58 1260 Infinity QuatPump VL User Manual
5 Optimizing Performance
Optimize the Compressibility Compensation Setting
Optimize the Compressibility Compensation Setting
The compressibility compensation default setting is 100 × 10
-6
/bar for the
pump. This setting represents an average value. Under normal conditions the
default setting typically reduces the pressure pulsation to values below 1 % of
system pressure that are sufficient for most applications and for all gradient
analyses. The compressibility settings can be optimized by using the values for
the various solvents described in Table 5 on page 59. If the solvent in use is not
listed in the compressibility tables, when using isocratic mixtures of solvents
and if the default settings are not sufficient for your application the following
procedure can be used to optimize the compressibility settings.
1 Start the pump with the required flow rate.
2 Before starting the optimization procedure, the flow must be stable. Check
the tightness of the system with the pressure test.
3 Your pump must be connected to a data system or Instant Pilot with which
the pressure and %-ripple can be monitored, or connect an external
measurement device to the analog pressure output (see “Electrical
Connections” on page 177)
4 Starting with a compressibility setting of 10 × 10
-6
/bar increase the value
in steps of 10. Re-zero the signal display as required. The compressibility
compensation setting that generates the smallest pressure ripple is the
optimum value for your solvent composition. If ChemStation (classic view)
is used and the ripple shown is positive, then the compressibility setting
should be decreased. If it is negative, it should be increased.
When using mixtures of solvents it is not possible to calculate the compressibility of the
mixture by interpolating the compressibility values of the pure solvents used in that mixture
or by applying any other calculation. In these cases the following empirical procedure has
to be applied to optimize your compressibility setting.
Inappropriate settings would mainly affect retention times of peaks eluted at the beginning
of a gradient. Therefore optimize settings for the solvent at the beginning of the gradient.
For mixtures containing up to 50 % water, use compressibility settings of water.
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