Although the protocol and parameters are identical, the pH curve, dissolved oxygen profile and yield vary from run to run.
Although their control loop compensates automatically, CO₂ concentrations and actual gas flow still drift over the course of weeks.
Ten identical reactors, ten identical protocols. Yet the yield varies from unit to unit.
The bench-scale system is running smoothly; pH and dissolved oxygen are under control. In the pilot phase, however, the same setpoints reveal a different reality, and the troubleshooting process starts all over again.
Your control system constantly adjusts the CO₂ and O₂ levels, but the setpoint is never actually reached in a stable manner. Each batch runs under slightly different conditions.
The last calibration has been documented and took place less than twelve months ago. But was it calibrated using actual process gas, or using air and a K-factor?
Five factors that undermine reproducibility in the bioreactor
Three practical gas handling checks from bench-scale to scale-up
What You need to get right before moving from the bench to pilot and production
The greatest threat to reproducible processes is not initial inaccuracy, but gradual drift over time.
Vögtlin uses drift-free MEMS sensors and precise temperature compensation to ensure that a setpoint consistently generates the same physical gas flow – regardless of cabinet temperature, operating time or ageing.
What sets Vögtlin apart:
Gas flow is an invisible process variable – without transparency, deviations remain undetected for a long time.
Vögtlin displays the actual gas flow directly and makes it available digitally, so that setpoint, actual value and system behaviour can be checked at any time.
Reproducibility is only possible if gas metering functions with absolute reliability during day–to–day operations.
Vögtlin combines robust hardware with rapid technical support, calibration services and long–term support. This ensures that the gas line does not introduce any uncertainty into the process.
What sets Vögtlin apart:
Thermal mass flow meters and controllers directly measure the number of gas molecules (mass) flowing past the sensor.
This measuring principle allows for significant fluctuations in temperature and pressure without the measurement result being significantly affected.
A sophisticated temperature compensation system results in barely measurable differences in the range between 0 and 50°C.
Gases can be compressed. Their volume changes when the temperature and/or pressure change.
Consequently, when specifying a gas volume, the reference temperature and reference pressure must always be stated as well.
Our specifications are based on the requirements of DIN 1343 (standard conditions):
Temperature Tn = 273.15 K, corresponding to 0°C
Pressure Pn = 1013.25 mbar abs
See also: http://de.wikipedia.org/wiki/Normbedingungen
Not everyone understands ‘standard conditions’ in the same way. Whilst there is agreement on the reference pressure, there are differences regarding the reference temperature:
The US standard litre corresponds to our standard litre according to DIN 1343. Gas suppliers in Europe specify 15°C rather than 0°C.
To avoid misunderstandings, the reference conditions are clearly stated in our correspondence.
On request, we can also supply the devices with a different reference temperature (e.g. based on room temperature of 20°C).
The reference pressure is set at 1013.25 mbar for all units. If, for example, you wish to calculate the difference between 0°C and 20°C, the formula is as follows:
(Flow rate at 0°C / 273.15) * 293.15
Example: 100 ln/273.15*293.15 = 107.32 ls
This corresponds to a correction of 0.366% per degree Celsius
We recommend the following calibration interval:
1. Initial check after one year
2. Once several consecutive calibrations have been carried out, the variation between calibrations must be analysed. Based on this data, a decision can be made to adjust the calibration intervals.
Yes. In many cases, it is much easier for our service team and for customers if we can access the customer’s computer directly.
Often, it is just minor issues that cause devices to malfunction. Please get in touch with us.
Moist gas up to approx. 97% RH has only a minor effect on measurement accuracy. However, appropriate measures must be taken to ensure that no condensation forms inside the measuring instrument.
Condensate adheres to the sensor and leads to incorrect measurements. If a measuring instrument has come into contact with condensate, it can usually be purged with a dry gas such as N2. Please also refer to the instructions in the user manual.
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