Online Solid-Phase Extraction of Prometon and Prometryne Using MIL-101(Cr) as Sorbent before Gas Chromatographic Analysis: A Computational and Experimental Study and Comparison between Splitless and PTV Inlets.

In this study, prometryne and prometon were extracted and preconcentrated from aqueous media using an online solid-phase extraction-thermal desorption method coupled with gas chromatography-flame ionization detector (GC-FID), equipped with two different inlets: split and programmable temperature vaporizer (PTV). For this purpose, the applicability of Tenax and a metal-organic framework were investigated as solid-phase sorbents. Several effective parameters on the extraction efficiency, such as the amount of sorbent, sample volume, sample pH and thermal desorption procedure were optimized. The analytical performance of the proposed methods showed an excellent linear dynamic range for prometon and prometryne (0.25-100 µg/L) and relative standard deviation less than 4.01%. Moreover, the detection limits below 0.20 and 0.35 µg/L were determined for prometon and prometryne, respectively. Additionally, molecular docking was applied to clarify the adsorption nature and binding energy of MIL-101(Cr) toward the studied analytes, which indicated an appropriate correlation between computational and experimental results. Finally, the proposed method was developed and validated for prometon and prometryne and successfully applied for their extraction from agricultural water, spiked with prometon and prometryne through its direct introduction into the GC inlet.

Simple and Sensitive Quantification of Ghrelin Hormone in Human Plasma Using SBSE-HPLC/DAD-MS.

During a decade and more since its discovery, the emerging physiological roles of ghrelin in mammalian are increasingly being introduced, proposing a critical need for its quantification in biological milieu. Here in, a simple and sensitive single-step method for extraction and quantification of ghrelin in human plasma was developed and validated using stir bar sorptive extraction (SBSE) followed by high-performance liquid chromatography (HPLC) with diode array detection (DAD) coupled to mass spectrometry (MS). Influential parameters of SBSE procedure were optimized including extraction and desorption times of 45 and 30 min, respectively; pH of 4; no addition of salt. The sum of peak heights of three most intense selected ions in mass spectrum (844, 1125 and 1686 m/z) related to 4-, 3- and 2-fold-charged ions of ghrelin was used for quantification. Validation parameters containing linear dynamic range, limit of quantification and limit of detection were 0.02-80, 0.02 and 0.007 µg L-1, respectively, and calculated relative standard deviation for peak heights was 6.5% (0.7 µg L-1 standard solution). Mean recovery for ghrelin in spiked plasma samples was 96% ± 3. The efficiency of the SBSE-HPLC/DAD-MS procedure was proved by analysis of plasma samples from obese patients undergoing gastric plication surgery. The suggested methodology would contribute to simple and fast analysis of ghrelin levels in obesity and related diseases and also biochemical cycles in which gherlin is present.

Preparation of a novel sorptive stir bar based on vinylpyrrolidone-ethylene glycol dimethacrylate monolithic polymer for the simultaneous extraction of diazepam and nordazepam from human plasma.

A new monolithic coating based on vinylpyrrolidone-ethylene glycol dimethacrylate polymer was introduced for stir bar sorptive extraction. The polymerization step was performed using different contents of monomer, cross-linker and porogenic solvent, and the best formulation was selected. The quality of the prepared vinylpyrrolidone-ethylene glycol dimethacrylate stir bars was satisfactory, demonstrating good repeatability within batch (relative standard deviation < 3.5%) and acceptable reproducibility between batches (relative standard deviation < 6.0%). The prepared stir bar was utilized in combination with ultrasound-assisted liquid desorption, followed by high-performance liquid chromatography with ultraviolet detection for the simultaneous determination of diazepam and nordazepam in human plasma samples. To optimize the extraction step, a three-level, four-factor, three-block Box-Behnken design was applied. Under the optimum conditions, the analytical performance of the proposed method displayed excellent linear dynamic ranges for diazepam (36-1200 ng/mL) and nordazepam (25-1200 ng/mL), with correlation coefficients of 0.9986 and 0.9968 and detection limits of 12 and 10 ng/mL, respectively. The intra- and interday recovery ranged from 93 to 106%, and the relative standard deviations were less than 6%. Finally, the proposed method was successfully applied to the analysis of diazepam and nordazepam at their therapeutic levels in human plasma. The novelty of this study is the improved polarity of the stir bar coating and its application for the simultaneous extraction of diazepam and its active metabolite, nordazepam in human plasma sample. The method was more rapid than previously reported stir bar sorptive extraction techniques based on monolithic coatings, and exhibited lower detection limits in comparison with similar methods for the determination of diazepam and nordazepam in biological fluids.