Improved SFE recovery of trace analytes from liver using an integral micrometering valve-SPE column holder assembly

A novel integral restrictor–collector has been designed for use with a conventional supercritical fluid extraction (SFE) apparatus. The assembly reduces the path length between a micrometering valve and collector (a solid phase extraction (SPE) column), obviating the need for the complicated tubing and connectors usually associated with such devices. Also described is a heating‐block assembly which encases the micrometering valve and provides uniform heating of the valve during extraction. The valve–SPE column assembly was part of a system used to perform the first reported SFE multi‐residue drug recovery from fortified liver. Extractions used carbon dioxide pressurized to 690 bar as the supercritical fluid. Flow rates of expanded gas through the SPE columns were 3–4 L/min with concomitant quantitative trapping of the analytes on the sorbent bed. After SFE the three nitrobenzamide antimicrobial drug residues from the liver were eluted from the SPE columns by off‐line analysis. The results demonstrated that losses of trace level analytes in tissue may be significantly reduced by including an integral metering valve‐collector assembly as part of the SFE apparatus.