Ev. Alonso et al., INDIRECT DETERMINATION OF NITRATE BY ELECTROTHERMAL ATOMIC-ABSORPTIONSPECTROMETRY USING AN ONLINE CADMIUM MICROCOLUMN, Analyst (London. 1877. Print), 123(7), 1998, pp. 1561-1564
The proposed indirect automatic method is based on the reduction of ni
trate to nitrite using a cadmium reductant microcolumn where the flow
of the sample through the microcolumn oxidizes the metallic cadmium to
Cd-II which is measured by electrothermal atomic absorption spectrome
try. The automatic system is achieved simply by replacing the sample t
ip of the autosampler arm with the reductant microcolumn. This system
results in a powerful integrated system which permits fully automated
operation, avoiding time-consuming manual work and enhancing the sensi
tivity. The manifold was evaluated with respect to accuracy, precision
and sensitivity for nitrate determination in water, the detection lim
it achieved being 0.05 mu g ml(-1) (3s) with a sampling rate of about
35 h(-1). A 2.3% relative standard deviation was obtained in a repeata
bility study (n = 11) at the 0.2 pg ml-l level of nitrate and 2.6% at
the 8.0 mu g ml(-1) level. Some ions which commonly occur with nitrate
in mater samples, such as Na+, Ca2+ and Mg2+, interfered to a certain
extent, although these interferences were minimized by passing of the
sample through an Amberlite cation-exchange resin, The method was app
lied to samples of bottled and spring waters with good results, The ma
trix effects were minimized by using the standard addition method.