Adsorption Of Vitamin Research Articles

Vitamin C Affinity to TiO2 Nanotubes: A Computational Study by Hybrid Density Functional Theory Calculations

Titanium dioxide nanotubes (TNT) have been extensively studied because of their unique properties, which make such systems ideal candidates for biomedical application, especially for the targeted release of drugs. However, knowledge about the properties of TiO2 nanotubes with typical dimensions of the order of the nanometer is limited, especially concerning the adsorption of molecules that can be potentially loaded in actual devices. In this work, we investigate, by means of simulations based on hybrid density functional theory, the adsorption of Vitamin C molecules on different nanotubes through a comparative analysis of the properties of different structures. We consider two different anatase TiO2 surfaces, the most stable (101) and the more reactive (001)A; we evaluate the role of the curvature, the thickness and of the diameter as well as of the rolling direction of the nanotube. Different orientations of the molecule with respect to the surface are studied in order to identify any trends in the adsorption mechanism. Our results show that there is no preferential functional group of the molecule interacting with the substrate, nor any definite spatial dependency, like a rolling orientation or the concavity of the nanotube. Instead, the adsorption is driven by geometrical factors only, i.e., the favorable matching of the position and the alignment of any functional groups with undercoordinated Ti atoms of the surface, through the interplay between chemical and hydrogen bonds. Differently from flat slabs, thicker nanotubes do not improve the stability of the adsorption, but rather develop weaker interactions, due to the enhanced curvature of the substrate layers.

Comparative study of different polar adsorbents for adsorption of water soluble vitamins

The comparative study of adsorption properties of several adsorbents with focus on selective isolation of water-soluble B vitamins (B2, B, B6 and B12) from food products and some pharmaceutical formulations by solid-phase extraction is performed. The adsorption of vitamins was investigated for eleven adsorbents including bare silica, silica modified with polyvinylpyrrolidone, octadecyl-, aminopropyl-, cyanobutyl-functional groups, poly(styrene–divinylbenzene) modified with lactam groups, hypercrosslinked polystyrene, activated carbon and porous microdispersed sintered detonation nanodiamond. Dynamic adsorption capacities of adsorbents for each of the tested vitamins were determined from the dynamic output curves. The highest adsorption capacity was found for HCPS-based sorbents, but complete desorption from these sorbents required harsh conditions. On this reason MSDN was suited better for the preconcentration of water soluble vitamins.

Synthesizing Vitamin E Molecularly Imprinted Polymers via Precipitation Polymerization

Molecularly imprinted polymers (MIPs) were prepared by the precipitation polymerization process, with vitamin E as the template molecule, ethylene glycol dimethacrylate as the cross-linker, and three different functional monomers, respectively. Adsorption experiments were conducted to investigate the performance of each MIP and compared to the nonimprinted polymers (NIPs). It was found that MIPs are superior to NIPs in general, with acrylamide-based MIP showing the best adsorption capacity of 38.8 mg·g–1 and an imprinting factor of 2.6. The optimal imprinting ratio and cross-linking ratio to be 1:5 and 5:1, respectively. The Freundlich equation was found superior to Langmuir to describe the adsorption isotherm data on the MIP/NIP. The adsorption of vitamin E on the MIP was found to be a heterogeneous process and consists of two mechanisms, which were confirmed by the analysis of the thermodynamic properties of the adsorption process.

Mathematical Modelling of Micronutrient Recovery from Vegetable Oil by Silica-based Adsorption: Vitamin E from Palm Fatty Acid Distillate

Mathematical modelling on kinetics of batch adsorption of vitamin E separation from palm fatty acid distillate (PFAD) has been set-up and then applied for literature experimental data. Since the sizes of adsorbent particles used are usually relatively small, the concentration in the particles is assumed to be uniform. Hence, the adsorption rate is controlled by the rate of solute mass transfer from the bulk fluid to the surface of particles. In this model, the rate of mass transfer is assumed to be proportional to the concentration deviation from the equilibrium state. Meanwhile, the equilibrium models applied were coefficient distribution, Freundlich, and Langmuir with the values of the parameters obtained from literature data. It turned out that the model set-up can quantitatively describe the experimental kinetics data from literature. The value of mass transfer coefficient per unit adsorbent mass (kca) is obtained by curve fitting. It is also observed that the model proposed quantitatively describes the batch adsorption process well. The three equilibrium models applied are suitable for the mathematical modelling. Adjustment of the values of equilibrium isotherm parameters from literature significantly improves the accuracy of the model.

Adsorption of vitamin E on mesoporous titania nanocrystals

Tri-block nonionic surfactant and titanium chloride were used as starting materials for the synthesis of mesoporous titania nanocrystallite powders. The main objective of the present study was to examine the synthesis of mesoporous titania nanocrystals and the adsorption of vitamin E on those nanocrystals using X-ray diffraction (XRD), transmission electron microscopy, and nitrogen adsorption and desorption isotherms. When the calcination temperature was increased to 300 °C, the reflection peaks in the XRD pattern indicated the presence of an anatase phase. The crystallinity of the nanocrystallites increased from 80% to 98.6% with increasing calcination temperature from 465 °C to 500 °C. The N 2 adsorption data and XRD data taken after vitamin E adsorption revealed that the vitamin E molecules were adsorbed in the mesopores of the titania nanocrystals.

Adsorption of Vitamin E on Mesoporous Carbon Molecular Sieves

The adsorption of vitamin E onto mesoporous carbons CMK-1 and CMK-3 from vitamin E solutions with different concentrations in nonpolar (n-heptane) and polar (n-butanol) solvent has been studied for the first time, and the results are compared to a conventional microporous carbon adsorbent, activated carbon. The amount of vitamin E adsorption on the different adsorbents depends on the solvent as well as the mesopore volume and the surface area of the adsorbent. It has been found that n-heptane is preferred to achieve a maximum amount of vitamin E adsorption. Among the carbon materials studied, CMK-3 shows the highest vitamin E adsorption due to the large specific mesopore volume of this adsorbent. CMK-3 was characterized after vitamin E adsorption to confirm the structure of the adsorbent and prove that the adsorption takes place in the channels of the mesoporous carbon adsorbent. XRD and nitrogen adsorption data recorded after vitamin E adsorption confirm the tight packing of the vitamin E molecules insid...

Separation of vitamin E from palm fatty acid distillate using silica: II: Kinetics of batch adsorption

The kinetics of vitamin E batch adsorption onto silica was detailed in this study; as functions of initial vitamin E concentration, reaction temperature, agitation rate and silica mass. For all systems, the adsorption occurred rapidly initially and then proceeded gradually to equilibrium in about 5 min. It was found that the fraction of vitamin E adsorbed onto the silica at equilibrium was higher when the initial vitamin E concentration in the solution was lower. However, the reverse was true for the effects of agitation rate and silica mass. Increasing the reaction temperature would result in lower adsorption capacity, suggesting that adsorption of vitamin E onto silica was exothermic in nature. Two main adsorption mechanisms were involved during the vitamin E adsorption, namely external mass transfer and intraparticle diffusion. The external mass transfer coefficient, k f, and rate constant of intraparticle diffusion, k id, were determined for each system. It was noted that increasing the initial vitamin E concentration resulted in a decrease in k f values, but an increase in k id values. Increase in agitation rate facilitated the adsorption processes and therefore increased both k f and k id values. Meanwhile, a higher silica mass gave a lower k id value, indicating that the intraparticle diffusion rate was lower. The activation energies were considered high (−25.45 and −54.13 kJ mol −1 for external mass transfer and intrapartiele diffusion, respectively) suggesting that the adsorption appeared to be a chemosorption rather than low energy physiosorption process.

Adsorption of vitamin B 12 to alumina, kaolinite, sand and sandy soil

Vitamin B 12 is an important component of media used to stimulate the growth of many anaerobic microbes that dechlorinate aliphatic compounds. Its delivery to the subsurface is therefore a concern for enhanced in situ bioremediation and bioaugmentation. In situ circulation of vitamin B 12 and a chemical reductant has also been field tested for treatment of chlorinated methanes, ethanes, and ethenes. The objective of this study was to determine the extent of B 12 (added as cyanocobalamin) adsorption to aquifer solids. Batch studies indicated a minor amount of adsorption to kaolinite clay (Freundlich K f=1.5 (μg/g) (mL/μg) 1/ n and 1/ n=0.39) and sand ( K f=0.70 (μg/g) (mL/μg) 1/ n and 1/ n=0.84), and no detectable adsorption to alumina. Column studies using a 3H 2O tracer and vitamin B 12 in distilled water (10 μM) resulted in a B 12 retardation factor ( R) of approximately 2 for both sand (0.14% organic carbon) and a sandy soil (2.5% organic carbon). Using groundwater containing organic carbon (2.8 mg/L) in place of distilled water did not significantly change R. The relatively low value for R indicates vitamin B 12 can be distributed throughout a contaminated aquifer without experiencing significant losses to adsorption.

Selective adsorption of limonin and naringin from orange juice to natural and synthetic adsorbents

In the majority of citrus juices, bitterness is mainly ascribed to the presence of limonoids (triterpenes) and flavanone glycosides (flavonoids), namely limonin and naringin. In this study, the selective removal of limonin and naringin from citrus juice by batch adsorption to different materials was investigated. Since the removal of reducing sugars, pigments and vitamin C may also occur, the eventual adsorption of these compounds was also investigated. The following adsorbents were tested: activated diatomaceous earths, granulated activated carbon and synthetic neutral resins (Amberlite XAD-4, XAD-7 and XAD-16). Both Freundlich and Langmuir isotherm models showed a good fit to the adsorption of limonin to the resins used. Concerning naringin adsorption, a good fit of these models was only observed when the XAD-7 resin was used. Sigmoidal profiles were obtained for the adsorption of limonin to granular activated carbon. Unfavourable isotherms were also observed for limonin and naringin adsorption to activated earths. These isotherm adsorption profiles can be explained by a multilayer adsorption phenomenon. The highest adsorption efficiency for the bitter compounds was observed when synthetic neutral resin, Amberlite XAD-7 was used. The separation factor limonin/naringin varied from 16 (with earths) to 57 (with XAD-7 resin). The adsorption of sugars and pigments to the resins was low. No adsorption of vitamin C was detected for any of the adsorbents tested. The estimated affinity and separation factors show that the neutral resins tested are adequate for the selective removal of limonin from orange juices. The estimated values of free energy of adsorption, lower than –13.3 kJ mol–1 K–1, indicate that a physiosorption process occurred.

Preparation of mesoporous activated carbon fibers and their adsorption properties

Activated carbon fibers from pitch/organometallics, viz Y (acac) 3, TiO (acac) 2, Al (acac) 3, composites by steam invigoration were prepared. The pitch /organometallics homogeneous composites as starting materials were prepared using an organic solvent such as quinoline. Highly mesoporous activated carbon fibers with high specific surface area (1200-1400m2/g, mesopore ratio>70%) were obtained from pitch/Y (acac) 3 composites. On the other hand, TiO (acac) 2 and Al (acac) 3 exhibited no ability for the formation of mesoporous carbons. The adsorption of vitamin, humic acid, and cyclodextrin on the activated carbon fibers was investigated. Mesoporous activated carbon fibers from pitch/Y (acac) 3 composites showed excellent adsorption characteristics for these large molecular substances KEYWORDS: Activated carbon fiber, Mesopore, Organometallics, Rare earth metal complex

Comparison of lyophilized plasmas with fresh plasmas for calibration of thromboplastin reagents in oral anticoagulant control

In a multicentre study of four thromboplastin reference materials (three from rabbit brain and one from bovine brain combined with adsorbed bovine plasma), three types of lyophilized plasmas were included. One was a pooled normal plasma, another was made by pooling plasmas of coumarin-treated patients, and the third was prepared by adsorption of vitamin K dependent clotting factors (artificially depleted). The purpose of this study was to investigate whether these lyophilized plasmas could be used for reliable calibration of the four thromboplastins. Calibration line slopes were calculated for the lyophilized plasmas and compared to the slopes based on fresh plasmas. When a rabbit thromboplastin was calibrated against a similar but not identical reagent (like-to-like comparison), the slopes for lyophilized plasmas and for fresh plasmas were the same. However, significant differences between lyophilized and fresh plasmas were observed in the calibration of unlike thromboplastins. The deviation of the slope with artificially depleted plasma was greater than that with lyophilized coumarin plasma. Indiscriminate use of these lyophilized plasmas for thromboplastin calibration should be avoided.

Preparation of Mesoporous Activated Carbon Fibers and Their Adsorption Properties

Activated carbon fibers from pitch/organometallics, viz Y (acac) 3, TiO (acac) 2, Al (acac) 3, composites by steam invigoration were prepared. The pitch /organometallics homogeneous composites as starting materials were prepared using an organic solvent such as quinoline. Highly mesoporous activated carbon fibers with high specific surface area (1200-1400m2/g, mesopore ratio>70%) were obtained from pitch/Y (acac) 3 composites. On the other hand, TiO (acac) 2 and Al (acac) 3 exhibited no ability for the formation of mesoporous carbons. The adsorption of vitamin, humic acid, and cyclodextrin on the activated carbon fibers was investigated. Mesoporous activated carbon fibers from pitch/Y (acac) 3 composites showed excellent adsorption characteristics for these large molecular substances KEYWORDS: Activated carbon fiber, Mesopore, Organometallics, Rare earth metal complex

Adsorption of Vitamin K<sub>3</sub> on a Gold Electrode Studied by Specular Reflection and Absorption Spectroscopy

Adsorption of Vitamin K<sub>3</sub> on a Gold Electrode Studied by Specular Reflection and Absorption Spectroscopy

Electrocatalytic oxidation and flow detection of hydrazine compounds in liquid chromatography at a vitamin B‐12 adsorbed glassy carbon electrode

AbstractA vitamin B‐12 chemically modified electrode (CME) was constructed by adsorption of vitamin B‐12 onto a glassy carbon surface. The electrode catalyzes the electrooxidation of hydrazine compounds over a wide pH range. The electrocatalytic behavior of hydrazines is elucidated with respect to the CME preparation conditions, solution pH, operating potential, mobile phase flow rate, and other variables. When applied to liquid chromatographic detection of the analytes, the vitamin B‐12 CME yielded a linear response range over 2 orders of magnitude, and detection limits at the picomole level. The vitamin B‐12 CME offers acceptable catalytic stability in both batch and flow systems.

Voltammetric determination of vitamin D 3 with a rotating glassy carbon electrode

A voltamperometric study (DC and DP) on the electroanalytical behaviour of vitamin D 3 in a methanolic solution using LiClO 4 as the supporting electrolyte and working with a glassy carbon electrode was carried out. Vitamin D 3 exhibits an oxidation wave (DC) or peak (DP) at potentials close to +1.1 V (versus SCE). The optimum experimental conditions for the best reproducibility of the voltamperometric signal were determined and the different parameters affecting the electrochemical process were studied. The electrochemical process was seen to be irreversible and, under certain conditions, adsorption of vitamin D 3 onto the electrode surface was observed. A voltamperometric procedure for the determination of vitamin D 3 in a concentration range of 2 × 10 −6−2 × 10 −4 M is proposed. The detection limit is of the order of 2 × 10 −6 M and the relative standard deviations are 1.1% (DC) and 2.6% (DP), respectively.

Non-Decalcified Barium Sulfate-Adsorbed Plasma A Potentially Useful Reagent for Studying Blood Clotting, Platelets or Complement

Plasma was prepared by rapid centrifugation of native blood followed by adsorption of vitamin K-dependent clotting factors with BaSO4. Compared to fresh citrated plasma, BaSO4-treated plasma contained about 80% of factor V and factor VII and the same concentration of fibrinopeptide A. Assays were also carried out after overnight incubation of citrated plasma and BaSO4-adsorbed plasma with and without added citrate and compared to assays of fresh citrated plasma. Factor V decreased to about 25% in both citrated samples, factor VIII decreased to 45% in both samples of BaSO4-treated plasma, and fibrinopeptide A did not change. Thus loss of factor V activity depended on reduction in divalent cation concentration whereas loss of factor VIII activity may have resulted from effects of early traces of thrombin.

THE EFFECT OF SODIUM BENTONITE ADMINISTRATION ON VITAMIN A METABOLISM IN THE RAT

The inclusion of sodium bentonite in the diet severely limited the ability of vitamin A deficient rats to store the vitamin in the liver. This effect was observed both with vitamin A and with the provitamin β-carotene. Moreover, the liver weight per 100 gm. body weight was found to be less in most of the groups receiving sodium bentonite than in control groups. The results may be interpreted in terms of a physical adsorption of vitamin A or β-carotene on sodium bentonite present in the small intestine. Sodium bentonite cannot be regarded as an inert ingredient of the diet of rats and its prolonged administration might be expected to have deleterious effects.

THE EFFECT OF SODIUM BENTONITE ADMINISTRATION ON VITAMIN A METABOLISM IN THE RAT

The inclusion of sodium bentonite in the diet severely limited the ability of vitamin A deficient rats to store the vitamin in the liver. This effect was observed both with vitamin A and with the provitamin β-carotene. Moreover, the liver weight per 100 gm. body weight was found to be less in most of the groups receiving sodium bentonite than in control groups. The results may be interpreted in terms of a physical adsorption of vitamin A or β-carotene on sodium bentonite present in the small intestine. Sodium bentonite cannot be regarded as an inert ingredient of the diet of rats and its prolonged administration might be expected to have deleterious effects.

Refining of Oils Containing Vitamin A

THE alkali-refining of fish liver oils containing vitamin A has, in the last few years, acquired increased importance due to the development of molecular distillation. This method of distilling, while yielding concentrates of a high vitamin A content, requires, in order to obtain satisfactory results, oils free from impurities and with low acid-values. Alkali-refining provides the best means of satisfying this requirement; but it has been considered that a treatment of this kind decreases the potency of vitaminic oils because of the adsorption of vitamin A by soaps formed in situ1.

The Adsorption of Vitamin A from Fish Liver Oils

In experiments with fish liver oils, vitamin A alcohol was more readily adsorbed than it fatty acid esters or than triglycerides and other fatty acid esters. The vitamin A esters were less readily adsorbed than the triglycerides.