Guaifenesin EP Impurity B, chemically defined as 2-(2-Methoxyphenoxy)propane-1,3-diol and also known as the β-isomer of Guaifenesin (Isoguaifenesin, USP), is a positional isomeric impurity of Guaifenesin, with molecular formula C₁₀H₁₄O₄ and molecular weight 198.22 g/mol. Structurally, this compound differs from the parent expectorant only in the point of attachment of the guaiacol ether oxygen: it is bonded to the central (C-2) carbon of the propane-1,3-diol chain instead of the terminal (C-1) carbon. Unlike Guaifenesin, this symmetrical isomer has no stereocentre. It typically results from attack of guaiacol at the secondary carbon during etherification with glycidol or 3-chloropropane-1,2-diol-type synthons. This isomeric distinction makes it a key reference marker for monitoring regioselectivity, synthetic purity, and positional-isomer control during Guaifenesin API manufacturing. Manufactured at Chemicea under tightly controlled synthetic and analytical protocols, this reference standard supports impurity identification, method validation (AMV), and quality-control testing in accordance with EP and USP monograph requirements for Guaifenesin, and is routinely applied in ANDA and DMF regulatory filings. Each batch is supplied with a comprehensive Certificate of Analysis supported by HPLC, ¹H-NMR, and Mass Spectrometry characterization data, ensuring dependable analytical traceability for pharmaceutical R&D and QC laboratories. CAS No. 14007-09-1 | Explore complete technical documentation, Safety Data Sheet (SDS), and pricing.