Microliter sample introduction for open tubular column supercritical fluid chromatography using a packed capillary for solute focusing (original) (raw)

Llquld samples were Introduced Into an open tubular column wpercrltlcal fluld chromatograph (SFC) udng a short packed caplllary column as a solute focurlng devlce after a typlcal sample loop valve Injector. The packlng materlals were held lndde the caplllary by porous ceramlc frlts. Excess solvent was vented Into the atmosphere through the packed caplllary. Slnce the exit end of the packed caplllary column was at atmosplwrk pressure, a denslty gradlent was established along the length of the column and solutes preclpltated at the polnt where the dendty dropped below the carbon dloxlde solvating density for these compounds. The solutes were then backflushed from the precolumn Into the analytlcal column wlth wpercrltlcal COS. Thls method made lt pomlble to Inject rdatlvdy large volumes (1-3 pL) Into a 50-pm4.d. open tubular wpercrltlcal fluld chromatography column wlthout floodlng the column wlth the solvent. The reproduclblllty of thls InJectlon method was compared wlth other lnjectlon methods used wlth SFC; the relatlve standard devlatlon (five measurements) of peak areas of n-hexadecane was 5.5 %.