Spike-retrieval experiment
When using matched internal standards, mean percent recoveries ranged from 83 % to 110 % (Figure 2). RSDs were between 1.4 % to 9.4 % for all compounds, except corticosterone (18.8 %). Injection of one SRM sample onto the C18 column failed; therefore, we determined the mean SRM concentrations for adrenal steroids from two samples. One un-spiked replicate from the male sample and two spiked replicates from the female sample were improperly extracted and excluded from analyses.
For un-spiked samples, several mean analyte concentrations fell below the RL. Mean endogenous ALD concentrations fell below the RL in all three samples and endogenous B and 11DOC could only be quantified in the SRM, which had higher concentrations of all adrenal steroids. All biphenyl analytes were quantified above the RL in un-spiked samples, except for T, which was not quantifiable in the female sample or the SRM (also female).