Dispersive Liquid–Liquid Microextraction Method Utilizing a Novel Peripherally Tetra-Substituted Ni(II) Phthalocyanine as a Sensor Prior to UV-Visible Spectrophotometry for the Determination of Co2+

Dispersive liquid-liquid microextraction (DLLME) is an economical, rapid, sensitive, and environmentally friendly miniaturized liquid-liquid extraction format. It has been successfully applied in trace element analysis since 2006 when it was first proposed. This article describes a new dispersive liquid-liquid microextraction method for the determination of trace amounts of Co²⁺. In brief, this method involves the extraction of Co²⁺ from the sample to the trichloromethane phase by the dispersive action of methanol after the formation of a complex with a novel 9-(methylaminomethyl)anthracene-Ni(II) phthalocyanine (MAMA Ni(II)Pc <b>2</b>) as a sensor. The first step in this study was the synthesis and characterisation of the sensor. Later, the proposed method was optimized with respect to various parameters such as extraction and dispersive solvents and their amounts, pH, sensor concentration, and centrifugation time and rate. The calibration graph was linear between 0.40 and 260 µg/L, with an R² of 0.9978. The limit of detection and limit of quantification were found to be 0.19 µg/L and 0.46 µg/L, respectively. To evaluate the precision of this method, the analysis of a 50 µg/L Co²⁺ solution was carried out. The intra-day and inter-day relative standard deviation values were calculated as 1.7% and 2.4%, respectively (n = 7). The accuracy of the proposed method was investigated by means of a standard addition/recovery test.