Microextração líquido-líquido dispersiva em fase reversa para determinação de cobre, ferro, magnésio, manganês e níquel em gordura suína

Abstract

The pork lard, as well as other foods, is susceptible in its composition, either by natural means or by contamination, to contain metals (essential or not) that can interfere in the stability of the product or alter the quality by not meeting an identity and quality standard, as well as, in excess, can cause damage to the health of the consumer. This work had as a precursor the development of a method using the reverse phase dispersive liquid-liquid microextraction technique (RP-DLLME) aiming the extraction and preconcentration of Cu, Fe, Mg, Mn and Ni in pork lard for subsequent determination by flame atomic absorption spectrometry (F AAS). In order to obtain better extraction percentages the following were evaluated: dispersing solvents (isopropanol and n-propanol), extracting solvents (HNO3 and HNO3 + HCl 1:1(v/v)), proportion between dispersing solvent: extractant (50/50, 60/40, 70/30 and 80/20), extractant solvent concentration (0; 0.5; 1.0; 1.5 and 2 mol L-1), total volume of the dispersant: extractant solvent mixture (0.5; 1.0; 1.5 and 2 mL), ultrasound time (0, 5 and 10 minutes) and centrifugation time (5, 10, 15 minutes). All optimized results were expressed as percent recovery. The best RP-DLLME conditions obtained in the optimization were: use of Isopropanol as dispersing solvent, HNO3 + HCl (1:1 v/v) as extracting solvent; disperser: extractor solution ratio of 60/40 % (v/v), volume of 1 mL disperser: extractor for 5 g of matrix, 10 minutes of homogenization (solvents/matrix) in a 37 kHz ultrasound bath and 5 minutes of centrifugation at 6000 rpm. For the determination of analytes by F AAS, external calibration was performed for Cu, Fe, Mg, Mn, and Ni in the range of 0.25 to 1.5 mg L-1. The limits of quantification for Cu, Fe, Mg, Mn and Ni were 0.0106; 0.0136; 0.0042; 0.0169 and 0.0124 µg Kg -1, respectively. Accuracy was estimated to be between 95.64 to 104.42% and with precision (RSD) less than 1% for all analytes. The method was applied to six different brands of commercial lard (n = 5), where the recovery was between 90.2 and 103.2% and the RSD between 0.024 and 0.094. Then, risk characterization was performed, in which 0.43 to 2.79% and 0.21 to 4.22% were obtained for Fe compared to the recommended daily intake and 5.13 to 25.83% for Ni compared to the upper tolerable intake level. The risk quotient was less than 1 x 105, making it unlikely that even sensitive populations would suffer adverse effects. The analytical method possesses can be used for the determination of the elements in pork lard samples.