Detection of interrupted bubble flow in the Technicon automated immunoprecipitin system.

In an automated immunoprecipitin system for analysis of serum immunoglobulins (Technicon Instruments Corp., Tarrytown, N.Y. 10591) (1, 2) sampler lines of small inside diameter (0.0075 and 0.020 inch) must be used, and so flow is occasionally interrupted when the line becomes blocked by particulate matter. Cleaning the blocked line is simple; however, flow interruption is detected only by carefully observing the sampler probe line for lack of bubble flow when the probe switches between samples. Thus continuous operator attention is required; otherwise time and costly antiserum are lost before blockage is detected. This note describes a simple system that promptly warns the operator that the sampler probe line is blocked. Because the sampler probe picks up a new sample every 1.2 mm (50, 1/1 cam), an air bubble flows through the sampler probe every 0.6 mm. With the present accessory, the passage of each bubble is used as a signalto triggera retriggerablemonostable multivibratorwith a delay time greaterthan the bubble separation time. During normal operation the bubble pattern continues to trigger the monostable multivibrator and no change of logic state will appear at its output terminal. Should the flow pattern stop for any reason, after 1.4 mm a “Sonalert” alarm will sound.