ABSTRACT The ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) system consisting of a SCIEX QTRAP® 7500 MS System and Shimadzu Nexera Series 40 UHPLC system, contained in this proposal, represents the most innovative LC/MS-based instrumental platform for small-molecule quantitative bioanalysis on the market. At present, NIH-funded PIs working across a number of Texas Children’s Hospital (TCH) Departments are increasing their application of quantitative mass spectrometry (MS)-based bioanalysis in support of their translational research programs in pediatric medicine. These Departments include Pediatrics-Gastroenterology, Hepatology, and Nutrition; Nephrology; Cardiology; Obstetrics and Gynecology; and, Laboratory Medicine. Currently, the Texas Children’s Microbiome Center (TCMC) is the only TCH-based facility, in the entire Texas Medical Center (TMC) campus that possesses UHPLC-MS/MS instrumentation and expertise. The TCMC – Metabolomics and Proteomics Mass Spectrometry Laboratory (TCMC-MPMSL) has witnessed steady growth in sample volume from 2020 to 2023, and our single UHPLC-MS/MS system is currently analyzing ~9,000 samples per annum while consuming ~90% of the available instrument capacity. The reasons for our funding request are two-fold: 1) expand our bioanalytical capacity to support the increasing levels of pediatric-based translational research being performed at TCH; and, 2) upgrade our instrumental capabilities to drive new biomedically-relevant discovery in support of pediatric patient care at TCH. Altogether, the instrument included in this proposal will provide much needed capacity and new capabilities that the TCMC-MPMSL can leverage to advance the basic and clinical research efforts of NIH-funded investigators at TCH in pediatric medicine.