Ordinary valves serve for switching of packed columns (backflush valves, 6-port, 8-port and 10-port valves) that however do not fit for switching of capillary columns. Alternative way of capillary columns switching is the change of flows in capillary columns which is done by so called “Dins switch” (DS).
Photo: Column switching scheme with backflush of precolumn
One of the possible applications of DS is cutting off of more lightweight components from the sample with their further separation in the second column and backflushing of the first column from heavy sample components.
This scheme is used for example for time reduction of analysis of contents of hydrogen sulfide, methyl-, ethyl mercatan and other lightweight sulfur-containing components in oil and gas condensate by cutting off primary section of chromatogram from precolumn with further separation of components of the cut-off section in the second column and backflush of remaining oil components from the first column. Oil analysis with backflush of precolumn takes less than 8 minutes.
One more application is cutting off oxygenated components from the gasoline sample from polar column of TCEP type with their further separation in non-polar column. This switching is repeatedly done by “pneumatic bridge” on Dins’s switches.
Technical characteristics of DS
- Switching time setting range — from 0,1 to 999 min.
- Switching time — 0,1 s.
- Dead valve volume — less than 1 mcl.
- Valve temperature — no more than 350 °C.
- Valve line pressure — no more than 0,4 MPa.
- Electric current — 5 V.