Carryover; Reproducibility; Cycle Time (Between Injections) - Waters ACQUITY Arc System System Manual

• Keep the seal-wash line primed.
• Monitor the level in the waste vessel, to ensure that it can accommodate all of the
expected waste.
• Do not use the Load Ahead or Loop Offline options when troubleshooting
carryover problems.

2.2 Carryover

You observe carryover in chromatographic systems when a previously injected
analyte appears as a peak in the chromatogram of subsequent samples. Carryover
tends to occur when a small amount of analyte remains in the system after a sample
is injected. You can measure carryover by observing analyte peaks that appear when
you run a blank sample immediately after an analytical sample. Waters specifies
carryover on the ACQUITY Arc system at less than 0.002%
A common cause of carryover is inadequate washing of the system. Choosing an
appropriate wash solvent can minimize carryover for a particular analysis. The wash
solvent must be strong enough to dissolve any remaining sample, and the wash
duration must be long enough to remove the residue from the system.
Method conditions also affect carryover. Too short a hold-time at the final conditions
of a gradient, especially if the gradient is steep, can fail to remove all analytes from
the system. It is important to completely flush the system and re-equilibrate the
column before proceeding to a subsequent analysis. Use caution when choosing the
load-ahead and loop-offline options. Initiating these options before the highly organic
part of the gradient reaches the needle can leave sample residue in the system, and
whatever time savings you gain can be lost in terms of inadequate system cleaning.
The hydrophobicity and solubility of samples as well as cleanliness during sample
preparation are additional factors to consider when trying to minimize carryover, as
is contamination from sample preparation tools.

2.3 Reproducibility

The precision (area reproducibility) when using the SM FTN-R is less than 0.25%
RSD for injection volumes from 5.0 to 1000 µL.

2.4 Cycle time (between injections)

The sample manager's Load Ahead option can help decrease cycle time. It causes the
sample manager to aspirate the next sample while a current sample is running.
June 12, 2015, 715004747 Rev. A
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