Isotope-Labeled Food & Beverage Standards for Food Safety Testing

Food matrices are complex and variable—they contain proteins, fats, carbohydrates, and other components that can suppress or enhance ionization in LC-MS/MS, causing inaccurate quantitation. Isotope-labeled internal standards are chemically identical to the target analyte (same retention time, ionization efficiency, and fragmentation pattern) but differ in mass, allowing the mass spectrometer to distinguish them. By adding a known amount of labeled standard before sample preparation, you can correct for recovery losses during extraction, cleanup, and ionization, achieving accurate and reproducible results even in complex food matrices.

For LC-MS/MS, 13C-labeled standards are generally preferred because they co-elute exactly with the native analyte and exhibit identical ionization behavior. Deuterium-labeled standards can sometimes show a slight chromatographic shift (the "deuterium isotope effect") in reversed-phase LC, which can cause the labeled and unlabeled forms to experience different matrix effects at the moment of elution. However, deuterium-labeled standards are more cost-effective and are perfectly suitable for many applications—particularly when the deuterium labels are on non-exchangeable positions and the mass shift is adequate (typically ≥3 Da). For GC-MS/MS, both 13C and deuterium-labeled standards work well.

The internal standard should be added at a concentration in the middle of your calibration range. For multi-residue methods, choose a concentration that gives a good signal-to-noise ratio for the least sensitive analyte. Typical concentrations range from 10–100 ng/mL in the final extract for LC-MS/MS methods. The exact concentration should be optimized during method validation. For ready-to-use solutions, follow the concentration specified in your standard operating procedure.

Storage conditions vary by compound class. Neat standards (pure solids or oils) should generally be stored at -20°C in tightly sealed, light-protected containers. Ready-to-use solutions should be stored according to the solvent and concentration: most solutions in organic solvents are stable at -20°C or 4°C. Before opening, allow the container to warm to room temperature to prevent condensation. Always check the Certificate of Analysis for compound-specific storage recommendations. Avoid repeated freeze-thaw cycles for solutions.

Yes. We offer custom mixture preparation services for multi-residue methods. You can specify the exact compounds, concentrations, and solvent for your mixture. We will verify the compatibility of all components, prepare the mixture under controlled conditions, and provide a certificate documenting the identity and concentration of each component. This service is popular with laboratories running routine multi-residue screens for pesticides, veterinary drugs, and mycotoxins.

Every standard is supplied with a comprehensive Certificate of Analysis (CoA) that includes: product name and catalog number, lot number, chemical purity (HPLC or GC), isotopic enrichment (MS), identity confirmation (NMR, HRMS), and for solutions—verified concentration and solvent. For certified reference materials (CRMs), we also provide an uncertainty budget and traceability documentation. CoAs are available upon request.

Simple 13C or deuterium labeling of known food safety analytes typically requires 4–8 weeks. More complex targets or those requiring multi-step synthesis may require 8–16 weeks. We provide an estimated delivery date at the time of quotation and keep you informed of progress throughout the synthesis. Rush services may be available for time-critical projects.