Determination of fat- and water-soluble vitamins by supercritical fluid chromatography: A review

Progress in triacylglycerol isomer detection in milk lipids

In triacylglycerols (TAGs), position differences of fatty acids on the glycerol skeleton produce various TAG isomers. These TAG isomers have different pathways of digestion, absorption, and utilization in infants, thereby affecting TAG nutritional properties of TAGs. Here, we review the progress of research on methods for detecting TAG isomers, and identify direction and thought for improving these methods, including novel chromatographic combinations, perfect algorithm, and improved equipment. The ensuing optimization of these methods is expected to provide robust guarantee for the gradual improvement of milk-derived TAG isomer detection, and is an important prerequisite for infant formula to mimic the structured lipids of human milk.

A robust method for simultaneous determination of eight B vitamins in human serum by liquid chromatography tandem mass spectrometry

The level of vitamin B group in human serum is an important index of human health. Among B vitamins, cyanocobalamin in serum is unstable and its content is extremely low. Rapid and simultaneous detection of multiple B vitamins including cyanocobalamin is a challenge. Herein, we have developed a rapid and stable method that can realize the determination of thiamine, riboflavin, nicotinamide, pantothenic acid, pyridoxic acid, biotin, 5-methyltetrahydrofolate, and cyanocobalamin simultaneously in 6 min. The method was established based on protein precipitation with methanol and then chromatographic separation was achieved using Waters acquity ultra-high-performance liquid chromatography high strength silica T3 column, which was stable and sensitive especially for cyanocobalamin. Limit of quantification, precision, trueness, and matrix effect were validated according to the European Medicines Agency and United States Food and Drug guidelines and Clinical and Laboratory Standards Institute guidelines on bioanalytical method. The limit of quantification for thiamine, riboflavin, nicotinamide, pantothenic acid, pyridoxic acid, biotin, 5-methyltetrahydrofolate, and cyanocobalamin was 0.4, 0.4, 0.8, 2.0, 0.4, 0.1, 0.4, and 0.04 ng/mL separately, respectively. Intra- and interday precisions were 1.1%-12.4% and 2.0%-13.5%, respectively. The relative errors were between 0.3% and 13.3%, and the matrix effects were between 2.6% and 10.4%.

Simultaneously characterization of multiple constituents in Valeriana jatamansi Jones using an online supercritical fluid extraction-high-performance liquid chromatography/supercritical fluid chromatography-mass spectrometry system

Valeriana jatamansi Jones is a commonly used traditional Chinese medicine, boasting rich effective compositions with versatile chemical structures and wide polarity, including iridoids, chlorogenic acid, and flavonoids. Previous reports indicate that conventional high-performance liquid chromatography (HPLC) analytical methods have proven inefficient performance in comprehensively characterizing components in Valeriana jatamansi. In the present study, a hybrid online analytical platform combining supercritical fluid extraction with both conventional HPLC separation (reverse phase) and supercritical fluid chromatography (normal phase) has been established and validated. This system can provide online extraction with two different chromatographic separation modes to increase separation ability and has been connected to a mass spectrometer to acquire high-resolution mass spectrometry data. Then, the online platform was applied to screening components in Valeriana jatamansi. A total of 117 compounds were identified, including five lignans, 18 organic acids, six flavonoids, and 88 iridoids. Thirty-three compounds were reported from Valeriana jatamansi for the first time. These results enrich our understanding of the components of Valeriana jatamansi and prove that the developed online platform in this study is a robust approach for accelerating working efficiency in comprehensively analyzing complicated samples.

Punicesterones A-G, polyhydroxylated mycoecdysteroids from the deep-sea-derived fungus Aspergillus puniceus SCSIO z021

Seven undescribed polyhydroxylated mycoecdysteroids, punicesterones A-G, along with two known analogues, were isolated from the deep-sea-derived fungal strain Aspergillus puniceus SCSIO z021 (Trichocomaceae). Their structures with absolute configurations were elucidated by a combination of extensive NMR spectroscopic analysis, HRESIMS data, and single-crystal X-ray diffraction experiments. Punicesterone An unexpectedly possessed a nicotinoyl unit substituted at C-22 of a typical ecdysteroid skeleton. All of the isolated compounds were evaluated for their anti-inflammatory, lipid-lowering, and antibacterial activities. Punicesterones B and C showed the activity of reducing triglyceride in 3T3-L1 adipocytes in a dosage-dependent manner, and also exhibited antibacterial activity against five pathogens.

Rapid Analysis of α-Tocopherol and Its Oxidation Products Using Supercritical Carbon Dioxide and Proton Transfer Reaction Ionization Mass Spectrometry

We have developed a rapid and sensitive analytical method for α-tocopherol and its oxidative products by combining online hyphenation of supercritical fluid extraction-supercritical fluid chromatography (SFC) with proton transfer reaction (PTR) ionization mass spectrometry (MS). α-Tocopherol is a well-known antioxidant that plays a vital role in the antioxidant defense system in plant cells. However, studies on the cellular mechanisms of α-tocopherol have been limited owing to the lack of a rapid analytical method, which limits the comparison of plant cells incubated in various conditions. Additionally, complex sample preparation and long chromatography separation times are required. Moreover, the majority of the involved molecules are a combination of isomers, which must be separated before applying tandem MS. α-Tocopherol produces the α-tocopheroxyl radical in the first step of its antioxidant function; another ion with the same mass may also be generated from the source. SFC separation effectively distinguished the observed ions from their oxidative products in the sample and those produced during the ionization reaction process. This method enabled the measurement of α-tocopherol and its oxidative products such as α-tocopheroxyl radical and α-tocopheryl quinone in approximately 3 min per sample, including the time required for sample preparation.

Green determination of eight water-soluble B vitamins in cosmetic products by liquid chromatography with ultraviolet detection

B vitamins are a group of compounds with beneficious properties for dermatologic care, and therefore they are included in the cosmetic formulations as high added-value ingredients. In this paper, an analytical method for the simultaneous determination of eight water-soluble B vitamins in cosmetic products is reported for the first time. This method is based on liquid chromatography with ultraviolet detection (LC-UV) analysis after simple water leaching of the analytes from the cosmetic matrix. No organic solvents are required, beyond the ethanol used in the chromatographic mobile phase. The proposed method has been successfully validated showing good linearity, limits of detection in the low μg mL^-1 range (from 0.14 to 0.43 μg mL^-1) and good repeatability (relative standard deviation below 11 %). The accuracy of the method has been proven by the analysis of laboratory-made samples (i.e., a cream and a gel) with known concentrations of the analytes, providing low relative errors (below 12 %). Finally, the method has been successfully applied to four commercial cosmetic samples of different formulations without significant matrix effects. The results obtained and the environmentally friendly features of the method showed its usefulness for carrying out both pre- and in-market quality control of final cosmetic products.

Analysis of mobile chemicals in the aquatic environment-current capabilities, limitations and future perspectives

Persistent and mobile water contaminants are rapidly developing into a focal point of environmental chemistry and chemical regulation. Their defining parameter that sets them apart from the majority of regularly monitored and regulated contaminants is their mobility in the aquatic environment, which is intrinsically tied to a high polarity. This high polarity, however, may have severe implications in the analytical process and thus the most polar of these mobile contaminants may not be covered by widely utilized trace-analytical methods, and thus, alternatives are required. In this review, we infer the physical and chemical properties of mobile water contaminants from a set of almost 1800 prioritized REACH chemicals and discuss the implications these substance properties may have on four integral steps of the analytical process: sampling and sample storage, sample pre-treatment, separation and detection. We discuss alternatives to widely utilized trace-analytical methods, examine their application range and limitations, highlight potential analytical techniques on the horizon and emphasize research areas we believe still offer the most room for further improvement. While we have a comprehensive set of analytical methods to cover a large portion of the known mobile chemicals, these methods are still only infrequently utilized. Graphical abstract.

L-cysteine modified silver nanoparticles for selective and sensitive colorimetric detection of vitamin B1 in food and water samples

The use of L-cysteine modified silver nanoparticles (Cys-capped AgNPs) as a colorimetric probe for determination of vitamin B1 (thiamine) is described in the present work. This method is based on the measurement of red shift of localized surface plasmon resonance (LSPR) band of Cys-capped AgNPs in the region of 200–800 nm. The color of Cys-capped AgNPs was changed from yellow to colorless by the addition of vitamin B1. The mechanism for detection of vitamin B1 is based on the electrostatic interaction between positively charged vitamin B1, which causes the red shift of LSPR band from 390 nm to 580 nm. The interaction between Cys-capped AgNPs and vitamin B1 was theoretically explored by density function theory (DFT) using LANL2DZ basis sets with help of Gaussian 09 (C.01) program. The morphology, size distribution and optical properties of Cys-capped AgNPs were characterized by transmission electron microscope (TEM), UV-Visible spectrophotometry, Fourier transform infrared spectroscopy (FTIR) and dynamic light scattering (DLS) techniques. The method is linear in the range of 25–500 μg mL⁻¹ with correlation coefficient (R²) 0.992 and limit of detection of 7.0 μg mL⁻¹. The advantages of using Cys-capped AgNPs as a chemical sensor in colorimetry assay are being simple, low cost and selective for detection of vitamin B1 from food (peas, grapes and tomato) and environmental (river, sewage and pond) water samples.

Signal enhancement in supercritical fluid chromatography-diode-array detection with multiple injection

To circumvent the detrimental effects of large‐volume injection with fixed‐loop injector in modern supercritical fluid chromatography, the feasibility of performing multiple injection was investigated. By accumulating analytes from a certain number of continual small‐volume injections, compounds can be concentrated on the column head, and this leads to signal enhancement compared with a single injection. The signal to noise enhancement of different compounds appeared to be associated with their retention on different stationary phases and with type of sample diluent. The diethylamine column gave the best signal to noise enhancement when acetonitrile was used as sample diluent and the 2‐picolylamine column showed the best overall performance with water as the sample diluent. The advantage of multiple injection over one‐time large‐volume injection was proven with sulfanilamide, with both acetonitrile and water as sample diluents. The multiple injection approach exhibited comparable within‐ and between‐day precision of retention time and peak area with those of single injections. The potential of the multiple injection approach was demonstrated in the analysis of sulfanilamide‐spiked honey extract and diclofenac‐spiked ground water sample. The limitations of this approach were also discussed.

Supercritical fluid chromatography-a technical overview and its applications in medicinal plant analysis: an update covering 2012-2018

Medicinal plants with complex matrices are endowed with a wide scope of biological activities. The separation, quantification, characterization and purification of bioactive components from herbal medicine extracts have always challenged analysts. Fortunately, the advancement of various emerging techniques has provided potent support for improving the method selectivity, sensitivity and run speeds in medicinal plant analyses. In recent years, the advent of new-generation supercritical fluid chromatography (SFC) instruments and a wide diversity of column chemistries, coupled with the intrinsic technical features of SFC, have made it an alternative and prominent analytical platform in the medicinal plant research area. This work aims to give a comprehensive overview of the fundamentals, technical advancement and investigating parameters of SFC in combination with three prevalent detectors. Moreover, the latest research progress of SFC applications in medicinal plant analyses is illuminated, with focus on herbal medicine-related SFC papers on the analytical and preparative scale that were published during the period of 2012 to December 2018. The most relevant applications were classified based on the constituents to be analysed. As for the respective research cases, analytical protocols and data processing strategies were provided, along with the indicated restrictions or superiority of the method; thus, the current status of SFC in medicinal plant analysis was presented.

Extraction of Carotenoids and Fat-Soluble Vitamins from Tetradesmus Obliquus Microalgae: An Optimized Approach by Using Supercritical CO2

In recent years, great attention has been focused on rapid, selective, and environmentally friendly extraction methods to recover pigments and antioxidants from microalgae. Among these, supercritical fluid extraction (SFE) represents one of the most important alternatives to traditional extraction methods carried out with the use of organic solvents. In this study, the influence of parameters such as pressure, temperature, and the addition of a polar co-solvent in the SFE yields of carotenoids and fat-soluble vitamins from T. obliquus biomass were evaluated. The highest extraction of alpha-tocopherol, gamma-tocopherol, and retinol was achieved at a pressure of 30 MPa and a temperature of 40 °C. It was observed that overall, the extraction yield increased considerably when a preliminary step of sample pre-treatment, based on a matrix solid phase dispersion, was applied using diatomaceous earth as a dispersing agent. The use of ethanol as a co-solvent, under certain conditions of pressure and temperature, resulted in selectively increasing the yields of only some compounds. In particular, a remarkable selectivity was observed if the extraction was carried out in the presence of ethanol at 10 MPa and 40 °C: under these conditions, it was possible to isolate menaquinone-7, a homologous of vitamin K2, which, otherwise, cannot not recovered by using traditional extraction procedures.

Comparison of Retention Behavior between Supercritical Fluid Chromatography and Normal-Phase High-Performance Liquid Chromatography with Various Stationary Phases

The retention behavior of a wide variety of stationary phases was compared in supercritical fluid chromatography (SFC) and normal-phase high-performance liquid chromatography (NP-HPLC). We also attempted to elucidate the retention behavior in SFC by investigating the selectivity of the different stationary phases. SFC separation conditions with polar stationary phases, such as silica gel (SL) and diol (Diol) phases, operate via adsorptions that include hydrophilic and ionic interactions similar to those in NP-HPLC. Moreover, non-polar stationary phases, such as pentabromophenyl (PBr), pyrenylethyl (PYE), and octadecyl (C₁₈), could be used despite the non-polar mobile phase conditions, because the dispersion and π-π interactions were stronger in SFC than in HPLC. These results reflect the selectivity of the stationary phase and its retention factor, thus providing useful information for the selection of appropriate stationary phases for particular analytes.

Simultaneous profiling of vitamin D metabolites in serum by supercritical fluid chromatography-tandem mass spectrometry (SFC-MS/MS)

Simultaneous profiling of serum vitamin D (VD) metabolites with similar structures is a big challenge. Thus, we developed and validated a SFC-MS/MS method, which is capable of eluting hydrophobic molecules, for quantification of VD₂/VD₃, 25-OH VD₂/VD₃, 3-epi-25-OH VD₂/VD₃, 1,25-(OH)₂ VD₂/VD₃ and 24,25-(OH)₂ VD₂/VD₃. VD metabolites were extracted from human serum using acetonitrile solvent. Column stationary phase, elution gradients, flow rate, column temperature, ion-source type and buffer system in post-column make-up solvent were optimized. Baseline separation of 10 VD metabolites can be achieved using PFP column within 10 min; and detection performed under positive electrospray ionization mode allowed quantification of VD metabolites in serum matrix with a limit of quantification (LOQ) varrying from 0.071 to 0.704 ng/mL. The accuracy was controlled with relative bias lower than 5.5% for QC and NIST samples. The developed method showed excellent intra-assay (0.52-7.93% RSD) and inter-assay (1.35-9.04% RSD) precision. The methodology shows enhanced efficiency and sensitivity as compared to LC-MS/MS method using the same column and mass spectrometer, along with significant correlation and low mean difference bias on measurements. For analysis of trace 1,25-(OH)₂ VD₂ and 1,25-(OH)₂ VD₃ in normal human serum or plasma, further improvement of LOQ (like derivatization) should be considered. In conclusion, the use of supercritical fluid not only enhanced safety with reduced solvent cost, but also improved retention and sensitivity as compared to LC-MS/MS method. The developed SFC-MS/MS method is appropriate for high throughput analysis of multiple VD metabolites in human serum with reduced solvent and economic cost.

Advances of supercritical fluid chromatography in lipid profiling

Supercritical fluid chromatography (SFC) meets with great favor due to its high efficiency, low organic solvent consumption, and the specialty for the identification of the isomeric species. This review describes the advances of SFC in targeted and untargeted lipid profiling. The advancement of the SFC instruments and the stationary phases are summarized. Typical applications of SFC to the targeted and untargeted lipid profiling are discussed in detail. Moreover, the perspectives of SFC in the lipid profiling are also proposed. As a useful and promising tool for investigating lipids in vitro and in vivo, SFC will predictably obtain further development.

Metabolomics in chronic kidney disease: Strategies for extended metabolome coverage

Chronic kidney disease (CKD) is becoming a major public health issue as prevalence is increasing worldwide. It also represents a major challenge for the identification of new early biomarkers, understanding of biochemical mechanisms, patient monitoring and prognosis. Each metabolite contained in a biofluid or tissue may play a role as a signal or as a driver in the development or progression of the pathology. Therefore, metabolomics is a highly valuable approach in this clinical context. It aims to provide a representative picture of a biological system, making exhaustive metabolite coverage crucial. Two aspects can be considered: analytical and biological coverage. From an analytical point of view, monitoring all metabolites within one run is currently impossible. Multiple analytical techniques providing orthogonal information should be carried out in parallel for coverage improvement. The biological aspect of metabolome coverage can be enhanced by using multiple biofluids or tissues for in-depth biological investigation, as the analysis of a single sample type is generally insufficient for whole organism extrapolation. Hence, recording of signals from multiple sample types and different analytical platforms generates massive and complex datasets so that chemometric tools, including data fusion approaches and multi-block analysis, are key tools for extracting biological information and for discovery of relevant biomarkers. This review presents the recent developments in the field of metabolomic analysis, from sampling and analytical strategies to chemometric tools, dedicated to the generation and handling of multiple complementary metabolomic datasets enabling extended metabolite coverage to improve our biological knowledge of CKD.

Applicability of supercritical fluid chromatography - mass spectrometry to metabolomics. I - Optimization of separation conditions for the simultaneous analysis of hydrophilic and lipophilic substances

The aim of this study was to evaluate the suitability of SFC-MS for the analysis of a wide range of compounds including lipophilic and highly hydrophilic substances (log P values comprised between -6 and 11), for its potential application toward human metabolomics. For this purpose, a generic unified chromatography gradient from 2 to 100% organic modifier in CO₂ was systematically applied. In terms of chemistry, the best stationary phases for this application were found to be the Agilent Poroshell HILIC (bare silica) and Macherey-Nagel Nucleoshell HILIC (silica bonded with a zwitterionic ligand). To avoid system overpressure at very high organic modifier proportion, columns of 100 × 3 mm I.D. packed with sub-3 μm superficially porous particles were selected. In terms of organic modifier, a mixture of 95% MeOH and 5% water was selected, with 50 mM ammonium formate and 1 mM ammonium fluoride, to afford good solubility of analytes in the mobile phase, limited retention for the most hydrophilic metabolites and suitable peak shapes of ionizable species. A sample diluent containing 50%ACN/50% water was employed as injection solvent. These conditions were applied to a representative set of metabolites belonging to nucleosides, nucleotides, small organic acids, small bases, sulfated/sulfonated metabolites, poly-alcohols, lipid related substances, quaternary ammonium metabolites, phosphate-based substances, carbohydrates and amino acids. Among all these metabolites, 65% of the compounds were adequately analyzed with excellent peak shape, 23% provided distorted peak shapes, while only 12% were not detected (mostly metabolites having several phosphate or several carboxylic acid groups).