TY - JOUR
T1 - Formation of the bisulfite anion (HSO3 -, m/z 81) upon collision-induced dissociation of anions derived from organic sulfonic acids
AU - Jariwala, Freneil B.
AU - Wood, Ryan E.
AU - Nishshanka, Upul
AU - Attygalle, Athula B.
PY - 2012/4
Y1 - 2012/4
N2 - In the negative-ion collision-induced dissociation mass spectra of most organic sulfonates, the base peak is observed at m/z 80 for the sulfur trioxide radical anion (SO3 -·). In contrast, the product-ion spectra of a few sulfonates, such as cysteic acid, aminomethanesulfonate, and 2-phenylethanesulfonate, show the base peak at m/z 81 for the bisulfite anion (HSO3 - ). An investigation with an extensive variety of sulfonates revealed that the presence of a hydrogen atom at the β-position relative to the sulfur atom is a prerequisite for the formation of the bisulfite anion. The formation of HSO3 - is highly favored when the atom at the β-position is nitrogen, or the leaving neutral species is a highly conjugated molecule such as styrene or acrylic acid. Deuterium-exchange experiments with aminomethanesulfonate demonstrated that the hydrogen for HSO3 - formation is transferred from the β-position. The presence of a peak at m/z 80 in the spectrum of 2-sulfoacetic acid, in contrast to a peak at m/z 81 in that of 3-sulfopropanoic acid, corroborated the proposed hydrogen transfer mechanism. For diacidic compounds, such as 4-sulfobutanoic acid and cysteic acid, the m/z 81 ion can be formed by an alternative mechanism, in which the negative charge of the carboxylate moiety attacks the α-carbon relative to the sulfur atom. Experiments conducted with deuterium-exchanged and deuterium-labeled analogs of sulfocarboxylic acids demonstrated that the formation of the bisulfite anion resulted either from a hydrogen transfer from the β-carbon, or from a direct attack by the carboxylate moiety on the α-carbon.
AB - In the negative-ion collision-induced dissociation mass spectra of most organic sulfonates, the base peak is observed at m/z 80 for the sulfur trioxide radical anion (SO3 -·). In contrast, the product-ion spectra of a few sulfonates, such as cysteic acid, aminomethanesulfonate, and 2-phenylethanesulfonate, show the base peak at m/z 81 for the bisulfite anion (HSO3 - ). An investigation with an extensive variety of sulfonates revealed that the presence of a hydrogen atom at the β-position relative to the sulfur atom is a prerequisite for the formation of the bisulfite anion. The formation of HSO3 - is highly favored when the atom at the β-position is nitrogen, or the leaving neutral species is a highly conjugated molecule such as styrene or acrylic acid. Deuterium-exchange experiments with aminomethanesulfonate demonstrated that the hydrogen for HSO3 - formation is transferred from the β-position. The presence of a peak at m/z 80 in the spectrum of 2-sulfoacetic acid, in contrast to a peak at m/z 81 in that of 3-sulfopropanoic acid, corroborated the proposed hydrogen transfer mechanism. For diacidic compounds, such as 4-sulfobutanoic acid and cysteic acid, the m/z 81 ion can be formed by an alternative mechanism, in which the negative charge of the carboxylate moiety attacks the α-carbon relative to the sulfur atom. Experiments conducted with deuterium-exchanged and deuterium-labeled analogs of sulfocarboxylic acids demonstrated that the formation of the bisulfite anion resulted either from a hydrogen transfer from the β-carbon, or from a direct attack by the carboxylate moiety on the α-carbon.
KW - Anions
KW - Bisulfite
KW - CID
KW - Fragmentation
KW - Gaseous ions
KW - Sulfonates
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U2 - 10.1002/jms.2975
DO - 10.1002/jms.2975
M3 - Article
C2 - 22689630
AN - SCOPUS:84861541516
SN - 1076-5174
VL - 47
SP - 529
EP - 538
JO - Journal of Mass Spectrometry
JF - Journal of Mass Spectrometry
IS - 4
ER -