Traceability of pulsed flow rates consisting of constant delivered volumes at given time interval

Very low flow calibrations are important in several areas of pharmaceutical, microfluidic and health care applications where volumetric dosage or delivery at given flow rates are crucial for the process. Not only constant and steady flow rates are commonly used in the health sector, but also pulsed flow rates consisting of constant delivered volumes at given time intervals. One known application is the delivery of Insulin with tethered or patch pumps. These constant volumes can be in the order of several tens or hundreds of nanoliters. As the delivery times can vary up to several minutes, it is not appropriate to determine an average flow rate of the delivered volume. It is more advisable to determine the average volume and the average time interval of delivery. The METAS Microflow facility has been upgraded to perform measurements with insulin pumps delivering a volume of 500 nL at a given time interval of several minutes. The updated design and new aspects of the discontinuous volume collection from the tethered or patch pumps are discussed in this paper. First calibration results of insulin pumps are also presented