Improved measurement of formaldehyde in water-soluble polymers by high-performance liquid chromatography coupled with post-column reaction detection

An improved methodology for the analysis of free formaldehyde in water-soluble polymers used for industrial water treatment is reported. Previously, derivatization prior to HPLC or colorimetric techniques has been used. The data generated by these approaches are suspect in that the derivatizing agent can react with the polymer or other sample components to produce high results. Post-column reaction derivatization is applied after separation of the free formaldehyde from the product interferences. The type of polymer product analyzed influences the choice of column(s). The degree of high bias of the commonly used 2,4-dinitrophenylhydrazine pre-column derivatization is reported and the results are compared to those with the post-column reaction for two polymer products. This method, being more selective, should be applicable to any polymer containing formaldehyde.