Time-based injection approach for monosegmented continuous flow systems and related techniques

A time-based injection module for monosegmented continuous flow systems and related techniques, which uses three independently controlled solenoid valves, is described. A timer c'cuit employing three LC. 555s and three TIP-121 transistors was constructed to control the injection module valves. The injection device was tested with non-reacting chemical systems (for example with a spectro-photometric standard and calcium flame emission) and with reacting conditions (for example the determination of Cr(VI), using diphenylcarbazide as colour reagent, and acid-base titra-tion). The performance of this injection module demonstrates its suitability for everyday use.