Micromaterials and Interfaces

Abstract The corrosion inhibition efficiency of magnesium–aluminum (MgAl) by embedding the noble metals of Ni, Pd, Pt, Cu, Ag, Au on the surface has been investigated. The importance of the electrical double layer at the interface between a metal and an acid electrolyte together with its interaction with organic and inorganic molecules to produce initially electrostatic adsorption are highlighted. The important step in which molecules enable inhibition are production of a physical barrier where a physical adsorbed barrier of molecules prevent movement near the metal surface or decrease in metal reactivity where chemisorbed inhibitor molecules stick to active area on the metal surface. In the NMR spectroscopy, it has been observed the remarkable peaks around metal elements of Ni, Pd, Pt, Cu, Ag, Au through the doping on the MgAl nanoalloy, however there are some fluctuations in the chemical shielding behaviors of isotropic and anisotropy attributes. Furthermore, all accounted amounts are very close, which demonstrate the agreement of the measured specifications by all methodologies and the reliability of the computing values.

Abstract Background:  Accurate quantification of lidocaine in pharmaceutical products is crucial to ensure proper dosage, as incorrect concentrations can lead to therapeutic failure or adverse effects. High-performance liquid chromatography (HPLC) is the preferred method due to its precision and ability to separate complex mixtures. However, challenges remain in ensuring reproducibility and robustness, especially in formulations with excipients or impurities. Validating these methods is essential for reliable results. Aim of the Study:  This study aims to develop and validate an HPLC method for quantifying lidocaine hydrochloride in pharmaceutical forms. The focus is on optimizing chromatographic parameters and validating the method based on ICH guidelines to ensure reliable, consistent results for quality control. Materials and Methods : The study was conducted at the Centre of Advanced Research in Sciences, Dhaka University, using lidocaine hydrochloride (HPLC standard) and a local market sample. HPLC-grade methanol and Milli-Q water were used for solution preparation. A Shimadzu UV/Visible spectrophotometer and Shimadzu UFLC Prominence HPLC system with a C-18 column were used for analysis. The chromatographic conditions included a 50:50 methanol-water mobile phase, 1 mL/min flow rate, and 250 nm detection wavelength. Lidocaine stock solutions were prepared, and calibration curves were created using standard concentrations. For the gel sample, 50 mg of 2% lidocaine gel was dissolved in methanol and sonicated, followed by filtration and analysis. The λ max of lidocaine was determined to be 263 nm. Results : Stock solutions of lidocaine hydrochloride were prepared in 0.1M HCl, ethanol & water (1:99), and methanol & water (50:50). The λ max was found to be 263 nm for all preparations, and a calibration curve was constructed using standard concentrations (5–25 µg/ml) in 0.1M HCl, showing a linear relationship (R² = 0.998). For the HPLC analysis, a standard stock solution (100 µg/ml) of lidocaine was prepared in methanol. Working solutions were prepared with concentrations ranging from 20 to 60 µg/ml, and the retention time was 2.6 minutes. A calibration curve was plotted based on the average area values for each concentration, showing linearity (R² = 0.998). The market lidocaine gel was analyzed, revealing a concentration of 35.69 µg/ml, which is higher than the declared value of 20 mg per gram (2% concentration). The retention time of the sample matched that of the standard (2.6 minutes), confirming the presence of lidocaine. This higher-than-expected concentration may result from an improper extraction procedure or impurities in the formulation, potentially leading to elevated side effects despite being applied topically. Conclusion : A simple, rapid, and sensitive RP-HPLC method was developed for determining lidocaine hydrochloride in pharmaceutical forms. This cost-effective method is suitable for quality control in pharmaceutical and cosmetic products.