Efficient method for the quantitation of urinary leukotriene E-4: Extraction using an Empore C-18 disk cartridge

We describe here an efficient procedure for the precise quantitation of leukotriene E-4 (LTE4) in a small volume of urine, which was achieved mainly by the use of an Empore extraction disk cartridge. After addition of [H-3]LTE4 to 2 mi of urine, an Empore C-18 cartridge was used for initial extraction of the urine, which resulted in the extraction of LTE4 in a small volume of solvent. The eluate could then be injected onto a high-performance liquid chromatography column without further concentration. After separation by high-performance liquid chromatography, LTE4 was extracted from the effluent using an Empore C-18 cartridge. The concentration of LTE4 was subsequently quantified by enzyme immunoassay. LTE4 can be recovered from urine with sufficient efficiency (69.9+/-4.7%, mean+/-S.D., n=101). The coefficient of variation of the assay procedure was less than 10%. When urine was spiked with different amounts of LTE4, the recovery of LTE4 added to the urine specimen was less than 120%. The concentration of LTE4 in urine from normal healthy subjects was 48.0+/-15.3 pg/mg creatinine (n=15).