The temporal operation protocol of the SILFA system shown in
Table 1for the automated performance of the analytical operations
was set through the touchscreen controller. The procedures for
vanadium determination are described as follows. First, in mode 1,
a vanadium standard or sample solution through the port 2 (in the
case of blank measurement, a 0.01 mol L
–1
nitric acid through the
port 1) was aspirated by the P1, and the mixed solution of p-anisidine, acetate buffer and Tiron (in case higher iron was present,
diphosphate was added) in the RS1and bromate in the RS2were
aspirated by the P2. These solutions were well mixed and loaded
into the heated loop on the V2. In mode 2, the loop on the V2was
disconnected from theflow line to facilitate the catalytic reaction
at 85°C, and the P2was stopped. Meanwhile, the P1was aspirating
a 0.01 mol L
–1
nitric acid solution through the port 1 to clean the
flow line. The next step is mode 3; the P1was turned off, so that
the net waste can be equal to 0. In mode 4, only the P1was turned
on to send a 0.01 mol L
–1
nitric acid solution through the port 1, so
that a baseline can be established. After that (mode 5), the recorder was activated to perform the baseline measurement forfive
seconds. In mode 6, the reaction mixture wasfinally dispensed by
switching the V2(On) towards the detector obtaining a peak for
vanadium at 510 nm.
In the case of iron determination, the same procedures (modes
1 to 6) were carried out except the aspiration ports on the V1and
the position of V3