Fast separation of water-soluble vitamins by hydrophilic interaction liquid chromatography based on submicrometer flow-through silica microspheres

In the present study, submicrometer flow-through silica microspheres (Sub-FTSiO₂) was for the first time obtained via a suspension polymerization method coupled with sol-gel transition and phase separation. The Sub-FTSiO₂ was characteristic of rich mesopores, penetrable macropores and small particle size, which would be beneficial to fast mass transfer, low column backpressure and high column efficiency. It was directly used as the hydrophilic interaction liquid chromatographic (HILIC) stationary phase, and the fast separation of seven water-soluble vitamins in 2.2 min was realized. The proposed method was successfully applied to the determination of water-soluble vitamins in two functional beverages on the market. The prepared Sub-FTSiO₂ was well demonstrated for fast HILIC, and would be potential as the stationary phase matrix for fast liquid chromatography in diverse separation modes.

Characterization and Quantitation of Vitamin B12 Compounds in Various Chlorella Supplements

Vitamin B₁₂ was determined and characterized in 19 dried Chlorella health supplements. Vitamin contents of dried Chlorella cells varied from <0.1 μg to approximately 415 μg per 100 g of dry weight. Subsequent liquid chromatography/electrospray ionization-tandem mass spectrometry analyses showed the presence of inactive corrinoid compounds, a cobalt-free corrinoid, and 5-methoxybenzimidazolyl cyanocobamide (factor IIIm) in four and three high vitamin B₁₂-containing Chlorella tablets, respectively. In four Chlorella tablet types with high and moderate vitamin B₁₂ contents, the coenzyme forms of vitamin B₁₂ 5'-deoxyadenosylcobalamin (approximately 32%) and methylcobalamin (approximately 8%) were considerably present, whereas the unnaturally occurring corrinoid cyanocobalamin was present at the lowest concentrations. The species Chlorella sorokiniana (formerly Chlorella pyrenoidosa) is commonly used in dietary supplements and did not show an absolute requirement of vitamin B₁₂ for growth despite vitamin B₁₂ uptake from the medium being observed. In further experiments, vitamin B₁₂-dependent methylmalonyl-CoA mutase and methionine synthase activities were detected in cell homogenates. In particular, methionine synthase activity was significantly increased following the addition of vitamin B₁₂ to the medium. These results suggest that vitamin B₁₂ contents of Chlorella tablets reflect the presence of vitamin B₁₂-generating organic ingredients in the medium or the concomitant growth of vitamin B₁₂-synthesizing bacteria under open culture conditions.

Purification, identification, and characterization of methylcobalamin from Spirulina platensis

The present study reports methylcobalamin in Spirulina platensis using high-performance liquid chromatography (HPLC), thin-layer chromatography (TLC), microbiological assay, chemiluminescence assay, liquid chromatography-mass spectrometry (LC-MS), and tandem mass spectrometry (MS/MS). Extraction of vitamin B12 from S. platensis was carried out without using cyanide. Partial purification was achieved using Amberlite XAD-2 followed by elution with 80% (v/v) methanol. Activated charcoal facilitated removal of impurities in S. platensis extract and in further purification of vitamin B12. The purified fraction was identified to contain methylcobalamin as analyzed by HPLC and TLC. Authenticity of methylcobalamin was further confirmed by LC-MS and MS/MS. Quantitation of methylcobalamin in a test sample of S. platensis biomass was performed using microbiological assay and chemiluminescence assay and was found to be 38.5±2 and 35.7±2 μg/100 g of dry biomass, respectively.

[Improving the efficacy of synergetically facilitated pertraction of p-aminobenzoic acid by increasing the reextraction rate]

The studies on facilitated pertraction of PABA with Amberlite LA-2 and 1-octanol as phase modifier indicated the increase of the process efficiency and, implicitly, of the transport capacity of the liquid membrane by adding KOH in the stripping phase. Thus, the use of KOH led to the diminution of the kinetic resistance of the reextraction process, with positive effects on the acid final mass flow and permeability factor. Compared to the similar pertraction systems containing NaOH in the stripping phase and in direct correlation with the pertraction parameters (pH-gradient between the feed and stripping phases, carrier and alchohol concentrations inside the liquid membrane), the final mass flow can be accelerated for about 1.9 times, and the permeability through liquid membrane can be enhanced for about 1.5 times in presence of KOH.

[Comparative study on separation of p-aminobenzoic and p-hydroxy-benzoic acids by reactive extraction]

The comparative study on reactive extraction of p-aminobenzoic and p-hydroxybenzoic acid with Amberlite LA-2 and D2EHPA in two solvents with different polarity (n-heptane and dichloromethane) indicated that the nature of the specific substituents, extractant type and solvent polarity control the extraction mechanism. Although the reactive extraction with Amberlite LA-2 of the two acids occurs by means of rather similar interfacial reactions, the extraction with D2EHPA is based on different mechanisms, due to the participation of the two different substituents of aminic and phenolic type. In all cases, the most efficient extractions have been reached for the combination Amberlite LA-2-dichloromethane.

[The extraction and transport of folic acid through liquid membranes]

The study on the extraction and transport of folic acid (vitamin B9) with Amberlite LA-2 underlined the significant influences of the pH-gradient on the aqueous phases, carrier concentration and mixing intensity, in correlation with the extraction mechanism. Thus, for reaching the maximum efficiency of folic acid separation, the pH-value of the initial aqueous phase of 5, the pH-value of the final aqueous solution greater than 11 and the Amberlite LA-2 concentration in solvent layer over 80 g/l are required.

Extraction of water-soluble vitamins from pharmaceutical preparations using AOT (sodium di-2-ethylhexyl sulfosuccinate)/pentane reversed micelles

Reversed micelles can be used to concentrate water-soluble materials in the water pool. In this study, the extraction of water-soluble vitamins into reversed micelles was attempted, and a flow system was used to determine the time-course of the vitamin extraction. The efficiency of extraction was strongly affected by the extraction temperature and the concentration of reversed micelles, and the selectivity depended on the size of micelles. Water-soluble vitamins could be efficiently and rapidly extracted. The selective extraction of a model mixture of vitamins from pharmaceutical preparations was also attempted. Moreover, the usefulness of the proposed method for the determination of vitamins in various commercial tablets was also demonstrated. Using of this method, the surfactant remains mixed with the extracted compounds, and so we attempted to remove the surfactant from the extract by supercritical fluid extraction. Supercritical carbon dioxide containing 7.5% ethanol as entrainer was found to be the most efficient solvent for removing residual surfactant from the extract.

Micellar electrokinetic capillary chromatography analysis of water-soluble vitamins and multi-vitamin integrators

Micellar electrokinetic capillary chromatography (MECC) was applied to the determination of water-soluble vitamins (WSV) in pharmaceutical preparations. The analytical procedure employed in the WSV separation by MECC showed a satisfactory average column efficiency (195,000 N) and resolution (more than 100 theoretical peaks separable). The mean reproducibility in the retention time of consecutive and day-to-day runs was 1.1% and 5.1%, respectively. Analyses were performed after extraction of active ingredients by solid phase extraction. Recoveries (92-103%) and relative variation coefficients (less than 5%) confirmed the potential of MECC in the field of pharmaceutical analysis.