An apparatus and a method including exposing a first fluid to a pre-filter, observing the first fluid, introducing a second fluid to the first fluid, exposing the first and second fluids to a filter, and observing the first and second fluids wherein the observing the first fluid and observing the first and second fluids comprise optical measurements and the first fluid comprises material from a subterranean formation. Some embodiments may compare the optical measurements of the first fluid and the first and second fluids and/or estimate the first fluid's likelihood of forming precipitants with other fluids and/or the first fluid's asphaltene content. An apparatus and method for characterizing a fluid property including a pre-filter in communication with a fluid from a formation, an optical sensor to observe the fluid from the pre-filter, a fluid combination device in communication with the fluid and a second fluid source, a filter in communication with the combination device, a second optical sensor to observe a third fluid from the filter, and a processor to compare data collected by the sensor and second sensor.