β-naphthalene sulfonic acid sodium-formaldehyde condensate is an important additive as dispersant,water reducing agent,surfactant and antioxidant in electrolytic metal manganese process.The free formaldehyde in the condensate inevitably affects its performance.The content of free formaldehyde can be determined with HPLC method by previously reacting with 2,4-dinitrophenylhydrazine to derive 2,4-dinitrophenylhydrazone.This paper optimized the reaction condition for formaldehyde derivative formation,2,4-dinitrophenylhydrazone is totally transformed form formaldehyde in 20 min,at 30℃,in hydrochloric acid.For the external standard method,the correlation coefficient(r) and RSD were 0.9999,4.07%,respectively,and the detection limit was 0.1mg/L.To spike the samples with formaldehyde at concentration of 1.25,2.50,and 7.50 mg/L,the recoveries were 98.4%,94.0% and 97.0%,respectively.
