I am developing a method on a 5800 ICP-OES with an AVS 7 valve and a SPS 4 autosampler.
Since today all my ICP-OES measurements have high RSDs (>10%), even for the internal standard lines, which normally have RSDs around 0.40%. it's always the third/last replicate that is much lower than the first two.
I had just performed an Instrument Performance Test without the autosampler and this passed easily so i gathered the problem should be caused somewhere in the autosampler or switching valves.
When observing the filling and emptying of the sample loop, i noticed that the autosampler lets in air just after filling the sample loop, whilst the probe is already heading towards the rinse tray. These bubbles eventually enter the nebulizer and causes sputtering. Although the conditions i am using never caused any such malfunctions, i tried changing the uptake and injection speed to delay the bubbles entering the nebulizer during measurement. But it did not solve the problem.
I am pretty sure that I've identified the problem, but could use some advice on how to fix this issue.
Thanks in advance!