Preparing for Operation
Preparing the solvent and waste bottles
48
• Sample washes
The injector fills the syringe to eight-tenths of its volume with the next
sample and dispenses the contents into one of the waste bottles. Sample
washes occur before the injection. When sample is limited, you can use a
solvent prewash to wet the syringe before drawing sample.
• Pumps
The injector fills the syringe to eight-tenths of its volume with the next
sample and dispenses it back into the sample vial. Pumps occur after the
sample washes and immediately before the injection. Pumps serve to
eliminate bubbles. If the needle contains solvent from a previous wash, the
pumps may add a small amount of solvent that mixes with the sample and
can dilute a small volume.
The number and type of washes are determined with the run parameters. See
“Setting the run parameters” in chapter 3 for details.
Under ideal conditions, four washes reduce the carryover to one part in 10,000.
The actual number and type of washes you need depends on many factors,
including:
• The percentage of carryover that you can accept
• The viscosity and solubility of the analyte(s)
• The volatility of the solvent(s)
• The extent of wear in the syringe barrel
The number and type of washes is often set for you as a standard method. You
can also determine the number and type of washes experimentally.
To measure the percentage of carryover in your procedure, run a solvent blank
after a sample, and compare the peak areas of the components.
To Next Page
Loading...
Need help?
General
