Simultaneous Enrichment Research Articles

Green and Efficient Simultaneous Enrichment and Separation of Multiple Valuable Bioactive Compounds from Agricultural Waste Ginkgo biloba Exocarp Using a Two-Phase Deep Eutectic Solvent System

Green and Efficient Simultaneous Enrichment and Separation of Multiple Valuable Bioactive Compounds from Agricultural Waste <i>Ginkgo biloba</i> Exocarp Using a Two-Phase Deep Eutectic Solvent System

An Optimized Proteomics Approach Reveals Novel Alternative Proteins in Mouse Liver Development

Alternative ORFs (AltORFs) are unannotated sequences in genome that encode novel peptides or proteins named alternative proteins (AltProts). Although ribosome profiling and bioinformatics predict a large number of AltProts, mass spectrometry as the only direct way of identification is hampered by the short lengths and relative low abundance of AltProts. There is an urgent need for improvement of mass spectrometry methodologies for AltProt identification. Here, we report an approach based on size-exclusion chromatography for simultaneous enrichment and fractionation of AltProts from complex proteome. This method greatly simplifies the variance of AltProts discovery by enriching small proteins smaller than 40 kDa. In a systematic comparison between 10 methods, the approach we reported enabled the discovery of more AltProts with overall higher intensities, with less cost of time and effort compared to other workflows. We applied this approach to identify 89 novel AltProts from mouse liver, 39 of which were differentially expressed between embryonic and adult mice. During embryonic development, the upregulated AltProts were mainly involved in biological pathways on RNA splicing and processing, whereas the AltProts involved in metabolisms were more active in adult livers. Our study not only provides an effective approach for identifying AltProts but also novel AltProts that are potentially important in developmental biology.

Studies on Simultaneous Enrichment and Detection of Escherichia coli O157:H7 during Sample Shipment.

The USDA-FSIS has zero tolerance for E. coli O157:H7 in raw ground beef. Currently, FSIS collects samples from beef processing facilities and ships them overnight to regional testing laboratories. Pathogen detection requires robust methods that employ an initial 15-24 h culture enrichment. This study assessed the potential of using the ΦV10nluc phage-based luminescence detection assay during enrichment while the sample is in transit. Parameters including phage concentrations, temperature, and media-to-sample ratios were evaluated. Results in liquid media showed that 1.73× 103 pfu/mL of ΦV10nluc was able to detect 2 CFU in 10 h. The detection of E. coli O157:H7 was further evaluated in kinetic studies using ratios of 1:3, 1:2, and 1:1 ground beef sample to enrichment media, yielding positive results for as little as 2-3 CFU in 325 g ground beef in about 15 h at 37 °C. These results suggest that this approach is feasible, allowing the detection of a presumptive positive upon arrival of the sample to the testing lab. As the current cargo hold controlled temperature is required to be 15-25 °C, the need for elevated temperature should be easily addressed. If successful, this approach could be expanded to other pathogens and foods.

Electronic Structure Engineering of Highly-Scalable Earth-Abundant Multi-Synergized Electrocatalyst for Exceptional Overall Water Splitting in Neutral Medium.

Efficient neutral water splitting may represent in future a sustainable solution to unconstrained energy requirements, but yet necessitates the development of innovative avenues for achieving the currently unmet required performances. Herein, a novel paradigm based on the combination of electronic structure engineering and surface morphology tuning of earth-abundant 3D-hierarchical binder-free electrocatalysts is demonstrated, via a scalable single-step thermal transformation of nickel substrates under sulfur environment. A temporal-evolution of the resulting 3D-nanostructured substrates is performed for the intentional enhancement of non-abundant highly-catalytic Ni3+ and pSn 2- species on the catalyst surface, concomitantly accompanied with densification of the hierarchical catalyst morphology. Remarkably, the finely engineered NiSx catalyst synthesized via thermal-evolution for 24h (NiSx -24h) exhibits an exceptionally low cell voltage of 1.59V (lower than Pt/C-IrO2 catalytic couple) for neutral water splitting, which represents the lowest value ever reported. The enhanced performance of NiSx -24h is a multi-synergized consequence of the simultaneous enrichment of oxygen and hydrogen evolution reaction catalyzing species, accompanied by an optimum electrocatalytic surface area and intrinsic high conductivity. Overall, this innovative work opens a route to engineering the active material's electronic structure/morphology, demonstrating novel Ni3+ /pSn 2- -enriched NiSx catalysts which surpass state-of-the-art materials for neutral water splitting.

Resin adsorption as a means for the enrichment and separation of three terpenoid indole alkaloids: Vindoline, catharanthine and vinblastine from Catharanthus roseus extracts in ionic liquid solution

Simultaneous enrichment and separation of vindoline, catharanthine and vinblastine from Catharanthus roseus (Madagascar periwinkle) ionic liquid extracts was developed. To screen an appropriate resin, 12 commonly used macroporous resins were considered in terms of their performance and characteristics for adsorption and desorption of the target alkaloids . The adsorption capacity and desorption ratio of HPD750 resin for vindoline, catharanthine and vinblastine are found to be higher than that for the other resins, and, thus, this resin was chosen as the most suitable macroporous resin for the enrichment and separation of vindoline, catharanthine and vinblastine. The dynamic adsorption and desorption technical parameters of the target alkaloids were studied and optimized in an HPD750 resin-filled column. The optimum conditions for the adsorption process were determined to be as follows: vindoline, catharanthine and vinblastine loading concentrations in the sample solution of 10.22, 5.41 and 0.98 mg/L, respectively, sample volume of 45 mL, flow rate of 2 BV/h, and a temperature of 25 °C. For the desorption process, 5 BV of pure water was used to wash the impurities and ionic liquid, and then 10–80 % volume fraction of ethanol was used as the eluant (10–30 % volume fraction ethanol was used to remove impurities, and 40–80 % volume fraction ethanol was used to desorb and collect the target alkaloids as the final product). After enrichment and separation under these conditions, the vindoline, catharanthine and vinblastine contents in the products are determined to be 13.59 %, 7.42 % and 1.34 %, with recoveries of 71.37 %, 73.58 % and 75.00 %, respectively. In addition, the recycling of ionic liquid was attempted, which led to the achievement of better results. • Catharanthus roseus 1-allyl-3-methylimidazolium bromide extracts were considered. • C. roseus alkaloids adsorption/desorption performance of 12 resins were compared. • The static and dynamic tests on a non-ionic polymeric resin was investigated. • Macroporous resin was attempted for separation target analytes from AmimBr solution. • Resin HPD750 was the most suitable one from the testing of 12 types of resins.

A case study: what attracts teachers to augmented reality

This study aimed to identify the reasons why teachers are interested in augmented reality (AR) technology. AR is a technology that allows simultaneous enrichment of real-world images with virtual objects. AR is used at all levels of education from preschool to graduate school. The teachers who liked the Facebook page were sent the online survey via a message. 205 teachers who responded voluntarily to the questionnaire constituted the study group. Criterion sampling method, which is a purposeful sampling method, was used in the research. Case study design which is one of the qualitative research methods was used in this research. To ensure the reliability of the study, the coding process was conducted by the first researcher and another domain expert, and the codes were cross-checked. The results of the study showed that the reasons teachers are interested in AR were classified under three themes: educational benefit (teaching more effective lessons, attracting students' attention to lessons, enriching the content of the course, facilitating easier understanding of subjects, ensuring more permanent learning, making lessons more fun were attractive for teachers), professional development (follow current educational technologies, develop specialized course materials, share what they know with other teachers, use this information with other subjects) and personal development (learning new things, benefit from academic studies, prepare projects).

Ultrasonic-assisted dispersive liquid–liquid microextraction based on hydrophilic deep eutectic solvents: Application to lead and cadmium monitoring in water and food samples

A green and innovative ultrasonic-assisted dispersive liquid–liquid microextraction using hydrophilic deep eutectic solvents (UA-HDES-DLLME) was developed for the selective and simultaneous extraction and enrichment of Pb (II) and Cd (II) in water and food samples for flame atomic absorption spectrometry. Several natural deep eutectic solvents (NADES) were used for the preparation of six different HDES and methyl violet was used as chelating reagent. Effective parameters such as pH, sonication time, methyl violet amount, DES type, dispersive solvent types, etc were optimized. Relative standard deviation (RSD) and preconcentration factor (PF) were 4.0% and 80. Low limits of detection (LOD, 1.3 ng mL−1 for Pb (II) and 0.33 ng mL−1 for Cd (II)) and quantification (LOQ, 4.0 ng mL−1 for Pb (II) and 1.0 ng mL−1 for Cd (II)) were found. The method accuracy was confirmed with analyses of certified reference materials.

Mixed cation transport behaviours in electrodialysis during simultaneous ammonium enrichment and wastewater desalination

This study explored using electrodialysis (ED) to simultaneously enrich ammonium from wastewater for post nutrient recovery and desalt wastewater to enhance post-treatment for water recovery. It focused on the investigation of various factors affecting the efficiencies of ammonium concentration and cation removal and the elucidation of the mechanisms of mixed cation transport behaviours in ED. It was found that using an ED stack with the typical membrane arrangement (i.e., the cation exchange membranes (CEMs) are adjacent to electrode chambers), increasing applied current density and dilute solution/concentration solution volume ratio can generally increase the efficiency of ammonium concentration and the selectivity of NH4+ over other cations (i.e., Na+, K+, Ca2+ and Mg2+) by CEMs. However, the extent of such increases was constrained by severe ammonium leakage from the feedwater into the electrode solution. A total net transport number quantifying ion transport across ion exchange membranes was introduced to analyze ammonium leakage, which revealed that the less competitive migration of NH4+ than Na+ leads to the substantial accumulation of NH4+ in the electrode solution. To reduce ammonium leakage and increase the ammonium concentration efficiency, altering the membrane arrangement with the anion exchange membranes (AEMs) adjacent to the electrode chambers was demonstrated to be an effective strategy. This study provides important implications for developing ED-based technologies for nutrient enrichment and wastewater desalination.

Redox-Mediated Electrodialysis for Resource Recovery and Energy-Efficient Desalination

In the chemical and biochemical manufacturing industry, separation processes are amongst the most energy-demanding processes. Electrochemical separations have been growing in interest as promising candidates for both downstream processing for resource recovery and producing clean water due to their energy-efficient, environmentally benign, and modular features.1 Leveraging a sustainable redox reaction, we developed a redox-mediated electrodialysis system for energy-efficient desalination coupled with resource recovery of valuable resources such as lithium, and even biomolecules.2, 3 Our proposed redox-mediated electrodialysis system utilizes a reversible redox reaction as a driving force of salt removal at a much lower voltage than a water-splitting reaction (>1.2 V). As the redox materials are reduced or oxidized, all charged species migrate across the membranes to balance the charge in the electrolyte compartment. As the redox materials circulate in the cathode and anode compartments, they sustainably regenerated without additional regeneration steps, one of the major bottlenecks for industrializing the electrosorption system. We demonstrated the redox-mediated electrochemical system for resource recoveries such as simultaneous lithium recovery from brine3 and valorization of whey proteins and lactose from whey waste.2 Especially for the valorization of whey waste, our system treated 99% of salt from the whey solution within a single step and recovered > 98% of various whey proteins (e.g., valuable protein contents such as beta-lactoglobulin, alpha-lactalbumin, and lactose). The preliminary techno-economic analysis confirmed the economic potential of redox-mediated ED with 51−73% lower energy consumption compared to conventional ED. Overall. we envision the system can become a breakthrough in tackling the environmental challenges coupled with the limited resources. Kim, N.; Jeon, J.; Chen, R.; Su, X., Electrochemical separation of organic acids and proteins for food and biomanufacturing. Chemical Engineering Research and Design 2022, 178, 267-288.Kim, N.; Jeon, J.; Elbert, J.; Kim, C.; Su, X., Redox-mediated electrochemical desalination for waste valorization in dairy production. Chemical Engineering Journal 2022, 428, 131082.Kim, N.; Su, X.; Kim, C., Electrochemical lithium recovery system through the simultaneous lithium enrichment via sustainable redox reaction. Chemical Engineering Journal 2021, 420, 127715.

Multivariate analysis of liquid biopsies for real-time detection of patients with biofilm-associated infections (BAI)

Biofilm-associated infections (BAI) are chronic infections that are refractory to standard antibiotic therapy and challenging to diagnose. Detecting biofilms in patients remains a major challenge in the clinical field. Here, we introduced a microfluidic-based label-free and multivariate analysis (LF-MA) platform to assess biofilm-associated infection disease via multivariate analysis of severity parameters for point-of-care (POC) management. The integrated LF-MA platform consisted of two components: Biofilm Enrichment Device (BED) and Severity Detection Device (SDD), and allowed simultaneous real-time biofilm enrichment and viscosity-based BAI severity detection. High recovery efficiencies (>80 %) were observed for both gram-positive and gram-negative strains. A novel biosensor HMS indicator (Healthy: 1–3+, Mild: 1–3-, Severe: 1 + 3-) was developed to evaluate the severity of BAI based on microbeads distribution in target outletsSDD (for viscosity assessment) and the presence of biofilms. The one-step strategy was validated with patient-derived clinical isolates and could be completed within 2 h. We envisioned that the ease of operations and derived HMS biosensor indicator could facilitate new patient-centric approaches for rapid and multivariate assessment of patients with BAI.

Simultaneous enrichment and sequential separation of glycopeptides and phosphopeptides with poly-histidine functionalized microspheres.

Protein phosphorylation and glycosylation coordinately regulate numerous complex biological processes. However, the main methods to simultaneously enrich them are based on the coordination interactions or Lewis acid-base interactions, which suffer from low coverage of target molecules due to strong intermolecular interactions. Here, we constructed a poly-histidine modified silica (SiO2@Poly-His) microspheres-based method for the simultaneous enrichment, sequential elution and analysis of phosphopeptides and glycopeptides. The SiO2@Poly-His microspheres driven by hydrophilic interactions and multiple hydrogen bonding interactions exhibited high selectivity and coverage for simultaneous enrichment of phosphopeptides and glycopeptides from 1,000 molar folds of bovine serum albumin interference. Furthermore, “on-line deglycosylation” strategy allows sequential elution of phosphopeptides and glycopeptides, protecting phosphopeptides from hydrolysis during deglycosylation and improving the coverage of phosphopeptides. The application of our established method to HT29 cell lysates resulted in a total of 1,601 identified glycopeptides and 694 identified phosphopeptides, which were 1.2-fold and 1.5-fold higher than those obtained from the co-elution strategy, respectively. The SiO2@Poly-His based simultaneous enrichment and sequential separation strategy might have great potential in co-analysis of PTMs-proteomics of biological and clinic samples.

Chromitite deposits of Ufaley ultramafic massif (South Urals)

Data on the morphology, composition, textural and structural features of chromite deposits of the Ufaley ultramafic massif are presented. The mineralogical and compositional features of the host ultramafic rocks allow us to interpret them as depleted restite from partial melting of mantle peridotites. Relatively wide variations in the composition of ore-forming chromian spinel grains (#Cr 0.6–0.8) and noticeable metamorphism of disseminated ores with replacement of chromite by Cr-magnetite are noted. It is assumed that chromitite bodies were initially formed under the conditions of the upper mantle by a rheomorphic mechanism, and then their structural and geochemical transformation took place in the collisional setting of the upper part of the crust. Flattened bodies of disseminated chromitites have been preserved near competent gabbroid blocks, while other deposits have been transformed into lenses and podiform bodies of densely disseminated and massive ores of smaller size. The “cold tectonics” of the crustal stage led to the disintegration of deposits and the simultaneous local enrichment of deformed chromitite bodies.

A simple and versatile strategy for sensitive SIDA-UHPLC-MS/MS analysis of Alternaria toxins in olive oil

Alternaria toxins are naturally occurring contaminants found in natural products. Given the prevalence of Alternaria toxins and the complexity of oil-rich matrices, achieving ultra-trace analysis has become a daunting task. A new sample pretreatment technique, i.e., cold-induced liquid-liquid microextraction combined with serially-coupled-columns for SIDA-UHPLC-MS/MS, was developed and reported for the first time. Theoretical and experimental investigations on the mechanism and key parameters revealed that the proposed method achieved simultaneous purification and enrichment in one-step sample extraction with a superior limit of quantitation (0.15–1.5 μg kg−1), without further sample manipulation, such as fat removal or solvent exchange procedures prior to LC-MS. The method was validated taking into consideration EU guidelines and showed acceptable linearity (r ≥ 0.9991), accuracy with recoveries between 75 and 114% and precision with RSD≤9.7% for all of the analytes studied. It was successfully applied to the analysis of twenty samples sourced from the Mediterranean region in order to gain first insights into Alternaria toxins contaminations in olive oils. This technical approach is well suited for large-scale studies in a high-throughput and cost-effective quality assurance laboratory environments, and it has the potential to detect ultra-trace levels of toxins in complex samples, which may lead to the development of new and sustainable sample preparation procedures.

Soil bacteria are more sensitive than fungi in response to nitrogen and phosphorus enrichment.

Anthropogenic activities have dramatically increased nitrogen (N) and phosphorous (P) enrichments in terrestrial ecosystems. However, it is still unclear on how bacterial and fungal communities would respond to the simultaneously increased N and P enrichment. In this study, we used a field experiment to simulate N and P input, and examined the effects of N and P additions on the abundance, alpha-diversity, and community composition of soil bacteria and fungi in a riparian forest. Six nutrient-addition treatments, including low N (30 kg N ha–1 year–1), high N (150 kg N ha –1 year–1), low P (30 kg P2O5 ha–1 year–1), high P (150 kg P2O5 ha –1 year–1), low N+P, high N+P, and a control (CK) treatment were set up. We found that the N and P additions significantly affected bacterial abundance, community composition, but not the alpha diversity. Specifically, 16S, nirK, and nirS gene copy numbers were significantly reduced after N and P additions, which were correlated with decreases in soil pH and NO-3-N, respectively; Co-additions of N and P showed significantly antagonistic interactions on bacterial gene copies; Nutrient additions significantly increased the relative abundance of Proteobacteria while reduced the relative abundance of Chloroflexi. Mantel’s test showed that the alteration in bacterial composition was associated with the changes in soil pH and NO-3-N. The nutrient additions did not show significant effects on fungal gene copy numbers, alpha diversity, and community composition, which could be due to non-significant alterations in soil C/N and total P concentration. In conclusion, our results suggest that soil bacteria are more sensitive than fungi in response to N and P enrichment; the alterations in soil pH and NO-3-N explain the effects of N and P enrichment on bacterial communities, respectively; and the co-addition of N and P reduces the negative effects of these two nutrients addition in alone. These findings improve our understanding of microbial response to N and P addition, especially in the context of simultaneous enrichment of anthropogenic nutrient inputs.

Direct immersion dual-drop microextraction for simultaneous separation and enrichment of Cr(III) and Cr(IV) in food samples prior to graphite furnace atomic absorption spectrometry detection

Non-chromatographic speciation methods generally involve speciation conversion, which may cause sample contamination, analysis errors and tedious operations. In this work, a direct immersion dual-drop microextraction (DIDDME) was firstly developed for separation and preconcentration of Cr(III) and Cr(VI). In DIDDME, two organic drops on needle tips of microsyringes were concurrently immersed in a stirred sample solution. Each drop contains a chelating reagent for reacting with a specific species. Thus, Cr(III) and Cr(VI) were selectively extracted into different drops. This method afforded detection limits of 3.0 and 4.1 ng/L, quantification limitof 10 ng/L and 14 ng/L, linear range of 0.01–30 ng mL−1 and enrichment factors of 354-fold and 326-fold for Cr(III) and Cr(VI), respectively. Precisions like repeatability and reproducibility were assessed by calculating relative standard deviations, which were lower than 5.4 % and 6.9 %, respectively. This procedure was used successfully for quantification of Cr(III) and Cr(VI) in food samples.

Spread and driving factors of antibiotic resistance genes in soil-plant system in long-term manured greenhouse under lead (Pb) stress

Livestock manure is often used as fertilizer in greenhouses, resulting in simultaneous enrichment of heavy metals and antibiotic resistance genes (ARGs) in soils. The soil-plant system is a non-negligible way to spread ARGs; however, the effects of lead (Pb) on the spread of ARGs and their driving factors in the greenhouse soil-plant system remain unclear. In this present study, the occurrence of ARGs in greenhouse soils and their spread into plants under Pb stress were studied. Overall, Pb promoted the accumulation of ARGs in root endophytes at 10, 50, and 100 mg/kg as well as in soils at 10 and 200 mg/kg, but reduced the total relative abundance of ARGs in leaf endophytes. Particularly, Pb increased the mobile genetic elements (MGEs) relative abundance and endophytic bacterial community diversity in roots, consistent with the change in the total relative abundance of ARGs. Network analysis revealed that bacterial community and MGEs may jointly affect the migration of ARGs in the soil-plant system of greenhouses. Overall, this study extended our knowledge of how Pb can promote the transmission of ARGs to plant roots from greenhouse soils receiving long-term manure applications, which must be considered when assessing the risk of ARGs to public health.

Harmful cyanobacterial aerosolization dynamics in the airshed of a eutrophic estuary

In addition to obvious negative effects on water quality in eutrophic aquatic ecosystems, recent work suggests that cyanobacterial harmful algal blooms (CHABs) also impact air quality via emissions carrying cyanobacterial cells and cyanotoxins. However, the environmental controls on CHAB-derived aerosol and its potential public health impacts remain largely unknown. Accordingly, the aims of this study were to 1) investigate the occurrence of microcystins (MC) and putatively toxic cyanobacterial communities in particulate matter ≤ 2.5 μm in diameter (PM2.5), 2) elucidate environmental conditions promoting their aerosolization, and 3) identify associations between CHABs and PM2.5 concentrations in the airshed of the Chowan River-Albemarle Sound, an oligohaline, eutrophic estuary in eastern North Carolina, USA. In summer 2020, during peak CHAB season, continuous PM2.5 samples and interval water samples were collected at two distinctive sites for targeted analyses of cyanobacterial community composition and MC concentration. Supporting air and water quality measurements were made in parallel to contextualize findings and permit statistical analyses of environmental factors driving changes in CHAB-derived aerosol. MC concentrations were low throughout the study, but a CHAB dominated by Dolichospermum occurred from late June to early August. Several aquatic CHAB genera recovered from Chowan River surface water were identified in PM2.5 during multiple time points, including Anabaena, Aphanizomenon, Dolichospermum, Microcystis, and Pseudanabaena. Cyanobacterial enrichment in PM2.5 was indistinctive between subspecies, but at one site during the early bloom, we observed the simultaneous enrichment of several cyanobacterial genera in PM2.5. In association with the CHAB, the median PM2.5 mass concentration increased to 8.97 μg m−3 (IQR = 5.15), significantly above the non-bloom background of 5.35 μg m−3 (IQR = 3.70) (W = 1835, p < 0.001). Results underscore the need for highly resolved temporal measurements to conclusively investigate the role that CHABs play in regional air quality and respiratory health risk.

Simultaneous enrichment and sequential separation of O-linked glycopeptides and phosphopeptides with immobilized titanium (IV) ion affinity chromatography materials

Protein phosphorylation and O-linked glycosylation are two critical posttranslational modifications (PTMs) and they both target identical amino acid residues, generating “crosstalk”. Analysis of the crosstalk between these PTMs is crucial for deciphering their biological functions. Although several strategies have been established to enrich N-linked glycopeptides and phosphopeptides simultaneously, they are not appropriate for O-linked glycopeptides and phosphopeptides. In this study, we established a method for the simultaneous enrichment and sequential elution of O-linked glycopeptides and phosphopeptides into two fractions using commercially available immobilized titanium (IV) ion affinity chromatography (Ti4+-IMAC) materials. The established method exhibited high selectivity, repeatability, and recovery of the targeted peptides. Particularly, the overlap between the O-linked glycopeptide and phosphopeptide fractions was very low (∼3%). The application of this method to cell lysates of the colon cancer HT29 cell line resulted in a comparable number of enriched phosphopeptides as the coeluted method. However, the number of identified O-linked glycopeptides with our established method was 9.7-fold higher than that with the coelution method. Our study demonstrated that the established strategy was beneficial for the simultaneous analysis of O-linked glycopeptides and phosphopeptides, which might facilitate the study of the biological function of PTM crosstalk.

Speciation of inorganic vanadium by direct immersion dual-drop microextraction coupled with graphite furnace atomic absorption spectrometry detection

In this work, a new method based on direct immersion dual-drop microextraction (DIDDME) was proposed for simultaneous speciation and enrichment of V(IV) and V(V) by graphite furnace atomic absorption spectrometry. This strategy was initiated with the chelation of V(IV) and V(V) in sample solutions with 1-(2-Pyridylazo)-2-naphthol (PAN). In the following step, two organic solvent drops hold on needle tips of microsyringes were concurrently immersed in the stirred sample solution to selectively and simultaneously separate V(IV)-PAN and V(V)-PAN complexes under the same pH value. This procedure avoided the tedious and complicated pre-oxidation/pre-reduction and centrifugation/filtration operations, which may cause the risk of sample contamination and analysis errors. Main parameters affecting the separation, preconcentration of the target species were investigated. Under the optimized conditions, the detection limits of this method were 2.4 ng/L and 1.5 ng/L for V(IV) and V(V) with relative standard deviations of 6.1 and 5.3 %, respectively. An enrichment factor of 300-fold was achieved for V(IV) and V(V). This method was applied successfully for the determination of V(IV) and V(V) in water samples. In order to validate the proposed procedure, a certified reference material of water sample was analyzed, and the determined value was in good agreement with the certified value.

Molecularly imprinted polymers based on magnetic metal-organic frameworks for surface-assisted laser desorption/ionization time-of-flight mass spectrometry analysis and simultaneous luteolin enrichment

UiO-66(NH2), a metal-organic framework, exhibits excellent UV absorption and energy transfer performance and can be used as a substrate for surface-assisted laser desorption/ionization (SALDI) analysis of small molecules. Molecularly imprinted polymers (MIPs) exhibit outstanding selectivity toward certain targets. The complexes of UiO-66(NH2) and MIPs can be applied as both an adsorbent and substrate for SALDI-time-of-flight mass spectrometry (SALDI-TOF MS) analysis of small molecules. Herein, magnetic UiO-66(NH2)-molecularly imprinted polymers (MUMIPs) were prepared for the selective enrichment and detection of luteolin via SALDI-TOF MS. The amino group on UiO-66(NH2) were used as functional monomer to prepare MIPs that interact with luteolin via hydrogen bonding. The surface functional monomer can effectively control the coating thickness of the MIPs to avoid embedding template molecules and enhance adsorption performance. In addition, Fe3O4 particles were introduced for rapid magnetic separation. The physicochemical properties of the MUMIPs were characterized via scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, vibrating sample magnetometry, Brunauer-Emmett-Teller analysis, and X-ray photoelectron spectroscopy. Adsorption experiments and selectivity studies indicated that MUMIPs exhibited good adsorption capacity, fast adsorption rates, and excellent luteolin selectivity. MUMIPs are efficient substrates for the SALDI analysis of luteolin and its structural analogs. In addition, the MUMIPs-SALDI-TOF MS method successfully detected luteolin in rat plasma and urine after administration of oral Chrysanthemum morifolium Ramat extracts. This method possessed high sensitivity with a limit of detection of 0.5 ng/mL. The traditional precipitation method combined with high-performance liquid chromatography-mass spectrometry was also used to analyze luteolin in biological samples. Compared with the traditional method, the novel MUMIP-SALDI-TOF MS method can more effectively detect the target compounds in complex samples. Ultimately, the MUMIP-SALDI-TOF MS method was applied to detect luteolin and its metabolites in rat liver after oral luteolin treatment. Three luteolin metabolites (apigenin, chrysoeriol, and diosmetin) were analyzed using the newly developed MUMIP-SALDI-TOF MS method.