Leak Rate and Their Detection

The leak rate is a measure of the quantity of material that flows through a leak per time unit. For air-displacement pipettes the PLT unit determines the rate through a differential pressure measurement, i.e., after creating a negative pressure, the pressure rise over a given time is measured.

▪ Complex Determinations
The leak rate is determined by considering complex physical relationships.
Calculation of the limit values resident in the PLT must include factors such as the dead volume of the pipette/tip system, flow cross-setion of the pipette tip, pressure rise per time unit, pipette volume and type, etc.

▪ The pV Value
The pV value is the product of the pressure and the volume of a certain quantity of a gas at the prevailing temperature. This is a measure of the quantity of material or the mass of the gas.

▪ The Leak Rate QL
The leak rate QL is the ratio of the pV value and the period of time during which the gas flows through a path cross-section.

▪ The volume loss
For the pipette test, hPa ml/s is a suitable unit for the leak rate. A leak rate of e.g., 1 hPa ml/s at an air pressure of 1000 hPa means a volume loss of about 1 ul/s.