An Automatic Lab-in-Syringe Dispersive Liquid-Liquid Microextraction Platform for the on-Line Flame Atomic Absorption Spectrometric Determination of Copper in Environmental Water Samples

A novel fully automatic dispersive liquid-liquid microextraction platform based on the lab-in-syringe concept was developed for on-line preconcentration and/or separation, as a front-end to flame atomic absorption spectrometry. The microextraction procedure was performed within the syringe after on-line merging of the methanol stream (disperser solvent), containing 2.0% (v/v) xylene (extraction solvent) and 0.3% (m/v) ammonium diethyldithiophosphate (chelating agent), with the aqueous sample stream. By this way, the formation of cloudy solution, composed of fine droplets of the extraction solvent entirely dispersed into the aqueous phase, was accomplished on-line, and microextraction was completed within the syringe barrel of lab-in-syringe. Furthermore, the fine droplets of the extractant organic phase were separated on-line from the aqueous phase for the first time using a microcolumn packed with poly(etheretherketone) turnings, encountering the major problem of centrifugation. All chemical and hydrodynamic factors that affected the performance characteristics of the method were optimized using copper as the model analyte. The limit of detection was 0.51 μg L−1 within a working range from 1.7 to 100 μg L−1. The relative standard deviation (RSD) was 2.7% at 10.0 μg L−1 Cu (II), demonstrating good precision. As a proof-of-concept the proposed system was used for environmental water analysis, providing relative recoveries within the range of 96 and 103%. Finally, the complex modified green analytical procedure index, the blue applicability grade index, and the violet innovation grade index, were employed to evaluate method’s greenness, practicality, and innovation, respectively.