Separation and determination of polyaromatic hydrocarbons by capillary electrokinetic chromatography

Poliaromatik hidrokarbonların (PAH çevrede bulunma sıklığı ve insan sağlığı üzerindeki zararlı etkileri nedeniyle bu bileşikler, pek çok alanda ön plana çıkmakta ve bunların bir karışımdan ayrılarak tayinleri de önem kazanmaktadır. Bu çalışmada sodyum dodesilbenzensülfonat (SDBS), hidrofobik poliaromatik hidrokarbonların (PAH) su-organik faz ortamında elektrokinetik kromatografi yöntemi ile ayrılmalarında sahte sabit faz olarak kullanılmıştır. PAH moleküllerinin, SDBS iyonu ile solvofobik etkileşimi sonucu negatif yük kazanan PAH türleri, elektrik alan altında hareket edebilirler. Böylece farklı halka (1-5) sayısına sahip 8 adet PAH ve 3 adet aromatik bileşik içeren örnek karışımının 130.000-230.000 arası teorik plaka etkinliği ile ayırımı başarılmıştır. Geliş zamanına göre bağıl tekrarlanırlık değerleri % 1.15-1.55 RSD, pik alanına göre ise % 2-9 RSD arasındadır.  Anahtar Kelimeler: Poliaromatik hidrokarbonlar, sodyum dodesilbenzensülfonat, kapiler elektroforez, elektrokinetik kromatografi.Due to the abundance of polyaromatic hydrocarbons (PAHs) in the environment and the adverse health effects to which they have been linked, these compounds have been the focus of considerable attention in a number of areas including chemical separations. Especially, nowadays due to many advantages of the capillary electrophoresis technique (CE), detection and analyses of these kinds of compounds by using CE have become more important. In order to separate nonionic compounds in CE, an interaction with a charged carrier in the buffer should be provided. Both PAHs can be separated in CE by using additives which cause selectivity change and resolution of PAHs having the same electrophoretic mobility, not only due to electrostatic interaction but also due to a combination of other effects like hydrophobicity, hydrogen bonding, dipole-dipole interaction, etc. Sodium dodecylbenzenesulfonate (SDBS) was evaluated as potential pseudo-stationary phase for the separation of highly hydrophobic polycyclic aromatic hydrocarbons (PAHs) with electrokinetic chromatography in aqueous-organic media. PAH molecules undergo a solvophobic interaction with the SDBS ion, forming negatively charged species that can migrate in an electric field. Thus electrophoretic separations of 8 PAHs and 3 aromatic compounds having different ring numbers (1-5) were achieved with efficiencies between 130.000-230.000 theoretical plates. Reproducibilities of migration times range between 1.15 and 1.55 %RSD and peak areas between 2 and 9 %RSD. Keywords: Polyaromatic hydrocarbons, sodium dodecylbenzenesulfonate, capillary electrophoresis, electrokinetic chromatography

Determination of Vitamin B2 Content in Black, Green, Sage, and Rosemary Tea Infusions by Capillary Electrophoresis with Laser-Induced Fluorescence Detection

Vitamin B2, also known as riboflavin (RF) is an essential micronutrient for human health and must be obtained from dietary sources. Plants biosynthesize riboflavin and are important dietary sources of vitamin B2 for humans. Our present study reports sensitive detection of vitamin B2 in widely consumed tea infusions, namely black, green, sage and rosemary tea infusions, by a capillary electrophoresis method combined with laser induced fluorescence detection. Moreover, the correlation between the vitamin B2 content of tea plants with their total phenolics (TPs) and antioxidant capacity are evaluated in this study. Whereas green teas have the highest TPs and antioxidant capacity, the highest RF content isin sage infusions. The RF content ranged between 0.34 and 10.36 µg/g for all tea samples studied. Comparing the RF content of tea samples found in this study to the RF content of known RF sources, tea infusions are proposed as important dietary sources of vitamin B2

Removal of hexavalent chromium from aqueous solution by barium ion cross-linked alginate beads

Barium ion cross-linked alginate beads have shown great affinity to toxic hexavalent chromium ions in aqueous solution, contrary to the traditional calcium alginate beads. The adsorption experiments were carried out by the batch contact method. The optimal pH for removal was found to be pH 4. The equilibrium was established in 4 h and the removal efficiency of chromium (VI) was found as 95%. The adsorption data fit well with Langmuir and Freundlich isotherms. The maximum chromium (VI) adsorption capacity determined from Langmuir isotherm was 36.5 mg/g dry alginate beads. Our study suggests that barium alginate beads can be used as cost-effective and efficient adsorbents for the removal of chromium (VI) from contaminated waters

Sustainable alginate-carboxymethyl cellulose superabsorbents prepared by a novel quasi-cryogelation method

The research in biopolymer-based superabsorbents is gaining importance in the green chemistry field thanks to their environmentally friendly properties. In this study, a biopolymer-based superabsorbent made of calcium ion crosslinked alginate/carboxymethyl cellulose composite was prepared by a new quasi-cryogelation process, where the complete ionic gelation takes place before the freezing step, in contrast to the conventional cryogelation technique in which gelation occurs under semi-frozen conditions. Thanks to the facile quasi-cryogelation method, the morphology of the gels changed and a significant increase in water absorption properties has been achieved. The swelling properties of the material were investigated in distilled water and different physiological fluids. Results show that the proposed material shows good water absorption property where a water absorption of 2343% was reached and even after five cycles this value was 1200%. As a result, this study reports a biopolymer-based sustainable superabsorbent which is appropriate for various applications such as the removal of pollutants from water or diaper production

A Biopolymer Superabsorbent Based on Alginate-Carboxymethyl Cellulose Quasi-cryogels

The research in biopolymer-based superabsorbents is gaining importance in the green chemistry field thanks to their environmentally friendly properties. In this study, a biopolymer-based superabsorbent made of calcium ion crosslinked alginate/carboxymethyl cellulose composite was prepared by a new quasi-cryogelation process, where the complete ionic gelation takes place before the freezing step, in contrast to the conventional cryogelation technique in which gelation occurs under semi-frozen conditions. Thanks to the facile quasi-cryogelation method, the morphology of the gels changed and a significant increase in water absorption properties has been achieved. The swelling properties of the material were investigated in distilled water and different physiological fluids. Results show that the proposed material shows good water absorption property where a water absorption of 2366% was reached and even after five cycles this value was 1200%. As a result, this study reports a biopolymer-based sustainable superabsorbent which is appropriate for various applications such as the removal of pollutants from water or diaper production

Electric-field induced phase transitions in capillary electrophoretic systems

The movement of particles in a capillary electrophoretic system under electroosmotic flow was modeled using Monte Carlo simulation with the Metropolis algorithm. Two different cases with repulsive and attractive interactions between molecules were taken into consideration. Simulation was done using a spin-like system, where the interactions between the nearest and second closest neighbors were considered in two separate steps of the modeling study. A total of 20 different cases with different rates of interactions for both repulsive and attractive interactions were modeled. The movement of the particles through the capillary is defined as current. At a low interaction level between molecules, a regular electroosmotic flow is obtained; on the other hand, with increasing interactions between molecules, the current shows a phase transition behavior. The results also show that a modular electroosmotic flow can be obtained for separations by tuning the ratio between molecular interactions and electric field strength