Spectroscopic assays and tagging

A multiplex spectroscopic assay comprising:

• a motive particle configured to move within a solution, the motive particle comprising a first analyte binding reagent for selectively binding to a first target analyte and a second analyte binding reagent for selectively binding to a second target analyte;
• and
• a first spectroscopic reporter particle configured to provide a first predetermined spectroscopic signal in response to being interrogated by a spectrometer, the first spectroscopic reporter particle comprising a third analyte binding reagent for selectively binding to the first target analyte,
• a second spectroscopic reporter particle configured to provide a second predetermined spectroscopic signal in response to being interrogated by the spectrometer, the second spectroscopic reporter particle comprising a fourth analyte binding reagent for selectively binding to the second target analyte,
• wherein the motive particle and the first spectroscopic reporter particle are configured to provide a first sandwich assay in the presence of the first target analyte via the first and third analyte binding reagents, and the motive particle and the second spectroscopic reporter particle are configured to provide a second sandwich assay in the presence of the second target analyte via the second and fourth analyte binding reagents.