Dysregulation of metal homeostasis can cause toxicity, inflammation, and contribute to diseases like cancer by influencing cell mobility, invasion, and metastasis. However, essential metals, such as Fe, Cu, Zn, and Mo, are often present in cells at extremely low concentrations (fg/cell), making their detection challenging. While inductively coupled plasma-mass spectrometry (ICP-MS) is effective for trace elemental analysis, traditional bulk analysis overlooks cell-to-cell variability. Single-cell ICP-MS (SC-ICP-MS) offers high-throughput analysis of individual cells, providing insights into heterogeneous populations. Nevertheless, challenges arise when analyzing mammalian cells, as chemical fixatives (e.g., methanol or paraformaldehyde) are requried and they can alter elemental composition. Also, analysing live cells require high-concentration salt matrices, leading to matrix effects that reduce sensitivity and accuracy of the results. In this work an online microdroplet (MD) calibration system is evaluated for accurate elemental determination in individual mammalian cells. The system uses MD containing ionic disolved elements as calibrants, introduced into the ICP online with nebulized cells. This matrix-matched calibration minimizes matrix effects, enabling accurate constituent element analysis in cells. Coupled with an ICP-Time-Of-Flight-MS unit, the method was evaluated on red blood cells (RBCs) to measure Fe, Zn, and Cu under various conditions: fixed cells in water, cells in different PBS concentrations, and live cells in PBS. It will be validated on other cell types. The results were compared to traditional single-cell methods using ionic standards. Additonally, MD are tested as cell carriers into the ICP. While MD improve transport efficiency (100% for MD), throughput remains a limitation (few % of MD contains a cell). This technique shows promise for gentler cell transport.