Sample preparation for gas chromatography with electron capture detection: determination of total and free thyroxin in serum.
Relatively clean gas chromatography with electron capture detection (GC-ECD) chromatograms are obtained for both total and free thyroxin (T4) in serum by improving sample preparation. This is based on establishing a sequence of steps that cumulatively overcome two classes of interference: those present in the initial sample and those introduced by the procedure. The main source for the latter contaminants is the derivatization step, a problem that was largely overcome by employing HPLC after this step. Also it is helpful to use ion-exchange columns early in the procedure under fast-flow conditions with intermediate flows of air to speed up and enhance their reliability. The work establishes some guidelines for future applications of GC-ECD to the determination of sub-nanogram analytes requiring derivatization, an area in which GC-ECD has been remiss in the past. As a side benefit, total T4 in serum is determined by HPLC for the first time with uv detection.
Rogers
E J
EJ
Department of Medicinal Chemistry, College of Pharmacy and Allied Health Professions, Boston, Massachusetts.
Giese
R W
RW
D002849:Chromatography, Gas / Q000379:methods*; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D006801:Humans; D013974:Thyroxine / Q000097:blood*
D013974:Thyroxine