A: Liquid volume may be determined by weighing the sample tube, however this requires the tare weight of the empty tube to be known, which may not always be available. Whilst an estimated tare weight may be used, significant variation in tube and cap weights has been observed, which can lead to inaccuracies.
Weighing sample tubes by hand is extremely time consuming and prone to error. Whilst instruments are available to help automate this process, they still take between 20 to 30 minutes to audit a rack of 96 tubes.
Liquid volume may also be calculated by determining the position of the meniscus using ultrasonic or other similar sensing technologies. Instruments using this technology rely on the tube being uncapped so that the sensor can ‘look down’ into the tube. This exposes the sample to possible moisture uptake and/or cross-contamination.
The Tube Auditor avoids the need to weigh sample tubes, operates with capped (or uncapped) tubes and combines accuracy with high speed operation.