Roche Diagnostics May 2009
A-26 Service Manual · Version 9.0
2 Fluid actions cobas b 221 system
Measurement
Aspirate sample The sample is aspirated by turning the MSS output pump and opening the VSI.
e
For more information, see Sample distribution on page A-23.
The tearing of the standby solution and the start of the sample is detected by the
conductivity at the MSS input. Then it must also be possible to detect the tearing of
the standby solution and the sample start, at which the MSS output pump is stopped.
The completed sample positioning is checked again for freedom from bubbles via the
conductivity distances.
Aspiration of standby solution
(2) to determine glu and lac
The determination of the MSS measurement values is always based on the reference
potential of the standby solution; for this reason the MSS cassette is filled with
standby solution (by stopping the MSS input pump) after washing out the sample
(with a mixture of standby solution and air by rotating the two MSS pumps). The
quality of the aspiration is assessed by the conductivity distance at the MSS output.
The MSS input pump is used to fill the tube in the lateral channel (with standby
solution), for defined aspiration (aspirating the standby solution) of the MSS
measuring chamber cassette and for washing valve V10.
Aspiration of standby solution
(3) to determine urea
The MSS cassette is filled with standby solution again. The quality of the aspiration
and the stroke (after repeated aspiration of standby solution) is assessed by the
conductivity distance at the MSS output.
The sample segment for measurement of tHb/SO
2
or COOX is positioned last. The
valves V2, V4, V17 and V16 are opened and aspirated with the main pump.
e
For more information, see Sample distribution on page A-23.
The sample is still hemolyzed in the event of a COOX measurement.
At the same time the FMS is started for these procedures (for the pending
recalibration of the BG and ISE modules) and mixed from the A and B Mix1
solutions.
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