Recently developed biopolymers can contain lead due to contamination from the origin of the material used to make them. A method for determining the presence of lead is proposed, using GF-AAS in thermoformed and biodegradable flexible films and flour and starch samples from Cassava. Acid digestion with reflux was optimized and the statistical quality parameters were standardized. The graphite furnace heating program was adjusted through pyrolysis and atomization curves. The working range was from 2.0 to 7.0 μg/L, with limits of detection and quantification of 0.618 and 1.853 μg/L, respectively. The precision was evaluated using intermediate precision and repeatability of the method, which showed standard deviations of less than 4.70% and 4.36%, respectively. The percentage of recovery ranged from 94.8% to 106.5%. The results obtained support the suitability of the method for determining the presence of lead. Lead concentrations were below 1 mg/Kg, indicating that these polymers can be used for food containers.