Ahmad Makahleh

A new analytical method for the simultaneous determination of the antidiabetic drugs rosiglitazone (ROS) and metformin hydrochloride (MH) with marked differences in their affinity towards organic solvents (log P of 2.4 and −1.43, respectively) was developed. Prior to the HPLC separation, the drugs were subjected to a sequential hollow fiber liquid phase microextraction (HF-LPME) procedure. Two sequential HF-LPME approaches were considered, the preferred one involves the use of two vials containing solution mixtures for the extraction of ROS (vial 1) and MH (vial 2), respectively, but using the same fiber and acceptor phase. Important parameters that affect the extraction efficiency such as extracting solvent, donor phase conditions, HCl concentration, agitation, extraction time, addition of salt, etc. were studied. Under the optimum conditions, good enrichment factors (EF, 471 and 86.6 for ROS and MH, respectively) were achieved. Calibration curves were linear over the range 1–500 (r2=0.998) and 5–2500 ng mL−1 (r2=0.999) for ROS and MH, respectively. The relative standard deviation values (RSD%) for six replicates were below 8.4%. Detection and quantitation limits based on S/N ratio of 3 and 10 were 0.12, 1.0 and 0.36, 3.0 ng mL−1 for ROS and MH, respectively. The proposed method is simple, sensitive and opens up new opportunities for the microextraction of analytes with contrasting properties.

A sensitive and rapid reversed-phase ultra performance liquid chromatographic (UPLC) method for the simultaneous determination of tocopherols (α‐, β‐, γ‐, δ‐), tocotrienols (α‐, β‐, γ‐, δ‐), α‐tocopherol acetate and α‐tocopherol nicotinate is described. The separation was achieved using a Kinetex pentafluorophenyl (PFP) column (150×2.1 mm, 2.6 µm) with both photodiode array (PDA) and fluorescence (FL) detectors that were connected in series. Column was thermostated at 42 °C. Under a gradient system consisting of methanol and water at a constant flow rate of 0.38 mL min−1, all the ten analytes were well separated in less than 9.5 min. The method was validated in terms of linearity, limits of detection and quantitation, precision and recoveries. Calibration curves of the ten compounds were well correlated (r2>0.999) within the range of 100 to 25,000 μg L−1 for α‐tocopherol acetate and α‐tocopherol nicotinate, 10 to 25,000 μg L−1 for α‐tocotrienol and 5 to 25,000 μg L−1 for the other components. The method is simple and sensitive with detection limits (S/N, 3) of 1.0 to 3.0 μg L−1 (FL detection) and 30 to 74 μg L−1 (PDA detection). Relative standard deviations for intra- and inter-day retention times (<1%) and peak areas (≤4%) were obtained. The method was successfully applied to the determination of vitamin E in vegetable oils (extra virgin olive, virgin olive, pomace olive, blended virgin and refined olive, sunflower, soybean, palm olein, carotino, crude palm, walnut, rice bran and grape seed), margarines and supplements.

A fast and simple solvent microextraction technique using salting out-vortex-assisted liquid–liquid microextraction (salting out-VALLME) was developed for the extraction of furfurals (2-furfural (2-F), 3-furfural (3-F), 5-methylfurfural (5-MF) and 5-hydroxymethylfurfural (5-HMF)) and patulin (PAT) in fruit juice samples. The optimum extraction conditions for 5 mL sample were: extraction solvent, 1-hexanol; volume of extractant, 200 µL; vortex time, 45 s; salt addition, 20%. The simultaneous determination of the furfurals and PAT were investigated using high performance liquid chromatography coupled with diode array detector (HPLC–DAD). The separation was performed using ODS Hypersil C18 column (4.6 mm i.d×250 mm, 5 μm) under gradient elution. The detection wavelengths used for all compounds were 280 nm except for 3-F (210 nm). The furfurals and PAT were successfully separated in less than 9 min. Good linearities (r2>0.99) were obtained within the range 1–5000 μg L−1 for all compounds except for 3-F (10–5000 µg L−1) and PAT (0.5–100 μg L−1). The limits of detection (0.28–3.2 µg L−1) were estimated at S/N ratio of 3. The validated salting out-VALLME-HPLC method was applied for the analysis of furfurals and PAT in fruit juice samples (apple, mango and grape).

A three phase hollow fiber liquid-phase microextraction with in situ derivatization (in situ HF-LPME) followed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV) method was developed for the trace determination of metformin hydrochloride (MH) in biological fluids. A new derivatization agent pentafluorobenzoyl chloride (PFBC) was used. Several parameters that affect the derivatization and extraction efficiency were studied and optimized (i.e., type of organic solvent, volume of NaOH (4 M) and derivatization agent in the donor phase, acceptor phase (HCl) concentration, stirring speed, temperature, time and salt addition). Under the optimum conditions (organic solvent, dihexyl ether; volume of NaOH (4 M) and derivatization agent (10 mg PFBC in 1 mL acetonitrile) in the donor phase, 600 and100 μL, respectively; acceptor phase, 100 mM HCl (10 μL); stirring speed, 300 rpm; extraction time, 30 min; derivatization temperature, 70 °C; without addition of salt) an enrichment factor of 210-fold was achieved. Good linearity was observed over the range of 1–1000 ng mL−1 (r2 = 0.9998). The limits of detection and quantitation were 0.56 and 1.68 ng mL−1, respectively. The proposed method has been applied for the determination of MH in biological fluids (plasma and urine) and water samples. Prior to the microextraction treatment of plasma samples, deproteinization step using acetonitrile was conducted. The proposed method is simple, rapid, sensitive and suitable for the determination of MH in a variety of samples.

The development of a two phase hollow fiber liquid-phase microextraction technique, followed by gas-chromatography-flame ionization detection (GC-FID) for the profiling of the fatty acids (FAs) (lauric, myristic, palmitic, stearic, palmitoleic, oleic, linoleic, linolenic and arachidic) in vegetable oils is described. Heptadecanoic acid methyl ester was used as the internal standard. The FAs were transesterified to their corresponding methyl esters prior to the extraction. Extraction parameters such as type of extracting solvent, temperature, extraction time, stirring speed and salt addition were studied and optimized. Recommended conditions were extraction solvent, n-tridecane; extraction time, 35 min; extraction temperature, ambient; without addition of salt. Enrichment factors varying from 37 to 115 were achieved. Calibration curves for the nine FAs were well correlated (r(2)&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;0.994) within the range of 10-5000 μg L(-1). The limit of detection (signal:noise, 3) was 4.73-13.21 ng L(-1). The method was successfully applied to the profiling of the FAs in palm oils (crude, olein, kernel, and carotino cooking oil) and other vegetable oils (soybean, olive, coconut, rice bran and pumpkin). The encouraging enrichments achieved offer an interesting option for the profiling of the minor and major FAs in palm and other vegetable oils.