Preparation and characterization of quercetin-loaded lipid liquid crystalline systems.

The aim of the present study was to investigate mixtures of soy phosphatidylcholine (SPC) and glycerol dioleate (GDO) as encapsulation matrices for antioxidant quercetin. The effects of quercetin loading into non-aqueous formulations, non-lamellar liquid crystalline phases and their colloidal dispersions were studied by using synchrotron small angle X-ray diffraction, dynamic light scattering, cryogenic electron microscopy and high performance liquid chromatography. Quercetin incorporation is discussed in the context of lipid aggregation behavior, self-assembled nanostructure and chemical stability. The obtained results show that SPC/GDO-based formulations can incorporate relatively high amounts of quercetin and serve as liquid crystalline delivery vehicles in the form of bulk phases or colloidal dispersions.

Analysis of dioxins, furans and DL-PCBs in food and feed samples from Lithuania and estimation of human intake.

The methods, validated for determination of dibenzo-p-dioxins, dibenzofurans and dioxin like-polychlorinated biphenyls were applied for investigation of food and feed matrixes. Validation criteria on repeatability and reproducibility conditions comply with the requirements of European Commission. Validated methods were successfully applied for determination of PCDD/F and DL-PCB in fish, meat and feed using HRGC-HRMS. Statistical data was evaluated. One focal point of this work was to determine a fit for dioxins, furans and DL-PCBs of fatty fish for human consumption from the Baltic Sea ICES 26. Daily intake was found to be in the range of 2-4 TEQ pg/kg body weight and it is in the range of recommended TDI of 1-4 TEQ pg/kg body weight. The range of Baltic cod liver was 2-4 pg TEQ kgbw(-1)d(-1) WHO-TEQ((1998)) PCDD/F, PCB and its consumption was forbidden in Lithuania in 2011. Baltic fish represents 97.9% of human daily intake. Other matrixes like meat, eggs and feed did not exceed the maximum limit set by EU during the period of 2005-2011.

On-line preconcentration and determination of chromium(VI) in waters by high-performance liquid chromatography using precolumn complexation with 1,5-diphenylcarbazide.

A method for on-line chromatographic preconcentration and determination of chromium(VI) traces has been developed. Chromate was preconcentrated on a C18 column (50 x 6 mm I.D.) after complexation with diphenylcarbazide (DPC). Following the preconcentration step, analysis of the sample was performed using a C18 column (100 x 6 mm I.D.) with an eluent containing 6.10(-3) mol/l sulphuric acid and 20% (v/v) acetonitrile. Direct spectrophotometric detection at 546 nm was used. Experimental parameters such as mobile phase pH, DPC concentration, preconcentration flow-rate, sample volume were optimized for preconcentration and detection of Cr(VI)-DPC complex. Under the optimum conditions, most metal ions [Cr(III), Fe(III), Cu(II), Hg(II), Mo(VI), V(V)] and inorganic anions did not interfere. A detection limit of 0.02 ng/ml Cr(VI) can be attained when a sample volume of 100 ml is used. The technique has been applied successfully to the determination of Cr(VI) traces in drinking, surface and groundwater samples and the recoveries of added chromium were in the range 94-104%.