing different smokeless tobacco (SLT) products in Pakistan. For comparative purpose, boys of the same age group (12-15 years), not consumed any SLT products were selected as referents. To determine trace levels of Cd and Pb in blood samples, a preconcentration method, vortex-assisted liquid-liquid microextraction (VLLME) has been developed, prior to analysis by flame atomic absorption spectrometry. The hydrophobic chelates of Cd and Pb with ammonium pyrrolidinedithiocarbamate were extracted into the fine droplets of ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate, while nonionic surfactant, Triton X-114 was used as a dispersing medium. The main factors affecting the recoveries of Cd and Pb, such as concentration of APDC, centrifugation time, volume of IL and TX-114, were investigated in detail. It was also observed that adolescent boys who consumed different SLT products have 2- to 3-fold higher levels of Cd and Pb in their blood samples as compared to referent boys (p < 0.001).

Synthesis and application of p-tert-butylcalix[8]arene immobilized material for the removal of azo dyes.

The present study describes synthesis of a new resin through immobilization of p-tert-butylcalix[8]arene onto silica and its application for the removal of azo dyes from aqueous media as well as from textile effluents. The newly synthesized material 4 is characterized by FT-IR spectroscopy, scanning electron microscope (SEM) and thermogravimetric analysis (TGA). Reactive Black-5 (RB-5) and Reactive Red-45 (RR-45) azo dyes were used as sorbate. Batch wise sorption experiments were conducted to optimize various experimental parameters such as the effect of sorbent dosage, electrolyte, pH, dye concentration, and contact time. The optimized pH for the effective removal of RB-5 and RR-45 dyes was 9 and 3, respectively. The increase in material 4 dosage increased the percent sorption. Both Langmuir and Freundlich isotherm models were applied to experimental data and Langmuir isotherm model found to be best fit. The results revealed that material 4 was potentially more effective sorbent for the sorption of selected azo dyes as compared to pure silica and p-tert-butylcalix[8]arene. The field studies also supported the effectiveness of material 4, which could be useful for the removal of both the dyes and also for the normalization of pH, TDS, conductivity and salinity near to the drinking water.