Is there documentation that explains the "Load Ahead" option with an ACQUITY UPLC Sample Manager? - WKB8852

Using load ahead

The load-ahead option minimizes the injection cycle time of samples through the system. The sample manager overlaps the sample preparation portion of the injection cycle for the next sample while injecting the current sample for analysis.

Allow sufficient re-equilibration time to ensure that the system returns to initial conditions before activating the load-ahead option.

Exception: The first injection of a sample set, and injection sets with different methods, cannot use the load-ahead mode.

Requirement: You must take the extension loop offline when you use the load-ahead option.

Tips for a sample manager with a fixed loop:

• If you select Load Ahead in partial-loop with needle-overfill (PLNO) injection mode, you need not modify the Loop Offline parameter setting.
• If you select Load Ahead in Partial-Loop mode and Full-Loop mode, you must specify a time in the Loop Offline parameter setting that is less than the run time, to put the loop offline.

Placing the loop offline

To specify the interval during which the sample is flushed from the sample loop before the loop is set to the load position, select Loop Offline. To decrease delay volume during the separation, isolate the loop from the flow stream by specifying a time allowance for the sample to exit the sample loop before the loop is set to the load position.

The loop-offline option can improve chromatographic performance by producing a sharp trailing sample edge as the sample leaves the needle and extension loop. Choose the option to specify an interval, in minutes, following an injection, after which the needle and extension loop return to the load position. Doing so reduces the delay volume by taking the needle and extension loop offline before the gradient reaches the injection valve and after the sample transfers to the injection port.

Note: Putting the loop offline can cause a baseline disturbance.

Allow sufficient re-equilibration time to ensure that the system returns to initial conditions before activating the loop-offline option. Then specify a value (in minutes) for Loop Offline. Ensure that the value you enter is not less than the time needed for the current sample to leave the loop. The default value is Disable, in which the sample loop remains in the "inject" position throughout the injection.

A programmed gradient typically flows through all parts of the instrument that contact the sample. If you initiate the loop-offline option before the gradient reaches its final conditions, the highly organic portion of the gradient does not pass through the needle. The gradient can therefore fail to remove all sample from the needle, resulting in low sample recovery and an increased risk of carryover.