CKD	chronic kidney disease
EI	electron impact ionization
ESBL	extended-spectrum beta-lactamase
FDA	U.S. Food and Drug Administration
GC-MS	gas chromatography-mass spectrometry
GC-MS/MOS	gas chromatography-mass spectrometry/metal oxide sensor
GC-MS/MS	gas chromatography-tandem mass spectrometry
GC-TOFMS	gas chromatography-time of flight mass spectrometry
GC × GC-TOFMS	two-dimensional gas chromatograph-time of flight mass spectrometry
HS	headspace
HRMS	high resolution mass spectrometry
IBD	inflammatory bowel disease
IBS	irritable bowel syndrome
LC	liquid chromatography
LLE	liquid-liquid extraction
LOD	limit of detection
LPME	liquid phase microextraction
MALDI	matrix-assisted laser desorption/ionization
MOS	metal oxide sensor
MS	mass spectrometry
m/z	mass to charge ratio
NIST	The National Institute of Standards and Technology
ppb	part per billion
ppqv	part per quadrillion per volume
pptv	parts per trillion by volume
PTR-MS	proton transfer reaction-mass spectrometry
PTR-TOFMS	Proton transfer reaction-time of flight mass spectrometry
ROC	receiver operating characteristic
SBSE	stir bar sorptive extraction
SDME	single-drop microextraction SPDE: solid-phase dynamic extraction
SESI-MS	secondary electrospray ionization—mass spectrometry
SIFT-MS	selected ion flow tube-mass spectrometry
SPME	solid-phase microextraction
TD	thermal desorption
VASE	vacuum-assisted sorbent extraction
VCs	volatile compounds