Sodium phosphate buffer (0.1 M, pH 9.0) is used to maintain a stable alkaline pH in laboratory applications requiring mildly basic conditions. It is suitable for biochemical experiments, such as certain enzyme reactions, protein handling, and chromatographic techniques where pH stability around 9.0 is needed. Also applied in diagnostic assays, pharmaceutical formulations, and cleaning solutions to ensure pH control. Its low toxicity and high solubility make it appropriate for medical, food, and industrial uses.