A green flow-batch liquid phase microextraction lab-in-syringe platform based on natural deep eutectic solvents for toxic metal determination

Abstract

In this work, a novel functional and reliable computer-controlled flow-batch lab-in-syringe (LIS) platform was developed for liquid phase microextraction (LPME) based on the use of natural deep eutectic solvents (NADES) as green alternatives to conventional extractants. The proposed automatic on-line LIS system is reported for the first time and demonstrated for the determination of toxic metals in aqueous samples, as a front-end to flame atomic absorption spectrometry (FAAS). To the best of our knowledge, the determination of metals by atomic spectrometric techniques processing a LIS preconcentration system using NADES has not been previously reported. The analytical process included the in-syringe metal complexation of Cd, Cu, and Pb (model analytes) with ammonium pyrrolidine dithiocarbamate and the subsequent microextraction of the resulted complexes by a mixture of menthol:heptanoic acid at a molar ratio of 1:2. After phase separation, the NADES was transferred towards the flame for direct atomization in an automatic and precise manner. The main attributes that affect the performance of the method were thoroughly studied. Under optimum conditions, the limits of detection ranged between 0.54 and 4.52 μg L−1 corresponding to a sample consumption of 4000 μL. The relative standard deviations were less than 3.8% demonstrating good method precision. As a proof-of-concept, the developed system was used for the analysis of drinking and environmental water samples resulting in good relative recoveries (i.e., 94.0–104.0%). The green character and the applicability of the proposed approach were demonstrated by the Green Analytical Procedure Index (GAPI), and Blue Applicability Grade Index (BAGI), respectively.