Graphene-based Solid-phase Extraction Research Articles

Graphene as adsorbent for highly efficient extraction of modified nucleosides in urine prior to liquid chromatography-tandem mass spectrometry analysis

RNA modifications have been involved in numerous biological processes, and aberrations of these modifications are tightly associated with various diseases including cancer. Herein, we developed graphene-based solid-phase extraction and robust ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) combined with stable isotope-dilution for simultaneous enrichment and accurate determination of 17 modified nucleosides in human urine. We found graphene could effectively adsorb various modified nucleosides in human urine samples. With this method, we identified and quantified these modified nucleosides in urine samples collected from lung cancer patients and healthy controls. We revealed that the levels of 12 modified nucleosides were all diminished in urine from lung cancer patients, compared with healthy controls. It is worth noting that we demonstrated, for the first time, the presence of 5,2′-O-dimethyluridine (m5Um) in human urine. Together, we established a robust analytical method for simultaneous determinations of 17 modified nucleosides in human urine, and our results revealed a close correlation between the concentrations of urinary modified nucleosides and the occurrence of lung cancer, implying the potential applications of these modified nucleosides as noninvasive biomarkers for the early detection of lung cancer. Moreover, this study will stimulate future investigations on the regulatory roles of RNA modifications in the initiation and progression of lung cancer.

Self-supporting crumpled graphene balls as stable and reusable adsorbents for solid-phase extraction

The substantial aggregation of pristine graphene nanosheets or the possible escape of graphene from the supporting materials decreases its powerful adsorption capacity and diminishes its practical applications in graphene-based solid-phase extraction (SPE). It is highly desirable for these graphene-based adsorbents to be dispersive, stable and reusable. In this study, we report the use of self-supporting crumpled graphene balls as stable and reusable adsorbents for SPE. Comparative studies shows crumpled graphene balls are superior to other common SPE adsorbents in terms of recovery (approaching 100% for all four chlorophenols) and adsorption capacity (826.4 and 1457.4 μg/g for pentachlorophenol and 2-chlorophenol). Notably, the stability and reusability of crumpled graphene balls was remarkable due to their unique chemical structure with wrinkles and ridges. The application of the obtained crumpled graphene balls was further successfully extended to the enrichment and desalination of proteins.

Determination of Tetracyclines in Milk by Graphene-Based Solid-Phase Extraction and High-Performance Liquid Chromatography

ABSTRACTA graphene-based solid-phase extraction (SPE) column was prepared for the isolation of tetracyclines from milk followed by determination by high-performance liquid chromatography. Graphene provided better separation for tetracyclines than amine-modified graphene and carboxyl-modified graphene. The optimized graphene-based SPE column showed high absorption capacities (greater than 4,660 ng) and high recoveries (exceeding 92%) for tetracycline, oxytetracycline, chlortetracycline, and doxycycline and was successfully reused at least fifty times. The limits of detection in milk were from 10 to 20 ng/mL, with recoveries between 82.3 and 103.6%. Furthermore, the system showed superior performance than two commercial SPE cartridges with respect to recovery, purification, and reusability. Therefore, this approach is suitable for the determination of tetracyclines in milk.

Application of Graphene as Solid Phase Extraction Absorbent for the Determination of Parabens in Cosmetic Products by Capillary Electrophoresis

A graphene-based solid phase extraction (SPE) technique was developed for the extraction of parabens (methylparaben, ethylparaben, propylparaben, and butylparaben) in cosmetic samples, followed by determination by capillary electrophoresis (CE). The SPE extraction parameters such as eluent reagent and eluent volume, washing solution, sample pH, and flow-rate of sample loading, were investigated for satisfied recoveries. The running buffer, consisting of 25 mM borate solution (pH 10.0), was used for the separation of four parabens with the CE method within 10 min. The limits of detection were 0.14 mg/L, 0.13 mg/L, 0.15 mg/L, and 0.10 mg/L for methylparaben, ethylparaben, propylparaben, and butylparaben, respectively, and the mean recoveries obtained were between 62.6% and 100.4%. The developed method was used for the determination of parabens in real cosmetic products.

Application of graphene-based solid-phase extraction for ultra-fast determination of malachite green and its metabolite in fish tissues

An ultra-fast analytical protocol using graphene-based solid-phase extraction coupled with ultra-performance liquid chromatography–tandem mass spectrometry for the rapid determination of malachite green and its metabolite, leucomalachite green in fish tissues has been developed. In the present work, graphene was synthesized and evaluated as novel solid-phase extraction sorbents for the analytes enrichment and clean-up. The target analytes were separated on an ultra-pressure BEH C8 column and quantified by a triple-quadrupole linear ion trap mass spectrometer in multiple-reaction monitoring mode. The proposed analytical procedures were carefully optimized and validated. The matrix-matched calibration curves were performed at six concentration levels and good linear relationship (R2>0.9990) was observed within the range of 0.25–50μgkg−1. The proposed method has been successfully applied to the analysis of MG and LMG in several fish samples, indicating that graphene was an efficient SPE sorbent for the enrichment of trace residues in food analysis.

Graphene-based solid-phase extraction disk for fast separation and preconcentration of trace polycyclic aromatic hydrocarbons from environmental water samples

Graphene has great potentials for the use in sample preparation due to its ultra high specific surface area, superior chemical stability, and excellent thermal stability. In our work, a novel graphene-based SPE disk was developed for separation and preconcentration of trace polycyclic aromatic hydrocarbons from environmental water samples. Based on the strong π-π stacking interaction between the analytes and graphene, the analytes extracted by graphene were eluted by cyclohexane and then determined by GC-MS. Under the optimized conditions, high flow rate (30 mL/min) and sensitivity (0.84-13 ng/L) were achieved. The proposed method was successfully applied to the analysis of real environmental water samples with recoveries ranging from 72.8 to 106.2%. Furthermore, the property of anticlogging and reusability was also improved. This work reveals great potentials of graphene-based SPE disk in environmental analytical.

Application of Graphene-based Solid-Phase Extraction Coupled with Ultra High-performance Liquid Chromatography-Tandem Mass Spectrometry for Determination of Macrolides in Fish Tissues

A novel analytical protocol for the determination of five macrolides (MLs) in crucian carp tissues has been developed. Two-dimensional (2D) planar graphene powder was utilized as the solid-phase extraction (SPE) sorbent for analyte enrichment and cleanup. The target analytes were separated by ultra high-performance liquid chromatography (LC) and quantified by a triple–quadrupole linear ion trap mass spectrometer. The proposed analytical procedures were carefully optimized and validated. Average recoveries of MLs were between 81.7 and 110.5 %, which was the highest comparing with the conventional sorbents including C18 silica and multiwalled carbon nanotubes (MWCNTs). Method validation proved the feasibility of the developed nanoparticles for the quantificatation of the investigated analytes at trace levels obtaining low limit of quantitation values in the microgram per kilogram range. Good precision with coefficients of variations always lower than 10 % was obtained. The proposed method has been successfully applied to the analysis of ML in several aquaculture product samples, indicating that graphene was a potential SPE sorbent for the enrichment of trace residues in food samples.

Graphene-based solid-phase extraction combined with flame atomic absorption spectrometry for a sensitive determination of trace amounts of lead in environmental water and vegetable samples

Graphene, a novel class of carbon nanostructures, has great promise for use as sorbent materials because of its ultrahigh specific surface area. A new method using a column packed with graphene as sorbent was developed for the preconcentration of trace amounts of lead (Pb) using dithizone as chelating reagent prior to its determination by flame atomic absorption spectrometry. Some effective parameters on the extraction and complex formation were selected and optimized. Under optimum conditions, the calibration graph was linear in the concentration range of 10.0–600.0μgL−1 with a detection limit of 0.61μgL−1. The relative standard deviation for ten replicate measurements of 20.0 and 400.0μgL−1 of Pb were 3.56 and 3.25%, respectively. Comparative studies showed that graphene is superior to other adsorbents including C18 silica, graphitic carbon, and single- and multi-walled carbon nanotubes for the extraction of Pb. The proposed method was successfully applied in the analysis of environmental water and vegetable samples. Good spiked recoveries over the range of 95.3–100.4% were obtained. This work not only proposes a useful method for sample preconcentration, but also reveals the great potential of graphene as an excellent sorbent material in analytical processes.

Graphene-Based Solid-Phase Extraction for a Sensitive Determination of Trace Amounts of Lead in Water Samples

Graphene, a novel class of carbon nanostructures, has great promise for use as sorbent materials because of its ultrahigh specific surface area. A new method using a column packed with gaphene as sorbent was developed for the preconcentration of trace amounts of lead (Pb) prior to its determination by flame atomic absorption spectrometry. Some effective parameters on the extraction and complex formation were selected and optimized. Under optimum conditions, an enrichment factor of 250 was obtained. The calibration graph was linear in the concentration range of 2.4x 10.8 mol L-1-2.9x 10.6 mol L-1 with a detection limit of 1.9x 10.9 mol L-1. The relative standard deviation for ten replicate measurements of 9.7x 10.8 mol L-1 and 1.4x 10.6 mol L-1 of Pb were 3.45 %and 3.28 %, respectively. The proposed method was successfully applied in the analysis of four real environmental water samples and good spiked recoveries over the range of 95.5–99.6 %were obtained. This work not only proposes a useful method for environmental water sample pretreatment, but also reveals the great potential of gaphene as an excellent sorbent material in analytical processes.