In the knotted mixing coil (MC) immersed in water bath of 60 °C, nitrate was reduced by VCl3 and reacted with Griess reagent to form a pink dye, which was monitored in the detection system (D) and the waste (W) was collected
in a waste bottle.
The detection system consisted of a “U” shaped flow cell of 1-cm path length, a laboratory-made cell holder, a white LED fixed as light source, a USB 2000 miniature fibre optic CCD spectrometer (www.oceanoptics.com) as detector,an done
QP 600-2-SR fibre optic (www.oceanoptics.com) connecting the cell holder and spectrophotometer.
Light absorption was mon-itored at 540 nm and 437 nm for detection and for correction of light intensity variation.
Detailed data processing procedures are described elsewhere