Lv. Rao et al., Development of a urinary free cortisol assay using solid-phase extraction-capillary electrophoresis, J CHROMAT B, 730(1), 1999, pp. 123-128
In clinical practice, the measurement of urinary free cortisol (UFC) provid
es the most sensitive and specific diagnostic information for excess adrena
l production of cortisol. The existing methodologies (RIA and HPLC) are tim
e consuming, costly, involve tedious extractions, derivatizations and probl
ems with non-specific interactions with cortisol metabolites in urine. In t
he present study, we describe the development of an SPE-CE method for the r
apid analysis of UFC. UFC was concentrated using SPE C-18 cartridges (3M Em
pore) under a vacuum and eluted with acetonitrile-SDS. The use of 10% aceto
ne to wash cartridges before final elution with acetonitrile-SDS showed sig
nificant improvements in the free cortisol recovery. The complete extractio
n was accomplished in 10-15 min with a recovery of 89-94%. CE analysis was
done on a Beekman P/ACE 5010 with detection at 254 nm using a neutral capil
lary. Detection limits of free cortisol in urine was improved to 10 mu g/l
with SPE compared to 500 mu g/l without SPE. No interferences either from B
SA or other urinary cortisol metabolites affected the free cortisol determi
nations. The results showed the feasibility of a rapid UFC detection with i
mproved sample handling capacity. (C) 1999 Published by Elsevier Science B.
V. All rights reserved.