The pH of the
PAR solution determines which metals that can be detected. The PAR
postcolumn reagent solution was continuously degassed with helium,
because PAR is easily oxidized by oxygen. The PDCA eluent flow
was kept at 0.8 mL/min, and the PAR postcolumn flow was 0.4 mL/
min. This combination showed the optimal absorption. The standard
solutions were prepared to contain 0.05 M HCl and ascorbic acid 2
g/L.