ON-LINE FULLY AUTOMATED MEASUREMENT OF CR(VI) CONCENTRATION IN WATER BY A FIBER OPTIC PROBE AND A LOW COST SPECTROPHOTOMETER

A measurement system conjugating the flow-injection technique in an automatic system and a low cost spectrometer as the photo-detecting device has been set in order to evaluate the concentration of Chromium (VI) in water. Light absorption spectra of the complex Chromium (VI) – Diphenylcarbazide, carried into the measuring cell, were analysed to detect the effect of interfering quantities and substances by also operating with suitable data processing techniques, like neural network. The aim of this work is to check the feasibility of this approach, for on-line and distributed measurements. Aspects concerning instrumentation system and operating steps are analysed in order to evaluate uncertainty causes and their effects on the whole uncertainty of the methodology, taking into account requirements of method reproducibility and standardization.