Multiclass Steroid Profiling in Short-Finned Pilot Whale Blubber Using Liquid Chromatography–Tandem Mass Spectrometry (LC-MS/MS)

Rationale

Wildlife scientists are quantifying steroid hormones in a growing number of tissues and employing novel methods that must undergo validation before application. This study tested the accuracy and precision of liquid chromatography–tandem mass spectrometry (LC-MS/MS) methods for use on blubber samples from short-finned pilot whales (Globicephala macrorhynchus). We expanded upon a method for corticosteroid quantification by adding analytes and optimizing internal standard (IS) application.

Methods

We optimized a method for the quantification of seven steroid hormones using LC-MS/MS with a C18 column. We assessed the accuracy and precision of this updated C18 method and an existing biphenyl method for use with pilot whale blubber by conducting a spike recovery experiment and calculating percent recovery and relative standard deviation (RSD) for each analyte. To explore the potential for running this method with fewer matched ISs, we compared the performance of multiple ISs for each analyte.

Results

All 11 adrenal and gonadal analytes showed good accuracy and precision in the spike recovery experiment, with recoveries between 82% and 110% and recovery RSDs below 10%. The C18 method detected all analytes at endogenous concentrations, except aldosterone. Although endogenous DHEA was detected, variability was high. IS comparisons showed 10 of 11 analytes could be calculated with comparable accuracy and precision using an IS substitute, but some substitutions significantly altered the analyte concentrations calculated.

Discussion

The C18 method was not sensitive enough for endogenous aldosterone detection. DHEA, which has not been previously quantified in blubber, was detected in all samples, but with high variability at lower concentrations. The methods in this study provide reliable detection and quantification of the other nine hormones tested and can be used for assessments of adrenal and gonadal steroid hormones from whales. Laboratories can reduce costs through IS substitution but should consider how these substitutions affect results.