Multianion analysis, applications of ion chromatography - Determination of Anions in Natural and Treated Waters - page 619

Society [9]
limits are generally in the sub parts per million range. No attempt was made to optimise
the chromatographic conditions for a particular anion.
Out of the 27 anions listed in Table 12.1 all but eight absorb in the ultraviolet above
190nm. This demonstrates that the commonly held assumption regarding the lack of
suitable chromophores by inorganic ions for ultraviolet detection is incorrect. This
misconception has probably come about from the fact that although many anions absorb
in the 190-220nm region, few of them show an absorption maximum above 190nm. This
has limited the analytical usefulness of direct ultraviolet absorbance measurement for the
determination of inorganic anions. However, the lack of an absorption maximum does not
severely limit the analytical usefulness when the ultraviolet spectrometer is combined
with a separation technique such as ion chromatography.
The ultraviolet detector, in combination with the conductivity detector, offers a number
of advantages in ion chromatography. Fig. 12.2 shows the separation of sub-part-per
million iodate and bromate monitored using
Fig. 12.3 Separation of nitrate and chlorate by ion chromatography: (a)
conductivity detector (--) 30mg L −1 NO 3 − UV detector (- - -) at
195nm, position 2; (b) conductivity detector (--) 30mg L −1 , ClO 3
UV detector (- - -) at 195nm respectively
Source: Reproduced with permission from the American Chemical
Society [9]