Octadecanoids are broadly defined as oxylipins (i.e., lipid mediators) derived from 18-carbon fatty acids.
In contrast
to the well-studied eicosanoids, there is a lack of analytical methods
for octadecanoids, hampering further investigations in the field.
We developed an integrated workflow combining chiral separation by
supercritical fluid chromatography (SFC) and reversed-phase liquid
chromatography (LC) coupled to tandem mass spectrometry detection
for quantification of a broad panel of octadecanoids. The platform
includes 70 custom-synthesized analytical and internal standards to
extend the coverage of the octadecanoid synthetic pathways. A total
of 103 octadecanoids could be separated by chiral SFC and complex
enantioseparations could be performed in <13 min, while the achiral
LC method separated 67 octadecanoids in 13.5 min. The LC method provided
a robust complementary approach with greater sensitivity relative
to the SFC method. Both methods were validated in solvent and surrogate
matrix in terms of linearity, lower limits of quantification (LLOQ),
recovery, accuracy, precision, and matrix effects. Instrumental linearity
was good for both methods (R
2 > 0.995)
and LLOQ ranged from 0.03 to 6.00 ng/mL for SFC and 0.01 to 1.25 ng/mL
for LC. The average accuracy in the solvent and surrogate matrix ranged
from 89 to 109% in SFC and from 106 to 220% in LC, whereas coefficients
of variation (CV) were <14% (at medium and high concentrations)
and 26% (at low concentrations). Validation in the surrogate matrix
showed negligible matrix effects (<16% for all analytes), and average
recoveries ranged from 71 to 83%. The combined methods provide a platform
to investigate the biological activity of octadecanoids and expand
our understanding of these little-studied compounds.