The use of silica gel impregnanted glass fiber sheets in plasma estriol assays.

The f luor imetr ic quantitation of nanogram amounts of es t r io l extracted f rom plasma is somet imes impaired by impuri t ies which in ter fere with f luorescence. Instant th inlayer chromatography on sil ica gel impregnated glass fiber sheets (ITLC-SG) removes such impuri t ies originating from extracts as well as from solvents used in the course of analysis . This convenient, rapid and effective chromatographic procedure does not introduce interfer ing substances by itself. With the uti l ization of ITLC, plasma es t r io l assays proved to be precise , specific and accurate. The f i r s t relat ively simple and generally applicable method for ser ia l clinical determinat ions of plasma es t r io l (3) concentrations during the second half of human pregnancy was published by Nachtigall et al. (4). With this method, f luor imetry has proven to be a pract ica l way of quantitating nanogram amounts of es t r iol derived from plasma 636 S T E R O I D S 16:6 extracts . In attempting to adapt our method of measur ing ur inary es t r io l in pregnancy (5) to the determination of plasma es t r io l in the second half of gestation, unsat isfactory precis ion and accuracy were encountered although methylation, additional solvent parti t ion and chromatography on alumina were used to remove impurit ies which not infrequently in ter fere with fluoresence. Such impurit ies may ar ise from plasma or other biological fluids as well as from solvents used during the extraction and purification procedures. A purifioation step appeared necessary which would effectively remove these impur i t ies and not introduce interfer ing substances inherent in many chromatographic procedures. This report describes the use of instant th inlayer chromatography (ITLC) on sil ica gel impregnated glass fiber sheets to improve specificity, accuracy and precision in the measurement of plasma estr iol .