Automated titrations with an alternate flow exponential speed variation system

The alternate flow exponential speed variation system for automatic titrations is described. The system consists of two peristaltic pumps, two three-way valves, a mixing coil and a detector. Each determination consists of a twin cycle titration procedure. In the forward cycle, the sample and the reagent are propelled by the first and the second pump with the rotation speeds of the first and second pump decreasing and increasing with time, respectively. In the reverse cycle the solution inlets are switched so that the sample and the reagent are now propelled by the second and the first pump, respectively. This procedure allows the calculation of the accurate sample concentration without recourse to a precalibration step and, at the same time, eliminates the error caused by tubing deterioration. Results indicate accuracy better than 0.5%. Titration time and sample volume are of the order of 2 min and 2 ml, respectively.