Analytical Methods in Environmental Chemistry Journal

Abstract The performance of solvent-impregnated resin (SIR) technology for extracting pollutants from aqueous solutions has been extensively studied by impregnating macroporous copolymers with organophosphorus extractants. In this study, the adsorption of thorium by XAD-16 resin beads impregnated with (1-Hydroxy-1-phosphonohexadecyl) phosphonic acid/Tributyl phosphate (TBP) as an organophosphorus compound was examined and optimized as a function of pH, equilibrium time, temperature, initial Th (IV) concentration, and ionic strength of the aqueous phase. The validated UV-Visible spectroscopic method for thorium quantification demonstrated high linearity, precision, and accuracy, with an LOD of 0.044 mg L⁻¹ (0.19 μmol L^-1), an LOQ of 0.439 mg L⁻¹ (1.89 μmol L^-1), and an RSD of 4.9% (n=7, 100 μmol L^-1 or 23.2 mg L⁻¹), confirming its sensitivity and reproducibility. It was found that over 90% removal was achieved under optimal conditions. Th(IV) extraction by the functionalized resin is governed by pseudo-second-order kinetics, while the adsorption follows the Langmuir model, with a capacity of 44.84mg g^-1. Further, the effect of temperature was realized, and the thermodynamic parameters were calculated. Increasing the temperature increases the reaction rate constant and the diffusivity. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° indicate that the adsorption of Th(IV) onto impregnated XAD-16 resin was spontaneous, endothermic, and involved an increase in randomness. Desorption experiments proved that the SIR could be reused three times without any significant loss of its initial performance. The results of this study revealed that SIR XAD-16 is a promising, cost-effective material for the removal of metal pollutants in practical environmental remediation.

Abstract The interaction of cobalt (Ⅱ) with Jordanian humic acid from Azraq in aqueous solutions was studied across different pH levels and temperatures (25-65°C) using Schubert’s ion exchange method, along with a modified version of this method at a constant ionic strength of 0.05 mol L^-1. The cobalt-humate complex formed in solution was characterized by polarography and UV-Vis spectroscopy. The linear range and LOD were 10-70 µg L^-1 and 0.0625 µg L^-1, respectively. The conditional stability constant (logβ_n) was determined to assess the strength of the binding between Co (Ⅱ) and humic acid. The relationship between logβn and temperature facilitated the calculation of thermodynamic parameters (∆G, ∆H, and ∆S), indicating that all reactions were spontaneous. The results obtained from both methods were comparable. The number of metal ions (j values) stated the formation of a mononuclear cobalt-humate complex, while the number of ligands-Co (Ⅱ) (i value) suggested the presence of 1:1 and 1:2 cobalt-humate complexes. It was observed that the stability constants increased with increasing pH and temperature, confirming that all reactions occur spontaneously in accordance with thermodynamic principles. Additionally, the results demonstrated that (∆G < 0) for both approaches at all pH levels, indicating a spontaneous nature. At the same time, Schubert's method's ∆H and ∆S values reveal endothermic, favorable reactions at pH 4 and 5. The E₄/E₆ ratio (humification index) indicated a high organic matter content in the humic acid; it was determined by analyzing a humic acid solution with a UV–vis spectrophotometer.

Abstract In this research, titanium dioxide nanotubes (TiO₂-NTs) were synthesized by anodization on a titanium (Ti) sheet. Then, nickel (Ni), silver (Ag), and Ag/Ni nanoparticles were deposited on TiO2-NTs via electrochemical deposition. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to characterize the synthesis of TiO₂-NTs and nanoparticles deposited on TiO₂-NTs. SEM images and XRD data indicated that the nanotubes were well synthesized, and the Ni, Ag, and Ag(Ni) particles were well dispersed on their surfaces. In the next step, the electrocatalytic activity of the synthesized catalysts (TiO₂-NTs, Ni/TiO₂-NTs, Ag/TiO₂-NTs and Ag (Ni)/TiO₂-NTs) in relation to NaBH₄ (at four concentrations 0.00, 0.01, 0.03 and 0.05 M of NaBH₄) oxidation were examined by various methods including: chronoamperometry (CA), chornopotantiometry (CP), cyclic voltametry (CV), linear sweep voltametry (LSV). These experiments showed that bimetallic electrocatalysts (Ag(Ni)/TiO2-NTs) are more efficient than monometallic electrocatalysts. The results showed that bimetallic electrodes are more efficient in the electrooxidation of borohydrate.

Abstract Beta-lactam medications are among the commonly used antibiotics. These drugs kill germs by disrupting cell wall formation. This drug treats bacterial infections in numerous body sections. A new, quick, high-performance liquid chromatography approach has been developed and verified by the FDA and EMA for the simultaneous estimation of drugs in their medicinal and pure forms. This study deals with the determination of beta-lactam drugs (Amoxicillin, Ampicillin, Cephalexin, Cefotaxime, Cefoxitin, Cefamandole, Cephalothin, Piperacillin, Penicillin, Oxacillin, Cloxacillin, Nafcillin, Carbenicillin, Mezlocillin, Dicloxacillin) by a Reversed-Phase High-Performance Liquid Chromatography (RP-HPLC) technique based on an UV detector using a column NEUCLEODUR C-18 (4.0 mm × 100 mm, 5µm particle size), The heat of the chromatographic column was 30^oC, and the mobile phase of acetonitrile and KH₂PO₄ using a progression elution with a total separation time of 19.54 minutes, The buffer solution was pH 4.5, and the wavelength was 220 nm. The concentration range was from 0.2 to 20 µg mL^-1, with coefficients of determination (R²) of 0.9994. Recoveries ranged from 90.86% to 100.4%. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.0069 to 0.0639 µg mL^-1 and 0.0211 to 0.1997 µg mL^-1, respectively. In this study, the chromatographic method was used to simultaneously identify drugs in medicinal dosage forms obtained from pharmacies.

Abstract The current study investigated the suitability of Fuller’s Earth-China Clay (FECC) as an adsorbent for removing toxicants, including free fatty acid (FFAs) and peroxides, from waste cooking oil (WCO). Key quality indicators, such as FFAs, peroxide value (PV), and color change, were measured to evaluate the effectiveness of using indigenous FECC material. FECC was activated using sodium hydroxide (NaOH) and acetic acid to enhance its adsorption ability, surface area, and active sites. The structural and functional properties of activated FECC were characterized using techniques like Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), BET surface area analysis, and scanning electron microscopy (SEM). The FFA content in the WCO reduced from 2.98 % to 0.91 % after being treated with activated FECC, having a reduction percentage of 69.64 %, and the peroxide value reduced from 5.5 meq/1000 g to 1.0 meq/1000 g, thus, having a reduction percentage of 81.82% and RSD<2%. There was a marked increase in the oil's quality, with significant absorption capacity, with about 80-85% of the oil purified. These results show that activated FECC can be potentially used as an efficient, environmentally friendly, and economical solution for purifying waste cooking oil. This research provides a promising method to enhance oil quality and a step towards addressing food safety challenges, with the potential for broader application of oil refining in the food sector.

Abstract In this study, diazinon, as a widely used organophosphate pesticide, is critical for environmental and public health monitoring at extreme levels. Agarose magnetic nanoparticles were investigated as a novel adsorbent for the extraction and preconcentration of diazinon from aqueous samples. The effective parameters, including pH, adsorbent amount, ionic strength (IS), sample volume, and time, were systematically optimized. Also, the MSPE (magnetic solid-phase extraction) technique demonstrated significant advantages, including high speed, reduced solvent requirements, and ease of use. The synthesized adsorbent, under optimized conditions, demonstrates high extraction efficiency for diazinon across various real samples, as determined by gas chromatography-mass spectrometry (GC-MS). The limit of detection (LOD) and limit of quantification (LOQ) for diazinon were 0.08 µg L^-1 and 0.24 µg L^-1, respectively, indicating the high sensitivity of the developed method. A linear range and correlation coefficient (R²) of diazinon were obtained in the concentration range of 0.25–16.0 µg L^-1, with a value of 0.992, respectively (%RSD<5). As a result, agarose magnetic nanoparticles have great potential for use in the extraction and preconcentration of pollutants, serving as efficient, recyclable adsorbents. This method can also be used to analyze other organic contaminants in environmental and food samples.

Abstract This study explores the utilization of pumpkin seeds as an abundant biomass resource and carbon precursor for the production of activated carbons. The precursor was activated at a 1:1.5 w/w ratio of pumpkin seeds to KOH at 650 °C to produce the activated carbons. SEM-EDX was used to observe the surface morphologies and compositions of the prepared activated carbons, which exhibit a clear porous surface structure and irregularly shaped particles. The activated carbons were used to remove methylene blue dye from aqueous solutions. The methylene blue concentration was determined using a UV-Vis spectrophotometer with a standard curve ranging from 5 to 25 mg L^-1, and the limit of detection and limit of quantification were 0.1027 and 0.3424 mg L^-1, respectively. A dosage of 0.05 g of activated carbon was sufficient to effectively remove more than 80% of the methylene blue within 5.0 min. The removal of methylene blue increases with contact time, reaching a maximum of 90% at 25 min. The removal of methylene blue is not affected by increasing temperature, but it is influenced by pH, with removal increasing as the medium becomes more alkaline. The adsorption isotherms show that the Freundlich and Temkin isotherms do not apply to the adsorption of the methylene blue onto the activated carbons. Still, the data fit well with the Langmuir isotherm model, which exhibits a high R² value (0.998). 

Abstract Rosemary (Salvia Rosmarinus) peroxidase was purified by chromatographic techniques, yielding an enzyme recovery of 35%. The estimated molecular mass was 47 kDa, determined by Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE), and it has an isoelectric focusing point at 4.33. The optimal pH and temperature were 6.0 and 40ºC, respectively.  Michaelis constant (Km) values were 3.7 mg mL^-1, and the specific activity (SA) values were 28.10 U min^-1 mL^-1 towards guaiacol. The purified peroxidase activity was increased with calcium, ferric, magnesium, and manganese ions but decreased with copper, mercury, and zinc ions at all tested concentrations. The data indicate that this enzyme is a promising source of industrial peroxidase. Flame atomic absorption spectroscopy (FAAS) was used to detect metals in rosemary. To validate peroxidase levels in rosemary using high-performance liquid chromatography (HPLC), we would typically extract the enzyme, purify it (ammonium sulfate), and then separate and quantify it using an HPLC-UV method. The method usually involves using a C18 column and UV detection, with specific wavelengths chosen based on the peroxidase products. The mean LOD and LOQ methods, based on microgram injections, were determined to be 0.051 and 0.153 µg mL^-1, respectively, using the standard deviation of blank peak areas from 10 blank samples (RSD% < 4%). The rosemary extract is injected into the HPLC, and the calibration curve identifies the peroxidase peak.  

Abstract In this research, etodolac and diclofenac were determined using ionic-liquid dispersive liquid–liquid microextraction (IL-DLLME), followed by dilution/back-extraction with ethanol, and then analyzed by reversed-phase high-performance liquid chromatography (RP-HPLC). Each drug was measured at 274nm and 279nm for Diclofenac (DIC) and Etodolac (ETO), respectively. Beer's law was obeyed in the linear ranges of 0.6-20 µg mL^-1 for Diclofenac sodium (r = 0.999) and 0.5-35 µg mL^-1 for etodolac (r = 0.997). The relative standard deviation (RSD%) and detection limit were 1.623% and 0.102 µg mL^-1 for Diclofenac, and 1.607% and 0.098 µg mL^-1 for Etodolac. The chromatographic system consists of an HPLC equipped with a C18 column (250 mm x 4.6 mm). The mobile phase consisted of methanol/acetonitrile: phosphate buffer (pH=5-6) in the ratio of 55:45 v/v at a flow rate of 1.0 mL min^-1. This method has been successfully applied to determine diclofenac and etodolac, which is a cost-effective and straightforward method that allows the simultaneous analysis in tablet dosage forms in pharmaceutical formulations, where the error and recovery ratios for diclofenac (100 mg) were obtained at 4.17%, 95.83%, and etodolac (400 mg), 3.25%, 96.75%, respectively. RP-HPLC methods based on ionic liquid extraction exhibit high sensitivity, linearity, and repeatability for the detection of etodolac and diclofenac in their pure and pharmaceutical forms.

Abstract Herbal medicines and medicinal plants are widely used worldwide. In this Study, thiol-functionalized mesoporous silica nanoparticles (HS-MSNs) were used as adsorbents for the extraction of metal composition in four medicinal plants by the micro solid-phase extraction method (µ-SPE). The metal concentration was determined using flame atomic absorption spectroscopy (F-AAS) and a flame atomic-emission spectrophotometer (F-AES) after a digestion procedure was applied to all medicinal plants. Concentrations of eleven potentially toxic (Ba, Cd, Cr, Cu, Fe, Pb, and Zn) and essential elements (Ca, Na, Li, K) in samples from Maysan Governorate, Iraq, were measured using the proposed method. The relative standard deviation (RSD%), extraction recovery (R%), and preconcentration factor were obtained at less than 5%, more than 95%, and 5, respectively (linear range and LOD for Cd (0.1-0.4 µg mL-1; 0.03 µg mL-1) and Pb (0.4-1.6 µg mL-1; 0.11 µg mL-1). The study aims to determine the presence of various metals in herbal medicines and medicinal plants, including Curcuma longa, Zingiber officinale, Cinnamomum cassia, and Cuminum cyminum. The validation method was verified using spinach leaves (Certified Reference Material CRM 1570a), which showed acceptable agreement with the values of the spinach leaves CRM sample for Cd, Cu, and Zn. The results showed that a quick, efficient, simple, reliable, and straightforward method for estimating multiple elements in herbal medicines and medicinal plants was obtained using the HS-MSNs adsorbent and the µ-SPE procedure.

Abstract In this research, a modified chitosan (NH₂-CS-COOH) with natural citric acid was used for the adsorption and removal of lead (Pb²⁺) and cadmium (Cd²⁺) ions in the liquid phase. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) were achieved using the sorbent. The concentrations of Cd(II) and Pb(II) ions were determined by flame atomic absorption spectrometry (F-AAS). Parameters in batch adsorption were studied, including adsorbent amount, contact time, concentration, and temperature. Optimized conditions were obtained for lead and cadmium using 10 mg and 20 mg of adsorbent (NH₂-Cs-COOH), respectively. Also, the contact times of 105 min for lead and 120 min for cadmium were obtained with an initial concentration of 10 mg L^-1. The data showed a better agreement with the Langmuir model, indicating maximum adsorption capacities (qₘₐₓ) of 3.18 mg g^-1 and (qₘₐₓ) of 2.07 mg g^-1 for lead and cadmium ions, respectively. Thermodynamic studies confirmed that the process is exothermic with negative ΔG° values. The results demonstrate that the adsorbent is highly effective for removing heavy metals from polluted water.