Rapid analysis of dimer acid by HPLC/FID

A method was developed for the rapid analysis of polymerized fatty acids (dimer acid) using normal phase HPLC with a flame ionization detector (FID). The use of analytical scale HPLC with the FID is a significant limprovement over existing methodology for dimer analysis. The HPLC analysis takes only 25 min per sample, with no derivatization required. The FID response is linear for dimer samples from 10% to 90% monomer content. Absolute measurement precision is typically less than 0.5 area percent. Recovery of synthetic dimer blends averaged 102%. Results for the analysis of commercial dimer acid are comparable to those obtained using an HPLC/gravimetric method. The HPLC/FID method is applicable to the analysis of crude dimer as well as the finished dimer product.