Reproducibility and Solvent Degassing 167
C
Appendix C
Reproducibility and Solvent
Degassing
This appendix covers:
• Factors affecting reproducibility
• Solvent degassing
C.1 Factors Affecting Reproducibility
During sample withdrawal, the Waters autosampler creates a closed loop between the
metering syringe and the sample vial. The behavior of the sample and solvent within this
loop determines the performance and reproducibility of the injection.
Factors that affect the behavior of the solvent in the loop include:
Chemical Factors
• Intrinsic compressibility
• Dissolved gas
• Viscosity
Instrument Factors
• Integrity of sample loop
• Volume of sample loop
C.1.1 Chemical Factors Affecting Reproducibility
If the mobile phase acts like a perfect hydraulic fluid, the volume of sample withdrawn is
the same as the volume of solvent pulled into the syringe. The autosampler measures the
hydraulic property of a solvent by compressing it within the sample loop (compression
check). The true injection volume is less than the programmed injection volume by the
compressibility factor. If the compressibility increases, the actual injected volume
decreases.
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