Capillary electromigration techniques as tools for assessing the status of vitamins A, C and E in patients with cystic fibrosis

Nanoemulsion supported microemulsion electrokinetic chromatography coupled with selected preconcentration techniques as an approach for analysis of highly hydrophobic compounds

In this paper, an oil-in-water (O/W) nanoemulsion (NE) prepared by water cold dilution of an O/W microemulsion (ME) was introduced as a sample matrix in microemulsion electrokinetic capillary chromatography (MEEKC) for the highly hydrophobic compounds analysis. Several model compounds with log P_O/W values in the 4.1-10.9 range, from different chemical groups, including retinol, α-tocopherol, cholecalciferol, phylloquinone, menaquinone-7, dichlorodiphenyltrichloroethane, ivermectin have been tested. As a proof of the concept of NE formation, a dynamic light scattering technique was employed to determine the size distribution profile of NE particles. Moreover, due to relatively low conductivity of the NE matrix (50-100 times lower in comparison to the separation buffer) and a negative electric charge provided to hydrophobic compounds through NE dispersed phase, NE matrices have been combined with preconcentration techniques based on electrokinetic dosing, namely field amplified sample injection (FASI) and pressure assisted electrokinetic injection (PAEKI). The detection limits for vitamin K₁ and K₂-MK7 in the NE matrix in combination with FASI (NE-MEEKC-FASI) as well as PAEKI (NE-MEEKC-PAEKI) were up to 42.9 and 12.1 ng mL^-1, respectively. In comparison to standard hydrodynamic injection for microemulsion sample matrix NE-MEEKC-PAEKI grant 45-fold improvement in signal sensitivity. The study presents an innovative approach, as it enables the use of preconcentration techniques for highly hydrophobic compounds (log P_O/W > 4), which was not previously possible for implementation in the electromigration techniques. Likewise, the use of organic solvents has been reduced by using ME as a solvent for stock solutions and diluting with water prior to the analysis. The application to real samples was investigated using a dietary supplement containing vitamin K₂-MK7 obtained from the fermentation product of soybeans.

Vitamin C-Sources, Physiological Role, Kinetics, Deficiency, Use, Toxicity, and Determination

Vitamin C (L-ascorbic acid) has been known as an antioxidant for most people. However, its physiological role is much larger and encompasses very different processes ranging from facilitation of iron absorption through involvement in hormones and carnitine synthesis for important roles in epigenetic processes. Contrarily, high doses act as a pro-oxidant than an anti-oxidant. This may also be the reason why plasma levels are meticulously regulated on the level of absorption and excretion in the kidney. Interestingly, most cells contain vitamin C in millimolar concentrations, which is much higher than its plasma concentrations, and compared to other vitamins. The role of vitamin C is well demonstrated by miscellaneous symptoms of its absence—scurvy. The only clinically well-documented indication for vitamin C is scurvy. The effects of vitamin C administration on cancer, cardiovascular diseases, and infections are rather minor or even debatable in the general population. Vitamin C is relatively safe, but caution should be given to the administration of high doses, which can cause overt side effects in some susceptible patients (e.g., oxalate renal stones). Lastly, analytical methods for its determination with advantages and pitfalls are also discussed in this review.

Simultaneous Separation and Quantification of Vitamins by Microemulsion Liquid Chromatography

Microemulsion eluents have been found to have excellent potential uses in high-performance liquid chromatography (HPLC). Here, a novel, environmentally benign and simple method using concentration/flow-rate double-gradient elution using a microemulsion eluent was used to separate water- and fat-soluble vitamins simultaneously and rapidly. Preliminary screening experiments were performed to determine the optimum column type, surfactant concentration, co-surfactant to surfactant ratio, oil, mobile phase pH and microemulsion concentration. The resolution and analysis time were simultaneously optimized using concentration/flow-rate double-gradient elution. The optimized method simultaneously separated water- and fat-soluble vitamins using a Venusil ASB C8 column and a combination of isocratic and linear gradient elution modes using a microemulsion mobile phase (solvent A) consisting of 3.5% (w/w) sodium dodecyl sulfate, 10.5% (w/w) n-butanol, 0.8% (w/w) n-octanol and 85.2% (w/w) water and water (solvent B) at pH 2.50. The optimum detection wavelength was 283 nm. The method was validated and used to analyze a solid pharmaceutical sample.

Recent trends in analytical methods for water-soluble vitamins

In this review, recent advances in the analysis of water-soluble vitamins (WSVs) have been reported considering the advantages and disadvantages of various extraction, separation and detection techniques, commonly used for their quantification. Acid hydrolysis, enzyme treatment, SPE based methods and some other extraction methods have been discussed. Particular attention has been devoted to the analytical techniques based on liquid chromatography and electrophoresis. Furthermore, suitability and selectivity of hydrophilic interaction liquid chromatography (HILIC) for WSVs has been discussed in detail. Problems related to these techniques and their possible solutions have also been considered. Special focus has been given to the applications of liquid chromatography (since 2014-2019) for the simultaneous analysis of WSVs and their homologous in complex food samples.

Microemulsion Electrokinetic Chromatography in Combination with Chemometric Methods to Evaluate the Holistic Quality Consistency and Predict the Antioxidant Activity of Ixeris sonchifolia (Bunge) Hance Injection

In this paper, microemulsion electrokinetic chromatography (MEEKC) fingerprints combined with quantification were successfully developed to monitor the holistic quality consistency of Ixeris sonchifolia (Bge.) Hance Injection (ISHI). ISHI is a Chinese traditional patent medicine used for its anti-inflammatory and hemostatic effects. The effects of five crucial experimental variables on MEEKC were optimized by the central composite design. Under the optimized conditions, the MEEKC fingerprints of 28 ISHIs were developed. Quantitative determination of seven marker compounds was employed simultaneously, then 28 batches of samples from two manufacturers were clearly divided into two clusters by the principal component analysis. In fingerprint assessments, a systematic quantitative fingerprint method was established for the holistic quality consistency evaluation of ISHI from qualitative and quantitative perspectives, by which the qualities of 28 samples were well differentiated. In addition, the fingerprint—efficacy relationship between the fingerprints and the antioxidant activities was established utilizing orthogonal projection to latent structures, which provided important medicinal efficacy information for quality control. The present study offered a powerful and holistic approach to evaluating the quality consistency of herbal medicines and their preparations.