High-performance Chromatographic Separation Research Articles

Core-shell metal-organic framework/silica hybrid with tunable shell structure as stationary phase for high performance liquid chromatography

Metal-organic framework/silica composite (SSU) were prepared by growing UiO-66 on the amino-functionalized SiO2 core-shell spheres (SiO2@dSiO2) via a simple one-pot synthesis approach. By controlling the concentration of Zr4+, the obtained SSU have two different morphologies: spheres-on-sphere and layer-on-sphere. The spheres-on-sphere structure is formed by the aggregation of UiO-66 nanocrystals on the surface of SiO2@dSiO2 spheres. SSU-5 and SSU-20, which contain spheres-on-sphere composites have mesopores with a pore size of about 45 nm in addition to the characteristic micropores of UiO-66 with a pore size of 1 nm. In addition, UiO-66 nanocrystals were grown both inside and outside the pores of SiO2@dSiO2, resulting in a 27% loading of UiO-66 in the SSU. The layer-on-sphere is the surface of SiO2@dSiO2 covered with a layer of UiO-66 nanocrystals. SSU with this structure has only a characteristic pore size of about 1 nm belonging to UiO-66 and is therefore not suitable as a packed stationary phase for high performance liquid chromatography. The SSU spheres were packed into columns and tested for the separation of xylene isomers, aromatics, biomolecules, acidic and basic analytes. With both micropores and mesopores, SSU with spheres-on-sphere structure achieved baseline separation of both small and large molecules. Efficiencies up to 48,150, 50,452 and 41,318 plates m − 1 were achieved for m-xylene, p-xylene and o-xylene, respectively. The relative standard deviations of the retention times of anilines for run-to-run, day-to-day and column-to-column were all less than 6.1%. The results show that the SSU with spheres-on-sphere structure has great potential for high performance chromatographic separation.

Ionic liquid-functionalized dendrimer grafted silica for mixed-mode chromatographic separation and online solid-phase extraction

The efficient sample pretreatment and high-performance chromatographic separation are essential for an accurate analysis of the complex sample. Finding a material that can apply as both sorbent for sample preparation and stationary phase for chromatography is greatly important for analytical chemistry. With a large number of active sites and designable properties, the dendrimers displayed potential performance for sample preparation and chromatographic separation. In order to improve its selectivity restricted by the limited type of functional groups (amide, ethylidene, amino groups), ionic liquid (1,1′-(1,4-butyricdiyl)bis(1-aminopropyl imidazolium)dibromide) were introduced to functionalize dendrimers. With porous silica as the base, ionic liquid-functionalized dendrimer grafted silica (SiO2@G1.5-IL) was obtained and characterized by X-ray photoelectron spectroscopy, elemental analyzer, as well as specific surface and porosity analyzer. The material was used as stationary phase for mixed-mode chromatography and sorbent for SPE, respectively. Under reversed-phase liquid chromatography (RPLC), it successfully separated some hydrophobic analytes (five polycyclic aromatic hydrocarbons (PAHs), two bisphenols, diphenylpropane, and diphenylmethane), by utilizing hydrophobic, π-stacking and hydrogen bonding interactions. Based on the hydrophilic effect, it could separate hydrophilic analytes (nucleosides and alkaloids), which coincident with hydrophilic interaction liquid chromatography (HILIC). And it exhibited better separation capacity than NH2@SiO2 and SiO2@G1.5 under the above two modes. Furthermore, the thermodynamic parameters (ΔH, ΔS, and ΔG) of the above types of analytes on the SiO2@G1.5-IL column were also investigated in detail, revealing the controlling factors during the chromatographic separation. And the relative standard deviations (RSDs, 0.03–2.95%, n = 10) of the repeatability of chromatographic separation were satisfactory. After that, SiO2@G1.5-IL-based SPE column was online combined with high-performance liquid chromatography to investigate the extraction selectivity for three types of hydrophobic organic pollutants (PAHs, estrogens, and bisphenols), and compared to SiO2 and C18 columns. According to their extraction performance, PAHs were selected as the target analytes, and the online analytical method was established. The limits of detection were as low as 0.001 μg L-1 due to the high enrichment factor reach to 3869, limits of quantity were 0.003–0.17 μg L-1, linear ranges were from 0.003 to 15.0 µg L-1, the adsorption capacity was 16.10 μg g−1, as well as RSDs were 0.5–3.7%, 0.6–6.7%, and 4.2–9.0% for intraday, interday tests and reproducibility. Finally, it was applied to analyze the environmental water samples (tap water, snow water, and rainwater), and satisfactory results were obtained (spiked recoveries were 86.8%-120.9%). Therefore, SiO2@G1.5-IL was a powerful material that can be used for the chromatographic separation of both hydrophobic and hydrophilic samples by RPLC or HILIC mode, as well as the efficient online extraction of hydrophobic targets prior to C18 column-based high-performance liquid chromatography.

A monolithic azacalix[4]pyridine column for high-resolution and high-efficiency pressurized capillary electrochromatographic separation

Herein, a highly stable (NAllyl)4-bridged alyzacalix[4]pyridine monolithic column (nAC4P@capillary) was fabricated by copolymerizing nAC4P with GMA and EDMA into a stationary phase through a simple olefin addition reaction. The physicochemical properties of the prepared materials were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy dispersive X-ray (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (EA). A wide range of analytes with various properties was well separated and demonstrated the synergistic effect of the various interaction sites. The maximum column efficiencies (Nmax) for all the analytes reached 62,368 plates/m, and the relative standard deviations (RSDs) of the daily retention times of alkylbenzenes, measured over six months were all lower than 5.63%. Non-covalent interaction analysis reveals that nAC4P@capillary can effectively combine the advantages of electronic configurations, π-π interactions, CH-π interactions, O–H…N hydrogen bonds and lone pair-π interactions, providing excellent prospects for high-performance chromatographic separation.

High-Performance Chromatographic Separation of Cerebrosides.

High-performance thin layer chromatography (HPTLC) is a very robust, fast, and inexpensive technique that enables separation of complex mixtures. Here, we describe the analytical separation of glucosylceramide and galactosylceramide by HPTLC. This technique can be used for quantitation purposes but also with small modification for subsequent mass spectrum analysis for structural determination.

Homomesoporous Metal-Organic Framework for High-Performance Electrochromatographic Separation.

Metal-organic frameworks (MOFs) have exhibited tremendous potential in the area of separation science. However, most of the developed MOF-based stationary phases contained only microporous structures and suffer from limited separation performance. Herein, homomesoporous MOFs with excellent mass transfer capability and strong thermodynamic interactions are first explored as the novel stationary phase for high-performance capillary electrochromatographic separations. As a proof of concept, noninterpenetrated mesoMOF-1 with uniform mesopore sizes (22.5 × 26.1 Å) and good stability was facilely grown on the inner surface of capillaries and applied as a homomesoporous MOF coating-based stationary phase for high-efficiency electrochromatographic separation. Seven types of analytes with different molecular dimensions were all baseline separated on a mesoMOF-1 coated column with high theoretical plate numbers and excellent repeatability, exhibiting significantly improved separation selectivity and column efficiency in comparison to a microporous HKUST-1 coated column. The maximum column efficiencies of the mesoMOF-1 coated column for substituted benzenes and halobenzenes reached up to 1.4 × 105 plates/m, and its mass loadability was also much higher than that of the HKUST-1 coated column. In addition, based on the analysis of adsorption kinetics and chromatographic retention behaviors, the interaction and retention mechanisms of different molecular-weight analytes on mesoMOF-1 coated stationary phases were systematically explored and disclosed in detail. These results indicate that the homomesoporous MOF-based stationary phase can effectively balance the kinetic diffusion (mass transfer capability) and thermodynamic interactions (the strength of adsorption interaction), having great potential for high-performance chromatographic separation.

Recent advances in chemical derivatization-based chromatography-mass spectrometry methods for analysis of aldehyde biomarkers

人体接触环境中的化学污染物会导致多种疾病,包括癌症、糖尿病、心血管疾病、神经退行性疾病(阿尔茨海默症、帕金森病等)等。作为一类具有高反应活性的亲电化合物,醛类(包括外源性醛类或环境污染物暴露后产生的内源性醛类)可与人体中多种重要生物分子形成共价修饰产物而产生毒害作用。暴露组研究自2005年被首次提出以来一直是一个前沿热门领域,暴露组研究可绘制生物标志物与疾病风险之间的复杂关系,因此,所有生物标志物的可测量的和特征性的变化共同构成了暴露组研究的关键基础。醛类是化学暴露组的主要成分之一。由于醛类化合物自身物理化学性质和样品大量基质干扰存在,对它们进行分析和表征特别困难。醛类化合物的分析检测方法主要有传感分析法、电化学法、荧光成像、色谱法、质谱法、色谱-质谱联用法等。基于色谱-质谱的分析技术已成为化学暴露组研究的主要方法之一。化学衍生化,特别是稳定同位素标记衍生化(亦称化学同位素标记)结合液相色谱-质谱(LC-MS)技术能够解决靶向和非靶向代谢组和暴露组分析工作中的诸多问题。化学衍生化联合色谱-质谱的分析策略是复杂体系中醛类精准分析非常重要的解决方案之一。特别是近5年,基于化学衍生化的色谱-质谱分析方法开发与应用已成为醛类分析方法中的热点和亮点。该文主要总结与评述了近5年基于化学衍生化的气相色谱-质谱(GC-MS)和LC-MS最新进展,重点关注生物基质(血液、尿液、唾液、生物组织等)中醛类暴露标志物的分析方法进展。通过探讨标记小分子醛的各种衍生试剂、定性/定量分析方法及应用价值,评述醛类暴露标志物不同分析方法的优缺点以及未来发展趋势,为暴露组学、代谢组学、脂质组学的整合发展和环境生态健康研究提供一定的帮助。为了阐明外源性和内源性醛类化合物在生理和病理事件中所起的复杂作用,需要大力改进研究醛组学(aldehydome)的分析表征技术和工具。随着更先进的质谱仪的研发和使用,以及高效色谱分离和不断进步的生物信息学手段,并同时伴随着单细胞分析、质谱成像的兴起,未来的醛类暴露组分析方法会具有更高的灵敏度、更高的分析通量,更有希望筛选鉴定未知醛类化合物并发现新的暴露组生物标志物。

Nanoscale Hierarchically Micro- and Mesoporous Metal-Organic Frameworks for High-Resolution and High-Efficiency Capillary Electrochromatographic Separation.

Metal-organic frameworks (MOFs) have been widely applied in a variety of fields. However, most of the developed MOFs are micrometer scale in crystal size and contain only micropores, which will limit the mass transport and diffusion of various analytes into their internal interaction sites, severely restricting the potential of MOFs in separation science. Herein, nanoscale hierarchically porous MOFs (NHP-MOFs) were first explored as a novel MOF-based stationary phase with excellent mass transfer performance and abundant accessible interaction sites for high-performance chromatographic separation. As a proof-of-concept demonstration, the nanoscale hierarchically micro- and mesoporous UiO-66 (NHP-UiO-66) was firmly immobilized on the capillary inner surface and utilized as the porous stationary phase for high-resolution and high-efficiency electrochromatographic separation. A wide range of low-, medium-, and high-molecular-weight analytes, including substituted benzenes, chlorobenzenes, polycyclic aromatic hydrocarbons, nucleosides, polypeptides, and proteins were all separated well on a NHP-UiO-66-coated column with excellent resolution and repeatability, exhibiting significantly improved column efficiency and separation ability compared to those of a microporous UiO-66-modified column. The maximum column efficiencies for all the six kinds of analytes reached up to 1.2 × 105 plates/m, and the relative standard deviations of the migration times of substituted benzenes for intraday, interday, and column-to-column were all lower than 5.8%. These results reveal that NHP-MOFs can effectively combine the advantages of the high specific surface area of microporous MOFs and the excellent mass transfer performance and abundant accessible interaction sites of NHP materials, possessing great prospect for high-performance chromatographic separation.

Bioanalytical and Mass Spectrometric Methods for Aldehyde Profiling in Biological Fluids.

Human exposure to aldehydes is implicated in multiple diseases including diabetes, cardiovascular diseases, neurodegenerative disorders (i.e., Alzheimer’s and Parkinson’s Diseases), and cancer. Because these compounds are strong electrophiles, they can react with nucleophilic sites in DNA and proteins to form reversible and irreversible modifications. These modifications, if not eliminated or repaired, can lead to alteration in cellular homeostasis, cell death and ultimately contribute to disease pathogenesis. This review provides an overview of the current knowledge of the methods and applications of aldehyde exposure measurements, with a particular focus on bioanalytical and mass spectrometric techniques, including recent advances in mass spectrometry (MS)-based profiling methods for identifying potential biomarkers of aldehyde exposure. We discuss the various derivatization reagents used to capture small polar aldehydes and methods to quantify these compounds in biological matrices. In addition, we present emerging mass spectrometry-based methods, which use high-resolution accurate mass (HR/AM) analysis for characterizing carbonyl compounds and their potential applications in molecular epidemiology studies. With the availability of diverse bioanalytical methods presented here including simple and rapid techniques allowing remote monitoring of aldehydes, real-time imaging of aldehydic load in cells, advances in MS instrumentation, high performance chromatographic separation, and improved bioinformatics tools, the data acquired enable increased sensitivity for identifying specific aldehydes and new biomarkers of aldehyde exposure. Finally, the combination of these techniques with exciting new methods for single cell analysis provides the potential for detection and profiling of aldehydes at a cellular level, opening up the opportunity to minutely dissect their roles and biological consequences in cellular metabolism and diseases pathogenesis.

Well-Defined Materials for High-Performance Chromatographic Separation.

Chromatographic separation has been widely applied in various fields, such as chemical engineering, precision medicine, energy, and biology. Because chromatographic separation is based on differential partitioning between the mobile phase and stationary phase and affected by band dispersion and mass transfer resistance from these two phases, the materials used as the stationary phase play a decisive role in separation performance. In this review, we discuss the design of separation materials to achieve the separation with high efficiency and high resolution and highlight the well-defined materials with uniform pore structure and unique properties. The achievements, recent developments, challenges, and future trends of such materials are discussed. Furthermore, the surface functionalization of separation ma-terials for further improvement of separation performance is reviewed. Finally, future research directions and the challenges of chromatographic separation are presented.

High-Performance Chromatographic Separation of Cerebrosides.

High-performance thin-layer chromatography (HPTLC) is a very robust, fast, and inexpensive technique that enables separation of complex mixtures. Here, we describe the analytical separation of glucosylceramide and galactosylceramide by HPTLC. This technique can be used for quantitation purposes but also with small modification for subsequent mass spectrum analyses for structural determination.

Solutions for low and high accuracy mass spectrometric data matching: a data-driven annotation strategy in nontargeted metabolomics.

Ultra high pressure liquid chromatography coupled to mass spectrometry (UHPLC-MS) has become a widespread analytical technique in metabolomics investigations, however the benefit of high-performance chromatographic separation is often blunted due to insufficient mass spectrometric accuracy. A strategy that allows for the matching of UHPLC-MS data to highly accurate direct infusion electrospray ionization (DI-ESI) Fourier transform ion cyclotron resonance/mass spectrometry (FTICR/MS) data is developed in this manuscript. Mass difference network (MDiN) based annotation of FTICR/MS data and matching to unique UHPLC-MS peaks enables the consecutive annotation of the chromatographic data set. A direct comparison of experimental m/z values provided no basis for the matching of both platforms. The matching of annotation-based exact neutral masses finally enabled the integration of platform specific multivariate statistical evaluations, minimizing the danger to compare artifacts generated on either platform. The approach was developed on a non-alcoholic fatty liver disease (NAFLD) data set.

Optimum separation condition of five bioactive compounds by HCI program in HPLC

Summary An efficient method used to separate five bioactive compounds from Gelidium amansii was optimized by the HCI software. The optimum composition of mobile phase for high-performance liquid chromatographic (HPLC) separation was obtained. The elution profiles were calculated by the polynomial theory based on the retention factor ln k = A + BF + CF2 (F was the volume percentage of acetonitrile with 1.0% acetic acid); then, the theory was applied to calculate the elution profile in both isocratic and gradient modes by modifying different mobile phase conditions with HCI program. The calculated results of mobile phase condition suggested that acetonitrile-water (containing 1.0% acetic acid) with a linear gradient elution of 0∼30 min from 15:85 to 50:50 (v/v) was the optimized component. In the experimental conditions, the agreement between the experimental elution profiles and the calculated values of eluted concentration was relatively good.

Impact of solvent conditions on separation and detection of basic drugs by micro liquid chromatography–mass spectrometry under overloading conditions

In this study the impact of solvent conditions on the performance of μLC/MS for the analysis of basic drugs was investigated. Our aim was to find experimental conditions that enable high-performance chromatographic separation particularly at overloading conditions paired with a minimal loss of mass spectrometric detection sensitivity. A focus was put on the evaluation of the usability of different kinds of acidic modifiers (acetic acid (HOAc), formic acid (FA), methansulfonic acid (CH 3SO 3H), trifluoroacetic acid (TFA), pentafluoropropionic acid (PFPA), and heptafluorobutyric acid (HFBA)). The test mixture consisted of eleven compounds (bunitrolol, caffeine, cocaine, codeine, diazepam, doxepin, haloperidol, 3,4-methylendioxyamphetamine, morphine, nicotine, and zolpidem). Best chromatographic performance was obtained with the perfluorinated acids. Particularly, 0.010–0.050% HFBA (v/v) was found to represent a good compromise in terms of chromatographic performance and mass spectrometric detection sensitivity. Compared to HOAc, on average a 50% reduction of the peak widths was observed. The use of HFBA was particularly advantageous for polar compounds such as nicotine; only with such a hydrophobic ion-pairing reagent chromatographic retention of nicotine was observed. Best mass spectrometric performance was obtained with HOAc and FA. Loss of detection sensitivity induced by HFBA, however, was moderate and ranged from 0 to 40%, which clearly demonstrates that improved chromatographic performance is able to compensate to a large extent the negative effect of reduced ionization efficiency on detection sensitivity. Applications of μLC/MS for the qualitative and quantitative analysis of clinical and forensic toxicological samples are presented.

Determination of Simmondsins and Simmondsin Ferulates in Jojoba Meal and Feed by High-Performance Liquid Chromatography

Methods are described for the extraction and high-performance chromatographic separation and quantitation of simmondsins and simmondsin ferulates in jojoba meal, detoxified jojoba meal, and animal ...

HPLC Separation of Selected Cardiovascular Agents on Underivatized Silica Using an Aqueous Organic Mobile Phase

Abstract High performance chromatographic separations of selected cardiovascular agents (propranolol, atenolol, metoprolol, verapamil, diltiazem, nifedipine, clonidine and prazosin) on underivatized silica using aqueous phosphate buffer—acetonitrile mobile phases were studied. Mobile phases differing in organic modifier concentration, ionic strength and buffer pH were prepared and tested for chromatographic separation of selected mixtures of the analytes grouped according to pharmacological activity. The best separations of all analytes were obtained using a mobile phase of 60:40 v/v aqueous pH 3 phosphate buffer—acetonitrile at a 1.0 mL/min flow rate. Substitution of methanol for acetonitrile gave increased retention of the analytes with some reduction in column efficiency measured as plate counts. Although ion-pairing appears to be the primary interactive force between the silica column and the analytes, other forces such as hydrogen bonding and hydrophobic interactions are also involved in the separation.

Preparation of anhydrochymotrypsin diol silica as selective adsorbent for affinity chromatography of peptides with aromatic amino acids at C-termini

Anhydrochymotrypsin (AHC), a catalytically inert derivative of chymotrypsin in which the serine-residue active site has been converted chemically to a dehydroalanine residue, was immobilized on diol silica by activation with trifluoroethanesulfonyl chloride. A AHC-diol-silica column was used for high-performance affinity chromatographic separation of peptides with aromatic amino acids at their C-termini from other peptides. Faster separations were achieved.

Synthesis of tin(IV) vanadopyrophosphate as a novel stationary phase for high-performance liquid chromatography and its application to amino acid analysis

The preparation and ion-exchange properties of a novel microcrystalline ion exchanger, tin(IV) vanadopyrophosphate (SVPP), were studied. The exchanger has a high ion-exchange capacity (3.17 mequiv g–1), and its chemical and thermal stabilities are excellent. It was used as a stationary phase for the high-performance ion-exchange chromatographic separation of amino acids. Optimum conditions for high-performance liquid chromatography were investigated. Five amino acids were separated rapidly on a short SVPP column.

Dehydrogenase-silica as a stationary phase for the separation of alcohols and ketones

Horse liver alcohol dehydrogenase was immobilized on tresyl-activated silica particles and slurry packed into a PTFE-coated stainless-steel column. The stationary phase enzyme column was used for the high-performance chromatographic separation of alcohols and ketones. Baseline resolution of the secondary alcohols terbutaline and bambuterol and their respective ketones was obtained. In addition, discrimination of closely related isomers, including the positional isomers of ethylphenethyl alcohol and the optical isomers of 1-phenyl-1-butanol, was achieved.

Determination of fungistatic quaternary ammonium compounds in beverages and water samples by high-performance liquid chromatography

Fungistatic and fungicidal quaternary alkylammonium compounds are widely used in the prevention of staining of timber. They may also find application in the steeping of barley for restricting the growth of fungi. Although they show only low toxicity, sensitive methods are required for their trace determinations as contaminants in food products and water. Problems arise with their analysis because they are of low volatility, they do not carry any chromphore and they are difficult to derivatize. The traditional method for their determination has been based on ion-pair extraction followed by photometric detection. Naturally such a system has low selectivity and is therefore most suitable for quality control purposes. Ion-pair extraction has also been applied as a detection system after high-performance liquid chromatographic (HPLC) separation’, and the other method applied is so-called vacancy chromatography’. The former method requires specific equipment and the latter is susceptible to disturbances from the matrix. The use of a refractive index detector, although possible for various formulations3, is normally affected by other substances in more complicated matrices. The aim of this study was to develop a simple procedure for the determination of quaternary alkylamines at the pg/ml level.

New latex-bonded pellicular anion exchangers with multi-phase selectivity for high-performance chromatographic separations

A new polymeric “multi-phase” chromatographic packing material that combines ion exchange in a pellicular format with adsorption and ion-pair retention on a neutral macroporous core bead is described. The material is stable from pH 0 to 14 and from 1 to 100% (v/v) of common reversed-phase solvents in aqueous mixtures. The ability of independently control ion exchange and adsorption or ion-pair retention is demonstrated on a variety of inorganic and organic analytes.