Overview

Targeted metabolomics is a hypothesis-driven approach that quantifies a predefined panel of metabolites with high accuracy, specificity, and sensitivity. Unlike untargeted metabolic profiling, which aims for comprehensive coverage, targeted methods focus on known metabolites — often those belonging to a specific pathway or class — and use authentic chemical standards to achieve absolute quantification. The approach is typically implemented on triple quadrupole mass spectrometers using multiple reaction monitoring (MRM) or on high-resolution instruments with parallel reaction monitoring (PRM). Targeted metabolomics is the method of choice when the metabolites of interest are well characterized and quantitative precision is paramount.

Methods

Internal standards — ideally stable isotope-labeled analogs of each target metabolite — are added to every sample at known concentrations to correct for matrix effects, extraction losses, and instrumental drift. Standard curves prepared in the same biological matrix establish the linear range and limit of quantification for each metabolite. MRM transitions are optimized by direct infusion of each standard to select the most sensitive and specific precursor-to-fragment pairs. Sample preparation is tailored to the metabolite class: protein precipitation for polar metabolites, liquid-liquid extraction for lipids, or solid-phase extraction for targeted enrichment. Data are processed using software that integrates peak areas, applies calibration curves, and performs quality control assessments with pooled reference samples.

Applications

Targeted metabolomics is used to verify biomarkers discovered in untargeted studies, to monitor flux through specific metabolic pathways such as glycolysis and the citric acid cycle, and to profile metabolic changes in clinical cohorts. It is the gold standard for clinical metabolomics assays, often coupled with HPLC separation and mass spectrometry detection to ensure robust, high-throughput quantification.