Gram-negative and -positive bacteria differentiation in blood culture samples by headspace volatile compound analysis

Table 2 Ionization method and masses identified by the random forest method

Ionization	Ion	Identified masses [m/z]	Tentative compound
EI-MS	e⁻	2	H₂
IMR-MS	Hg⁺	34–36, 64, 66	H₂S (34)^a
IMR-MS	Xe⁺	35, 64, 76, 80	–

EI-MS electron impact mass spectrometry; IMR-MS ion–molecule reaction mass spectrometry
^aSignalling at m/z 36 is 4.20 % of m/z 34 signalling which matches exactly the expected value of 4.21 % for the presence of the ³⁴S isotope of H₂S

ISSN: 2241-5793