In order to evaluate the conditions that provide better
sensitivity and lower detection limit, the volumes of sample
studied were: (a) 5 mL; (b) 10 mL; and (c) 15 mL. The calibration
standards and carrier solutions were prepared in the same medium
as the samples (containing HNO3, or HCl, KBr/KBrO3 and
hydroxylamine). All the blank, sample and calibration solution
were analysed in triplicate. A process blank was run every time, in
the same way and with the same amount of chemicals employed
for the samples.