Miniaturized system for bioanalysis have been constantly gaining importance and interest within the recent years. The reduction of sample consumption and reaction time are some of the major advantages of such lab-on-a-chip applications. One of the greatest challenges in these systems is the handling of small sample volumes. A possible way is to manipulate such volumes in the form of small droplets. This work demonstrates the potential of a modular magnetic droplet manipulation system for its application in bioanalysis. We studied the parameters of the droplet manipulation, and their application for the on-chip detection of an enzyme labeled antibody. By using sample volumes of ll size we are able to detect quantities in the pg-range of enzyme labeled antibodies, which is the first step to a miniaturized immunoassay on a chip.