Eluent Volume Research Articles

Nitrogen-rich covalent organic frameworks as solid-phase extraction adsorbents for separation and enrichment of four disinfection by-products in drinking water

Disinfection by-products (DBPs) in drinking water can pose a health risk to humans. In this work, a new nitrogen-rich covalent organic frameworks (TpTt-COFs) was synthesized and applied firstly as a novel solid-phase extraction (SPE) trapping media for four ultra-trace levels of DBPs in drinking water samples. Under the optimal conditions, these DBPs were absorbed on a SPE cartridge; then, the DBPs were eluted with the optimized volume of eluent. The concentrated elution was detected and quantified by gas chromatography-mass spectrometry. Low limits of detection (0.0004–0.0063 ng mL−1), wide linearity (0.002–50 µg L−1), good reproducibility (1.54–2.88%) and repeatability (1.28–3.40%) were obtained. This novel method has been successfully applied to the analysis of ultra-trace levels DBPs in real drinking water samples. These accurate experimental results by this method indicated that the novel TpTt-COFs as a SPE trapping material was an attractive option for efficient and effective analysis of ultra-trace levels DBPs in future.

A simple magnetic solid-phase extraction method based on magnetite/graphene oxide nanocomposite for pre-concentration and determination of melamine by high-performance liquid chromatography.

In this study, a clean and simple magnetic solid-phase extraction (MSPE) procedure using magnetite/graphene oxide nanocomposite as an adsorbent was developed for melamine separation and preconcentration from water and dairy products. After synthesis and characterization of the adsorbent, adsorption isotherms and kinetic studies of the adsorption were carried out. The analyte quantification was performed by reversed phase high-performance liquid chromatography after elution of the preconcentrated analytes from the adsorbent surface. Several factors affecting the extraction/preconcentration procedure such as pH, adsorbent amount, extraction time, sample volume, type, and volume of eluent were investigated. The optimizing of some important parameters was assessed by employing a response surface method. The constructed calibration curve in the optimized conditions is linear in the working range of 0.10-100μgL-1 with a correlation coefficient of 0.9999. The detection limit, limit of quantification, and enrichment factor are 0.03μgL-1, 0.10μgL-1, and 500, respectively. The melamine relative recoveries from different real samples are between 97.20 and 103.10% with relative standard deviations of 1.07-4.98%.

Development of Molecularly Imprinted Membranes for Selective Determination of Urinary Ultra-Trace 5-Fluorouracil as Antineoplastic Drug Used in Chemotherapy

The incidence of neoplasm has significantly increased around the world over the last decades, resulting in use of anti-neoplastic drugs and the potential for occupational exposure to these drugs. One of the most commonly used chemotherapeutic drugs for treatment of malignancies is 5-fluorouracil (5-FU). In this study, in order to develop an appropriate adsorbent for selective extraction of ultra-trace 5-fluorouracil from urine samples, molecularly imprinted membranes (MIMs) of 5-FU were prepared by encapsulating molecularly imprinted polymer nanoparticles (MIP-NPs) into the electrospun polyethylene terephthalate (PET) nanofibers. The MIP-NPs encapsulated into electrospun PET nano-fibers were prepared by precipitation polymerization technique. These MIMs were used as selective sorbents for solid-phase extraction (SPE) of ultra-trace 5-FU from different samples prior to the analysis by high performance liquid chromatography (HPLC). Central Composite Design (CCD) was used for optimization of effective parameters in sorption and desorption steps of the molecularly imprinted membrane solid phase extraction (MIMSPE). The optimum operating conditions for the proposed method were pH: 6.2, amount of sorbent: 10.3 mg and absorption time: 20.5 h, the volume of eluent: 1 mL, the composition of elution solvent: the ratio of 90.3:9.7 methanol and acetic acid, and desorption time: 1.27 h. Under these optimized conditions, the limit of detection for 5-FU by MIMSPE was 0.07 μ L-1. The recoveries of 5-FU from urine sample ranged from 92.95±3.85 to 94.85±2.85%. The proposed MIMSPE-HPLC method can potentially be applied for selective detection of 5-FU in real samples with no special sample pretreatment steps.

Isotopic and optical heterogeneity of solid phase extracted marine dissolved organic carbon

Marine dissolved organic carbon (DOC) is the ocean's largest exchangeable reservoir of organic carbon. The biogeochemical cycling of DOC plays an important role in ocean carbon storage on various timescales. Solid-phase extraction (SPE) is a process used to isolate DOC from seawater for biogeochemical analysis. This study examines how DOC isotopic (Δ14C, δ13C) and optical (absorbance) properties of SPE-DOM change as a function of eluent volume (and hydrophobicity). These properties were measured in 28 SPE-DOC fractions incrementally eluted from Bond Elut PPL (styrene-divinylbenzene polymer) cartridges, totaling 32 mL of methanol. We show that the early eluted SPE-DOC has distinctly different ∆14C and δ13C values than those eluted later. This study reveals isotopic heterogeneity as a function of SPE-DOC elution volume. These results show a partitioning of two distinct sources of SPE-DOC during elution, indicating a gradual transition from “marine-like” DOC to “terrestrial-like” DOC along a hydrophobicity continuum.

Detection Method, Distribution, and Risk Assessment of Pharmaceuticals and Personal Care Products in the Yellow Sea and the East China Sea

At present, research findings on pharmaceuticals and personal care products (PPCPs) in coastal areas are still unclear, and there is a need to develop a method to detect more PPCPs simultaneously in seawater. In this study, nine compounds of non-steroidal anti-inflammatory drugs, antibiotics, lipid regulators. and stimulants were selected as analytes. Solid phase extraction (SPE) was used to extract the compounds, which were then analyzed by high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS). The optimum experimental conditions, such as the filler, eluent, pH, flow rate, and the reduction of matrix effect were optimized during the SPE. The results showed that the best extraction column was CNW HLB, the best eluent was methanol:acetonitrile (1:1, volume ratio), the best eluent volume was 6 mL, the best pH was 7, the best flow rate was 5 mL·min-1, the amount of EDTA-Na2 added was 1 g, and the best concentration multiple was 500. The linear regression equations of all PPCPs had good linearity. Correlation coefficients were>0.999, recovery rates were between 82%-106%, relative standard deviations were between 1.6%-14%, and detection limits were between 0.01-2 ng·L-1, thus satisfying the requirement of trace analysis in seawater. Distribution characteristics and sources of PPCPs were studied in the Yellow Sea and the East China Sea during summer 2018. All nine PPCPs were detected and the main pollutants were NAP, IBU, GEM, CAF, and ASA. High concentrations of PPCPs were generally detected in the nearshore area and displayed conspicuous decreasing tendencies from the inshore towards the offshore. The concentrations of PPCPs in the Yellow Sea were higher than of those in the East China Sea, and this was related to there being more sources of pollutions and poor water exchange capacity in the Yellow Sea. Principal component analysis showed that the main source of PPCPs was terrestrial input. The environmental risk assessment of PPCPs indicated that risk quotients (RQs) of IBU and NAP (0.1-1) posed a medium risk to the aquatic environment, while others posed low risk to organisms.

Optimization Strategies for Purification of Mycophenolic Acid Produced by Penicillium brevicompactum.

The microbial fermentation of Penicillium brevicompactum produces secondary metabolite mycophenolic acid (MPA), which exhibits antifungal, antiviral, antibacterial, and antitumor activity. It is also a potent, selective, non-competitive, and reversible inhibitor of the human inosine monophosphate dehydrogenase (IMPDH). This study is an attempt to optimize the MPA production through a fermentation process using Penicillium brevicompactum and its further purification process optimization. In the batch fermentation process, the maximum concentration of MPA (1.84g/L) was attained in a 3.7L stirred tank reactor. Response surface methodology (RSM) using central composite design (CCD) was employed as a statistical tool to investigate the effect of pH, the volume of eluent and flow rate of the mobile phase on MPA purification process. Under optimum conditions, the experimental yield was observed to be 84.12%, which matched well with the predictive yield of 84.42%. High-performance liquid chromatography (HPLC) and Fourier-transform infrared spectroscopy (FTIR) analysis of the fermented product was carried out to confirm the presence of mycophenolic acid. The MPA purification was done by using column chromatography technique. The purification of broth involved mycophenolic acid extraction by selecting different solvents on the basis of polarity and the extraction efficiency of solvent. Various solid support materials were used for MPA purification in column chromatography. The MPA recovery through alumina column was observed to be 84.12% under the optimum conditions, which was maximum elution as compared with other support materials. The optimized purification process yielded pure MPA crystals.

Magnetic graphene oxide as sorbent for SPE of melamine from water

Melamine introduced into environment water through various industrial effluents can pose negative effects on ecosystem, thus it is required to establish suitable analytical methods for detection of melamine in environmental water samples. In this work, magnetic graphene oxide was synthesized and used as the sorbent for solid phase extraction (SPE) of melamine. The parameters that affect the extraction efficiency of melamine were studied. The optimum conditions, including sample pH, extraction and desorption time, and eluent volume were obtained. The analytical performance of the method was evaluated, and it was found that the limit of detection for melamine was 0.15μg/L and the relative standard deviation was 3.6 %. The proposed method was utilized in the detection of melamine in various water samples with recoveries of 92.0-95.8%.

Highly Sensitive Determination of Bisphenol A in Bottled Water Samples by HPLC after Its Extraction by a Novel Th-MOF Pipette-Tip Micro-SPE.

In this study, a novel thorium metal organic framework was synthesized, characterized and used as a sorbent for very efficient pipette tip micro solid-phase extraction of bisphenol A in bottled drinking water samples using high-performance liquid chromatography as detecting instrument. Parameters which influence extraction efficiency such as pH, sample volume, amount of sorbent, type and volume of eluent, number of aspirating and dispensing cycles for extraction and elution, and volume of the sample solution were studied and optimized. A linear calibration curve was obtained in the range of 0.002-0.456ngmL-1 (r2=0.996) with a detection limit of 0.0010ngmL-1. Repeatability of batch-to-batch extraction was better than 5.0% and a reproducibility of 3.2% for real samples obtained.

An effective configuration for automated magnetic micro solid-phase extraction of phenylurea herbicides from water samples followed by high-performance liquid chromatography

In this study, a new automated magnetic micro solid-phase extraction was introduced. A Tygon tube was folded and fixed around the pole of a cylindrical magnet. Nanosized magnetic sorbents modified with diphenyldichlorosilane were uniformly immobilized on one side of the inner wall of the tube. Sample solution and desorption solvent were passed through the tube using a peristaltic pump. Four phenylurea herbicides (tebuthiuron, monolinuron, isoproturon, and monuron) were used as the model compounds to evaluate the method performance. HPLC-UV was used to separate and quantify the analytes. The effective parameters influencing the performance of the extraction process (i.e., extraction and desorption flow rates, eluent and sample volumes, type of eluent and sample ionic strength) were investigated. The limit of detection was 0.04 μg L−1 for all studied compounds. Calibration curves were linear in the range of 0.1–500 μg L−1 with a determination coefficient between 0.9988 and 0.9999. Intra-day, inter-day and batch-to-batch precisions expressed as relative standard deviation were less than 7%. Several environmental water samples were investigated to assess the applicability of the method for real sample analysis.

Coconut Shell Activated Carbon as Solid-Phase Extraction Adsorbent for Preconcentration of Selected Pesticides from Water Samples

Solid-phase extraction (SPE) on activated carbon derived from coconut shell (CSAC) for the preconcentration of four varying polarity pesticides (imidacloprid, acetamiprid, simazine, and linuron) prior to their determination using high performance liquid chromatography with diode array detector (HPLC-DAD) was investigated. The characteristics of the CSAC were analyzed through X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) method. The effects of the solution pH, eluent type, eluent volume, and flow rate were investigated for optimization of the presented procedure. The adsorption was achieved quantitatively on the CSAC column in the pH range of 2.0–7.0, and then the retained pesticides were eluted with dichloromethane. The detection limit was found to be 0.025–0.039 μg L−1, depending on the pesticide. The proposed SPE-CSAC method was used to determine selected pesticides in tap water samples. The recoveries ranged from 58.2 to 105.3%, with low relative standard deviations. The obtained results indicated that the CSAC could be efficiently used as a low cost alternative to commercially available SPE adsorbents for the determination of the varying polarity pesticides in environmental water samples at trace levels.

Extraction of aflatoxins by using mesoporous silica (type UVM-7), and their quantitation by HPLC-MS.

A solid-phase extraction procedure has been developed by using a sorbent derived from UVM-7 mesoporous silica. The sorbent was applied to the extraction of aflatoxins B1, B2, G1 and G2 from tea samples followed by HPLC with mass spectrometric detection. The sorbent was characterized by transmission electron microscopy, nuclear magnetic resonance, X-ray diffraction and nitrogen adsorption-desorption. UVM-7 is found to be the best solid phase. The amount of solid-phase, type and volume of eluent, pH value and ionic strength and breakthrough volume were optimized. Following the recommended procedure, recoveries between 96.0 and 98.2% were achieved, with RSD values of <5.1%, and the limits of detection are in the range from 0.14 to 0.7μg·kg-1. The material is reusable. The method was applied to the analysis of real tea samples. A low matrix effect is found, and recoveries are >88%. The results were compared with those obtained by immunoaffinity columns as a reference method. Only low concentrations of aflatoxin G2 were found in some samples, and results obtained with both methods are shown to be statistically sound and comparable. Graphical abstractSchematic representation of a mesoporous silica sorbent (type UVM-7) for the extraction of aflatoxins (AF) from tea by solid-phase extraction (SPE), and its determination by liquid chromatography. The morphology of the material allows to retain the analytesvery well.

Analysis and processing of sulfate accumulation in uranium hydrometallurgy for acid in-situ leaching

ABSTRACT In order to alleviate the sulfate accumulation in uranium hydrometallurgy process, the sulfate accumulating path was studied and a new elution process was proposed. The eluate composition as a function of eluent volume during the conventional and new elution process was studied. The result showed that pre-elution of saturated resin with 0.5–0.8 BV (bed volume) mother liquor was beneficial to the discharge of accumulated sulfate and could alleviate the accumulation of sulfate. Field tests showed that the new process ensured more stable production and reduced the amount of wastewater. Finally, the mechanism of the pre-elution process was analyzed.

SiO2@Fe3O4-SB nano-hybrids as nanosorbent for preconcentration of cadmium ions from environmental water samples

Magnetic nano structured materials provide new functionalities not found in their individual nano components. Removal and recovery of Cd(II) from aqueous solution was investigated using SiO2@Fe3O4-SB nano-hybrid materials. To enhance the potential of adsorbent material, we explored a new type Schiff’s base functionalized silica coated iron-oxide nano-hybrids (SiO2@Fe3O4-SB). The combination of both adsorption and magnetic separation properties were employed selectively for removal and recovery of Cd(II) from water and wastewater samples. Effect of different parameters influencing adsorption of Cd(II) for instance; interference of distinct cations and anions, effect of pH, concentration and volume of eluent, amount of adsorbent and ultra-sonication time were appraised and examined. The adsorbed Cd(II) was then desorbed and determined spectrophotometrically. The synthesized material was characterized with UV–vis spectroscopy, XRD, FTIR and TEM. The Limit of Detection under optimized conditions for Cd (II) in water samples was determined to be 0.741 μg L−1 using synthesized nano-hybrids.

Covalently bonded dithiocarbamate-terminated hyperbranched polyamidoamine polymer on magnetic graphene oxide nanosheets as an efficient sorbent for preconcentration and separation of trace levels of some heavy metal ions in food samples

Graphene oxide nanosheets were modified with magnetite nanoparticles, and a dithiocarbamate-terminated hyper branched polyamidoamine dendrimer was then covalently attached to their surface. The resulting material is shown to be an efficient sorbent for preconcentration of the Pb(II), Cd(II), Ni(II), Cu(II) and Cr(III) via ultrasound-assisted magnetic solid phase extraction. The sorbent was characterized by transmission electron microscopy, field emission scanning electron microscopy, FT-IR, X-ray diffraction and vibrating sample magnetometry. The effects of pH value, sorbent dosage, eluent volume, and sonication time were optimized by central composite design. The metals were quantified by flame atomic absorption spectroscopy (FAAS). Under optimized conditions, the method has a linear response in 3.5–150, 0.9–15, 3–100, 1.8–50 and 2.6–75 µg L−1 concentration range for Pb(II), Cd(II), Ni(II), Cu(II) and Cr(III), respectively. The detection limits are as low as 1.0, 0.27, 0.9, 0.54 and 0.8 µg L−1 for Pb(II), Cd(II), Ni(II), Cu(II) and Cr(III), respectively.

A Beta/ZSM-22 Zeolites-Based-Mixed Matrix Solid-Phase Dispersion Method for the Simultaneous Extraction and Determination of Eight Compounds with Different Polarities in Viticis Fructus by High-Performance Liquid Chromatography.

Viticis Fructus (VF) was named Manjingzi as a commonly used traditional Chinese medicine (TCM) targeting various pains and inflammation for more than 2000 years. To guarantee the quality of Viticis Fructus, a simple, quick and eco-friendly Beta/ZSM-22 zeolites-based-mixed matrix solid-phase dispersion method (B/Z-MMSPD) was established for simultaneous extraction and determination of eight compounds (two phenolic acids, two iridoid glycosides, vanillin and three flavonoids) with different polarities from Viticis Fructus by high performance liquid chromatography coupled with a diode array detector (HPLC-DAD). Beta and ZSM-22 were mixed as the sorbent. Water, tetrahydrofuran and methanol were blended with certain ratio as the eluent. Several parameters including types of sorbents, mass ratio of Beta to ZSM-22, mass ratio of matrix to sorbent, grinding time, types, concentration and volume of eluent were optimized. The recoveries of eight analytes were within the range of 95.0%–105% (RSDs ≤ 4.13%). The limits of detection and limits of quantitation ranged from 0.5 to 5.5 μg/g and from 1.5 to 16 μg/g, respectively. Compared to the traditional extract methods, it was a simple, rapid, efficient and green method. The results demonstrated that a simple, rapid, efficient and green B/Z-MMSPD was developed for the simultaneous extraction and determination of eight target analytes with different polarities for quality control of Viticis Fructus.

Saccharine based carbonyl multi-walled carbon nanotubes: novel modification, characterization and its ability for removing Cd(II) and Cu(II) from soil and environmental water samples

This research highlights the chemical modification of one of the carbon nanostructures (multi-walled carbon nanotubes-COOH) with an artificial sweetener (saccharine) to synthesize a highly efficient absorbent material (MWCNTs-CO-Sac). This material was thereafter used to the packing column in solid phase extraction of cadmium and copper divalent ions from real samples. This nano-adsorbent was diagnosed with different techniques: infrared spectroscopy (FTIR), Thermogravimetry (TG), Differential thermal analysis (DTA), powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDX), Particle size distribution (PSD) and scanning electron microscopy (SEM). The effect of pH, sample and eluent flow rates, volume, type and concentration of eluent, volume of sample and interfering ions were studied to achieve the optimal conditions for solid phase extraction of Cd(II) and Cu(II) based on the inductively coupled plasma-optical emission spectrometry (ICP-OES). Moreover, the preconcentration factors were calculated to be 75. The results of a limit of detection (LOD) 0.07 μgL−1 and 0.09 μgL−1 for Cd(II) and Cu(II) respectively. The relative standard deviation (RSD %) of this study was 0.45% for Cd(II) and 0.51% for Cu(II). The optimized method was applied to soil and environmental water samples.

Extraction of biologically active compounds from the residues of pericarps of sugar beet (Beta vulgaris L. ssp. vulgaris)

Aim. In the regulation of germination of seeds and of growth and development of seedlings, an important role belongs to biologically active substances that are found in the root of sugar beet (Beta vulgaris L. ssp. vulgaris), mainly in the pericarp. Extraction of secondary metabolites and study of the influence of a multicomponent system of endometabolites (phenolic compounds) of sugar beet pericarps on germination of plant seeds. Methods. The chemical composition of the metabolites of fruits and pericarps of sugar beet was determined by thin-layer chromatography; their differentiated isolation was carried out using column chromatography and gel filtration; The total content of phenolic compounds in fruits and pericarps was determined spectrophotometrically. Results. It was found that sugar beet pericarps contain a considerable amount of phenolic compounds (5-10 %). Four groups of phenolic compounds with different molecular masses were detected. By studying the influence of aquatic extracts on radish seeds, it was found that the eluents of the first volumes of water (3-5 ml) showed a pronounced stimulating effect, whereas further volumes of eluents (8-9 ml) were characterized by inhibitory action. Conclusions. Phenols, flavonoids and their glycosides were detected in extracts of sugar beet pericarps, which can be characterized as highly active inhibitors and growth promoters, therefore they could be used as natural biologically active substances.&#x0D; Keywords: sugar beet, pericarp, biologically active compounds, phenols, flavonoids.

Microextraction by packed sorbent using a new restricted molecularly imprinted polymer for the determination of estrogens from human urine samples

Microextraction by packed sorbent (MEPS) was employed with a new restricted access molecularly imprinted polymer (MIP) for the determination of estrone (E1) and estriol (E3) from human urine samples. Several parameters affecting the extraction efficiency during the procedure of sample preparation were systematically optimized, including washing solvent, sample volume, amount of sorption material, elution solution, eluent volume, number of cycles of aspersion/dispersion and sample pH. Mean recoveries with their respective relative standard deviations (RSD%) for E1 and E3 were 79.5 ± 7.1% and 69.5 ± 1.5%, respectively. The method was linear in the concentration range of 100 to 1100 ng mL−1 for each hormone, with correlation coefficient of 0.9954 and 0.9952 for E1 and E3, respectively. The developed method was successfully applied in urine sample from volunteer pregnant.

Enrichment and sensitive determination of phthalate esters in environmental water samples: A novel approach of MSPE-HPLC based on PAMAM dendrimers-functionalized magnetic-nanoparticles

Phthalate esters (PAEs) are an important kind of environmental endocrine disrupting chemicals, and have attracted great attention in environmental field. Present study described a new method for rapid and sensitive determination of PAEs including dibenzyl phthalate (DPhP), dibutyl phthalate (DnPP), and dicyclohexyl phthalate (DCHP) from aqueous matrices based on magnetic solid-phase extraction. Polyamidoamine (PAMAM) dendrimers-grafted magnetic-nanoparticles were synthesized and characterized, and the expected integration of more multifunctional sites of PAMAM dendrimers and rapid separation property was utilized for method development. To achieve the best extraction efficiency, several important parameters were optimized including the dosage of the adsorbent, sample pH, kind and volume of eluent, extraction time, desorption time, ionic strength. Under the optimal conditions, three phthalate esters were well enriched and simultaneously determined by high performance liquid chromatography with variable wavelength detector (VWD). Excellent linearities were observed in the range of 0.1–600 μg L−1 for DPhP and DnPP and 0.5–600 μg L−1 for DCHP, and all correlation coefficients (R2) were larger than 0.997. The limits of detection (LODs, S/N = 3) were ranged from 0.025 to 0.16 μg L−1. The spiked recoveries of PAEs in real water samples were in the range of 93.5–101.8% with satisfied relative standard deviations (RSDs) ranging from 0.9 to 4.1%. The prepared magnetic materials have shown good adsorption capability for PAEs and the developed method earned merits such as high sensitivity, simplicity, rapidness and environmental friendliness, which can be used as a robust alternative tool for monitoring PAEs in water samples.

Surfactant-modified Zn/Al-layered double hydroxides for efficient extraction of alkyl phenols from aqueous samples

Zn/Al-layered double hydroxides (LDHs) modified by sodium dodecylsulfate (SDS) were synthesized as a hydrophobic organic sorbent via urea hydrolysis. LDHs were applied as adsorbent for solid phase extraction (SPE) analysis to determine three alkylphenols (namely, p-tert-amylphenol (PTAP), p-cumylphenol (PCP), and p-n-octylphenol (POP)) in water samples using gas chromatography-mass spectrometry. The extraction efficiency was optimized by adjusting key variables of eluent volume, eluent type, sample flow rate, adsorbent amount, pH, and the effect of salt addition. Under the optimal conditions, APs showed excellent linearity (1–250 ng/mL: R2 > 0.99) and reproducibility (relative standard deviation: <5%). The detection limits for PTAP, PCP, and POP were 19, 16, and 33 pg/mL, respectively. LDHs based SPE method offered high recovery for aqueous samples (e.g., 83.2–99.46%) with enhanced reusability (e.g., up to 10 cycles). The feasibility of the developed method has thus been validated for quantitation of three alkyl phenols (i.e., PTAP, PCP, and POP) in aqueous environmental samples with high sensitivity and good stability.