In a chemical laboratory of analysis of concentrates of minerals there are delays in the delivery of results report to the clients, failing to meet the deadlines; so this research aims to solve the problem through the 5 Lean Six Sigma steps that consists in: Defining, Measuring, Analyzing, Improving and Controlling (DMAIC). The findings suggested that the focus on the data collection, by the technical analyst, of the following values: the molar mass in the EDTA solution and the volumetric expense of the chemical reaction of the sample would have the greatest impact on the decrease of the retests.