Block diagram of how A4F will be coupled to LTEM.  The commercial A4F instrument with an integrated dynamic light scattering detector (DLS) automatically determines whether particles are present in the A4F eluate and controls a 3-way solenoid valve (SV) to choose whether it goes to waste (if particle free) or the TEM (if it contains particles).  A buffer volume allows the sample to be staged for TEM so that the flow rates of A4F and LTEM can be decoupled.  One-way check valves (CV) prevent undesired back flow.  Alternatively, this setup can also be used to calibrate the A4F size distribution by selectively sending the sample of a known retention time to the TEM.