Issue Resolution
Background
When solvent verification limits are much higher than the actual cleanliness of the solvent, the system will accept count data that is within the high limits but not representative of the actual cleanliness of the solvent. When this happens the reported counts on all samples will be lower than they should be because the corrections applied for the solvent background counts will be too high. This is not as issue for samples with high particle counts (i.e. > 15/13/11) as the error is minimal and insignificant, but this is not the case with very clean samples (i.e. < 14/12/10).
Resolution
The solvent verification limit parameters (Micron setting parameters) should be set based on the cleanest samples expected to be analyzed on the system and the highest dilution ratio used to dilute the samples. The parameters in the particle counter must be set to ensure the method requirement for the solvent not contributing more than 12.5% of the counts in the diluted sample is met on all samples.
Service Media
CINRG-CS-APC-SUPPORT-ZERO-COUNTS
CINRG Support - Adjusting Solvent Verification Settings to Eliminate Negative Counts.