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    Development of a New Methodology for Determination of Vitamin B9 at Trace Levels by Ultrasonic-Assisted Cloud Point Extraction Prior to HPLC
    (Springer, 2017) Ulusoy, Halil Ibrahim; Acidereli, Hilal; Ulusoy, Songul; Erdogan, Selim
    A new analytic methodology based on ultrasonic-assisted cloud point extraction coupled with high-performance liquid chromatography (UA-CPE-HPLC) was developed and successfully applied to determine vitamin B9 in food samples. Polyethylene glycol 6000 (PEG-6000) was used as nonionic surfactant due to its chemical properties and trade availability. All parameters such as surfactant concentration, ionic strength, and the other conditions were also investigated and optimized. The optimal conditions for UA-CPE method were presented with 2.4 % w/v PEG-6000, 14.6 % w/v Na2SO4, and ultrasonic heating assistance at 40 A degrees C for 20 min. The calibration curve for vitamin B9 was linear ranging from 20 to 800 mu g L-1, with correlation coefficients being 0.9944 determined by a HPLC-diode array detector (DAD) detector. Relative standard deviation for 150 mu g L-1 was calculated as 2.87 %. Recovery values in different concentration levels were in the range of 95.6-104.2 %. The obtained results demonstrate that the proposed method can be applied for determination of vitamin B9 in real samples.
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    A new approach to the determination of folic acid at trace levels: using a Fe(III)-folic acid complex to amplify analytical signal
    (Royal Soc Chemistry, 2016) Ulusoy, Songul; Acidereli, Hilal; Erdogan, Selim; Ulusoy, Halil Ibrahim
    A fast, efficient, cost-effective, and environmental-friendly analytical methodology was developed for preconcentration and determination of trace folic acid in food samples prior to high performance liquid chromatography with diode array detection (HPLC-DAD). The method is based on formation of stable complexes between folic acid and Fe(III) ions at pH 8.0. The formed complexes were extracted to a nonionic surfactant phase containing PONPE 7.5. The surfactant rich phase (SRP) was separated by decantation and diluted with 300 mu L of a mixture of 1 M HCl and methanol at a 1 : 1 ratio. The parameters and variables that affected the method were also investigated and optimized in detail. The limit of detection (LOD) of folic acid was 6.06 ng mL(-1), the linear range of quantitation for folic acid was 20-1200 ng mL(-1) and the correlation coefficients of the calibration curves were 0.9976. The average recoveries and relative standard deviations in the analysis of real samples were in the range of 95.1-105.1% and 1.73-5.25%, respectively. After validation of the method was carried out, the method was applied to the determination of folic acid in real samples, including baby foods, vegetables, cereals, and pharmaceutical samples.