Used as an internal standard in mass spectrometry-based bioanalytical studies to accurately quantify sorafenib in biological samples such as plasma, serum, or tissue extracts. Its primary application lies in pharmacokinetic and metabolism studies, where it helps ensure precise measurement of sorafenib levels during clinical research and therapeutic drug monitoring. The deuterium-labeled structure provides a distinct mass difference that allows clear differentiation from the unlabeled compound in LC-MS/MS analysis, improving assay accuracy and reliability.