When the injection valve switches to the BYPASS position, the mobile phase in the sample loop is depressurized. When the syringe begins drawing sample, the pressure of the mobile phase is decreased further. If the mobile phase is not degassed adequately, small gas bubbles can form in the sample loop during the injection sequence. When using injection volumes < 2 µL, these gas bubbles can affect the injection-volume precision. Use degassed mobile phases for best injection-volume precision with injection volumes < 2 µL.
If the pump has no degasser, it is recommended to use an Agilent 1260 Infinity degasser.
Also, using the automated needle wash (see Optimization for Lowest Carryover) between injections reduces carryover to a minimum, further improving the injection volume precision.
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id: 3714944011