Figure 4 shows peaks obtained for nitrate + nitrite
calibrants in the concentration range of 0.25-5.00 mg-N/L
by the CdR (a) and NaR (b) methods operating at a sampling
rate of 90 samples h-1. Insets in this figure reveal the
outstanding linearity of calibration functions obtained with
both methods. Slopes of the calibration functions for both
methods are about the same because the variable gain output
settings of both photometersssee, standard calibration
control information in Figures 1 and 2swere adjusted to
obtain peak heights of about 90% of full scale for the highest
concentration calibrant. Actually, full-scale (5 V) absorbance
was about 1.0 and 0.4 for the CdR and NaR methods,
respectively. This sensitivity difference between the CdR and
NaR methods resulted from the larger sample dilution factor
designed into the NaR method analytical cartridge to
minimize enzyme consumption. Sample interaction (% I),
as measured by the interaction test patterns (25) shown in
Figure 5, was less than 1% for both methods. The 2.5 and