Phenanthrene-d10 is widely used as an internal standard in analytical chemistry, particularly in gas chromatography-mass spectrometry (GC-MS) for the quantification of polycyclic aromatic hydrocarbons (PAHs). Its deuterated structure ensures it behaves similarly to non-deuterated phenanthrene during analysis while providing distinct mass spectral peaks for accurate identification and measurement. This compound is essential in environmental testing, helping to monitor PAH levels in soil, water, and air samples, which is critical for assessing pollution and ensuring regulatory compliance. Additionally, it is employed in research studies to investigate the behavior and degradation of PAHs in various environmental and biological systems. Its stability and isotopic purity make it a reliable tool for precise analytical applications.