## 1 Introduction  
The classification of metals and metalloids with an atomic density above 5 g cm\({}^{-3}\) is referred to as heavy metals [1]. In recent times, the growing discharge of agricultural, industrial, and household waste into water sources has elevated the public apprehension regarding the presence of heavy metals, posing a significant threat to human health [2, 3]. Heavy metals exhibit a propensity to engage with biological ligands, inducing alterations in protein molecular structures and enzyme inhibition, thereby leading to toxicological and carcinogenic consequences [4, 5]. Mercury (Hg) emerges as a highly hazardous metal contaminant in the environment, with its occurrence stemming from natural processes like the breakdown of minerals in rocks, volcanic eruptions, and soil degradation. Additionally, human activities contribute significantly to its presence through industrial processes, utilization in batteries, thermometers, and catalysts [6, 7]. Mercury induces significant health issues in humans, including elevated blood pressure, glioma, acute cognitive impairments, nervousness, depression, eye problems, and dysfunction of the central nervous system. The World Health Organization (WHO) recommends acceptable mercury levels in water samples for human consumption to be 1.0 \(\upmu\)g L\({}^{-1}\) and in food samples within the range of 0.02 to 0.9 mg kg\({}^{-1}\)[8]. Therefore, accurate and precise analytical methods are essential for the reliable determination of mercury in various types of samples. Various conventional enrichment-separation techniques, such as liquid-liquid micro-extraction (LLME) [9; 10], solid-phase extraction [11; 12], cloud point extraction [13; 14], dual cloud point extraction [15], online enrichment [16], micro-columns [17] supramolecular solvent-based liquid-phase micro-extraction with ultrasonic assistance [18], and coprecipitation [19], have been employed for the preconcentration of trace levels of mercury. The integration of green chemistry principles into laboratory practices signifies a recent advancement in the field of chemistry. This shift is characterized by a reassessment of experiments, placing a strong emphasis on the utilization of environmentally friendly materials and the implementation of efficient waste-management strategies. In this context, innovative systems have been introduced to evaluate the efficacy of green chemistry methodologies in comparison to traditional approaches. Analytical chemistry, in particular, faces a notable challenge in developing sample preparation methods that are not only more effective but also environmentally sustainable. The Green Analytical Chemistry (GAC) approach is influenced by various factors, encompassing sample collection, preparation, reagents, instrumentation, and the overall method type. To comprehensively assess the environmental impact of any procedure, it is essential to elucidate and consider these factors thoroughly. Within the domain of Green Analytical Chemistry (GAC), sample preparation assumes a crucial role, involving the concentration of trace-level analytes and the elimination of interfering substances. The solidified floating organic drop micro-extraction (SFODME) method addresses these objectives with notable advantages. Noteworthy features include its requirement for only small amounts of extraction liquid, simplicity, affordability, minimal use of organic solvents, absence of chelating agents, and the ability to achieve a high enrichment factor. These attributes distinguish SFODME from conventional methodologies, highlighting its environmental friendliness and efficiency [20]. In the present study, the solidified floating organic drop micro-extraction method has been developed with the help of ionic liquid (IL-SFODME) for the preconcentration and graphite furnace atomic absorption spectroscopy (GFAAS) determination of mercury ions in various water samples.