Preconcentration/Extraction of Phthalate Esters in Milk Samples Using MFe2O4-Based Magnetic Ionic Liquid Effervescent Tablets Consisting of Accessory Functional Fillers

摘要

Magnetic effervescent tablet-based (MEFTs) microextraction has recently gained much attention because it requires no physical energy inputs or dispersive solvent. A prominent shortcoming of MEFTs results from the short tablet storage period owing to rapid absorption of moisture, thereby making it impracticable for field use. Physico-chemical properties of MEFTs were greatly improved by the addition of water-soluble starch, such as hygroscopicity, storage/stability period, adherence, effervescent time, and intensity. MEFTs were used in a MFe2O4-based magnetic ionic liquid effervescent tablet microextraction (MMIL-ETM) for preconcentration/extraction of trace phthalate esters (PAEs) in milk matrices. This MMIL-ETM method provided three distinct advantages: (1) MEFTs integrate water-soluble starch as a functional filler, leading to longer tablet storage/stability; (2) combined effervescent dispersion and rapid retrieval of NiFe2O4 magnetic nanoparticles (MNPs) result in substantial time saving; and (3) integration of ionic liquid-based extraction with MNP adsorption produces high PAEs extraction recoveries. Optimized experimental parameters were as follows: 0.77 g mixture of Na2CO3 and water-soluble starch, 7 mg NiFe2O4 (30 nm), 50 mu L [HMIM]NTf2, solution pH 2.3, and 300 mu L acetonitrile as elution solvent. Under optimized conditions, extraction recoveries for four PAEs reached as high as 94.8-105.6%, LODs were as low as 0.042 mu g L-1, and RSDs were 5.4% for intra- and inter-day precisions. Due to the longer stable storage period and rapid dispersion without additional physical energy inputs, the proposed MMIL-ETM method shows great potential application for routine food monitoring under field conditions.