The invention provides a mixing flow apparatus. The mixing flow apparatus consists of a 
waveguide and a mixing flow chamber; the 
waveguide having a higher index of 
refraction material than its surroundings for propagation of a 
signal, and the mixing flow chamber having a body forming a flow chamber with an inlet, an outlet, a 
radiation transmissive wall and a surface positioned to disrupt flow regularity of a sample fluid, the body of the mixing flow chamber surrounding at least a portion of the 
waveguide, wherein constituents of a sample fluid entering the inlet are mixed by disruption of sample fluid flow regularity prior to 
discharge at the outlet. Also provided is a detection apparatus. The detection apparatus consists of a waveguide, a mixing flow chamber and a 
radiation detector; the waveguide having a higher index of 
refraction material than its surroundings for propagation of a 
signal; the mixing flow chamber having a body forming a flow chamber with an inlet, an outlet, a 
radiation transmissive wall and a surface positioned to disrupt flow regularity of a sample fluid, the body of the mixing flow chamber surrounding at least a portion of the waveguide, wherein constituents of a sample fluid entering the inlet are mixed by disruption of sample fluid flow regularity prior to 
discharge at the outlet, and the radiation 
detector being disposed facing the direction of oncoming propagated 
signal from the waveguide. The detection apparatus can include an illumination source.