A method for increasing a spectroscopic signal in a biological assay is provided. The method includes forming a suspension of magnetically attractable particles. The method also includes introducing a first magnetic field at a first location to draw the magnetically attractable particles towards the first location and form a first agglomeration. The method also includes removing the first magnetic field. The method further includes introducing a second magnetic field at a second location to draw the first agglomeration towards the second location and form a second agglomeration. The method further includes focusing an excitation source on the second agglomeration formed at the second location.