Preparation of a soluble solid sample by a continuous ultrasound assisted dissolution system for the flow-injection atomic absorption spectrometric determination of iron in milk powder and infant formula

A simple and new flow-injection manifold (CUDS) for the continuous ultrasound assisted dissolution of a soluble solid sample coupled to a flow-injection flame atomic absorption spectrometric manifold for the continuous iron determination is described. An experimental design was used for the evaluation of factors involving the CUDS. The method was applied to a certified reference material (CRM-151, skim milk powder) for quality assurance/validation and to real samples (milk powder and infant formulas). The total sampling frequency achieved was 80 samples per hour with a relative standard deviation for the complete procedure of 1.1%. The detection limit was 0.60 μg g⁻¹ for a sample amount of 30 mg. The results demonstrated that the CUDS is an innovative and efficient tool as compared to the manual-traditional sample preparation methods, but with drastic increase of both sample throughput and precision.