Fast and Considerable Adsorption of Methylene Blue Dye onto Graphene Oxide

The quite efficient adsorption of methylene blue dye from an aqueous solution by graphene oxide was studied. The favorable electrostatic attraction is the main interaction between methylene blue and graphene oxide. As graphene oxide has the special nanostructural properties and negatively charged surface, the positively charged methylene blue molecules can be easily adsorbed on it. In the aqueous solution of methylene blue at 293 K, the adsorption data could be fitted by the Langmuir equation with a maximum adsorption amount of 1.939 mg/mg and a Langmuir adsorption equilibrium constant of 18.486 mL/mg. The adsorption amount increased with the increase of the solution pH (3–11), was not affected significantly by KCl under the examined condition and the adsorption process was exothermic in nature. The fast and considerable adsorption of graphene oxide could be regarded as a potential adsorbent for cationic dye removal in wastewater treatment process.     

Determination of clomazone residues in soybean and soil by high performance liquid chromatography with DAD detection

A simple analysis method to detect clomazone residues in soybean and soil was developed using solid phase extraction coupled with high performance liquid chromatography with diode-array detection. The pesticide residues present in soybean and soil matrices were extracted with methanol–water and extracts purified with Florisil cartridges. The analytes from soybean and soil matrix were eluted with petroleum ether-acetic ether (10 mL, 95:5, v/v) and petroleum ether-acetic ether (2 mL, 95:5, v/v), respectively. The overall recovery of fortified soybean and soil at the levels of 0.01, 0.1 and 0.5 mg/kg ranged from 89.75% to 106.6%, and the coefficients of variation (CV) ranged from 1.68% to 4.93% (n = 3). The limit of quantification (LOQ) is 0.01 mg/kg. This method has been applied to the analysis of clomazone in real samples of soybean and soil. The dissipation of residue over the time in soil coincided with C = 1.189e^−0.0926t and the half-lives (T_1/2) was 7.48 days. The final residue in soybean was lower than 0.01 mg/kg at harvest time. Direct confirmation of the analyte in real samples was achieved by gas chromatography-mass spectrometry.     

Headspace solvent microextraction-gas chromatographic thermionic specific detector determination of amitraz in honey after hydrolysis to 2,4-dimethylaniline

A novel headspace solvent microextraction (HSME) method for the extraction of trace amounts of 2,4-dimethylaniline (2,4-DMA), produced after hydrolysis of amitraz, is presented. The hydrolysis reaction and HSME were carried out in a single step, and then the preconcentrated 2,4-DMA was analyzed gas chromatographically using a thermionic specific detector (TSD). Different parameters affecting the HSME procedure including the type of solvent, headspace volume, stirring rate, Na₂SO₄ content, solution and microdrop temperature, drop volume and extraction time were studied and optimized. The optimized conditions were 25 min solution equilibrium time, 10 min solvent equilibrium time, 5 mL headspace volume, 600 rpm stirring rate, 15% Na₂SO₄, solution temperature 60 °C, microdrop temperature 4 °C and microdrop volume 3 μL. The limit of detection (LOD) and limit of quantification (LOQ) of the method were 10 and 30 ng_amitraz g⁻¹_honey, respectively, and the dynamic linear range was from 0.03 to 10 μg_amitraz g⁻¹_honey. Finally, the proposed method was applied to the quantification of amitraz in spiked honey samples. Because of performing hydrolysis and extraction processes in a single step, the method provided a rapid, simple and sensitive approach to analysis of amitraz.     

Biochar Modified by Nano-manganese Dioxide as Adsorbent and Oxidant for Oxytetracycline

Biochar has limited capacity to adsorb oxytetracycline (OTC). Here we have used bamboo willow biochar (BC) as a carrier to produce nMnO₂-loaded biochars (MBC) by a co-precipitation method. Their chemical compositions, morphological features, specific surface area, and surface functional groups were observed or determined. Batch experiments were conducted to assess the effects of reaction time, initial OTC concentrations, pH, salt concentrations, and natural organic matter (NOM) on OTC removal. Kinetics and isotherms indicated that OTC was mainly adsorbed via chemical interactions, and mono- and multi-layer adsorption occurred on the surface. MBC removed 19–25 times more OTC than BC, and the removal was highest at near-neutral pH, not influenced by NaCl (2, 10 mM), slighted reduced by NOM (0–20 mg L⁻¹), and enhanced by NaHCO₃ (2, 10 mM). Besides being an adsorbent, MBC acted as an oxidant and degraded 58.5% of OTC at 24 h.

     

High Efficiency Adsorption Removal of Arsenilic Acid and Arsenate(V) by Iron-Modified Corncob Biochar

It is crucial that a highly effective adsorbent can be used to simultaneously remove the composite pollution including both inorganic and organic arsenic from wastewater. In this work, the iron modified corncob biochar (MCCB), prepared via the co-precipitation of ferric chloride hexahydrate (FeCl₃?6H₂O) with sodium hydroxide (NaOH) on corncob biochar, was studied for the high efficiency removal of arsenilic acid (ASA) and arsenate [As(V)] in wastewater. X-ray diffraction, scanning electron microscopy, and fourier transform infrared spectroscopy were carried out to characterize the MCCB. At pH of 4.0–5.0, initial concentration of 10 mg/L ASA and 1 mg/L As(V), adsorbent dose of 0.4 g/L, the maximum adsorption capacities of ASA and As(V) were 49.20 and 4.89 mg/g, respectively. The adsorption performance of MCCB for ASA and As(V) was fitted well to the pseudo-second-order kinetic model. Results from this study indicate the promise of MCCB as an efficient, low-cost and environmentally friendly adsorbent for composite arsenic pollution.

     

Experimental Central Composite Design-based Dispersive Liquid-liquid Microextraction for HPLC-DAD Determination of Diazinon in Human Urine Samples: Method Development and Validation

Diazinon poisoning is an important issue in occupational, clinical, and forensic toxicology. While sensitive and specific enough to analyse diazinon in biological samples, current methods are time-consuming and too expensive for routine analysis. The aim of this study was therefore to design and validate a simple dispersive liquid-liquid microextraction (DLLME) for the preparation of urine samples to be analysed for diazinon with high performance liquid chromatography with diode-array detector (HPLC-DAD) to establish diazinon exposure and poisoning. To do that, we first identified critical parameters (type and volume of extraction and disperser solvents, pH, surfactant, and salt concentrations) in preliminary experiments and then used central composite design to determine the best experimental conditions for DLLME-HPLC-DAD. For DLLME they were 800 µL of methanol (disperser solvent) and 310 µL of toluene (extraction solvent) injected to the urine sample rapidly via a syringe. The sample was injected into a HPLC-DAD (C₁₈ column, 250×4.6 mm, 5 μm), and the mobile phase was a mixture of acetonitrile and buffer (63:37 v/v, pH 3.2; flow rate: 1 mL/ min). Standard calibration curves for diazinon were linear with the concentration range of 0.5–4 µg/mL, yielding a regression equation Y=0.254X+0.006 with a correlation coefficient of 0.993. The limit of detection and limit of quantification for diazinon were 0.15 µg/mL and 0.45 µg/mL, respectively. The proposed method was accurate, precise, sensitive, and linear over a wide range of diazinon concentrations in urine samples. This method can be employed for diazinon analysis in routine clinical and forensic toxicology settings.     

Simultaneous Determination of Acetochlor and Propisochlor Residues in Corn and Soil by Solid Phase Extraction and Gas Chromatography with Electron Capture Detection

A sensitive and simple method for simultaneous analysis of acetochlor and propisochlor in corn and soil has been developed. Two herbicides were extracted from soil and corn matrices with methanol/water and acetone, respectively, followed by solid phase extraction (SPE) to remove co extractives, prior to analysis by gas chromatography with electron capture detection (GC-ECD). Primary secondary amine (PSA) SPE cartridges (500 mg, 3 mL) were used for sample preparation. The analytes from corn and soil matrices were eluted with 5 mL petroleum ether-acetic ether (95/5, v/v) and 3 mL petroleum ether-acetic ether (95/5, v/v), respectively. The recoveries of two pesticides ranged from 73.8% to 115.5% with relative standard deviations (RSD) less than 11.1% and sensitivity of 0.01 mg/kg, in agreement with directives for method validation in residue analysis. The method was successfully applied to determine the fate of acetochlor and propisochlor in real corn and soil samples. For acetochlor and propisochlor, the half-life times (t1/2) in soil was 5.541 and 6.074 days, respectively. No acetochlor and propisochlor residues (<0.01 mg/kg) were detected in corn at harvest time withholding period of 2.5 months after treatments of the pesticides. Direct confirmation of the analytes in samples was achieved by gas chromatography–mass spectrometry (GC–MS).     

Response Surface Modeling of Ultrasound-Assisted Dispersive Liquid–Liquid Microextraction for Determination of Benzene, Toluene and Xylenes in Water Samples: Box–Behnken Design

A simple, fast and effective pre-concentration procedure for the extraction of benzene, toluene and xylenes isomers (BTX) was developed using an ultrasound-assisted dispersive liquid–liquid microextraction coupled with gas chromatography-flame ionization detector in water samples. The effects of different experimental parameters in the extraction step including type and volume of extraction and dispersive solvents, ionic strength, extraction time and sample volume were studied using two techniques, namely one-variable-at-a-time and response surface methodology. The results of “one-variable-at-a-time” showed that the ionic strength and extraction time were not significant on the extraction efficiency. Therefore, a three-factor, three-level Box–Behnken experimental design was employed to optimize the BTX extraction. The optimal conditions were determined to be a volume of extraction solvent (chloroform) of 51 μL, volume of dispersive solvent (methanol) of 514 μL and volume of sample of 12 mL. The enrichment factors of 241.2–305.1, the limit of detections of 205–382 ng L⁻¹ were obtained for the BTX at the optimum conditions. In addition, the relative standard deviations for 50 μg L⁻¹ of the BTX in the water samples were found to be in the range of 1.9 %–5.7 % (n = 5). The developed procedure was then applied for the extraction and determination of BTX in the water samples.     

Application of Silicate-Based Coating on Pyrite and Arsenopyrite to Inhibit Acid Mine Drainage

The prevention of acid generation from sulfidic mine wastes is a problem that challenges the global scientific community for decades. A promising strategy is related to the formation of coating layer around sulfides for inhibiting surface oxidation. In the current research, the conditions favoring the formation of an efficient silicate-based coating around pyrite and arsenopyrite were studied, using batch tests. The coating solutions contained silicate-oxyanions, an oxidant (H₂O₂) and buffered at pH 6. The effect of Si concentration (0.1–50 mM), liquid/solid ratio (5–100 mL/g) and contact time (up to 24 h) was investigated. Pyrite tailings treated with a solution of 1 mM Si/0.1 M H₂O₂ at L/S:100 mL/g for 24 h resulted in the optimum formation of a coating, which reduced the amount of SO₄^?2-released by 72%, compared to the sample treated in the absence of Si. However, silicate treatment had a negative effect on arsenopyrite tailings inducing As mobilization.

     

Rapid preparative extraction and determination of major organic acids in honeysuckle (Lonicera japonica Thunb.) tea

In this study, ionic liquid based microwave-assisted extraction (IL-MAE) followed by high-performance liquid chromatography (HPLC) was developed for determination of major organic acids in honeysuckle tea. The results suggest that varying the anion and cation had significant effects on the preparative extraction efficiency; aqueous solution of [C₆mim]Br was selected as solvent. The optimized extraction parameters were obtained as follows: IL concentration 0.5 M, temperature 50 °C, solvent to material ratio 20:1 mL/g and duration 9 min. Moreover, principal component analysis (PCA) was used to analyze the significances of these factors for IL-MAE and their interactions, and IL concentration was proved to be the most significant parameter. Compared with conventional sample preparation method, the content of organic acids in analytical sample was enhanced about 1.5-fold using IL-MAE in a shorter duration. In addition, a kinetic model of the preparative extraction process was established to fit the experimental data (R² > 0.99). The proposed HPLC method was successfully applied for determination of 5 organic acids in honeysuckle tea. The present research supported necessary data for sample preparation and quality analysis of honeysuckle tea.     

Determination of taxifolin in Polygonum orientale and study on its antioxidant activity

A high-performance liquid chromatographic method was developed to determine taxifolin in Polygonum orientale. The chromatographic separation was performed on a Lichrospher ODS column. The mobile phase consisted of CH₃OH–0.3%CH₃COOH (35:65, v/v) with a flow-rate of 0.8 mL/min. The chromatographic peak area was linear to the concentration of taxifolin in the range of 5.0–100 μg/mL with a detection limit of 0.23 μg/mL. Good recovery results were also obtained with the range of 97.4–101.2%. In addition, radical scavenging capacity of taxifolin was studied by means of 1,1-diphenylpicrylhydrazyl free radical. The IC₅₀ value was 4.11 μmol/L, which indicated that taxifolin had a very potent antioxidant activity.     

Development of a sensitive competitive indirect ELISA for parathion residue in agricultural and environmental samples

A sensitive competitive indirect enzyme-linked immunosorbent assay (ELISA) for the insecticide parathion was developed. The optimal immunogen was 5-(ethoxy(4-nitrophenoxy)phosphorothioylamino)pentanoic acid. In addition, five competitors were applied for development of a heterologous competitive indirect ELISA. Then several physicochemical factors (organic solvent, ionic strength and pH) that influence assay performance were studied and optimized. The IC₅₀ and IC₁₀ of the optimized ELISA were 0.95 and 0.15 ng/mL, respectively, which meant almost 86-fold and 6-fold improvement in the assay sensitivity in comparison with the homologous assay (81.74 ng/mL) and the non-optimized heterologous assay (5.60 ng/mL). Finally, the assay was applied to the analysis of parathion in spiked agricultural and environmental samples without extraction or cleanup. The average recoveries of parathion added to water, soil, cucumber, rice and corn were between 78.57% and 107.67%. The limit of detection (LOD) for water and soil samples was 5 ng/mL, and the LOD for cucumber, rice and corn samples was 10 ng/mL.     

The isolation of soyasaponins by fractional precipitation,solid phase extraction,and low pressure liquid chromatography

Bioactive soyasaponins are present in soybean (Glycine max). In this study, the isolation of soyasaponins in relatively pure form (>80%) using precipitation, solid phase extraction and reverse phase low pressure liquid chromatography (RP-LPLC) is described. Soy flour soyasaponins were separated from non-saponins by methanol extraction and precipitation with ammonium sulphate. Acetylated group A soyasaponins were isolated first by solid phase extraction followed by RP-LPLC (solvent: ethanol-water). Soyasaponins, from a commercial preparation, were saponified and fractionated into deacetylated group A and group B soyasaponins by solid phase extraction (methanol-water). Partial hydrolysis of group B soyasaponins produced a mixture of soyasaponin III and soyasapogenol B monoglucuronide. RP-LPLC of deacetylated group A soyasaponins separated soyasaponin A₁ and A₂ (38% methanol); of group B soyasaponins isolated soyasaponin I (50% ethanol); and of the partial hydrolysate separated soyasaponin III from soyasapogenol B monoglucuronide (50% ethanol). This methodology provides soyasaponin fractions that are suitable for biological evaluation.     

Determination of polycyclic aromatic hydrocarbons in aquatic products by HPLC-fluorescence

This paper analyzed 12 polycyclic aromatic hydrocarbons (PAHs), benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, dibenzo[a,h]anthracene, benzo[g,h,i]perylene, fluoranthene, anthracene, benzo[a]anthracene, chrysene, fluorene, phenanthrene and pyrene, in aquatic products by using a fluorimetric-detection RP-HPLC method. The preliminary treatment procedure was based on microwave-assisted extraction and neutral Al₂O₃ solid phase purification, and a selective isolation of PAHs from aquatic samples was carried out. The isolated fractions of PAHs were determined by HPLC with fluorescence detection. The test results suggest that the detection limits for the PAHs were from 0.0048 ng/mL to 0.075 ng/mL based on a signal-to-noise ratio of 3:1. The recoveries were from 85.26 ± 5.12% to 104.63 ± 0.95%. This proposed method was successfully applied to 35 aquatic samples, in which variable levels of summed PAHs were detected, ranging from 0.0 to 57.76 μg/kg.     

Two-phase hollow fiber liquid phase microextraction for preconcentration of pyrethroid pesticides residues in some fruits and vegetable juices prior to gas chromatography/mass spectrometry

A sensitive and reliable extraction method based on two-phase hollow fiber liquid phase microextraction followed by gas chromatography–mass spectrometry has been developed for determination of three pyrethroid pesticides. The various parameters affecting the extraction efficiency were studied via rotatable-centered cube central composite design (CCD). The optimization results showed that speed of agitation, extraction time and ionic strength were significantly important in the extraction process. A response surface equation was derived, and the statistical parameters of the derived model were obtained as R² = 0.9862 and F = 142.46. The response surface plots revealed a separation optimum with 480 rpm speed agitation, extraction time of 41 min and NaCl concentration of 3% (w/v). Method detection limits were obtained in the range of 0.02–0.07 ng/mL, and limits of quantitation were between 0.08 and 0.10 ng/mL. The proposed method was successfully applied for the determination of pyrethroid pesticides in some fruits and vegetable juice samples and satisfactory results were obtained.     

Spectrofluorometric and high-performance liquid chromatographic determination of all-rac-α-tocopheryl acetate in virgin olive oil

A high-performance liquid chromatographic (HPLC) method was developed for the analysis of all-rac-α-tocopheryl acetate in olive oil. After extraction of all-rac-α-tocopheryl acetate from olive oil into hexane/ethyl acetate (4:1, v/v), it was measured with HPLC-diode array detection and regular external standard calibration and confirmed with liquid chromatography–mass spectrometry. Spectrofluorometric and standard addition methods were also used to quantify all-rac-α-tocopheryl acetate in olive oil. A standard addition method is based on fortification of known concentrations of all-rac-α-tocopheryl acetate in a sample. The concentrations (30.4±1.2 μg/mL) of all-rac-α-tocopheryl acetate determined with the HPLC method were comparable with those (32.6±1.1 μg/mL) with the spectrofluorometric method. Standards were checked for linearity giving correlation coefficients of higher than 0.999 in a concentration range from 0.5 to 20 μg/mL.     

Development of a new method for determination of aluminum (Al) in Jordanian foods and drinks: Solid phase extraction and adsorption of Al3+-d-mannitol on carbon nanotubes

In this work, a new method was developed for determination of aluminum (Al) in traditional Jordanian foods (Mansaf, Kofta, Tabboola, Hummous, bread), tea, Arabian coffee and water samples. The method involved solid phase extraction (SPE) of Al³⁺ from the digested samples after complexation with d-mannitol using carbon nanotubes (CNT) as the extractive sorbent. Formation of the Al³⁺-d-mannitol complex was confirmed by infrared spectroscopy. Optimization of the SPE method involved sample pH, d-mannitol-to-Al mole ratio, sample loading and elution flow rates, adsorbent mass, eluent concentration and volume. Based on spiked water samples, the characteristics of the method were as follows: the limit of quantification: 23 μg l⁻¹; sensitivity: 0.0036 (mg l⁻¹)⁻¹; %RSD range: 0.4–1.9%; recovery range: 76.0–93.0%. The equilibrium, thermodynamic and kinetic adsorption studies of Al³⁺-d-mannitol on CNT revealed that adsorption was spontaneous, exothermic, preferred, of physical nature; followed second-order rate kinetics; pore diffusion was not the only rate-controlling step; both Langmuir and Freundlich isotherms represented the data satisfactorily.     

Sediment Matrix Effects in Analysis of Pyrethroid Insecticides Using Gas Chromatography–Mass Spectrometry

In the present study, we developed a gas chromatography–quadrupole mass spectrometry method for analyzing nine pyrethroid insecticides in sediment after accelerated solvent extraction and solid phase extraction cleanup. The operation was optimized, and negative chemical ionization was selected to improve analytical selectivity. The sediment matrix effects on qualification were evaluated, and matrix-matched standard solutions, along with the internal standard calibration, were used to reduce the matrix-induced chromatographic response enhancement. The method detection limits were 0.68 to 1.43 μg/kg dry weight (dw), and recoveries were 70.3 to 143.3%, 61.1 to 169.7%, and 65.7 to 118.8%, with relative SDs of 4.2% to 32.1%, 4.9 to 23.6%, and 1.5 to 23.3% at the spiked levels of 1.0, 5.0 and 20 μg/kg dw, respectively. The method was also validated by measuring pyrethroids in field-contaminated sediment samples collected in central California and southern Illinois.     

Immediate postpartum initiation of etonogestrel-releasing implant: A randomized controlled trial on breastfeeding impact

BackgroundBreast milk volume has never been evaluated when the etonogestrel (ENG) implant was inserted immediately postpartum. Thus, this study evaluated if the immediate postpartum insertion of the ENG implant alters breast milk volume.Study designTwenty-four postpartum women and their newborns (NBs) were randomized into two groups: Implant group (ENG implant inserted within 48 h after delivery) and Control group (absence of contraceptive method). The primary outcome was the amount of breast milk intake by the NBs in the first 6 weeks after delivery. Five and ten grams of deuterium (D₂O) were orally administered to the postpartum women on the day of randomization (day 0) and on the 29th study day, respectively. Saliva samples were collected from the mother–NB pairs prior to each D₂O dose administration and after D₂O ingestion (periodic collection). The amount of breast milk ingested by the NBs was estimated by the amount of deuterium (D₂O) ingested by the NBs through breastfeeding, using mass spectrometry in the saliva samples.ResultsTwenty-four postpartum women and their NB were randomized (12 per group). The median of breast milk intake by NBs following the two D₂O doses were similar between groups {first D₂O dose [Implant: 340 mL/day (240–420 mL/day) vs. Control: 330 mL/day (300–530 mL/day), p=.54]; second D₂O dose [Implant: 845 mL/day (770–980 mL/day) vs. Control: 785 mL/day (680–980 mL/day), p=.63]}. The exclusive breastfeeding rate and NB weight were similar between groups in the first 6 weeks postpartum.ConclusionENG implant insertion immediately postpartum does not alter the volume of breast milk intake by NBs.ImplicationsConsidering the benefits of immediate postpartum initiation of ENG implant on reducing unintended pregnancy and pregnancy recurrence, especially in vulnerable populations, our study adds safety data on breastfeeding effect of this practice.     

Adsorption of Methylene Blue Dye from Aqueous Solutions Using Eichhornia crassipes

Adsorption of methylene blue (MB) from aqueous solution using dried roots, stems, and leaves of Eichhornia crassipes biomass obtained from Lake Victoria was studied. Batch experimental results revealed that the adsorption process was highly dependent on adsorbent dosage, initial MB concentration, E. crassipes particle size and aqueous solution temperature. The isotherm data fitted Freundlich mathematical models with maximum dye adsorption of 35.37 mg g^?1. Roots adsorbed over 99 % of the MB in <5 min. Sorption kinetics followed a pseudo-second-order model. Results provide evidence that E. crassipes is an effective and inexpensive biomaterial for dye removal from aqueous dye solutions and industrial effluents.