Isotope-Labeled Internal Standard

Stable isotope-labeled internal standards (SIL-IS) occupy an indispensable role in quantitative mass spectrometry. Compounds labeled with deuterium (²H), carbon-13 (¹³C), or nitrogen-15 (¹⁵N) share near-identical physicochemical properties with their unlabeled analogs, behaving consistently through sample preparation, chromatographic separation, and electrospray ionization. This co-elution behavior enables effective compensation for matrix effects, recovery variability, and instrument signal drift — making SIL-IS the gold standard for internal standardization in LC-MS/MS quantitative workflows.

Key application areas include pharmacokinetic studies and bioanalytical method validation (per FDA and EMA BMV guidelines), clinical mass spectrometry (hormones, vitamins, amino acids, therapeutic drug monitoring), ultra-trace environmental contaminant quantification (PFAS, PAHs, PCBs, pesticides), and multi-residue quantitation of pesticide and veterinary drug residues in food and feed. In early drug development, deuterium- or ¹³C-labeled metabolite standards are also essential tools for quantitative metabolite identification in ADME studies.

CATO Research Chemicals Inc. offers over 15,000 isotope-labeled internal standards, spanning deuterated pharmaceuticals and impurities, agrochemicals, environmental contaminants, and food safety analytes. Isotopic purity is rigorously assigned by NMR, chemical purity is confirmed by HPLC, and batch-to-batch consistency is maintained throughout. Custom synthesis of deuterated or multiply-labeled compounds is available on request. The majority of catalog products are in stock, with same-day domestic dispatch and international shipping to major markets across North America, Europe, and Asia-Pacific.