Retention of Large Biological Molecules by Size-Exclusion Chromatography

Size-exclusion chromatography has been developed for the separation of large biological molecules including proteins, polymers, peptides, nucleic acids, and polysaccharide according to their molecular size. This study determined the retention factors for dextran (5, 25, 50, 270, 670, and 1100?kDa) and polysaccharides, such as fucoidan, alginic acid, and laminarin, in the size-exclusion chromatography stationary phase. In addition, the molecular weights and retention factor of three polysaccharides were calculated from the dextran standard curve. The largest retention factor was 4.26 using the size-exclusion chromatography columns (5?kDa dextran). The molecular weights of fucoidan, alginic acid, and laminarin were determined to be 250, 200, and 5 to 64?kDa, respectively.     

Application of Ionic Liquid Modified Silica for Solid-Phase Extraction of Polysaccharides from Laminaria japonica

Silica-confined ionic liquids were synthesized for solid-phase extraction of polysaccharides, which was determined by high-performance liquid chromatography coupled with RI detection. The sorbent with amino-imidazolium groups was found to be the optimal material by a comparison of the adsorption capacity of fucoidan and laminarin onto different synthetic sorbents. The proper elution solvents for both laminarin and fucoidan were decided from practical tests. The sorbent performed stably and selectively, demonstrating potential applications in the separation of hydrophilic biomacromolecules, such as polysaccharides.     

Magnetic molecularly imprinted polymers for recognition and enrichment of polysaccharides from seaweed

New magnetic molecularly imprinted polymers with two templates were fabricated for the recognition of polysaccharides (fucoidan and alginic acid) from seaweed by magnetic solid‐phase extraction, and the materials were modified by seven types of deep eutectic solvents. It was found that the deep eutectic solvents magnetic molecularly imprinted polymers showed stronger recognition and higher recoveries for fucoidan and alginic acid than magnetic molecularly imprinted polymers, and the deep eutectic solvents‐4‐magnetic molecularly imprinted polymers had the best effects. The practical recovery of the two polysaccharides (fucoidan and alginic acid) purified with deep eutectic solvents‐4‐magnetic molecular imprinted polymers in seaweed under the optimal conditions were 89.87, and 92.0%, respectively, and the actual amounts extracted were 20.6 and 18.7 μg/g, respectively. To sum up, the developed method proved to be a novel and promising method for the recognition of complex polysaccharide samples from seaweed.     

SPE of Tanshinones from Salvia miltiorrhiza Bunge by using Imprinted Functionalized Ionic Liquid-Modified Silica

Ionic liquid-modified silica, with functional groups based on imidazole as the cation, was obtained. A molecular imprinting technique was introduced to form the order of functional groups. The selectivity of the obtained ionic liquid-modified silica was successfully used as a special imprinted sorbent in the solid-phase extraction to isolate cryptotanshinone, tanshinone I and tanshinone IIA from Salvia miltiorrhiza Bunge. Several washing and elution solvents with different polarities were evaluated. The ionic liquid-modified silica as the sorbent exhibited a higher selectivity than blank ionic liquid-modified silica, traditional silica and C₁₈ cartridges. A quantitative analysis was conducted by liquid chromatography with a C₁₈ column and methanol/water (75:25, v/v, containing 0.5% acetic acid) as the mobile phase. A good linearity was obtained from 0.5 × 10^?4 to 0.1 mg mL^?1 (r ²  > 0.99) with relative standard deviations that were less than 4.6%.     

Investigation of π–π and ion–dipole interactions on 1-allyl-3-butylimidazolium ionic liquid-modified silica stationary phase in reversed-phase liquid chromatography

1-Allyl-3-butylimidazolium bromide ionic liquid [AyBIm]Br was prepared and used for the modification of mercaptopropyl-functionalized silica through surface radical chain-transfer addition. The obtained ionic liquid-modified silica (SiImBr) was characterized by elemental analysis, infrared spectroscopy, NMR spectroscopy, and thermogravimetric analysis. The selective retention behaviours of polycyclic aromatic hydrocarbons (PAHs) including some positional isomers were investigated using SiImBr as a stationary phase in reversed-phase liquid chromatography. The results showed that SiImBr presented multiple interactions including hydrophobic, π–π, and ion–dipole interactions during the separation of PAHs and dipolar compounds. However, it is proposed that π–π and ion–dipole interactions play important roles in the separation of PAHs and dipolar compounds. These results indicate that the ionic liquid-modified silica stationary phase is promising for future applications. A commercially available monomeric octadecylated silica (ODS) column and a custom-made poly(styrene)-grafted silica (Sil-St_n) column were used as references.     

Solid-Phase Colorimetric Method for the Quantification of Fucoidan

We described the simple, selective, and rapid method for determination of fucoidans using methylene blue staining of sulfated polysaccharides, immobilized into filter paper and consequent optic density (at A ₆₆₃?nm) measurement of the eluted dye from filter paper. This solid-phase method allows selective determination of 1?C20???g fucoidan in presence of potentially interfering compounds (alginic acid, DNA, salts, proteins, and detergents). Further, we demonstrated the alternative way of using image processing software for fucoidan quantification without extraction of methylene blue dye from stained spots of fucoidan?Cdye complex.     

Solid-Phase Extraction of Caffeine and Theophylline from Green Tea by a New Ionic Liquid-Modified Functional Polymer Sorbent

The new ionic liquid-modified polymer sorbent was developed by surface chemical modification of the synthesized polymer particles using ionic liquids. The obtained ionic liquid-modified polymer was successfully used as a special sorbent in a solid-phase extraction (SPE) process to isolate caffeine and theophylline from green tea. A comparison of different SPE cartridges using the blank polymer, C₁₈, and ionic liquid-modified polymer revealed that the highest recovery was obtained using ionic liquid-modified polymer sorbent. Quantitative analysis was carried out by using a C₁₈ column (5 µm, 150 × 4.6 mm) as an analytical column. Good linearity was obtained from 5 × 10^?4 to 0.5 mg/mL (r²>0.999) for the two analytes with relative standard deviations <4.5%.     

Composition,structural characteristics,and antitumor properties of polysaccharides from the brown algae <Emphasis Type="Italic">Dictyopteris polypodioides</Emphasis> and <Emphasis Type="Italic">Sargassum</Emphasis> sp.

The polysaccharide compositions of the brown algae Dictyopteris polypodioides and Sargassum sp. from the Mediterranean Sea were determined. The principal polysaccharide of the studied algae (about 12% of the dry alga weight) was alginic acid. The content of water-soluble polysaccharides was low. The amount of fucoidan was less than 1% of the dry alga weight; of neutral polysaccharides, less than 0.25%. The monosaccharide compositions of fucoidans and neutral polysaccharides were investigated. Experiments on soft agar-agar models showed that fucoidans from D. polypodioides and Sargassum sp. exhibited antitumor activity against RPMI-7951 human melanoma cells.     

Seasonal variations of the composition,structural features,and antitumor properties of polysaccharides from <Emphasis Type="Italic">Padina pavonica</Emphasis> (Lebanon) as a function of composition

The variation of the polysaccharide composition of the brown alga Padina pavonica from the Mediterranean Sea was studied as a function of the collection season (April–July). It was shown that the principal polysaccharide (8.0-13.3% of dry alga weight) was alginic acid. Its content did not undergo significant changes from April to July. The content of water-soluble polysaccharides (laminarans and fucoidans) was low (<0.3% of dry alga weight). Water-soluble polysaccharides of the studied alga were practically pure fucoidan. The amount of laminarans was insignificant (<0.01% of dry alga weight). The content of fucoidans increased in alga samples from May through July. It was shown that P. pavonica is a promising source of alginic acids, which have a high capacity for gelation, and fucoidans, which exhibit antitumor action against RPMI-7951 human melanoma cells.     

Magnetic graphene oxide modified by imidazole‐based ionic liquids for the magnetic‐based solid‐phase extraction of polysaccharides from brown alga

Magnetic graphene oxide was modified by four imidazole‐based ionic liquids to synthesize materials for the extraction of polysaccharides by magnetic solid‐phase extraction. Fucoidan and laminarin were chosen as the representative polysaccharides owing to their excellent pharmaceutical value and availability. Fourier transform infrared spectroscopy, field‐emission scanning electron microscopy, and thermogravimetric analysis were applied to characterize the synthesized materials. Single‐factor experiments showed that the extraction efficiency of polysaccharides was affected by the amount of ionic liquids for modification, solid–liquid ratio of brown alga and ethanol, the stirring time of brown alga and ionic liquid‐modified magnetic graphene oxide materials, and amount of 1‐(3‐aminopropyl)imidazole chloride modified magnetic graphene oxide materials added to the brown alga sample solution. The results indicated that 1‐(3‐aminopropyl)imidazole chloride modified magnetic graphene oxide possessed better extraction ability than graphene oxide, magnetic graphene oxide, and other three ionic‐liquid‐modified magnetic graphene oxide materials. The highest extraction recoveries of fucoidan and laminarin extracted by 1‐(3‐aminopropyl)imidazole chloride modified magnetic graphene oxide were 93.3 and 87.2%, respectively. In addition, solid materials could be separated and reused easily owing to their magnetic properties.     

Separation analysis of macrolide antibiotics with good performance on a positively charged C18HCE column

The separation of basic macrolide antibiotics suffers from peak tailing and poor efficiency on traditional silica‐based reversed‐phase liquid chromatography columns. In this work, a C18HCE column with positively charged surface was applied to the separation of macrolides. Compared with an Acquity BEH C18 column, the C18HCE column exhibited superior performance in the aspect of peak shape and separation efficiency. The screening of mobile phase additives including formic acid, acetic acid and ammonium formate indicated that formic acid was preferable for providing symmetrical peak shapes. Moreover, the influence of formic acid content was investigated. Analysis speed and mass spectrometry compatibility were also taken into account when optimizing the separation conditions for liquid chromatography coupled with tandem mass spectrometry. The developed method was successfully utilized for the determination of macrolide residues in a honey sample. Azithromycin was chosen as the internal standard for the quantitation of spiramycin and tilmicosin, while roxithromycin was used for erythromycin, tylosin, clarithromycin, josamycin and acetylisovaleryltylosin. Good correlation coefficients (r² > 0.9938) for all macrolides were obtained. The intra‐day and inter‐day recoveries were 73.7–134.7% and 80.7–119.7% with relative standard deviations of 2.5–8.0% and 3.9–16.1%, respectively. Outstanding sensitivity with limits of quantitation (S/N ≥ 10) of 0.02–1 μg/kg and limits of detection (S/N ≥ 3) of 0.01–0.5 μg/kg were achieved.     

Determination of Free and Total Underivatized Amino Acids Including L-Canavanine in Bitter Vetch Seeds Using Hydrophilic Interaction Liquid Chromatography

A new hydrophilic interaction liquid chromatography method coupled with diode-array detector was developed for the determination of 17 underivatized amino acids including L-canavanine in bitter vetch [Vicia ervilia (L.) Willd.] seeds. Amino acids were extracted as free as well as total extracts after acid hydrolysis, followed by chromatographic separation on a Zorbax Rx-SIL column with a mobile phase of acetonitrile/potassium phosphate buffer (12.5?mM; pH 3.0) using gradient elution and detection at 190?nm. The method is characterized by a wide linear range (0.01–200?µg/mL, r?>?0.9987), sufficient accuracy (relative error 86.3–109.1%), and suitable precision for the results (relative standard deviation <4.9% in the case of intra-day and <9.8% in the case of inter-day precision). The limits of detection and quantification for free amino acids ranged from 0.01 to 0.24?mg/g and 0.03 to 0.72?mg/g, respectively, whereas the total amino acids ranged from 0.02 to 0.47?mg/g and 0.07 to 1.43?mg/g, respectively. The mean recoveries of free and total amino acids in spiked samples exceeded 70.3% for most amino acids. The mean total content of free and total amino acids in bitter vetch seeds was 1.71 and 14.88?g/100?g seed, whereas the corresponding values for canavanine were 0.07 and 0.19?g/100?g seed, respectively.     

Sorption of Anionic Polysaccharides and Bovine Serum Albumin on a Macroporous Glass

Concentration and time dependences of the sorption of alginic acid and -carrageenan on an MPS-1000 macroporous glass were studied. The character of pH effect on the sorption of these polysaccharides was established. For a number of sorbents prepared by the preliminary adsorption of polysaccharides on an MPS-1000 glass, the dependence of the sorption of bovine serum albumin (BSA) on the surface content of alginic acid and -carrageenan was studied. The model of adsorption in the silica–polysaccharide–protein system accounting for the interaction between polysaccharide ionic groups and active sites at the sorbent surface and protein molecules was proposed. Acid-base properties of silica modified with polysaccharides were investigated by the potentiometric titration, and the results supporting the validity of the proposed model were obtained.     

Determination of Homologue Imidazolium Ionic Liquid Cations by Ion Chromatography Using a Carboxyl Acid Cation-Exchange Column with Direct Conductivity Detection

An investigation into the determination of four imidazolium ionic liquid cations by ion chromatography using a carboxyl acid cation exchange column and direct conductivity detection was carried out. This research has developed a simple, selective, and accurate ion chromatographic method for separation of imidazolium ionic liquid cations. Detection limits (S/N = 3) for the cations were 3.2–24.3 mg/L. Relative standard deviations (RSD, n = 5) for peak areas were less than 1.6%. The method has been successfully applied to the determination of two ionic liquids synthesized by organic chemistry lab.     

新型吡咯烷键合反相高效液相色谱固定相的制备与研究（英文）

正A new ionic liquid-based high-performance liquid chromatography stationary phase is reported.A derivative of N-methyl pyrrolidinium tetrafluoroborate was covalently immobilized on the surface of silica particles to prepare silica-based N-methyl pyrrolidinium tetrafluoroborate(SilprMP BF4)stationary phase.The obtained ionic liquid-modified silica was evaluated and confirmed by elemental analysis,infrared spectroscopy,and thermogravimetric analysis.A column was packed with the modified particles.The retention behavior of aromatic compounds,alkyl benzenes,and acidic and basic compounds on the SilprMP BF4 stationary phase was studied under reversed-phase liquid chromatography conditions.The effect of the eluent pH on the separation of the acidic and basic compounds was also studied.The new stationary phase involves multiple retention mechanisms,such as electrostatic,hydrophobic,ion-dipole,and anion-exchange interactions,which might lead to multipurpose separation media.     

Molecularly Imprinted Polymers Modified by Deep Eutectic Solvents and Ionic Liquids with Two Templates for the Simultaneous Solid-Phase Extraction of Fucoidan and Laminarin from Marine Kelp

Molecularly imprinted polymers modified by deep eutectic solvents and ionic liquids (ILs) were prepared as packing materials for the solid-phase extraction (SPE) of fucoidan and laminarin. The prepared materials were characterized by field emission scanning electron microscopy and Fourier transform infrared spectroscopy. The polymers modified by the deep eutectic solvent prepared by choline chloride and urea had the best extraction efficiencies for fucoidan and laminarin (95.5% and 87.6%, respectively) from marine kelp. The relative standard deviations for intraday and interday determination were less than 4.23%. The molecularly imprinted polymers modified by deep eutectic solvents and ILs showed outstanding applications for SPE and may offer novel sample pretreatment for other analytes.     

Quinolinium ionic liquid-modified silica as a novel stationary phase for high-performance liquid chromatography

A novel stationary phase based on quinolinium ionic liquid-modified silica was prepared and evaluated for high-performance liquid chromatography. The stationary phase was investigated via normal-phase (NP), reversed-phase (RP), and anion-exchange (AE) chromatographic modes, respectively. Polycyclic aromatic hydrocarbons, phthalates, parabens, phenols, anilines, and inorganic anions were used as model analytes in chromatographic separation. Using the newly established column, organic compounds were separated successfully by both NP and RP modes, and inorganic anions were also separated completely by AE mode. The obtained results indicated that the stationary phase could be applied in different chromatographic modes, with multiple-interaction mechanism including van der Waals forces (dipole–dipole, dipole–induced dipole interactions), hydrophobic, π–π stacking, electrostatic forces, hydrogen bonding, anion-exchange interactions, and so on. The column packed with the stationary phase was applied to analyze phthalates and parabens in hexane extracts of plastics. Tap water and bottled water were also analyzed by the column, and nitrate was detected as 20.1 and 13.8 mg L^?1, respectively. The results illustrated that the stationary phase was potential in practical applications.

Preparation and evaluation of o‐phenanthroline immobilized on a hybrid silica monolith modified with ionic liquids for reversed‐phase pressurized capillary electrochromatography

A novel o‐phenanthroline‐immobilized ionic‐liquid‐modified hybrid monolith for capillary electrochromatography was synthesized based on chloropropyl‐silica, which was prepared by the in situ polymerization of tetramethoxysilane and 3‐chloropropyltrimethoxysilane via a sol–gel process. The morphology of the hybrid monolith was characterized by scanning electron microscopy, and relatively stable anodic electroosmotic flow was observed under a broad pH ranged from pH 3.0 to 9.0. The separation mechanism was investigated by separating four neutral molecules (toluene, dimethylformamide, formamide, and thiourea). The obtained hybrid monolith possessed an obviously reversed‐phase retention mechanism, but when the acetonitrile content in the mobile phase was >90% v/v, a weak hydrophilic mechanism was observed on the resultant o‐phenanthroline‐modified chloropropyl‐silica hybrid monolith. The reproducibility of the column was also investigated by measuring relative standard deviations of the migration time for four neutral molecules. Relative standard deviations of run to run (n = 3), day to day (n = 3), and column to column (n = 3) were in the range of 0.4–0.7, 0.9–2.1, and 1.4–3.3%, respectively. Basic separations of various polar analytes including phenols and aromatic amines were successfully achieved.     

Rapid determination of nosiheptide in feed based on dispersive SPE coupled with HPLC

A novel, simple, and reliable method based on high‐performance liquid chromatography coupled with fluorescence detection has been developed for the determination of nosiheptide in feed. The feed samples were extracted with acetonitrile 0.1% formic acid aqueous solution and then purified via a dispersive solid‐phase extraction procedure using silica gel powder as the sorbent. Using a mixture of acetonitrile and 5 mM ammonium acetate solution (containing 0.1% formic acid) as the mobile phase, good separation and peak shape were obtained for nosiheptide on a Poroshell C₈ column (250 × 4.6 mm id, 4 μm) via the isocratic elution program. The resulting calibration curve shows high levels of linearity (r² > 0.999) for nosiheptide concentrations of 50–1000 μg/L. At three spiked levels, i.e., 0.500, 2.50 and 5.00 mg/kg, the intra‐ and interday recoveries of nosiheptide in five types of feed ranged from 78.5–96.8 and 84.9–94.2%, respectively. The intra‐ and interday relative standard deviations were less than 10.8%. The limits of quantification for nosiheptide in complete feed and premixes were measured as 50 and 100 μg/kg, respectively. Compared with other common adsorbents, silica gel presents stronger recovery and purification results for feed samples during the dispersive solid‐phase extraction process.     

Rapid analysis of 14 ultraviolet absorbents in plastic food contact materials by supercritical fluid chromatography on Sub-2-micron particles

Abstract

A rapid and reliable method based on supercritical fluid chromatography (SFC) technology was established for the analysis of 14 ultraviolet (UV) absorbents in plastic food contact materials. The separation was optimized by employing different chromatographic conditions including stationary phases, organic modifiers, column temperatures and back pressures to achieve appropriate selectivity and resolution. The 14 UV absorbents were analyzed within 4.5?min on the sub-2-micron particles column (ACQUTY UPC² HSS C18?SB) via gradient elution with methanol as the organic modifier. The calibrations were carried out in the concentration range of 0.1–50.0?mg/L (except for UV-329 and UV-320 were 0.2–50.0?mg/L, UV-360 was 0.3–50.0?mg/L), and excellent linearity was observed with correlation coefficients (R²) greater than 0.99. The limits of quantification (LOQ) were in the range of 0.10–0.30?µg/g. The recoveries for accuracy were ranged from 90.4 to 114.1%, and the relative standard deviation (RSD) for repeatability was between 0.67 and 7.23%, respectively. The established method was successfully applied for the analysis of UV absorbents in five plastic food contact materials samples. The SFC method developed in this study can provide an alternative route for routine analysis of UV absorbents in the future.