How does the QbD1200 avoid sample-to-sample carry-over?
Most TOC analyzers suffer from sample-to-sample carry-over due to varying amounts of the previous sample remaining in the sample tube from the autosampler tray to the analyzer. For this reason the first measurement the analyzer will report is a mixture of the new sample and a varying amount of the previous sample. As a work-around, the user must configure the TOC analyzer to ignore the first measurement. As a typical TOC analyzer takes around 3 minutes to carry out a TOC analysis on pharmaceutical-grade water, this wasted sample can add over 3 hours to the time taken to analyze a tray of 64 samples (3 minutes x 64 samples = 192 minutes).
To avoid sample-to-sample carry-over issues, the QbD1200 employs the following process:
- The sample line from the autosampler is back-flushed with the One reagent which is then sent to drain
- A sample of the next vial is draw down the sample line and then sent to drain
- The QbD1200 now takes a sample from the vial to be analyzed, confident that the sample will not contain any of the previous vial’s content
