Atomic absorption spectrometry for the quantification of cadmium in thermoformed and biodegradable flexible films made from cassava (Manihot esculenta crantz)

Abstract

A simple method for determining the presence of cadmium (Cd) in thermoformed and biodegradable flexible films and flour and starch samples from cassava, using graphite furnace-atomic absorption spectrometry (GF-AAS), is proposed. The biopolymers used in contact with foods can contain Cd due to contamination from the origin of the material used to make them. The nitric: perchloric acid digestion with reflux was optimized, and the statistical quality parameters were standardized. The GF-AAS instrumental conditions and the graphite furnace heating program were adjusted through pyrolysis and atomization curves, and the optimal temperatures were 530 and 1750°C, respectively. In addition, under optimal conditions, the working range was from 0.1 µg/L to 1.0 µg/L, with limits of detection and quantification of 0.02 and 0.07 µg/L, respectively. The precision was evaluated using intermediate precision and repeatability of the method, which showed standard deviations of 1.6–4.8% and 2.1–4.8%, respectively. The percentage of recovery of Cd ranged from 96.2% to 97.3%. The results obtained support the suitability of the method for determining the presence of Cd in these samples. Cd concentrations in flexible films and starch were below the quantification limit. The other samples (thermoformed and flours) contained less than 1 mg/kg (maximum level set by the NTC 4096), indicating that these polymers meet this standard and therefore can be used for food containers and packaging for fresh fruits and vegetables.

Cadmium Contents in Biodegradable Films Made from Cassava

“…The samples must be treated prior to analysis. The particle size of thermoformed samples are reduced via mechanical methods, starting with manual cracking; followed by maceration (Figure 3) to a particle size of less than 1,135 mm; and finally, the removal of water content by placing the particles in an oven at 70 °C for 3 hours [54].…”

“…For flexible film samples, all that is required is manual cutting as shown in Figure 4, and drying at 50 °C for 45 minutes [54][55][56][57][58].…”

“…Following drying in a furnace, the moisture values for thermoformed samples were between 3.71% and 5.80% (RSD lower than 3.4%). Biodegradable flexible films revealed higher values of moisture (following 45 mins of drying in a furnace) at 7.81-10.35%, with relative standard deviation (RSD) lower than 1.96% [54].…”

“…This study employed acid digestion in its sample preparation [51,54]. Optimizing acid digestion using the reflux system involved the determination of cadmium in a thermoformed sample (HMC-1) and flexible film (SM 707-17 hydrolyzed), taking four absorbance readings and considering the following variables: sample weight, temperature, time, and acid ratio.…”

“…Digestion was performed using the sample dissolved in 20 mL of a mixture containing HNO 3 (65%, Merck): perchloric acid (48%, Merck) at a 3:1 ratio [54].…”