Iron (Fe) standard solution at 1000 µg/mL in 1.0 mol/L HNO₃, used primarily in analytical laboratories for calibration and standardization of instruments such as Atomic Absorption Spectroscopy (AAS), Inductively Coupled Plasma (ICP) spectrometry, and other methods for determining iron content in samples. Serves as a reference material for quality control, method validation, and preparation of working standards in environmental, food, pharmaceutical, and water analysis. Not intended for direct agricultural or water treatment applications; suitable chelated forms (e.g., Fe-EDTA) are used for plant micronutrient supplementation.