U.S.  Patent  Oct.  5,  2010  Sheet  11 of  15  US  7,807,473  B2  Figure  11.  Typical  set  of  spectra  of a  sulfite  sensor  film  (prepared  to  withstand  highly  alkaline,  high  pH  water  samples)  at  various  sulfite  concentrations  in a  typical  boiler  water  matrix,  at pH  12, 1000  mg/L  M-alkalinity.  1.2  Q)  ()  1  C  (U  .c  0.8  ...  0  Ill  0.6  .c  <  0.4’  0.2  l  0  400  450  500  550  600  650  700  750  800  wavelength  (nm) 