Gas chromatographic—mass spectrometric determination of leukotriene E 4 in human urine using deuterium-labelled leukotriene E 4 standards

Abstract

The utility of two deuterium-labelled leukotriene (LT) E 4 analogs, e.g. [20,20,20- 2H 3]LTE 4 and [14,15,17,17,18,18- 2H 6]LTE 4, as internal standards for the determination of LTE 4 in human urine by gas chromatography—mass spectrometry (GC—MS) was investigated. 2H-Exchange during hydrogenation occurred both in [20,20,20- 2H 3]LTE 4 and [14,15,17,17,18,18- 2H 6]LTE 4 in an extent of 9.4 ± 0.5% and 67.3 ± 0.6% (mean ± S.D., n = 6), respectively. The lower extent of 2H-exchange in [20,20,20- 2H 3]LTE 4 allowed a more accurate quantitation than the use of [14,15,17,17,18,18- 2H 6]LTE 4. Applying [20,20,20- 2H 3]LTE 4 as internal standard the coefficients of variation for the intra- and inter-assay determination of LTE 4 in human urine were 5.7% and 6.2% ( n = 4), respectively. The inter-assay coefficient of variation for [14,15,17,17,18,18- 2H 6]LTE 4 was 15%. Using [20,20,20- 2H 3]LTE 4 as internal standard and GC—MS, healthy volunteers were found to excrete 17 ± 10 nmol LTE 4 per mol creatinine (mean ± S.D., n = 11). Similar excretion rates for LTE 4 in urine of healthy volunteers were found using GC—tandem MS with [1,1- 18O 2]LTE 4 as internal standard. Our results demonstrate that [20,20,20- 2H 3]LTE 4 is a suitable internal standard for the GC—MS determination of urinary LTE 4.