Resin screening and process optimization for erythritol mother liquor chromatographic separation.

In order to improve the utilization value of the erythritol mother liquor, the separation and purification of the erythritol mother liquor was selected in this study. The selected chromatographic separation programme for erythritol crystallizing mother liquor is as follows: Firstly, erythritol is resolved from mannitol and arabitol with DTF-01Ca (Suqing Group) resin and then mannitol is resolved from arabitol with 99Ca/320 (Dowex) resin. At the same time, the chromatographic conditions of the DTF-01Ca (Suqing Group) and 99Ca/320 (Dowex) resins were optimized, resulting in an optimal separation temperature and mobile phase flow rate of 70 °C, 10 ml/min. On this basis, a single-column chromatographic model was used to calculate the TD model parameter (N) and the mass transfer coefficient (km ) of the separation of erythritol mother liquor by DTF-01Ca (Suqing Group) and 99Ca/320 (Dowex) resins. The adsorption isotherms, TD model parameter (N) and the mass transfer coefficient (km ) provides data references for the design and operation of the simulated moving beds (SMB) separation system for the industrial-scale separation of erythritol crystallizing mother liquor.

Development of a novel UPLC approach to co-prediction of four active compounds in a multi-component pharmaceutical preparation.

In this work, a new ultra-performance liquid chromatography method based on photodiode array detection (UPLC-PDA) was first developed for the quantitative analysis of the quaternary mixture of ascorbic acid (AA), paracetamol (PAR), caffeine (CAF) and chlorpheniramine maleate (CPA) in a commercial dosage form. The developed UPLC-PDA method offered a new possibility for the co-determination of four active ingredients in a drug combination with short run time and simple sample preparation. The successful chromatographic separation of the four drugs was performed using a Waters Acquity UPLC BEH C18 column (1.7 µm 2.1 × 100 mm) (Mildford, USA) and a mobile phase consisting of water (12 %), acetonitrile (13 %) and 0.1 M H3PO4 (75 %) at a flow rate of 0.25 mL/min. The validation of the proposed UPLC-PDA approach was verified by analyzing synthetic mixtures, inter- and intra-day experiments, and commercial powder samples and provided satisfactory results.

Qualitative and Quantitative Analytical Techniques of Nucleic Acid Modification Based on Mass Spectrometry for Biomarker Discovery.

Nucleic acid modifications play important roles in biological activities and disease occurrences, and have been considered as cancer biomarkers. Due to the relatively low amount of nucleic acid modifications in biological samples, it is necessary to develop sensitive and reliable qualitative and quantitative methods to reveal the content of any modifications. In this review, the key processes affecting the qualitative and quantitative analyses are discussed, such as sample digestion, nucleoside extraction, chemical labeling, chromatographic separation, mass spectrometry detection, and data processing. The improvement of the detection sensitivity and specificity of analytical methods based on mass spectrometry makes it possible to study low-abundance modifications and their biological functions. Some typical nucleic acid modifications and their potential as biomarkers are displayed, and efforts to improve diagnostic accuracy are discussed. Future perspectives are raised for this research field.

Dispersive hierarchically porous composites based on defective MOFs as mixed-mode stationary phases for chromatographic separation.

Defective metal-organic frameworks-based composites with excellent separation properties were obtained. The mesoporous metal-organic frameworks were selected and deliberately designed to be deficient, and they were then combined with polyacrylamide to be modified on the surface of silica microspheres. The prepared composites were employed as mixed-mode stationary phase in chromatographic separation, and they were compared to both conventional microporous metal-organic framework-based columns and commercial columns. It showed improved selectivity and retention toward both hydrophilic and hydrophobic analytes, allowing for the effective separation of nine nucleosides and nucleobases, eight alkaloids, six antibiotics, and five alkylbenzenes. Additionally, the column was used to effectively separate the active ingredients in the daring substance of honeysuckle, revealing a wide range of possible applications. For the same batch of analytes, three batches of distinct materials demonstrated consistent separation effects. It also demonstrated excellent chromatographic repeatability and stability, with relative standard deviations of the retention time and/or column efficiency being found to be less than 0.8% and 0.9%, respectively. The dispersive hierarchically porous composites were demonstrated to be effective in chromatographic separation, and the results expanded the potential uses of defective MOFs with dispersed multi-level pores.

Mycotoxins in Vegetable Oils: A Review of Recent Developments, Current Challenges and Future Perspectives in Sample Preparation, Chromatographic Determination, and Analysis of Real Samples.

Mycotoxins are toxic compounds that are formed as secondary metabolites by some fungal species that contaminate crops during pre- and postharvest stages. Exposure to mycotoxins can lead to adverse health effects in humans, such as carcinogenicity, mutagenicity, and teratogenicity. Hence, there is a need to develop analytical methods for their determination in vegetable oils that possess high sensitivity and selectivity. In the current review (116 references), the recent developments, current challenges, and perspectives in sample preparation techniques and chromatographic determination are summarized. It is impressive that current sample preparation techniques such as dispersive liquid-liquid microextraction (DLLME), quick, easy, cheap, rugged, and safe method (QuEChERS) and solid phase extraction (SPE) have exhibited high extraction recoveries and minimal matrix effects. However, a few studies have reported signal suppression or enhancement. Regarding chromatographic techniques, high sensitivity and selectivity have been reported by liquid chromatography coupled to fluorescence detection, tandem mass spectrometry, or high-resolution mass spectrometry. Furthermore, current challenges and perspectives in this field are tentatively proposed.

Green chromatographic methods for determination of co-formulated lidocaine hydrochloride and miconazole nitrate along with an endocrine disruptor preservative and potential impurity.

Recently, green analytical chemistry (GAC) is a key issue towards the idea of sustainability, the analytical community is focused on developing analytical methods that incorporate green chemistry principles to minimize adverse impacts on the environment and humans. Herein, we present 2 sustainable, selective, and validated chromatographic methods. Initially, lidocaine hydrochloride (LDC) and miconazole nitrate (MIC) with two preservatives; methyl paraben (MTP) and saccharin sodium (SAC) were chromatographed via TLC-densitometric method which employed ethyl acetate: methanol: formic acid (9:1:0.1, by volume) as the mobile phase with UV detection at 220.0 nm, good correlation was obtained in the range of 0.3-3.0 µg/band for MIC and LDC. Following that, RP-HPLC was successfully applied for separating quinary mixture of LDC, MIC, MTP, SAC along with LDC impurity; dimethyl aniline (DMA) using C18 column, and a gradient green mobile phase composed of methanol and phosphate buffer (pH 6.0) in different ratios with a flow rate 1.5 mL/min and UV detection at 210.0 nm, linearity ranges from 1.00 to 100.00 µg/mL for MIC, 2.00-100.00 µg/mL for LDC and 1.00--20.00 µg/mL for MTP and DMA. No records to date regarding the determination of the two drugs, besides MTP and DMA. The proposed methods were validated according to the ICH guidelines and applied successfully to the analysis of the compounds. The methods' results were statistically compared to those obtained by applying the reported one, indicating no significant difference regarding both accuracy and precision. The methods' greenness profiles have been assessed and compared with those of the reported method using different assessment tools.

Isomer-specific analysis of nonylphenol and their transformation products in environment: A review.

Nonylphenols (NPs) are crucial fine chemicals widely employed in producing industrial and consumer surfactants that ultimately enter the environment through various pathways, leading to environmental pollution. NPs are suspected endocrine-disrupting chemicals that may accumulate in the body over time, resulting in unusual reproductive function. Due to limitations in analytical methods, NPs have typically been quantified as a whole in some studies. However, NPs are a mixture of multibranched structures, and different NP isomers exhibit distinct environmental behaviors and toxic effects. Therefore, it is critical to analyze environmental and human biological samples at the isomer-specific level to elucidate the contamination characteristics, human exposure load, and toxic effects of NPs. Accurately analyzing NP samples with various isomers, metabolites, and transformation products presents a significant challenge. This review summarizes recent advances in analytical research on NPs in technical products, environmental, and human biological samples, particularly emphasizing the synthesis and separation of standards and the transformation of NP homolog isomers in samples. Finally, the review highlights the research gaps and future research directions in this domain.

A quantitative description of the compatibility of technetium-selective chromatographic technetium-99m separation with low specific activity molybdenum-99.

Technetium-99m generators employing a technetium-selective stationary phase are a chromatographic instrument developed for use with 99Mo having low specific activity (LSA); particularly, 99Mo produced by electron accelerators. This paper presents a mathematical description of technetium-selective chromatographic (TSC) 99mTc separation and analyzes its compatibility with LSA 99Mo. We developed a theoretical formula for TSC 99mTc separation by discretizing its pertechnetate selectivity, and validated it using an electron linear accelerator and activated carbon-based TSC (AC-TSC) 99mTc generators. We confirmed that the activity concentration of 99mTc obtained from a TSC 99mTc generator can be calculated directly from its input 99Mo activity regardless of the 99Mo specific activity. The formula corroborates that TSC 99mTc separation is compatible with LSA 99Mo, and has a practical application in estimating the number of TSC 99mTc generators required for 99mTc demand of interest.

Chromatographic separation performance of silica microspheres surface-modified with triazine-containing imine-linked covalent organic frameworks.

In this work, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and 1,3,5-tris(4-formylphenyl)benzene (TFPB) were used as monomers to construct a triazine-containing imine-linked covalent organic framework (COF), which was then bonded onto the surface of aldehydized silica (SiO2-CHO), and finally a COF@silica composite material (TAPT-TFPB COF@SiO2) was successfully prepared. The chromatographic separation performance of SiO2-CHO, TAPT-TFPB COF@SiO2 and TAPT-TFPB COF@SiO2/SiO2-CHO (80/20, mass ratio) was evaluated and compared. It was found that separation efficiency was obviously enhanced by adding an appropriate amount of SiO2-CHO into TAPT-TFPB COF@SiO2. The obtained TAPT-TFPB COF@SiO2/SiO2-CHO showed more favorable separation ability than SiO2-CHO and TAPT-TFPB COF@SiO2. Various aromatic compounds including alkylbenzenes, polycyclic aromatic hydrocarbons, environmental endocrine disruptors, foodborne stimulants and phenyl ketones were effectively separated on the TAPT-TFPB COF@SiO2/SiO2-CHO column in reversed phase chromatography mode. The silica microspheres surface-modified with triazine-containing imine-linked COFs proved to be a new type of promising chromatographic packing materials.

Quantitative analysis of therapeutic proteins in biological fluids: recent advancement in analytical techniques.

Pharmaceutical application of therapeutic proteins has been continuously expanded for the treatment of various diseases. Efficient and reliable bioanalytical methods are essential to expedite the identification and successful clinical development of therapeutic proteins. In particular, selective quantitative assays in a high-throughput format are critical for the pharmacokinetic and pharmacodynamic evaluation of protein drugs and to meet the regulatory requirements for new drug approval. However, the inherent complexity of proteins and many interfering substances presented in biological matrices have a great impact on the specificity, sensitivity, accuracy, and robustness of analytical assays, thereby hindering the quantification of proteins. To overcome these issues, various protein assays and sample preparation methods are currently available in a medium- or high-throughput format. While there is no standard or universal approach suitable for all circumstances, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay often becomes a method of choice for the identification and quantitative analysis of therapeutic proteins in complex biological samples, owing to its high sensitivity, specificity, and throughput. Accordingly, its application as an essential analytical tool is continuously expanded in pharmaceutical R&D processes. Proper sample preparation is also important since clean samples can minimize the interference from co-existing substances and improve the specificity and sensitivity of LC-MS/MS assays. A combination of different methods can be utilized to improve bioanalytical performance and ensure more accurate quantification. This review provides an overview of various protein assays and sample preparation methods, with particular emphasis on quantitative protein analysis by LC-MS/MS.

Preparation and characterization of glucose-based covalent organic polymer coated silica as stationary phase for high-performance liquid chromatography.

Carbohydrate is a renewable, sustainable, hydrophilic, and biodegradable natural product, which is widely used in the field of adsorption. In this study, a glucose-based covalent organic polymer (COP) coated silica was fabricated by facile solvent knitting reaction between tetrabenzylglucose and silica-phenyl with anhydrous aluminum trichloride as catalyst, forming a core-shell stationary phase (donated as SiO2@COPBn-glu) for high performance liquid chromatography. The prepared SiO2@COPBn-glu was characterized by scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectrometry, solid-state 13C nuclear magnetic resonance spectrometry, X-ray photoelectron spectroscopy, and N2 adsorption-desorption experiments. Owing to the coexistence of benzene units and alkyl, hydroxyl and ether groups in the skeleton of COPBn-glu shell, the developed chromatographic packing exhibited reversed-phase/hydrophilic interaction mixed-mode with multiple retention mechanisms, such as hydrophobic, π-π, hydrogen bonding, and electron donor-acceptor interactions. The results revealed that the SiO2@COPBn-glu column demonstrated excellent selectivity and retention behavior for both hydrophilic and hydrophobic compounds with good repeatability and stability. Meanwhile, the chromatographic performance of the prepared SiO2@COPBn-glu column was compared with a C18 column to assess the role of the coating COPBn-glu shell. Therefore, the development of the SiO2@COPBn-glu stationary phase expands the potential application of COPs in separation field.

Fabrication and evaluation of dodecyl imide maleopimaric acid glycidyl methacrylate ester modified silica with multiple retention mechanisms for reversed phase liquid chromatography.

As green, less toxic, and abundant ligands with rich functional groups, natural products are widely used in synthesis of chromatographic stationary phases. In this work, dodecyl imide maleopimaric acid glycidyl methacrylate ester (C12-MPAGN) was prepared from maleopimaric acid through the imidization and ring-opening based esterification reaction. By using "thiol-ene" click chemistry, it was chemically bonded to the silica and (3-mercaptopropyl) trimethoxysilane (γ-MPS) was used as the coupling agent to obtain dodecyl imide maleopimaric acid glycidyl methacrylate ester bonded silica stationary phase (Sil-C12-MPAGN). Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopies (SEM), and elemental analysis (EA) were utilized to verify that the Sil-C12-MPAGN stationary phase was successfully prepared with C12-MPAGN immobilized on the silica surface. In order to evaluate the chromatographic performance and retention mechanisms of the Sil-C12-MPAGN column and compared with C18 column, a variety of compounds were used, including stander mixture of Tanaka, alkylbenzenes, polycyclic aromatic hydrocarbons (PAHs), phenols and flavonoids. Based on these multiple interactions, including hydrophobic, hydrogen-bonding, and π-π interactions, high selectivity and superior separation performance were demonstrated by the Sil-C12-MPAGN column for probe molecules what had previously been mentioned. In addition, the quantitative determination of paclitaxel content in Yew bark extract was conducted with this column, which was found that the concentration was 83.67 mg/L, respectively. In short, the present study proposes a new strategy for introducing rosin to liquid chromatography with high selectivity and separation performance.

[Recent advances in the research of chromatographic separation materials based on click chemistry].

Since Nobel Laureate K. B. Sharpless first introduced the concept of click chemistry in 2001, such reactions have become a powerful modular synthesis tool. Click chemistry reactions have rapidly expanded into many scientific fields, such as materials and life science, owing to their distinct advantages, which include mild conditions, fast reaction rates, high yields, low by-product generation, and simple separation and purification procedures. Nowadays, click chemistry reactions have become an essential means of designing and preparing separation materials; thus, interest in this synthetic technique has quickly grown. Here, the development of click chemistry and its unique advantages are briefly described firstly. The reports on click chemistry-based chromatographic separation materials published in the past five years are then systematically reviewed, focusing on two major separation fields: column chromatography and membrane chromatography. Meanwhile, recent advances in the separation materials obtained from three common types of click reactions, namely, azido-alkyne, thiol-alkene, and thiol-alkyne, are summarized. Finally, an outlook on the future of click chemistry is provided in developing efficient chromatographic separation materials.

Separation of Isomeric Forms of Urolithin Glucuronides Using Supercritical Fluid Chromatography.

Urolithins are gut microbiota metabolites produced in humans after consuming foods containing ellagitannins and ellagic acid. Three urolithin metabotypes have been reported for different individuals depending on the final urolithins produced. After absorption, they are conjugated with glucuronic acid (phase II metabolism), and these are the main circulating metabolites in plasma and reach different tissues. Different regioisomeric isomers of urolithin glucuronides have been described. Still, their identification and quantification in humans have not been properly reported due to resolution limitations in their analysis by reversed-phase high-performance liquid chromatography. In the present study, we report a novel method for separating these isomers using supercritical fluid chromatography. With this method, urolithin A 3- and 8-glucuronide, isourolithin A 3- and 9- glucuronide, and urolithin B 3-glucuronide (8-hydroxy urolithin 3-glucuronide; 3-hydroxy urolithin 8-glucuronide; 3-hydroxyurolithin 9-glucuronide; 9-hydroxyurolithin 3-glucuronide; and urolithin 3-glucuronide) were separated in less than 15 min. The proposed method was applied to successfully analyze these metabolites in urine samples from different volunteers belonging to different metabotypes.

Comparison of Usefulness of Four Chelating Agents (EDTA, NTA, ODA and IDA) for the Chromatographic Separation of Micro and Macro Amounts of Rare Earth Elements.

Literature on the use of four chelating agents namely: ethylenediaminetetraacetic acid, nitrilotriacetic acid, diglycolic acid and iminodiacetic acid for the chromatographic separation of micro and macro amounts of rare earth elements was critically reviewed and supplemented with some new unpublished data from our Laboratory. Advantages and disadvantages of ion exchange chromatography both in cation and anion mode as well as ion interaction chromatography techniques, which were used for rare earth elements separation, are discussed. The usefulness of some of the chromatographic systems for micro-macro separations was discussed and demonstrated. The importance of resilience of the separation method to column overloading in some analytical and larger scale separations was emphasized. The methods described in this article might suit well for recovering of individual lanthanides and yttrium from e-waste and other industrial wastes which were fast accumulating in recent years.

Phosphorus-doped deep eutectic solvent-derived carbon dots-modified silica as a mixed-mode stationary phase for reversed-phase and hydrophilic interaction chromatography.

In this work, phosphorus-doped carbon dots (P-DESCDs) were successfully prepared using choline chloride/lactic acid type deep eutectic solvent and phosphoric acid as ingredients, and (3-aminopropyl) trimethoxysilane was used as a bridge to graft P-DESCDs onto the silica surface to obtain a new mixed-mode stationary phase (Sil-P-DESCDs) for reversed-phase and hydrophilic interaction liquid chromatography. The successful preparation of the stationary phase was confirmed by laser scanning confocal microscopy, elemental analysis, and Fourier transform infrared spectrometry. Interestingly, the doping of phosphorus greatly improved the separation performance and hydrophilicity of the Sil-P-DESCDs column. The Sil-P-DESCDs column was found to have certain hydrophobicity, hydrogen bonding ability and shape selectivity by Tanaka and Engelhardt standard test mixtures, and a series of hydrophilic and hydrophobic compounds such as alkylbenzenes, polycyclic aromatic hydrocarbons, sulfonamides, aromatic amines, phenols, flavonoids, nucleoside bases, and alkaloids. In addition, the effects of mobile phase ratio, column temperature, flow rate, salt concentration, and pH on the retention of analytes on Sil-P-DESCDs columns were investigated. Finally, the Sil-P-DESCDs column was applied to the qualitative and quantitative analysis of calcein-7-glucoside in the real sample of medicinal Astragalus pellets, and it was found at a concentration of 0.02 mg/mL.

A simple and reliable method for separation of mineral oil/polychlorobiphenyl mixtures.

Polychlorinated biphenyls (PCBs) were broadly applied worldwide as electrical insulators in transformers and power capacitors, due to their high dielectric constant and non-flammability. They were often added to mineral oils (MOs) and used as dielectric fluids, which are nowadays classified as hazardous waste. Indeed, the Stockholm Convention aims to eliminate the use of equipment with PCB content greater than 0.005 wt-% (=50 ppm) by 2025. Accurate identification and quantification of small traces of PCBs contained in MO thus represent a great analytical challenge. To achieve this goal, a simple, cost-effective and fast chromatographic process was developed to separate PCBs from MO, allowing to obtain reliable data to determine the concentration of PCBs, reduced to 2-3 ppm. Experimental and analytical methods, such as thin layer chromatography, column chromatography as well as gas chromatography coupled with mass spectroscopy, were applied to acquire a high level of qualitative and quantitative determination of PCBs in transformer MOs.

GC-MS analysis of oxysterols and their formation in cultivated liver cells (HepG2).

Oxysterols play a key role in many (patho)physiological processes and they are potential biomarkers for oxidative stress in several diseases. Here we developed a rapid gas chromatographic-mass spectrometry-based method for the separation and quantification of 11 biologically relevant oxysterols bearing hydroxy, epoxy, and dihydroxy groups. Efficient chromatographic separation (resolution ≥ 1.9) was achieved using a medium polarity 35%-diphenyl/65%-dimethyl polysiloxane stationary phase material (30 m × 0.25 mm inner diameter and 0.25 µm film thickness). Based on thorough analysis of the fragmentation during electron ionization we developed a strategy to deduce structural information of the oxysterols. Optimized sample preparation includes (i) extraction with a mixture of n-hexane/iso-propanol, (ii) removal of cholesterol by solid phase extraction with unmodified silica, and (iii) trimethylsilylation. The method was successfully applied on the analysis of brain samples, showing consistent results with previous studies and a good intra- and interday precision of ≤20%. Finally, we used the method for the investigation of oxysterol formation during oxidative stress in HepG2 cells. Incubation with tert-butyl hydroperoxide led to a massive increase in free radical formed oxysterols (7-keto-chol > 7ß-OH-chol >> 7α-OH-chol), while 24 h incubation with the glutathione peroxidase 4 inhibitor RSL3 showed no increase in oxidative stress based on the oxysterol pattern. Overall, the new method described here enables the robust analysis of a biologically meaningful pattern of oxysterols with high sensitivity and precision allowing us to gain new insights in the biological formation and role of oxysterols.

Deep eutectic solvents-derivated carbon dots-decorated silica stationary phase with enhanced separation selectivity in reversed-phase liquid chromatography.

In this work, deep eutectic solvents-based carbon dots (DESCDs) were prepared and bonded to the silica surface for the first time to form a new hydrophobic chromatographic stationary phase (Sil-DESCDs). The successful preparation of DESCDs and Sil-DESCDs were demonstrated by a series of characterizations including transmission electron microscopies, laser scanning confocal microscope, Fourier transform infrared spectrometry, elemental analysis, etc. Retention behavior of Sil-DESCDs was evaluated using Tanaka and Engelhardt standard test mixtures. The results showed that this new stationary phase had excellent separation performance for polycyclic aromatic hydrocarbons, flavonoids, aromatic amines and phenolic compounds. Excellent separation selectivity for the 3-phenylene ring isomers including phenanthrene and anthracene, the 4-phenylene ring isomers including pyrene, triphenylene, chrysene and 1,2-benzanthracene was also obtained. Especially, prednisolone and hydrocortisone, which have very similar structures, can be separated using pure water as the mobile phase. In addition, the flavonoids in Astragalus extracts including calycosin-7-glucoside, ononin, calycosin and formononetin were determined using this new column, their concentrations were 0.050, 0.031, 0.023 and 0.034 mg/mL, respectively.

Covalent Organic Frameworks-Based Membranes as Promising Modalities from Preparation to Separation Applications: An Overview.

Covalent organic frameworks (COFs) are a promising class of porous crystalline materials made up of covalently connected and periodically protracted network topologies through organic linkers. The tailorability of organic linker and intrinsic structures endow COFs with a tunable porosity and structure, low density, facilely-tailored functionality, and large surface area, attracting increasing amount of interests in variety of research areas of membrane separations. COF-based membranes have spawned a slew of new research projects, ranging from fabrication methodologies to separation applications. Herein, we tried to emphasis the major developments in the synthetic approaches of COFs based membranes for a variety of separation applications such as, separation of gaseous mixtures, water treatment as well as separation of isomeric and chiral organic compounds. The proposed methods for fabricating COF-based continuous membranes and columns for real world applications are also thoroughly explored. Finally, a viewpoint on the future directions and remaining challenges for COF research in the area of separation is provided.