A simple, automated device for the precise addition of liquids

Metering liquid reagents into reaction mixtures in a controlled and reproducible manner has often been a problem in synthetic chemistry. Carrying out the real simultaneous addition of two or more liquid reagents (concurrent additions) is even more inconvenient. Difficulties increase when addition volumes become small, when addition times become long, or when the reagents are corrosive or air-sensitive. We have constructed and tested an inexpensive, automated device for the slow, precise delivery of liquid reagents into laboratory-scale reaction mixtures. Controlled by a standard personal computer, this slow adder can accommodate liquid volumes from hundreds of microlitres to litres and addition times from minutes to days. Its glass and Teflon construction makes it useful for nearly all reagents. By using multiple slow adders, true concurrent addition of several liquids can be easily achieved.