Ensuring Reproducibility 89
4
4.5.3 Performing a Compression Check
The compression check tests for gas in the mobile phase, and, when enabled, occurs
immediately after a purge. For most mobile phases, use the default parameters.
Note: The compression check is only valid using the standard 250-µL syringe and 200-µL
sample loop.
Change the default parameters if:
• Mobile phase is highly compressible (see Appendix C,
Reproducibility and Solvent
Degassing).
• Testing for leaks (see Section 6.4.2,
Valve Leak Test).
Compression Parameters
When enabled, the compression check is executed immediately after a purge. The
parameters are:
• Compression Pressure
• Pressure Decay Time
• Compressible Volume
Compression Pressure
For testing the compressibility of the mobile phase, use 30 psi. For leak testing, use the
maximum pressure.
Table 4-3 Purge Time Examples
Sample
Loop
Flow Rate
(mL/min)
Purge Time
(min)
Normal 0.2 12.5
0.5 5.0
>1 2.5
Auxiliary 0.5 19.4
1 9.7
2 4.8
Range 30 to 350 psi
Default 30
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