Synthesis of mesoporous silica for adsorption of chlordiazepoxide and its determination by HPLC: Experimental design.

In this work, mesoporous silica (SBA-15-NH2 ) was used as an efficient adsorbent for extraction of chlordiazepoxide from different samples based on dispersive nanomaterial-ultrasound assisted microextraction followed by high-performance liquid chromatography. The prepared sorbent was characterized by fourier transform infrared spectroscopy, scanning electron microscopy, low-angle X-ray diffraction, thermal analysis, and N2 adsorption-desorption surface area measurement. Several variables affecting the extraction efficiency of the chlordiazepoxide, including the amounts of adsorbent, time of adsorption, pH and volume of desorption solvent were optimized by central composite design combined with desirability function. The values of variables were set as 10 mg of SBA-15-NH2 , 15 min adsorption time, pH = 7.3 and 1 mL methanol. The linear response (0.998) was obtained in the range of 0.006-10 µgmL-1 with detection limit 0.0014 µg/mL and extraction recovery was in the range of 91-96% with relative standard deviation < 6%.

Dispersive solid-phase extraction of selected nitrophenols from environmental water samples using a zirconium-based amino-tagged metal-organic framework nanosorbent.

This study has centered on the establishment of an efficient, simple and reliable dispersive solid-phase extraction method followed by an accurate trace determination of selected nitrophenols as a class of compounds with high toxicity and low degradability. To achieve the above goal, a zirconium-based amino-tagged metal-organic framework nanosorbent was synthesized, characterized and eventually employed for the extraction of two nitrophenols from various environmental water samples. Once the extraction of analytes had occurred, they were desorbed from the metal-organic framework sorbent using an appropriate mixed solvent followed by high-performance liquid chromatography with ultraviolet detection. Under the optimal extraction conditions, the calibration curves for the analytes were linear over the concentration range of 1-200 µg/L. The accuracy of the method was tested by the relative recovery experiments on the fortified real samples with the results falling within the range of 91 to 106%, while the corresponding precisions varied in the span of 4.6-9.0%. Based on a signal-to-noise ratio of 3, the method detection limits were determined to be 0.5 µg/L for both analytes.

Trace quantification of selected sulfonamides in aqueous media by implementation of a new dispersive solid-phase extraction method using a nanomagnetic titanium dioxide graphene-based sorbent and HPLC-UV.

Herein, a new dispersive solid-phase extraction method using a nano magnetic titanium dioxide graphene-based sorbent in conjunction with high-performance liquid chromatography and ultraviolet detection was successfully developed. The method was proved to be simple, sensitive, and highly efficient for the trace quantification of sulfacetamide, sulfathiazole, sulfamethoxazole, and sulfadiazine in relatively large volume of aqueous media. Initially, the nano magnetic titanium dioxide graphene-based sorbent was successfully synthesized and subsequently characterized by scanning electron microscopy and X-ray diffraction. Then, the sorbent was used for the sorption and extraction of the selected sulfonamides mainly through π-π stacking hydrophobic interactions. Under the established conditions, the calibration curves were linear over the concentration range of 1-200 µg/L. The limit of quantification (precision of 20%, and accuracy of 80-120%) for the detection of each sulfonamide by the proposed method was 1.0 µg/L. To test the extraction efficiency, the method was applied to various fortified real water samples. The average relative recoveries obtained from the fortified samples varied between 90 and 108% with the relative standard deviations of 5.3-10.7%.

An amino-functionalized mesoporous silica (KIT-6) as a sorbent for dispersive and ultrasonication-assisted micro solid phase extraction of hippuric acid and methylhippuric acid, two biomarkers for toluene and xylene exposure.

The authors described a new application of amino-functionalized KIT-6 for dispersive ultrasonication-assisted micro solid phase extraction of hippuric acid (HA) and methyl hippuric acid (MHA) from human urine and water samples. In the first step, an amino-functionalized mesoporous silica of type KIT-6 was synthesized. It was characterized by field emission scanning electron microscopy, Fourier transform infrared spectrometry, nitrogen adsorption-desorption analysis, thermogravimetry and X-ray diffraction. Following sorption and desorption with 1.0 mL methanol/NH4OH (1%; v/v), HA and MHA were quantified by HPLC with UV detection. Various important parameters were optimized by Box-Behnken design. Under optimized conditions, The limit of detections (LOD) were calculated by a signal-to-noise ratio of 3, which were 0.5 µg L-1 and 0.2 µg L-1 for HA and MHA, respectively, and the calibration plot is linear in the 1-1000 µg L-1 concentration range. Only small matrix effects were found. The method was successfully implemented for the sensitive determination of HA and MHA in (spiked) human urine samples. Graphical abstract Schematic of a sorbent for dispersive micro solid phase extraction coupled with ultrasonic power. It consists of amino functionalized KIT-6 and was used for the simultaneous preconcentration and determination of low levels of hippuric and methyl hippuric acid in urine and water samples.

Application of a dispersive solid-phase extraction method using an amino-based silica-coated nanomagnetic sorbent for the trace quantification of chlorophenoxyacetic acids in water samples.

Herein, an amino-based silica-coated nanomagnetic sorbent was applied for the effective extraction of two chlorophenoxyacetic acids (2-methyl-4-chlorophenoxyacetic acid and 2,4-dichlorophenoxyacetic acid) from various water samples. The sorbent was successfully synthesized and subsequently characterized by scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The analytes were extracted by the sorbent mainly through ionic interactions. Once the extraction of analytes was completed, they were desorbed from the sorbent and detected by high-performance liquid chromatography with ultraviolet detection. A number of factors affecting the extraction and desorption of the analytes were investigated in detail and the optimum conditions were established. Under the optimum conditions, the calibration curves were linear over the concentration range of 1-250, and based on a signal-to-noise ratio of 3, the method detection limits were determined to be 0.5 µg/L for both analytes. Additionally, a preconcentration factor of 314 was achieved for the analytes. The average relative recoveries obtained from the fortified water samples varied in the range of 91-108% with relative standard deviations of 2.9-8.3%. Finally, the method was determined to be robust and effective for environmental water analysis.

Efficient sample preparation method based on solvent-assisted dispersive solid-phase extraction for the trace detection of butachlor in urine and waste water samples.

In this work, an efficient sample preparation method termed solvent-assisted dispersive solid-phase extraction was applied. The used sample preparation method was based on the dispersion of the sorbent (benzophenone) into the aqueous sample to maximize the interaction surface. In this approach, the dispersion of the sorbent at a very low milligram level was achieved by inserting a solution of the sorbent and disperser solvent into the aqueous sample. The cloudy solution created from the dispersion of the sorbent in the bulk aqueous sample. After pre-concentration of the butachlor, the cloudy solution was centrifuged and butachlor in the sediment phase dissolved in ethanol and determined by gas chromatography with flame ionization detection. Under the optimized conditions (solution pH = 7.0, sorbent: benzophenone, 2%, disperser solvent: ethanol, 500 µL, centrifuged at 4000 rpm for 3 min), the method detection limit for butachlor was 2, 3 and 3 µg/L for distilled water, waste water, and urine sample, respectively. Furthermore, the preconcentration factor was 198.8, 175.0, and 174.2 in distilled water, waste water, and urine sample, respectively. Solvent-assisted dispersive solid-phase extraction was successfully used for the trace monitoring of butachlor in urine and waste water samples.

Application of 1-(2-pyridylazo)-2-naphthol-modified nanoporous silica as a technique in simultaneous trace monitoring and removal of toxic heavy metals in food and water samples.

Solid-phase extraction is one the most useful and efficient techniques for sample preparation, purification, cleanup, preconcentration, and determination of heavy metals at trace levels. In this paper, functionalized MCM-48 nanoporous silica with 1-(2-pyridylazo)-2-naphthol was applied for trace determination of copper, lead, cadmium, and nickel in water and seafood samples. The experimental conditions such as pH, sample and eluent flow rate, type, concentration and volume of the eluent, breakthrough volume, and effect of coexisting ions were optimized for efficient solid-phase extraction of trace heavy metals in different water and seafood samples. The content of solutions containing the mentioned heavy metals was determined by flame atomic absorption spectrometry (FAAS), and the limits of detection were 0.3, 0.4, 0.6, and 0.9 ng mL(-1) for cadmium, copper, nickel, and lead, respectively. Recoveries and precisions were >98.0 and <4%, respectively. The adsorption capacity of the modified nanoporous silica was 178 mg g(-1) for cadmium, 110 mg g(-1) for copper, 98 mg g(-1) for nickel, and 210 mg g(-1) for lead, respectively. The functionalized MCM-48 nanoporous silica with 1-(2-pyridylazo)-2-naphthol was characterized by thermogravimetry analysis (TGA), differential thermal analysis (DTA), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), elemental analysis (CHN), and N2 adsorption surface area measurement.

Trace monitoring of silver ions in food and water samples by flame atomic absorption spectrophotometry after preconcentration with solvent-assisted dispersive solid phase extraction.

In this research, a new sample treatment technique termed solvent-assisted dispersive solid phase extraction (SADSPE) was developed. The new method was based on the dispersion of the sorbent into the sample to maximize the contact surface. In this approach, the dispersion of the sorbent at a very low milligram level was achieved by injecting a mixture solution of the sorbent and disperser solvent into the aqueous sample. Thereby, a cloudy solution formed. The cloudy solution resulted from the dispersion of the fine particles of the sorbent in the bulk aqueous sample. After extraction, the cloudy solution was centrifuged and the enriched analytes in the sediment phase dissolved in ethanol and determined by FAAS. Under the optimized conditions, the detection limit for silver ions was 0.8 µg L(-1). The relative standard deviations for six separate extraction experiments for determination of 5 and 200 µg L(-1) of silver ions was 3.4 and 3.1 %. The preconcentration factor was found to be 61.7. SADSPE was successfully applied for trace determination of silver ions in water and food samples.

Application of poly 1,8-diaminonaphthalene/multiwalled carbon nanotubes-COOH hybrid material as an efficient sorbent for trace determination of cadmium and lead ions in water samples.

Poly 1,8-diaminonaphthalene/multiwalled carbon nanotubes-COOH hybrid material as an effective sorbents in solid phase extraction has been developed for the separation and preconcentration of Cd(II) and Pb(II) at trace levels in environmental water samples. The results indicate that the novel nanocomposite show a high affinity for these heavy metals due to the presence of several good extractive sites, which are introduced to the synthesized nanocomposite The maximum adsorption capacity of the synthesized sorbent for cadmium and lead ions was found to be 101.2 and 175.2 mg g(-1) , respectively. The detection limits of this method were 0.09 and 0.7 ng ml(-1) for Cd(II) and Pb(II), respectively.

Application of a magnetic molecularly imprinted polymer for the selective extraction and trace detection of lamotrigine in urine and plasma samples.

Magnetic molecularly imprinted polymers have been synthesized for the selective preconcentration and trace determination of lamotrigine (LTG) in urine and plasma samples. The magnetic nanoparticles were modified by tetraethyl orthosilicate and 3-methacryloxypropyl trimethoxysilane before imprinting. The magnetic molecularly imprinted polymers were prepared via surface molecular imprinting technique, using Fe3 O4 as a magnetic component, LTG as template molecule, methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a cross-linker, and 2,2'-azobisisobutyronitrile as a radical initiator in methanol/acetonitrile (50:50, v/v) as the porogen. The obtained sorbent was characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and thermal analysis. Separation of the sorbent from the sample solution was simply achieved by applying an external magnetic field. Determination of the extracted drug was performed by high-performance liquid chromatography with UV detection. Under the optimum extraction conditions, the method detection limits were 0.7 µg/L (based on S/N of 3) for urine samples and 0.5 µg/L for plasma samples. A linear dynamic range of 1-1000 µg/L was obtained for LTF in plasma and urine samples. Finally, the applicability of the proposed method was evaluated by extraction and determination of LTG in urine and plasma samples.

Monitoring of trace amounts of heavy metals in different food and water samples by flame atomic absorption spectrophotometer after preconcentration by amine-functionalized graphene nanosheet.

We are introducing graphene oxide modified with amine groups as a new solid phase for extraction of heavy metal ions including cadmium(II), copper(II), nickel(II), zinc(II), and lead(II). Effects of pH value, flow rates, type, concentration, and volume of the eluent, breakthrough volume, and the effect of potentially interfering ions were studied. Under optimized conditions, the extraction efficiency is >97 %, the limit of detections are 0.03, 0.05, 0.2, 0.1, and 1 µg L(-1) for the ions of cadmium, copper, nickel, zinc, and lead, respectively, and the adsorption capacities for these ions are 178, 142, 110, 125, and 210 mg g(-1). The amino-functionalized graphene oxide was characterized by thermogravimetric analysis, transmission electron microscopy, scanning electron microscopy, and Fourier transform infrared spectrometry. The proposed method was successfully applied in the analysis of environmental water and food samples. Good spiked recoveries over the range of 95.8-100.0 % were obtained. This work not only proposes a useful method for sample preconcentration but also reveals the great potential of modified graphene as an excellent sorbent material in analytical processes.

Coupling of solvent-based de-emulsification dispersive liquid-liquid microextraction with high performance liquid chromatography for simultaneous simple and rapid trace monitoring of 2,4-dichlorophenoxyacetic acid and 2-methyl-4-chlorophenoxyacetic acid.

A simple, rapid, and efficient sample pretreatment technique, based on solvent-based de-emulsification dispersive liquid-liquid microextraction (SD-DLLME), followed by high performance liquid chromatography (HPLC) has been developed for simultaneous preconcentration and trace detection of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) in water and urine samples. Some parameters such as acidity of solution, the amount of salt, type, and volume of extraction solvents, type of disperser/de-emulsifier solvent, and its volume were investigated and optimized. Under optimum extraction conditions, the limits of detections (LODs) of this method for MCPA and 2,4-D were 0.2 and 0.6 µg L(-1) (based on 3S(b)/m) in water and 0.4 and 1.6 µg L(-1) in urine, respectively. Furthermore, dynamic linear range of this method for MCPA and 2,4-D was 1-300 and 2-400 µg L(-1), repectively. Finally, the applicability of the proposed method was evaluated by extraction and determination of the herbicides in urine and different water samples.

Decorated graphene oxide with gold nanoparticles as a sensitive modified carbon paste electrode for simultaneous determination of tyrosine and uric acid.

It is presented here as a simple, selective, rapid, low-cost, with a wide linear range method to simultaneously determine tyrosine and uric acid using a modified carbon paste electrode decorated with graphene oxide and gold nanoparticles (GO/AuNPs/MCPE). In order to characterize and evaluate the morphology and constituents of the nanostructures, X-ray diffraction spectroscopy, Transmission electron microscopes, Dynamic light scattering, Zeta potential, electrochemical impedance spectroscopy, and Voltammetry were employed. The current response on the surface of the modified electrode had a dynamic linear range relationship in the concentrations of 0.14-340.00 µmol L-1 and 0.06-141.00 µmol L-1 for tyrosine and uric acid, respectively, and the method detection limit (MDL) was 0.0060 µmol L-1 and 0.0037 µmol L-1, respectively. This modified electrode provided high stability, sensitivity, and acceptable reproducibility for voltammetric measurements of tyrosine and uric acid simultaneously in a biological matrix.

Magnetic activated carbon as an adsorbent for extraction of DMMP from aqueous samples followed by GC-IMS analysis.

Micro-porous magnetic activated carbon was prepared under ultrasonic irradiation as an adsorbent for dispersed solid phase extraction of dimethyl methyl phosphonate from water samples, before analysis by gas chromatography-ion mobility spectrometry. The magnetic activated carbon was synthesized and characterized by using a vibrating sample magnetometer, Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction techniques. Then, the effects of the amount of sorbent, extraction time and pH of the sample in the dispersive solid phase extraction method were investigated and optimized by the response surface method. The dispersion of 20 mg adsorbent powder in a 50 mL water sample for 5 minutes with chloroform as the desorption solvent showed an average recovery value of 95% for dimethyl methyl phosphonate. Afterward, the method was used successfully for the determination of dimethyl methyl phosphonate in river and spring water. The linear range was obtained to be 0.05-1 µg mL-1. The limit of detection and the limit of quantification were obtained to be 0.02 µg mL-1 and 0.05 µg mL-1 respectively. The analysis also showed good reproducibility with a relative standard deviation value of 3.1%. This method was shown to be easy, fast, reliable, and inexpensive.

Performance of LGAD strip detectors for particle counting of therapeutic proton beams.

Objective. The performance of silicon detectors with moderate internal gain, named low-gain avalanche diodes (LGADs), was studied to investigate their capability to discriminate and count single beam particles at high fluxes, in view of future applications for beam characterization and on-line beam monitoring in proton therapy.Approach. Dedicated LGAD detectors with an active thickness of 55µm and segmented in 2 mm2strips were characterized at two Italian proton-therapy facilities, CNAO in Pavia and the Proton Therapy Center of Trento, with proton beams provided by a synchrotron and a cyclotron, respectively. Signals from single beam particles were discriminated against a threshold and counted. The number of proton pulses for fixed energies and different particle fluxes was compared with the charge collected by a compact ionization chamber, to infer the input particle rates.Main results. The counting inefficiency due to the overlap of nearby signals was less than 1% up to particle rates in one strip of 1 MHz, corresponding to a mean fluence rate on the strip of about 5 × 107p/(cm2·s). Count-loss correction algorithms based on the logic combination of signals from two neighboring strips allow to extend the maximum counting rate by one order of magnitude. The same algorithms give additional information on the fine time structure of the beam.Significance. The direct counting of the number of beam protons with segmented silicon detectors allows to overcome some limitations of gas detectors typically employed for beam characterization and beam monitoring in particle therapy, providing faster response times, higher sensitivity, and independence of the counts from the particle energy.

Application of a modified MWCNT-based d-µSPE procedure for determination of bisphenols in soft drinks.

Herein, a facile dispersive micro-solid phase extraction (d-µSPE) procedure using carboxylated multi-walled carbon nanotubes modified with silver nanoparticles (Ag/MWCNTs-COOH) was successfully developed for the adsorption and subsequent determination of low levels of two well-known contaminants, namely bisphenol A and S (BPA and BPS) in water and soft drink samples. The detection and measurement of the above-mentioned compounds were performed by HPLC-UV instrument. The applied d-µSPE procedure has several advantages such as rapidity, high degree of sensitivity, precision and efficiency. A combination of polar/non-polar interactions seems to play a key role in the adsorption process. Under the optimized conditions, the calibration curves were linear over the concentration range of 1-500 µg/L for the both targets. The practical limit of quantifications (LOQ) for the both analytes were determined to be 1.0 µg/L. The average relative recoveries obtained from the fortified samples varied between 92 and 110% with the relative standard deviations (RSD%) of 2.9-9.5%.

Development of a New and Fast Extraction Method Based on Solvent-Assisted Dispersive Solid-Phase Extraction for Preconcentration and Trace Detection of Atrazine in Real Matrices.

BACKGROUND: Because of trace amounts of atrazine in water samples and the complexity of the matrix, direct trace monitoring of atrazine is not feasible by the abovementioned techniques. Hence, an efficient sample pretreatment procedure is necessary for cleanup and preconcentration of atrazine from sample matrices. OBJECTIVE: In the current paper, a new and efficient sample preparation method named solvent-assisted dispersive solid-phase extraction (SA-DSPE), followed by HPLC-UV, was introduced for the monitoring of atrazine at trace levels in environmental water samples. METHODS: In the present method, benzophenone was used as a sorbent for extraction of target molecules. For dispersing solid sorbents in sample solution, very low milligram amounts of benzophenone and dispersive solvent were mixed and fast-injected into the extraction media. A cloudy solution formed, and after interaction of atrazine and the dispersed solid sorbent, the cloudy solution was centrifuged. The extracted atrazine in the solid phase was dissolved in ethanol and analyzed by HPLC-UV. RESULTS: The introduced method showed a low method detection limit (0.1 µg/L), good precision (relative SD: 3.9-6.9%), and appropriate relative recoveries (95-105%). CONCLUSIONS: Within this study, a sensitive and reliable method for the quantification of atrazine in wastewater samples was successfully developed. HIGHLIGHTS: The obtained figures of merit for the presented sample preparation method were appropriate. The applicability of the method for analysis of atrazine in real matrices was excellent.

In silico assessment of new progesterone receptor inhibitors using molecular dynamics: a new insight into breast cancer treatment.

Nowadays, breast cancer is one of the most widespread malignancies in women, and the second leading cause of cancer death among women. The progesterone receptor (PR) is one of the treatment targets in breast cancer, and can be blocked with selective progesterone receptor modulators (SPRMs). Since administration of chemical drugs can cause serious side effects, and patients, especially those undergoing long-term treatment, can suffer harmful consequences, there is an urgent need to discover novel potent drugs. Large-scale structural diversity is a feature of natural compounds. Accordingly, in the present study, we selected a library of 20,000 natural compounds from the ZINC database, and screened them against the PR for binding affinity and efficacy. In addition, we evaluated the pharmacodynamics and ADMET properties of the compounds and performed molecular docking. Moreover, molecular dynamics (MD) simulation was carried out in order to examine the stability of the protein. In addition, principal component analysis (PCA) was performed to study the motions of the protein. Finally, the MMPBSA method was applied in order to estimate the binding free energy. Our docking results reveal that compounds ZINC00936598, ZINC00869973 and ZINC01020370 have the highest binding energy into the PR binding site, comparable with that of Levonorgestrel (positive control). Moreover, RMSD, RMSF, Rg and H-bond analysis demonstrate that the lead compounds preserve stability in complex with PR during simulation. Our PCA analysis results were in accordance with MD results and the binding free energies support the docking results. This study paves the way for discovery of novel drugs from natural sources and with optimal efficacy, targeting the PR. Graphical Abstract The binding mode of new progesterone receptor inhibitors.

Application of a surfactant-assisted dispersive liquid-liquid microextraction method along with central composite design for micro-volume based spectrophotometric determination of low level of Cr(VI) ions in aquatic samples.

A fast, simple, low cost surfactant-assisted dispersive liquid-liquid microextraction method along with central composite design for the determination of low level of Cr(VI) ions in several aquatic samples has been developed. Initially, Cr(VI) ions present in the aqueous sample were readily reacted with 1,5­diphenylcarbazide (DPC) in acidic medium through complexation. Sodium dodecyl sulfate (SDS), as an anionic surfactant, was then employed as an ion-pair agent to convert the cationic complex into the neutral one. Following on, the whole aqueous phase underwent a dispersive liquid-liquid microextraction (DLLME) leading to the transfer of the neutral complex into the fine droplet of organic extraction phase. A micro-volume spectrophotometer was used to determine Cr(VI) concentrations. Under the optimized conditions predicted by the statistical design, the limit of quantification (LOQ) obtained was reported to be 5.0 µg/L, and the calibration curve was linear over the concentration range of 5-100 µg/L. Finally, the method was successfully implemented for the determination of low levels of Cr(VI) ions in various real aquatic samples and the accuracies fell within the range of 83-102%, while the precision varied in the span of 1.7-5.2%.