BSTFA	N,O-bis(trimethylsilyl)trifluoroacetamide
CNS	central nervous system
CSF	cerebrospinal fluid
FDA	Food and Drug Administration
GC–MS	gas chromatography–mass spectrometry
5HIAA	5-hydroxyindole-3-acetic acid
HMDB	Human Metabolome Database
3IAA	indole-3-acetic acid
3ICA	indole-3-carboxylic acid
3ILA	indole-3-lactic acid
3IPA	indole-3-propionic acid
LLE	liquid-liquid extraction
LOD	limit of detection
LOQ	limit of quantitation
MEPS	microextraction by packed sorbent
MTBSTFA	N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide
NIST	National Institute of Standards and Technology
RE	relative error
RSD	relative standard deviation
Rt	retention time
TBDMS	tert-butyldimethylsilyl
TMS	trimethylsilyl