Mixing by Programmable Flow
In the movie clip on the left  (A) 20 microliters of  an indicator (bromothymol blue) in 0.01M borax  solution (pH=9.2) is aspirated via flow through port towards the holding coil. Next the valve is switched to reagent port, but no solution is aspirated. Finally valve is switched to detector position and the dispersing zone of a blue dye flows through the flow cell. Note that although parabolic, the shape of the dye zone changes to almost symmetrical following the  flow reversal .

In the movie clip on the right (B) the same sequence of events is repeated, except that aspirationthe dye, is followed by 30 microliters of 0.01N HCl, aspirated from reagent port., and stacked behind the indicator zone into the holding coil. Upon flow reversal indicator  and acid zones are mixed,  the  indicator rapidly changes its color from  yellow to blue, confirming fast and complete mixing of injected zones.