High RSDs

Issue

Inconsistent results. High RSD's

Environment

• iCAP 6000
• iCAP 7000
• iCAP PRO
• Qtegra

Resolution

Determine what is causing the decreased flow. Some potential causes:

1. Clogged autosampler probe

You can try clearing a clogged by probe by doing the following:

a. Disconnect the piece of capillary tubing going from the sample line from either the nebulizer or the Y fitting (if performing online internal standard dilution)

b. Place the end of the disconnected tubing in a rinse solution

c. Reverse the sample pump tubing on the peristaltic pump so that instead of pulling solution up through the autosampler probe, solution will now be dispensed through the probe

d. Turn on the peristaltic pump at a pump speed of 40 and see if the clog can be cleared.

e. If this fails to clear the clog, replace the autosampler probe.

2. Clogged capillary tubing. 

If the cause is determined to be clogged tubing, replace the tubing because tubing is relatively inexpensive and therefore not worth the time to try and resolve a clog.

3.  Peristaltic pump tubing

If the peristaltic pump tubing has been in use for more than 16 hours of operation, switch to unused set of stops in the case of 3-stop tubing or replace the tubing

4. Inadequate tension on the peristalic pump tubing

Utilize this video as a guide to optimize the tension:  Optimizing peristaltic pump tension on iCAP 6000/7000

Analysis

It was determined that there was a trend up across the replicates signifying that the solution has not stabilized in the plasma before the data acquisition started. This trend is often indicative of an issue in sample introduction system which is causing the sample flow to decrease and thus increased time to get to the nebulizer.

Cause

In the case that prompted this knowledge article, it was determined that the autosampler developed a clog. Once the clog was cleared, the RSD's were normal.