Hollow fibre-based liquid phase microextraction combined with high-performance liquid chromatography for the analysis of flavonoids in Echinophora platyloba DC. and Mentha piperita.

A simple, inexpensive and efficient three phase hollow fibre liquid phase microextraction (HF-LPME) technique combined with HPLC was used for the simultaneous determination of flavonoids in Echinophora platyloba DC. and Mentha piperita. Different factors affecting the HF-LPME procedure were investigated and optimised. The optimised extraction conditions were as follows: 1-octanol as an organic solvent, pHdonor=2, pHacceptor=9.75, stirring rate of 1000rpm, extraction time of 80min, without addition of salt. Under these conditions, the enrichment factors ranged between 146 and 311. The values of intra and inter-day relative standard deviations (RSD) were in the range of 3.18-6.00% and 7.25-11.00%, respectively. The limits of detection (LODs) ranged between 0.5 and 7.0ngmL(-1). Among the investigated flavonoids quercetin was found in E. platyloba DC. and luteolin was found in M. piperita. Concentration of quercetin and luteolin was 0.015 and 0.025mgg(-1) respectively.

Use of hollow fiber liquid phase microextraction and HPLC for extraction and determination of apigenin in human urine after consumption of Satureja sahendica Bornm.

The applicability of hollow fiber liquid phase microextraction (HF-LPME) was evaluated for extraction and preconcentration of apigenin prior to its determination by HPLC. Different parameters affecting the HF-LPME recovery such as nature of organic solvent, pH of donor and acceptor phases, extraction time, stirring speed, salt addition were optimized. Under optimum conditions (1-octanol as organic solvent, pH of the donor phase=3 and pH of acceptor phase=11.5, extraction time of 75 min, stirring speed of 1000 rpm) limit of detection (LOD) of 0.1 ng/mL, linear range of 0.5-300 ng/mL and correlation of determination (R(2)) of 0.9956 were obtained. The relative intra and inter-day standard deviations (RSD%) based on five replicate measurement were 3.5% and 10.7% respectively. Enrichment factor of 315 and recovery 85% were achieved. Finally, the applicability of the proposed method was evaluated by extraction and determination of apigenin in urine sample after consumption of Satureja sahendica Bornm. which is a native medicinal plant from Iran. Concentration of apigenin in urine sample was found to be 6.20 ng/mL.

Simultaneous optimization of the resolution and analysis time of flavonoids in reverse phase liquid chromatography using Derringer's desirability function.

The chemometrics approach was applied for simultaneous optimization of resolution and analysis time of seven flavonoids in reverse phase liquid chromatography. Derringer's desirability function, a multi-criteria decision making method, was used for the evaluation of two different chromatographic performance goals including resolution and analysis time. The selected flavonoids belong to different classes of flavonoids including: flavonols (myricetin, morin, quercetin and kaempferol) flavones (apigenin and luteolin) and flavanones (naringenin). The effect of five experimental factors on a chromatographic response function, formed using two sigmoidal desirability functions, was investigated. The sigmoidal functions were used to transform the optimization criteria, resolution and analysis time, into the desirability values. The factors studied were percentages of methanol, phosphoric acid and THF in mobile phase as well as flow rate and temperature. A rotatable, orthogonal central composite design was used to map the chromatographic response surface and then calculated chromatographic response functions were fitted to a polynomial model. The obtained regression model was characterized by both descriptive and predictive ability (R(2)=0.96). The model was verified, as good agreement was observed between the predicted and experimental values of the chromatographic response function in the optimal condition. The most effective factor on retention of flavonoids was percentage of methanol in mobile phase followed by temperature, flow rate, THF and H(3)PO(4) percentages. Optimum condition for separation of flavonoids was as follows: methanol:0.4% phosphoric acid in water:THF (45.3:54.4:0.3, v/v/v) as mobile phase with flow rate of 1 mL min(-1) at 30°C. The optimum condition was applied for separation of flavonoids of Satureja sahendica Bornm. which is an endemic medicinal plant of Iran.