Spectral interference -emission or absorption from interferent overlaps analyte Photomultiplier ck-in Chopper mirro Readou (（b) Fig9-13(b) Beam usually chopped or modulated at known frequency Signal then contains constant(background)and dynamic(time- varying)signals CEM 333 page 9.11 Spectral interference - emission or absorption from interferent overlaps analyte Fig 9-13(b) Beam usually chopped or modulated at known frequency Signal then contains constant (background) and dynamic (time￾varying) signals CEM 333 page 9.11