Hollow fiber liquid phase microextraction with in situ derivatization for the determination of trace amounts of metformin hydrochloride (anti-diabetic drug) in biological fluids

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.