Surface property and in vitro toxicity effect of insoluble particles given by protein corona: Implication for PM cytotoxicity assessment.

In vitro toxicological assessment helps explore key fractions of particulate matter (PM) in association with the toxic mechanism. Previous studies mainly discussed the toxicity effects of the water-soluble and organic-soluble fractions of PM. However, the toxicity of insoluble fractions is relatively poorly understood, and the adsorption of proteins is rarely considered. In this work, the formation of protein corona on the surface of insoluble particles during incubation in a culture medium was investigated. It was found that highly abundant proteins in fetal bovine serum were the main components of the protein corona. The adsorbed proteins increased the dispersion stability of insoluble particles. Meanwhile, the leaching concentrations of some metal elements (e.g., Cu, Zn, and Pb) from PM increased in the presence of proteins. The toxicity effects and potential mechanisms of the PM insoluble particle-protein corona complex on macrophage cells RAW264.7 were discussed. The results revealed that the PM insoluble particle-protein corona complex could influence the phagosome pathway in RAW264.7 cells. Thus, it promoted the intracellular reactive oxygen species generation and induced a greater degree of cell differentiation, significantly altering cell morphology. Consequently, this work sheds new light on the combination of insoluble particles and protein corona in terms of PM cytotoxicity assessment.

Full-Spectrum Utilization of ZIF-67/Ag NPs/NaYF4 :Yb,Er Photocatalysts for Efficient Degradation of Sulfadiazine: Upconversion Mechanism and DFT Calculation.

In this work, novel ternary composite ZIF-67/Ag NPs/NaYF4 :Yb,Er is synthesized by solvothermal method. The photocatalytic activity of the composite is evaluated by sulfadiazine (SDZ) degradation under simulated sunlight. High elimination efficiency of the composite is 95.4% in 180 min with good reusability and stability. The active species (h+ , ·O2 - and ·OH) are identified. The attack sites and degradation process of SDZ are deeply investigated based on theoretical calculation and liquid chromatography-mass spectrometry analysis. The upconversion mechanism study shows that favorable photocatalytic effectiveness is attributed to the full utilization of sunlight through the energy transfer upconversion process and fluorescence resonance energy transfer. Additionally, the composite is endowed with outstanding light-absorbing qualities and effective photogenerated electron-hole pair separation thanks to the localized surface plasmon resonance effect of Ag nanoparticles. This work can motivate further design of novel photocatalysts with upconversion luminescence performance, which are applied to the removal of sulphonamide antibiotics in the environment.

Effect of ionic liquids as mobile phase additives on retention behaviors of G-quadruplexes in reversed-phase high performance liquid chromatography.

G-quadruplexes (G4s) play an important role in a variety of biological processes and have extensive application prospects. Due to the significance of G4s in physiology and biosensing, studies on G4s have attracted much attention, stimulating the development or improvement of methods for G4 structures and polymorphism analysis. In this work, ionic liquids (ILs) were involved as mobile phase additives in reversed-phase high performance liquid chromatography (RP-HPLC) to analyse G4s with various conformations for the first time. How ILs affected the retention behaviors of G4s was investigated comprehensively. It was found that the addition of ILs markedly enhanced G4 retention, along with obvious amelioration on chromatographic peak shapes and separation. The influence of pH of mobile phase and types of ILs were also included in order to acquire an in-depth understanding. It appeared that the effect of ILs on G4 retention behaviors was the result of a combination of various interactions between G4s with the hydrophobic stationary phase and with the IL-containing mobile phase, where ion pair mechanism and enhanced hydrophobic interaction dominated. The findings of this work revealed that ILs could effectively improve the separation of G4s in RP-HPLC, which was conducive to G4 structural analysis, especially for G4s polymorphism elucidation.

Identification of Characteristic Peptides of Casein in Cow Milk Based on MALDI-TOF MS for Direct Adulteration Detection of Goat Milk.

It is widely acknowledged that casein is an important allergenic protein in milk which may cause danger to customers. The identification and confirmation of caseins through mass spectrometry requires the selection of suitable characteristic peptides. In this study, by means of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), the three most representative specific peptides of caseins in cow milk were screened out with mass-to-charge ratios (m/z) of 830, 1195, and 1759, respectively. By comparing 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (CHCA) MALDI matrices, it was found that DHB was more suitable for peptide detection with the limits of detection (LODs) of 0.1 mg/L for α, ß-casein. Furthermore, on the basis of verifying the characteristic peptides of casein from cow milk, this protocol was applied to goat milk authentication. Cow milk addition in goat milk was investigated by using the screened specific peptides. The results showed that the adulteration could be identified when the proportion of cow milk was 1% or more. When applied to inspect adulteration in five brands of commercial goat milk, specific peptides of bovine casein were detected in four of them. The method has the advantages of strong reliability, high throughput, simple preprocessing, and fast speed, which can provide powerful help for prewarning dairy allergen.

Prediction of the n-Octanol/Water Partition Coefficients of Basic Compounds Using Multi-Parameter QSRR Models Based on IS-RPLC Retention Behavior in a Wide pH Range.

The n-octanol-water partition coefficient (logP) is an important physicochemical parameter which describes the behavior of organic compounds. In this work, the apparent n-octanol/water partition coefficients (logD) of basic compounds were determined using ion-suppression reversed-phase liquid chromatography (IS-RPLC) on a silica-based C18 column. The quantitative structure-retention relationship (QSRR) models between logD and logkw (logarithm of retention factor corresponding to 100% aqueous fraction of mobile phase) were established at pH 7.0-10.0. It was found that logD had a poor linear correlation with logkw at pH 7.0 and pH 8.0 when strongly ionized compounds were included in the model compounds. However, the linearity of the QSRR model was significantly improved, especially at pH 7.0, when molecular structure parameters such as electrostatic charge ne and hydrogen bonding parameters A and B were introduced. External validation experiments further confirmed that the multi-parameter models could accurately predict the logD value of basic compounds not only under strong alkaline conditions, but also under weak alkaline and even neutral conditions. The logD values of basic sample compounds were predicted based on the multi-parameter QSRR models. Compared with previous work, the findings of this study extended the pH range for the determination of the logD values of basic compounds, providing an optional mild pH for IS-RPLC experiments.

Magnetic Ti3C2 MXene Nanosheets Prepared for Enrichment of Phosphopeptides.

MXenes have received lots of attention since discovered and have been applied in various fields. In this work, Ti3C2-Fe3O4 composites with exposed non-modified Ti3C2 MXene nanosheets were designed and prepared by an in situ growth strategy and then applied in the enrichment of phosphopeptides. The two-dimensional composites could interact with the phosphopeptides through a metal oxide affinity chromatography mechanism provided by Ti-O and Fe-O bonds and a hydrophilic interaction chromatography mechanism by surface hydroxyl groups. This magnetic nanomaterial with a specific surface area of 66.1 m2·g-1 had high sensitivity to phosphopeptides (0.5 nmol·L-1) and high selectivity (1:1000 of the molar ratio of ß-casein to bovine serum albumin). Non-fat milk was adopted as a real sample to preliminarily examine the applicability of the Ti3C2-Fe3O4-based protocol. Subsequently, Qingkailing injection, a kind of traditional Chinese medicine injection, was introduced to further explore the suitability of the nanocomposites for phosphopeptide enrichment from more complex matrices and satisfactory results were obtained.

Efficient and stable organic solar cells enabled by multicomponent photoactive layer based on one-pot polymerization.

Degradation of the kinetically trapped bulk heterojunction film morphology in organic solar cells (OSCs) remains a grand challenge for their practical application. Herein, we demonstrate highly thermally stable OSCs using multicomponent photoactive layer synthesized via a facile one-pot polymerization, which show the advantages of low synthetic cost and simplified device fabrication. The OSCs based on multicomponent photoactive layer deliver a high power conversion efficiency of 11.8% and exhibit excellent device stability for over 1000 h (>80% of their initial efficiency retention), realizing a balance between device efficiency and operational lifetime for OSCs. In-depth opto-electrical and morphological properties characterizations revealed that the dominant PM6-b-L15 block polymers with backbone entanglement and the small fraction of PM6 and L15 polymers synergistically contribute to the frozen fine-tuned film morphology and maintain well-balanced charge transport under long-time operation. These findings pave the way towards the development of low-cost and long-term stable OSCs.

Visible light and iodate/iodide mediated degradation of bisphenol A by self-assembly 3D hierarchical BiOIO3/Bi5O7I Z-scheme heterojunction: Intermediates identification, radical mechanism and DFT calculation.

Broadening the light absorption and inhibiting carrier's recombination are vital to the improvement of photocatalytic performance. Herein, self-assembly 3D hierarchical microsphere BiOIO3/Bi5O7I Z-scheme heterojunction with carrier transfer channel was firstly fabricated by in-situ solvothermal method. The degradation efficiency for bisphenol A (BPA) reached 98.9 % within 60 min visible light irradiation. The enhanced photocatalytic activity was benefited from the Z-scheme system assisted by iodate/iodide (IO3-/I-) as carrier transfer channel that not only accelerated the interfacial charge separation, but also provided massive reactive centers for obtaining high redox capacity. The vulnerable sites and the degradation pathways of BPA were identified by density functional theory calculations and liquid chromatography-mass spectrometry analyses. The toxicity of BPA and its intermediates were predicted by ECOlogical Structure Activity Relationship (ECOSAR) and the results demonstrated that BPA was eventually mineralized to harmless products. The Z-scheme charge transfer mechanism was deeply elucidated based on the role of active species (·O2-, ·OH and h+), band structure and carrier separation efficiency. This study provides a promising strategy for the photoactivity enhancement of bismuth based heterojunction in environment purification.

Study on the Interaction of a Peptide Targeting Specific G-Quadruplex Structures Based on Chromatographic Retention Behavior.

G-quadruplexes (G4s) are of vital biological significance and G4-specific ligands with conformational selectivity show great application potential in disease treatment and biosensing. RHAU, a RNA helicase associated with AU-rich element, exerts biological functions through the mediation of G4s and has been identified to be a G4 binder. Here, we investigated the interactions between the RHAU peptide and G4s with different secondary structures using size exclusion chromatography (SEC) in association with circular dichroism (CD), ultraviolet-visible (UV-Vis) absorption, and native polyacrylamide gel electrophoresis (Native-PAGE). Spectral results demonstrated that the RHAU peptide did not break the main structure of G4s, making it more reliable for G4 structural analysis. The RHAU peptide was found to display a structural selectivity for a preferential binding to parallel G4s as reflected by the distinct chromatographic retention behaviors. In addition, the RHAU peptide exhibited different interactions with intermolecular parallel G4s and intramolecular parallel G4s, providing a novel recognition approach to G4 structures. The findings of this study enriched the insight into the binding of RHAU to G4s with various conformations. It is noteworthy that SEC technology can be easy and reliable for elucidating G4-peptide interactions, especially for a multiple G4 coexisting system, which supplied an alternative strategy to screen novel specific ligands for G4s.

Residue screening and analysis of enrofloxacin and its metabolites in real aquatic products based on ultrahigh-performance liquid chromatography coupled with high resolution mass spectrometry.

The abuse of enrofloxacin (ENR) in aquaculture and the lack of monitoring of other metabolites except ciprofloxacin (CIP) may lead to unknown harmful effects on human health. In this study, ENR metabolites were screened in real fish samples based on ultrahigh-performance liquid chromatography coupled with Q-Orbitrap mass spectrometry combined with Compound Discoverer software, and another metabolite deethylene-ENR besides CIP was detected and identified for the first time. Correspondingly, a method for the determination of ENR and CIP and the semi-quantitative analysis of deethylene-ENR in aquatic products was established. Method validation illustrated that excellent linearity and satisfactory recoveries of analytes were obtained. Limits of detection of ENR and CIP were both 0.1 µg kg-1, and their limits of quantification both 1 µg kg-1. CIP and deethylene-ENR were detected in 12 of 14 ENR-positive fish samples, so deethylene-ENR should be of concern as a possible risk candidate in aquatic products.

Determination of chlorpromazine and its metabolites in animal-derived foods using QuEChERS-based extraction, EMR-Lipid cleanup, and UHPLC-Q-Orbitrap MS analysis.

Chlorpromazine (CPZ) is abused in animal husbandry and can be extensively metabolized in humans and animals. However, the actual monitoring mainly focuses on the parent compound but lacks attention to its metabolites. A method was developed and validated firstly for identification and determination of CPZ and its four major metabolites in animal-derived foods using ultrahigh-performance liquid chromatography coupled with quadrupole-Orbitrap mass spectrometry in combination with QuEChERS preparation method. Satisfactory recoveries of analytes spiked in fish and pork samples ranged from 72 to 117 %, and limits of quantification were 2.0 and 1.0 µg kg-1 for fish and pork samples respectively. Moreover, through the hydrolysis experiments of CPZ, its hydrolysates, such as CPZ-sulfoxide, CPZ-N-oxide and CPZ-sulfoxide-N-oxide, were identified as potential risk compounds. The developed method has been successfully applied to the determination of CPZ and its metabolites in actual commercial samples, as well as to the screening of other CPZ-related risk compounds.

[Magnetic ion imprinting techniques for the separation and analysis of elemental speciation].

Metal and metalloid elements have various possible isotopic compositions and oxidation states and often form coordination or covalent compounds with inorganic and organic small molecules or biological macromolecules, resulting in complex elemental speciation. Different species of the same element often have different properties, which dictate their behavior. Thus, elemental speciation analysis is vital for comprehensively and accurately assessing an element's environmental and biological effects and the corresponding risks. Because elemental speciation determines the behavior of an element in different environmental and biological processes, the analysis of elemental species has, in recent years, been important in various subjects, including analytical chemistry, environmental chemistry, geochemistry, ecology, agronomy, and biomedicine. The complexity of environmental and biological sample matrices, as well as the multiformity, low levels, and lability of chemical forms pose severe challenges in elemental speciation analysis. Therefore, the highly selective identification and efficient separation of native species is necessary for conducting the identification, quantification, ecotoxicity evaluation, and physiological function study of elemental speciation. Sample pretreatment by solid-phase extraction is an effective solution to the aforementioned problems, but the existing methods do not meet the requirements of current research. The transition of the target species from pre-processing to the detection device includes both on- and off-line arrangements. Compared with the on-line approach, the off-line approach requires more manual participation, increasing the analysis workload. However, the off-line approach can improve the analysis efficiency through high-throughput pretreatment when large batches of samples are encountered, meaning the off-line approach is still an effective model. Ion imprinting technology has been developed based on existing molecular imprinting technology, with four main steps present in the synthesis of ion imprinted polymers. First, ion imprinting technology uses metal ions as templates. Then, these templates are combined with the functional monomers through coordination, electrostatic or hydrogen bonding. The functional monomers simultaneously surround and fix the templates, after which the cross-linkers and functional monomers polymerize to prepare ion-imprinted polymers with a specific structure and composition. Finally, the imprinted holes are created in the polymers by eluting the template ions. Therefore, the template molecules, functional monomers, and cross-linkers are three precursors necessary for synthesizing ion-imprinted polymers. These polymers can specifically bind to the imprinted metal ions with accuracy, sensitivity, and reliability. In recent years, they have been widely used in separating, enriching, analyzing, and detecting elemental species. During solid-phase extraction, the non-magnetic adsorbent materials dispersed in the sample solution need to be separated by centrifugation or filtration, which is time-consuming and laborious. Because an external magnetic field can be used for rapid magnetic solid-phase extraction, it has become a potential method for separating and enriching elemental species. This review systematically summarizes the latest progress in ion-imprinting technology, including its principle and the preparation methods of ion-imprinted polymers. The challenges faced by ion imprinting technology are analyzed in the context of the development of ion-imprinting magnetic solid-phase extraction in elemental speciation analysis. Finally, the direction of future development and the strategies of ion imprinting technology in elemental speciation analysis are proposed. It is important to exploit novel organic-inorganic hybrid polymerization-based multifunctional ion-imprinted magnetic nanocomposites for the magnetic solid-phase extraction and separation of elemental species. By establishing the pretreatment protocols with high recognition selectivity, strong separation ability, large adsorption capacity, and good speciation stability, we expect to achieve the research objectives of simultaneously separating and enriching the multiple-species of typical metal/metalloid elements in environmental and biological samples.

[Determination of three penicillin residues in milk by solid-phase extraction-ultra performance liquid chromatography-tandem mass spectrometry using a covalent triazine framework sorbent].

A method based on solid-phase extraction-ultra performance liquid chromatography-tandem mass spectrometry (SPE-UPLC-MS/MS) was established for the determination of gpenicillin, cloxacillin, ampicillin residues in milk. Using self-made covalent triazine frameworks (CTFs) as the solid-phase extraction sorbents, the main factors influencing the efficiency of the solid-phase extraction columns, such as the sorbent amount, eluent type, eluent volume, and flow rate, were optimized. The extraction and purification conditions for the samples were also investigated. The optimal extraction effect was achieved at a flow rate of 3 mL/min with 60 mg CTFs and 6 mL eluent solution (acetonitrile). Separation was carried out on a Waters ACQUITY UPLC BEH C18 column, and 0.1% formic acid aqueous solution-acetonitrile was used as the mobile phases for gradient elution. The filtrate was detected by ultra performance liquid chromatography-tandem mass spectrometry, identified by electrospray ionization (ESI) in the positive mode using multiple reaction monitoring, and quantified using external standards. The calibration curves of the three penicillins showed good linearity and the correlation coefficients of the linear regression equations for the three target analytes were all greater than 0.999. The limits of detection (LODs) and limits of quantification (LOQs) were 0.05-0.10 µg/kg and 0.1-0.4 µg/kg, respectively. The average recoveries of the three analytes were 84.9%-94.1%, and the relative standard deviations (RSDs, n=5) were 1.66%-3.27%. Moreover, the mechanism of interaction between the CTFs and the target analytes was analyzed. The results revealed the existence of π-π and hydrogen-bond interactions between the CTFs and analytes. The results further indicated that the CTFs could be successfully used for the enrichment and purification of penicillins in milk. The proposed method has the advantages of high precision, good reproducibility, high resolution, and short analysis time, and it is suitable for the qualitative and quantitative determination of trace targets in complex matrices.

A novel particulate matter sampling and cell exposure strategy based on agar membrane for cytotoxicity study.

Laboratories use different strategies to sample and extract atmospheric particulate matter (PM), some of which can be very complicated. Due to the absence of a standard protocol, it is difficult to compare the results of PM toxicity assessment across different laboratories. Here, we proposed a novel PM sampling and cell exposure strategy based on agar membrane. The agar membrane, prepared by a simple freeze-drying method, has a relatively flat surface and porous interior. We demonstrated that the agar membrane was a reliable substitute material for PM sampling. Then the PM on the agar membranes was directly extracted with the culture medium by vortex method, and the PM on the polytetrafluoroethylene (PTFE) filters was extracted with water by the traditional ultrasonic method for comparison. The extraction efficiency was evaluated and in vitro cytotoxicity assays were carried out to investigate the toxic effects of PM extracted with two strategies on macrophage cells. The results showed that the PM extracted from agar membranes induced higher cytotoxicity and more differentially expressed proteins. Overall, the novel PM sampling-cell exposure strategy based on the agar membrane is easy to operate, biocompatible and comparable, and has low disturbance, could be an alternative sampling and extraction method for PM toxicity assessment.

A combination approach using two functionalized magnetic nanoparticles for speciation analysis of inorganic arsenic.

Mercapto- and amino-functionalized magnetic nanoparticles, Fe3O4@SiO2@MPTMS (SMNPs-MPTMS) and Fe3O4@SiO2@APTES (SMNPs-APTES), have been applied as magnetic solid-phase extraction (MSPE) sorbents to directly extract arsenite (As(III)) and arsenate (As(V)) respectively, followed by inductively coupled plasma-mass spectrometry (ICP-MS) detection. Various MSPE parameters were optimized including dose of magnetic adsorbent, pH of sample solution, loading and elution conditions of analytes, adsorption capacity and reusability of SMNPs-MPTMS and SMNPs-APTES for As(III) and As(V) respectively. Under the optimized MSPE conditions, this combined scheme possesses excellent selectivity and strong anti-interference ability without any oxidation or reduction prior to capture of these two species. It is found that with a 25-fold enrichment factor, the limits of detection of As(III) and As(V) were 23.5 and 10.5 ng L-1, respectively. To verify the reliability of the proposed protocol, a certified reference material of environmental water was analyzed, and the results for inorganic arsenic species were in close agreement with the certified values. The applicability of the combination strategy for speciation analysis of inorganic arsenic was evaluated in spiked tap, river, lake and rain water samples. Good recoveries of 89%-96% and 90%-102% were achieved for As(III) and As(V), respectively, with the relative standard deviation ranges of 3.2%-8.0% and 2.5%-7.6%. Through the characterization of functionalized magnetic nanoparticles and the optimization of MSPE experiment, it is confirmed that the existence of mercapto and amino groups on SMNPs-MPTMS and SMNPs-APTES sorbents are responsible for the extraction of As(III) and As(V), respectively, via coordination and electrostatic interactions.

[Prediction of n-octanol/water partition coefficient of strongly ionized compounds by ion-pair reversed-phase liquid chromatography with silica-based stationary phase].

The n-octanol/water partition coefficient (log P) is an important parameter to characterize the overall hydrophobicity of organic compounds. Reversed-phase liquid chromatography (RPLC) has been recommended as an effective method for the indirect determination of log P by the Organization for Economic Cooperation and Development (OECD). Using RPLC, most studies focus on the determination of log P or the apparent n-octanol/water partition coefficient (log D) of neutral compounds and weakly ionized compounds. However, the experimental log P or log D values of strongly ionized compounds have rarely been reported. In our previous work, the experimental log D of strongly ionized compounds could be determined well by ion-pair reversed-phase liquid chromatography (IP-RPLC) on an octadecyl-poly(vinyl alcohol) column using the log D-log kw-IP model established by different types of model compounds. However, the universality of this strategy for different chromatographic columns has yet to be verified. In this study, the retention behavior of neutral compounds, phenolic acids, carboxylic acids, sulfonic acids, and some amphoteric compounds was systematically investigated on a silica-based C18 column (150 mm×4.6 mm, 5 µm) via ion-suppressed RPLC (IS-RPLC) and IP-RPLC, respectively. In the IS-RPLC mode, methanol and 20 mmol/L ammonium dihydrogen phosphate buffer (pH 7.0) were used as the mobile phase to perform isocratic elution at different methanol ratios. The log kw values of the test compounds were obtained using the linear solvent strength (LSS) model. Neutral compounds, weakly ionized phenolic acids and benzene carboxylic acids were then used as model compounds to establish the log D-log kw-IS model. The quantitative structure-retention relationship (QSRR) model, including structure-related descriptors like the charge (ne) and Abraham solvation parameters (A and B), exhibited much better correlation than the unary linear regression model between log D and log kw-IS. The log D7.0 (log D under pH 7.0) values of 19 ionized compounds were then determined by the model; the determined compounds were used as model compounds and validation compounds in IP-RPLC. In the IP-RPLC mode, besides methanol and ammonium dihydrogen phosphate buffer, the mobile phase also contained tetrabutylammonium bromide, as an ion-pair reagent. The retention behaviors of all tested compounds conformed well with the LSS model even under IP-RPLC, with a log k-φ linear correlation coefficient (R 2) greater than 0.99. The log D-log kw-IP model was then established using 62 compounds as a mixed model set, including neutral, weakly ionized, and strongly ionized compounds. Similarly, by introducing ne, A, and B, the log D-log kw-IP model showed good linearity, with R 2 greater than 0.94. Comparing the log D-log kw-IP model established on the silica-based C18 column in this work with that established on a poly(vinyl alcohol)-based C18 column in our previous work, ne, A, and B contributed more to the model in this work, indicating there was a greater secondary effect on the silica-based column. To confirm the reliability of the log D-log kw-IP model, three different types of acidic compounds were used as validation compounds. The predicted log D of the three ionic compounds was very similar to that determined by the shake-flask method (SFM)/slow stirring method (SSM) or IS-RPLC method in this work, confirming the reliability of the model. Based on the above results, the log D7.0 values of eight strongly ionized compounds were predicted by IP-RPLC. The findings suggested that IP-RPLC is a promising method to predict the experimental log D of strongly ionized compounds, and that the conventional silica-based C18 column offers more flexible options in log D determination.

[Effects of buffer salt types and non-counter ions of ion-pair reagents on the retention behavior of strongly ionized acid compounds in ion-pair reversed-phase liquid chromatography].

Ion-pair reversed-phase liquid chromatography (IP-RPLC) enhances separation by adding ion-pair reagents to the mobile phase, thereby improving the retention of oppositely charged solutes. IP-RPLC is primarily used for the separation and analysis of strongly ionized compounds. In IP-RPLC, researchers often focus more on the influence of the counter-ion type and concentration, buffer salt concentration and pH, and column temperature, on the retention behavior of solutes. However, the effects of the buffer salt type and non-counter ions in ion-pair reagents on the retention behavior of solutes have rarely been investigated. Accordingly, in this work, the effects of buffer salt types and non-counter ions on the retention behavior of strongly ionized compounds were investigated by IP-RPLC using 14 sulfonic acid compounds as model compounds. Experiments were performed using a silica-based C18 column with methanol as the organic modifier. In the first type of experiment, tetrabutylammonium bromide was kept unchanged as the ion-pair reagent in the mobile phase, and ammonium dihydrogen phosphate, ammonium chloride, and ammonium acetate were used as buffer salts, respectively. The retention factor (k) was obtained at different methanol ratios, and linear solvent strength (LSS) models were established to determine the log kw (logarithm of retention factors of solutes when 100% aqueous phases were used as the mobile phase) and S (intercept of the LSS model) values of each solute. All solutes exhibited the highest log kw with the ammonium chloride buffer system; most compounds also exhibited the highest S values with this system, except for 1,5-naphthalenedisulfonic acid, 4-methylbenzenesulfonic acid, 5-amino-2-nanphthalenesulfonic acid, and 4-hydroxybenzenesulfonic acid. However, the chromatographic hydrophobic indices (CHIs, log kw/S) of the solutes with different buffer salts were approximately equal. In the second type of experiment, ammonium dihydrogen phosphate was kept unchanged as the buffer salt in the mobile phase, and tetrabutylammonium bromide, tetrabutylammonium dihydrogen phosphate, tetrabutylammonium hydrogen sulfate, tetrabutylammonium nitrate, and tetrabutylammonium acetate were used as ion-pair reagents, respectively. Almost all solutes exhibited the highest S with the tetrabutylammonium acetate system, indicating that weakly ionized anions (such as acetate ions) in ion-pair reagents will improve the S values of sulfonic acid compounds. Interestingly, the CHIs of the solutes were almost the same for solutes with different non-counter ions. These results suggest that both, the buffer salt types and non-counter ions, influence the log kw and S values of sulfonic acid compounds. Comparison of the retention behavior of solutes with different mobile phases suggested ion-pair mechanisms as well as dynamic ion-exchange mechanisms plays role in the IP-RPLC retention of sulfonic acid compounds. In addition, with all the experimental mobile phases, the apparent n-octanol/water partition coefficient (log D) presented a good linear correlation with log kw, S, and CHI, respectively, by the introduction of structure-related descriptors such as charge (ne), Abraham solvation parameters (A and B), and the polar surface area (PSA). Considering the differences in the log kw and S values obtained with different buffer salts and non-counter ions, the CHIs were relatively stable; therefore, the CHI is more suitable for establishing a quantitative structure-retention relationship (QSRR) model in IP-RPLC, compared to log kw and S.

Preparation of a novel amino functionalized ion-imprinted hybrid monolithic column for the selective extraction of trace copper followed by ICP-MS detection.

In this work, a novel amino functionalized Cu(II) ion-imprinted organic-inorganic hybrid monolithic column (Cu(II)-IIHMC) was prepared via one-pot co-condensation and the combination of sol-gel and ion-imprinting techniques in a fused capillary. The Cu(II)-IIHMC was used as solid phase microextraction (SPME) matrix followed by inductively coupled plasma-mass spectrometry (ICP-MS) for the analysis of trace Cu(II). The prepared Cu(II)-IIHMC has good mechanical strength, stable imprinting sites and homogeneous structure of network skeleton with large flow-through pores by optimizing the synthesis process. Under the optimized conditions, the Cu(II)-IIHMC can selectively adsorb Cu(II) with the adsorption capacity of 3.13 mg g-1. With enrichment factor of 10-fold, the calibration curve was established in the range of 0.05-50 µg L-1 with r2 of 0.9992 and the detection limit was 0.008 µg L-1 for Cu(II). Compared with the non-imprinted hybrid monolithic column (Cu(II)-NIHMC), the Cu(II)-IIHMC possesses better selectivity, anti-interference ability and adsorption capacity. The Cu(II)-IIHMC can specifically capture the target ion in the presence of competitive ions, with the selectivity coefficients exceeding 39.4. The protocol was validated by analyzing Certified Reference Materials of standard sediment, soil and iron ore, and the results were in good agreement with certified values. Moreover, the proposed in-tube SPME procedure can not only preconcentrate trace Cu(II), but also effectively reduce the matrix effect and powerfully eliminate the interference from the main metals in real samples. Therefore, the developed SPME-ICP-MS method with facile preparation, specific selectivity, high sensitivity and efficient analysis, was applied in the determination of trace Cu(II) in environmental and mineral samples with the recoveries of 89.8-111.8% in all spiked samples.

Tetrasulfonate calix[4]arene modified large pore mesoporous silica microspheres: Synthesis, characterization, and application in protein separation.

Effective protein adsorption by solid matrices from complex biological samples has attracted attention for broad application in biomedical field. Immobilization of calixarenes to solid supports is an essential process for their application in protein separation and purification. Silica is the most widely used support material in calixarene immobilization. With high concentration of polymer microspheres as templates, the large pore mesoporous silica microspheres with controllable, uniform size and structure were successfully synthesized and the resulting large pore mesoporous silica microspheres were modified with water-soluble tetrasulfonate calix[4]arene of unique hollow cavity-shaped structure. The tetrasulfonate calix[4]arene modified large pore mesoporous silica microspheres (SCLX4@LPMS) were characterized by diverse analytical techniques and their protein adsorption performance were also investigated. The obtained SCLX4@LPMS gave rise to an adsorption efficiency of >90% for cytochrome c and lysozyme within a wide pH range of 3.0-10.0 and possessed remarkably high adsorption capacity of cytochrome c (363.64 mg g-1) and lysozyme (166.11 mg g-1). The retained cytochrome c and lysozyme can be readily eluted by using phosphate buffer solution containing NaCl as a stripping reagent with the recoveries of 81% and 86% after 5 times enrichment, respectively. The SCLX4@LPMS microspheres have been applied for the selective adsorption of proteins in real samples and had the application potential in protein adsorption, drug delivery, biosensors, and other biomedical fields.

Universal gold nanoparticle modified hybrid monolithic substrate developed for facile in-column post-functionalization.

Organic-inorganic hybrid monolithic columns, due to the comprehensive advantages, have been applied as promising solid-phase separation matrices for pretreatment of complex samples in biomedical and environmental analyses, however, a tremendous time and efforts are cost to optimize the preparation methods of hybrid monolithic columns with different functional groups for various target analytes. Herein, we proposed a strategy to develop basic hybrid monolithic column materials for flexible and facile post-functionalization. Three kinds of single-functionalized (amine, thiol, and carboxyl) and two kinds of bi-functionalized (amine and thiol, and amine and carboxyl) hybrid monolithic columns were immobilized with gold nanoparticles (GNPs) as intermediary bridge to construct the universal substrates. The GNPs adsorption capacities of the five hybrid monoliths were compared through qualitative characterization and quantitative analysis. Thioglycolic acid (TGA) and an aptamer against human α-thrombin were respectively used for further functionalizing the substrates to select the most suitable hybrid monolith for optional post-functionalization. It was reported for the first time that the coverage density of TGA on functionalized monolithic column modified by GNPs was 168.41 nmol µL-1. Notably, the coverage density (2205.8 pmol µL-1) of the aptamer decorated on the hybrid monolithic column was significantly higher than most other similar materials in published works. After that, the aptamer functionalized hybrid monolithic column screened out was applied for the solid-phase microextraction of thrombin, which possessed excellent adsorption selectivity in interference experiment. Consequently, the developed GNPs modified amine- and thiol-bi-functionalized hybrid monolithic column is an attractive universal substrate to realize easy and efficient post-modification of separation materials for other target analytes in complex samples avoiding a lot of time and labor consumption in the optimization of process preparation.