Investigation of the pH effect on the stability of biocompatible magnetic fluids using time-dependent birefringence measurements

In this work we used the static magnetic birefringence together with transmissivity measurements to investigate the effect of the pH on the stability of a water-based, citrate-coated, maghemite magnetic fluid as a function of the time. We observed a peak on the SMB measurement due to the high birefringence of the material. The peak position shifted to lower field values as a function of time and decreasing the pH of the sample. The phenomena is explained as a result of agglomerate formation. In addition, the conductivity constant decreases by 6% changing the pH value of the sample from pH = 10 to pH = 7. (c) 2004 Elsevier B.V. All rights reserved.