An alkaline dissolution-based method using tetramethylammonium hydroxide for metals determination in cow milk samples

•An efficient analytical method was developed by multivariate optimization;•Tetramethylammonium hydroxide was used to milk samples treatment;•Sample dissolution was improved using ultrasound energy;•Calcium, Mg, Fe and Zn concentrations were evaluate in the milk samples; This study approaches the development of a method for the determination of Ca, Mg, Zn, and Fe in liquid and powdered cow milk. The method is based on sample dissolution assisted by ultrasound energy in tetramethylammonium hydroxide (TMAH) media and determination by flame atomic absorption spectrometry (FAAS). Central composite design (CCD) associated with response surface methodology and desirability function allowed the fast and efficient optimization of the variables involved in the performance of the dissolution. The developed dissolution method allowed Ca, Fe, Zn, and Mg determination in milk samples with adequate analytical characteristics for these determinations. Addition/recovery tests and analysis of a certified reference material of skimmed powdered milk (ERM-BD150) have shown that this method presents enough accuracy to carry out these analyses.