CHRNS: Stopped flow capabilities

Principle

In this device solutions are forced into a specially designed mixing chamber. After a time, perhaps as short as a few ms, the solution is pushed into the sample cell at a time recorded using the master clock. Thus, this device will allow automated sample preparation to be done on a time scale matching those accessible to vSANS and CANDOR and provide the time resolution necessary to characterize the kinetics of, for example, the formation of biocomplexes.

The in-house-built stopped flow apparatus has improved its time resolution from ~3 second to about 1 second with a remaining goal of reaching ~400 ms. This benchmark should be achievable once we receive the high-pressure neutron scattering cell that was procured with the commercial stopped-flow system (eta Feb 2023). 

Current status (accelerated for 22-24)

• Temperature-controlled (10-50 °C)
• 2 Syringe Pumps (for sample injection)
• Pressure sensors – automatic overpressure shutdown
• Selector valves for fluid path control
• High-speed mixer
• 2 sample cells 
• 2 Pressurized lines for solvent rinses & drying
• UV-Vis spectrometer (multi-modal data, NEW for FY23)
• Dead Volume: ~ .75 mL
• Dead Time: ~ 400 ms (NEW for FY23)
• SECoP controlled with GUI and indicator panel (https://gitlab.nist.gov/gitlab/ces7/sfsans)
• Commercial cell (Biologic)
• Also available a commercial Biologic stopped flow system (SMF-4000, 30 ms deadtime, low viscosities)

Many thanks to party of interested scientists that provided feedback and prioritized capabilities:

Lilo Pozzo – Washington; Ron Jones – NIST; Norm Wagner – Delaware; Drew Marquardt– Windsor;  Sarah Rodgers–RAL; Adrian Rennie– Uppsala  Andy Church–RAL;  Lionel Porcar– ILL