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Agilent InfinityLab LC Series 1260 Infinity II Isocratic- and Quaternary Pumps User Manual 91

Optimizing Performance

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 18 on page 92. 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 217)

4 Starting with a compressibility setting of 40·10

-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.

NOTE

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.

Agilent Technologies G7110B User Manual

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