New intelligent photometric titration system and its method for constructing chemical oxygen demand based on micro-flow injection

The characteristics of the signals during the process of chemical oxygen demand (COD) titration are analyzed in this paper. The signals are derived for normalized titration curves of reactions having the color mutation reaction. After analyzing the characteristics, the critical control points are observed. The switch, stop and end points are searched by the algorithm on a computer. Based on this three-point method, a new intelligent photometric titration system is constructed for COD, without using the calibration curves. Using this system, a new intelligent photometric titrator has been built for COD for automatic sampling and intelligent titrating. Under computer control, the process of titration is conducted intelligently and accurately; no manual operation or assistance is required. The titration chamber was homemade. The optimized conditions of the titration system are as follows: the titrant was consecutively micro-flow injected into the chamber with a velocity of 0.00576 mL·s−1; 100 points per second of the titrating process signal were collected; and the homemade agitator blade stirred at a speed of 420 rpm. The preferences tested by actual samples proved that this titrator meets the requirements of the standard method and is suitable for use in experiments. Overall, our approach facilitates adoption of an intelligent titrimetry system for the determination of photometric titration.