Assessment of matrix effects and determination of niacin in human plasma using liquid-liquid extraction and liquid chromatography-tandem mass spectrometry

A simple, sensitive and rapid liquid-liquid extraction method for the analysis of nicotinic acid (niacin) and its labeled internal standard nicotinic acid-d4 (niacin-d4) in human plasma was developed and validated. The analyte and its internal standard were isolated from acidified plasma using a single liquid-liquid extraction procedure with methyl-t-butyl ether. The extracted samples were analyzed by liquid chromatography-tandem mass spectrometry in positive electrospray ionization mode with multiple reaction monitoring. The calibration curves were linear in the measured range between 5 and 1000 ng/mL and the limit of detection was calculated as 122 pg/mL. The method required 250 microL of human plasma and the total run time between injections was 3.5 min. Matrix effects were assessed by post-column infusion experiments, phospholipids monitoring and post-extraction addition experiments. The extraction of phospholipids and niacin from plasma was studied under acidic, neutral and basic conditions. Acidic conditions were optimal for both the recovery of niacin and the removal of phospholipids; the degree of matrix effects for niacin was determined to be 2.5%. It was concluded that effective removal of matrix components can overcome low recovery issues associated with liquid-liquid extractions of polar analytes.     

Development and Greenness Assessment of HPLC Method for Studying the Pharmacokinetics of Co-Administered Metformin and Papaya Extract

Foods with medical value have been proven to be beneficial, and they are extensively employed since they integrate two essential elements: food and medication. Accordingly, diabetic patients can benefit from papaya because the fruit is low in sugar and high in antioxidants. An RP-HPLC method was designed for studying the pharmacokinetics of metformin (MET) when concurrently administered with papaya extract. A mobile phase of 0.5 mM of KH₂PO₄ solution and methanol (65:35, v/v), pH = 5 ± 0.2 using aqueous phosphoric acid and NaOH, and guaifenesin (GUF) were used as an internal standard. To perform non-compartmental pharmacokinetic analysis, the Pharmacokinetic program (PK Solver) was used. The method’s greenness was analyzed using two tools: the Analytical GREEnness calculator and the RGB additive color model. Taking papaya with MET improved the rate of absorption substantially (time for reaching maximum concentration (T_max) significantly decreased by 75% while maximum plasma concentration (C_max) increased by 7.33%). The extent of absorption reduced by 22.90%. Furthermore, the amount of medication distributed increased (30.83 L for MET concurrently used with papaya extract versus 24.25 L for MET used alone) and the clearance rate rose by roughly 13.50%. The results of the greenness assessment indicated that the method is environmentally friendly. Taking papaya with MET changed the pharmacokinetics of the drug dramatically. Hence, this combination will be particularly effective in maintaining quick blood glucose control.     

Statistically Significant Results for the Propagation of a Turbulent Flame Kernel Using Direct Numerical Simulation

Two major issues are always associated with DNS of turbulent combustion. First, the Reynolds number is limited to small values, considerably below those of practical applications. Second, it is difficult to obtain statistically significant results, since this condition would lead to even higher requirements in computing time. Both issues are considered in the present work for the propagation of an initially spherical, premixed methane flame kernel in a turbulent environment, using three-dimensional Direct Numerical Simulations. Chemical processes are described in a realistic manner using tabulation (FPI method), relying on two coordinates to enter a look-up table constructed with 29 species and 141 reactions. Compared to previous results, a considerably higher Reynolds number has been considered by accessing parallel supercomputers. Furthermore, statistically significant results are obtained by repeating several times the DNS simulations, allowing for ensemble averaging. More particularly, the evolution of flame surface area, flame thickness, flame front curvature and flame shape factor are considered in a quantitative manner.     

Synthesis and Characterization of Polyaniline/Zeolite X Composites as Anticorrosion Coating Materials

The main target of this work is to choose the best preparation conditions to have a perfect yield of the new composites prepared from mixing Zeolite X with polyaniline. The preparation of polyaniline and polyaniline/Zeolite X composites as anticorrosion coat was studied. The composites were synthesized and characterized by X-ray diffraction, Fourier transform infrared spectroscopy and UV–visible spectroscopy techniques, which showed the successful synthesis.