Preparation of amine-modified lignin and its applicability toward online micro-solid phase extraction of valsartan and losartan in urine samples.

In the present work, with the focus on an environmentally-friendly approach, some gels were prepared by synthesizing amine-modified lignin, extracted from sugarcane bagasse, and further esterification and subsequent freeze-drying. These lignin-based gels were implemented as extractive phases in an online micro-solid phase extraction (µSPE) setup in conjunction with high performance liquid chromatography (HPLC) with UV detector. The developed method was used for analytical determination of valsartan and losartan in urine samples. To study the effect of the functionalization process, the efficiency of the unmodified lignin and the functionalized lignin were compared both in the absence and the presence of graphene oxide (GO), presumably as a suitable doping agent. Surprisingly, higher extraction efficiency for the functionalized lignin, compared to both unmodified lignin and GO was observed. The amination process for the prepared gel was analyzed and proved by CHNS elemental analysis and Fourier transform infrared (FT-IR) spectroscopy. The morphology of sorbet was investigated via scanning electron microscope (SEM) imaging and a nanoscale cauliflower feature was observed. The method was optimized and subsequently applied to the analysis of the urine samples. Limits of detection (LOD) of 8 and 6 µg L - 1, limits of quantification (LOQ) of 27 and 20 µg L - 1 and linear dynamic range (LDR) of 27-2000 and 20-2000 µg L - 1 with intraday relative standard deviations (RSD%) of 4 and 3% were obtained for valsartan and losartan, respectively. The whole online µSPE-HPLC setup was conveniently used for the analysis of a patient urine sample and a quantity of 352 µg L - 1 of losartan was found. Acceptable relative recoveries (109-108 and 95-94% for valsartan and losartan) revealed the analytical potential of the method for the determination of drugs in complex urine samples.

Green preparation of dual-template chitosan-based magnetic water-compatible molecularly imprinted biopolymer.

In the current study, a green method was used for the fabrication of dual-template chitosan-based magnetic water-compatible molecularly imprinted biopolymer in water without using organic and toxic reagents and then, its application as a sorbent for the simultaneous pre-concentration and determination of valsartan (VAL) and losartan (LOS) from urine samples followed by HPLC-UV. Chitosan was used as a multi-functional monomer due to its unique properties in terms of non-toxic, cost-effectiveness, readily available, biocompatible, biodegradable and easy to polymerize in mild condition. The proposed sorbent represents the exceptional properties in terms of green synthesis, high magnetic strength, bio-compatibility, high selectivity, fast equilibrium adsorption as well as high adsorption capacity. In the optimized conditions, the developed MMIP-DMSPE-HPLC/UV method showed a wide linear range of 5.0 - 1500.0 µg L-1 for VAL and 8.0 - 1500 µg L-1 for LOS and low LODs of 1.4 and 2.3 µg L-1 for VAL and LOS, respectively with RSD% values less than 5.0, (n = 5). The obtained recoveries were 95.6-100.2 % for VAL and 92.0-98.1 % for LOS which showed the applicability of green, water-compatible and bio-compatibility of the proposed method for neat and selective extraction of VAL and LOS from complicated urine samples.

Preparation of hollow porous molecularly imprinted and aluminum(III) doped silica nanospheres for extraction of the drugs valsartan and losartan prior to their quantitation by HPLC.

Water compatible hollow porous molecularly imprinted nanospheres (HP-MINs) have been prepared for specific recognition and extraction of the blood pressure regulating drugs valsartan (VAL) and losartan (LOS). All synthetic steps were performed in aqueous medium and without consumption of organic solvents. The morphology and functionality of the materials were characterized by FT-IR, FE-SEM, and TEM techniques. The adsorption and selectivity experiments demonstrate that the HP-MINs possess a high binding capacity, fast kinetics, excellent water dispersibility and remarkable selectivity for VAL and LOS. The HP-MINs were utilized for dispersive solid phase extraction of VAL and LOS prior to their determination by HPLC-UV. Main variables and their interactions on extraction yield were optimized by multivariate analysis with least amount of experiments. Under optimized conditions, the method has a linear response in the 5-2000 µg L-1 concentration range of both VAL and LOS. The limits of detection are 1.5 µg L-1 for VAL and 1.4 µg L-1 for LOS. Graphical abstract Schematic representation of dispersive solid phase extraction (d-SPE) of valsartan (VAL) and losartan (LOS) from urine sample by hollow porous molecularly imprinted nanospheres (HP-MINs).

Preconcentration of valsartan by dispersive liquid-liquid microextraction based on solidification of floating organic drop and its determination in urine sample: Central composite design.

In this work, a fast, easy, and efficient dispersive liquid-liquid microextraction method based on solidification of floating organic drop followed by high-performance liquid chromatography with UV detection was developed for the separation/preconcentration and determination of the drug valsartan. Experimental design was applied for the optimization of the effective variables (such as volume of extracting and dispersing solvents, ionic strength, and pH) on the extraction efficiency of valsartan from urine samples. The optimized values were 250.0 µL ethanol, 65.0 µL 1-dodecanol, 4.0% w/v NaCl, pH 3.8, 1.0 min extraction time, and 4.0 min centrifugation at 4000 rpm min(-1) . The linear response (r(2) = 0.997) was obtained in the range of 0.013-10.0 µg mL(-1) with a limit of detection of 4.0 ng mL(-1) and relative standard deviations of less than 5.0 % (n = 6).

[Simultaneous determination of four drugs for kidney diseases in urine by high performance liquid chromatography].

A high performance liquid chromatographic (HPLC) method was proposed for the simultaneous determination of four drugs for kidney disease, enalapril, triamterene, furosemide and valsartan. After proteins being removed by acetone precipitation method, freeze drying and redissolving in mobile phase, the urine samples were analyzed by HPLC. Chromatographic separation was performed on a WondaSil C18-WR (150 mm x 4.6 mm, 5 µm) in gradient elution mode using 10.0 mmol/L ammonium acetate aqueous solution (pH 3.90) and acetonitrile as mobile phases at a flow rate of 1.0 mL/min. The detection wavelength was set at 254 nm. Under the optimized conditions, good linearities were obtained in the range of 0.15-300 mg/L, 0.05-100 mg/L, 0.75-750 mg/L, 0.05-100 mg/L, and the detection limits were 1.38 x 10(-2), 7. 67x103, 3.69x 10-2, 1. 16x 10-2 mg/L for enalapril, triamterene, furosemide and valsartan, respectively. The recoveries were in the range of 89.49%-99.20% with the relative standard deviations (RSDs) among 4.12%-9.44%. The method is simple, accurate and effective, and the results showed the method is applicable for the analysis of the four drugs for kidney diseases in real urine samples.