This paper describes work that formed a part of an investigation to increase the detection sensitivity of a magneto-immunoassay. The study involved the characterisation of paramagnetic particles (PMPs) from a range of manufacturers in order to determine parameters that influence the assay sensitivity. Magnetisation curves were produced for each PMP type using a vibrating sample magnetometer. A resonant coil magnetometer which incorporated of a planar, spiral coil integrated with a phase locked loop based detector was used to investigate the effect of PMP number and mass on the resonant frequency of the coil. In order to compare performance in an assay using a resonant coil magnetometer, the sensitivity for a monolayer of particles was evaluated. The results enabled the identification of parameters that were critical to achieving maximum sensitivity and, of the particles studied, the 0.75m diameter PMPs demonstrated the greatest sensitivity in the resonant coil magnetometer.
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