Solvent Bar Microextraction with HPLC for Determination and Protein-Binding Characteristics of Oleanolic Acid and Ursolic Acid

Solvent bar microextraction combined with HPLC-DAD for simultaneous determination of diuretics in human urine and plasma samples

BACKGROUND

A simple and powerful microextraction procedure, the solvent bar microextraction (SBME), was used for the simultaneous determination of two diuretics, furosemide and spironolactone in human urine and plasma samples, using high-performance liquid chromatography coupled with diode array detection (HPLC-DAD).

METHODS

The appropriate amount (2 µL) of 1-octanol as an organic solvent confined within (2.5 cm) of a porous hollow fiber micro-tube, sealed at both ends was used for this procedure. The conditions for the SBME were optimized in water and the analytical performance were examined in spiked human urine and plasma samples.

RESULTS

The optimized method exhibited good linearity (R2 > 0.997) over the studied range of higher than 33 to 104 µg L-1 for furosemide and spironolactone in urine and plasma samples, illustrating a satisfactory precision level with RSD values between 2.1% and 9.1%.

DISCUSSION

The values of the limits of detection were found to be in the range of 6.39 to 9.67 µg L-1, and extraction recovery˃ 58.8% for both diuretics in urine and plasma samples. The applicability and effectiveness of the proposed method for the determination of furosemide and spironolactone in patient urine samples were tested.

CONCLUSION

In comparison with reference methods, the attained results demonstrated that SBME combined with HPLC-DAD was proved to be simple, inexpensive, and promising analytical technology for the simultaneous determination of furosemide and spironolactone in urine and plasma samples.

Simultaneous Analysis of Ursolic Acid and Oleanolic Acid in Guava Leaves Using QuEChERS-Based Extraction Followed by High-Performance Liquid Chromatography

In this paper, a novel method of QuEChERS-based extraction coupled with high-performance liquid chromatography has been developed for the simultaneous determination of ursolic acid (UA) and oleanolic acid (OA) in guava leaves. The QuEChERS-based extraction parameters, including the amount of added salt, vortex-assisted extraction time, and absorbent amount, and the chromatographic conditions were investigated for the analysis of UA and OA in guava leaves. Under the optimized conditions, the method showed good linearity over a range of 1-320 μg mL^-1, with correlation coefficients above 0.999. The limits of detection of UA and OA were 0.18 and 0.36 μg mL^-1, respectively. The intraday and interday precision were below 1.95 and 2.55%, respectively. The accuracies of the UA and OA determinations ranged from 97.4 to 111.4%. The contents of UA and OA in the guava leaf samples were 2.50 and 0.73 mg g^-1, respectively. These results demonstrate that the developed method is applicable to the simultaneous determination of UA and OA in guava leaves.

Effect of the solvent and the sample preparation on the determination of triterpene compounds in two-phase olive-mill-waste samples

A simple and rapid extraction method has been employed to determine several value-added compounds, mainly triterpenes, in two-phase olive-mill-waste samples. The compounds were extracted with methanol or ethyl acetate, and the initial fresh samples were treated for classic techniques such as drying, drying and oil extraction, and drying and sifting of the olive stones. For the identification and quantitation of the compounds, an ultra performance liquid chromatography-mass spectrometry method was employed. The best results of the triterpenic compound content were achieved by extraction with methanol from the fresh sample for the oleanolic and ursolic acids, and erythrodiol and uvaol; and from the dried-extracted sample for the maslinic acid. Conversely, the best results for the linoleic acid content were reached by extraction with ethyl acetate from the dried-sifted sample. These are remarkable processes that make the solid wastes from the olive-oil industry reach a high added value.