Contamination - Waters ACQUITY UPLC M-Class System Manual

2 Optimizing Performance
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 reequilibrate 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 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 make sure that the
strong wash solvent does not cause either the analyte or the matrix to
precipitate.

Contamination

To minimize contamination, ensure that sample preparation tools and bottles
are cleaned thoroughly, and use high-purity chemicals.
Caution:
observe these 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 an additional source of contamination.
28 March 10, 2014, 715003588 Rev. A
To avoid contaminating glassware and rendering it unusable,