“…The feasibility of spectrophotometric determinations requiring reagent additions and spectrophotometric titrations was reported in relation to zinc and acidity determinations in electrolytic solutions [141]. Furthermore, a titrimetric procedure exploiting concentration gradients was proposed [142]: the sample travelled at a constant flow rate, being inserted by differential pumping into the carrier stream where a titrant concentration gradient had already been formed. In this way, ultrafast titrations (one titration every 25 s) were accomplished, yielding results comparable with classical titrations.…”