Table 3.

Characteristics of various analytical techniques used for breath test [7, 61, 98]

Analytical method	Typical compounds	Limit of detection	Advantages	Limitations
GC–MS	Sulfides, hydrocarbons, aldehydes	ppt–ppb ppt–ppb ppt–ppb	High selectivity and sensitivity	Large sampling time/requires standardization/requires preconcentration
PTR-MS	Aromatic compounds, isoprene	ppt ppt	Analysis is real-time	Small range of detectable compounds/compounds cannot be identified
SIFT-MS	Ethanol, ammonia	ppt–ppb ppt–ppb	Analysis is real-time/wide range of detection	Compounds cannot be identified
Sensor arrays/e-noses	Various VOCs	N/A	Analysis is real-time/potential for portability and miniaturization	Pattern recognition makes identification of compounds impossible
Ion mobility	Isoprene, acetone, ammonia	ppt–ppb ppt–ppb ppt–ppb	Vacuum systems are not required and ambient air can be used as a carrier gas	Not very useful for identifying unknown compounds in multi-component mixtures
Optical absorption	Ethane, carbon monoxide	ppt ppt	Analysis is real-time/potential for portability and miniaturization	Limited by available technology to meet sufficient specificity/selectivity required for practical use