Development of an RP-HPLC Method for the Determination of Lidocaine Hydrochloride in Injectable Formulation: Combining White Analytical Chemistry and Experimental Design with an Eco-Friendly and Cost-Effective Method

BACKGROUND: In recent years, environmental impact, human health, and cost have become increasingly important in chromatographic analysis of pharmaceutical compounds. Traditional methods use organic solvents like acetonitrile (ACN) and methanol (MeOH), which are volatile, flammable, toxic, and environmentally harmful. By using available comprehensive data on the effects of chemicals on human health and the environment, informed choices should be made about which chemicals are more suitable for a given synthesis or process, taking even a small step toward green chemistry. OBJECTIVE: In this study, the aim is to develop a green HPLC method for the analysis of lidocaine by replacing the toxic solvents traditionally used in the mobile phases of classical chromatographic methods with greener alternatives. To achieve this, ethanol is used as the organic modifier in the mobile phase without compromising analytical performance, thereby enabling a transition to green chromatography. METHODS: The independent variables considered were the pH of the mobile phase, flow rate, and ethanol content in the mobile phase for the optimization step. Experimental runs were selected randomly, and a total of 15 experiments were conducted. Response parameters for each HPLC chromatogram were calculated, evaluated using regression analysis, and the accuracy of the results was tested using analysis of variance (ANOVA).The Derringer desirable function was utilized to optimize the conditions. Accordingly, the optimal conditions determined were a mobile phase pH of 4.0, with a 1.3 mL/min flow rate, and an ethanol content in the mobile phase of 25%. RESULTS: The developed new green method offers an environmentally friendly, sensitive, and reliable alternative as lidocaine is determined using a HPLC technique. CONCLUSION: The developed and validated green HPLC method can be proposed as an alternative to the conventional HPLC methods reported by the United States Pharmacopeia (USP) and other sources, which are not environmentally or human health friendly, for the analysis of lidocaine in pharmaceutical preparations. The use of ethanol instead of potentially toxic organic solvents minimizes harm to both the environment and analyst health. Additionally, the method offers advantages such as reduced analysis time, solvent and time savings, and the absence of labor-intensive sample and solvent preparation steps, making it an attractive option. It is considered that the developed method could be particularly useful in the pharmaceutical industry, especially in QC laboratories where rapid and high-throughput analyses are conducted, as well as in R&D studies. HIGHLIGHTS: A green and sustainable HPLC method for lidocaine analysis was developed and validated. Chromatographic optimization was achieved using design of experiments and the Derringer desirability function. The method showed high accuracy, precision, and suitability for routine analysis of injectable formulations. White analytical chemistry evaluation was performed using the Red-Green-Blue 12 (RGB12) model, Analytical Eco-scale (AES), Green Analytical Procedure Index (GAPI), and Analytical Greenness (AGREE) metrics. The developed method offers reduced analysis time, reagent consumption, resource use, and cost compared to reported RP-HPLC methods in the literature.