When buying boronic acids or esters, a high assay number is only the starting point. Ask for HPLC or GC purity, depending on volatility and thermal stability. HPLC often reveals related boron compounds that a simple assay may miss. GC can expose residual solvents or volatile impurities. According to ICH Q2(R2), finalized in 2023, analytical methods should demonstrate specificity, accuracy, precision, and robustness. A reported 98% purity means little without the method, column, detector, and integration details.
Identity should be confirmed by NMR, not inferred from a product name. Check 1H, 13C, and, when useful, 11B NMR data against the structure. Moisture deserves equal attention. Boronic compounds can change during storage, especially in humid environments. Karl Fischer testing, referenced by USP General Chapter <921>, provides a more defensible moisture result than visual inspection. Request the actual KF value, test date, and sample handling conditions.
Read the CoA critically. It should connect the lot number, test methods, specifications, and release date. Missing chromatograms are a warning. So is a generic CoA issued years before shipment. A practical improvement is requesting a retain-sample result before scale-up. It costs time. It may prevent failed coupling reactions. Acceptance limits should match your reaction and process, not a copied template. Even experienced buyers sometimes overtrust a polished document. That mistake remains expensive.