Interference of thiomersal in biologicals during protein estimation

In the present report thiomersal was detected as interfering substance in hepatitis B vaccines during the total protein estimation by Lowry's protein assay. The thiomersal at different concentrations of 0.005%, 0.0075%, 0.01%, 0.02%, 0.05% and 0.1% was found to reduce the Folin Ciocalteu's phenol reagent and produce colour development between 0.024 O.D to 1.023 O.D. values. Further, the thiomersal was shown to interfere between 34.55% to 52.73% with Folin Ciocalteu's phenol reagent, when 10 batches of different hepatitis B vaccines were subjected to estimation of total protein content by Lowry's protein assay.