Contamination - Waters ACQUITY UPLC M-Class System Manual

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.
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. The time savings you gain from these options can be lost to cleaning the
system of the accumulated residue.
The hydrophobicity and solubility of samples are additional factors to consider when trying to
minimize carryover.
Tips:
• Use additional valve cycle timed events (actuate the valve) if you suspect that sample residue
in the valve is causing carryover problems.
• Test your sample in the strong wash solvent to ensure that the strong wash solvent does not
cause either the analyte or the matrix to precipitate.
• Do not use the Load Ahead or Loop Offline options when troubleshooting carryover problems,
as the shorter cycle times prevent effective troubleshooting.

2.5 Contamination

To minimize contamination, ensure that sample preparation tools and bottles are cleaned
thoroughly using high-purity chemicals.
Notice:
precautions:
• Do not wash it in detergent.
• Do not wash it with other glassware.
• Do not wash it using implements that can bear traces of detergent residues, which
can contain polyethylene glycol (PEG) or other sticky substances.
• Do not place washed glassware on vinyl-coated steel racks, which can be a source
of contamination.
See also:
Controlling Contamination in LC/MS Systems (715001307)
To avoid contaminating glassware and rendering it unusable, observe these
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