Therefore, NaOH was removed from the reagent solution
but the buffer capacity could not be increased as a high concentration
of NaCH3COO was already applied (2 mol l−1).
Hence, the sample injection volume was lowered in order to
increase sample dispersion inside the flow system. For an injection
value of 100 l, the sensitivity obtained when using
Fe(II) standards containing 0.9 mol l−1 of HClwas about90%
of that obtained for standards containing 0.2 mol l−1. Nevertheless,
similar calibration curves were obtained for both
acidity values when 50 or 75 l of sample were injected. The
chosen value was 75 l as it provided better sensitivity than
50l