Table 2 Rankings (smallest numbers indicating most acidic) and SMARTS strings to identify acid and base substructures for competitive ionization of molecules based on FDA 2007

OSO3H

OS(=O)(=O)[O;H]

OS(=O)(=O)[O-]

10

SO3H

[!O]S(=O)(=O)[O;H]

[!O]S(=O)(=O)[O-]

20

OSO2H

O[S;D3](=O)[O;H]

O[S;D3](=O)[O-]

30

SO2H

[!O][S;D3](=O)[O;H]

[!O][S;D3](=O)[O-]

40

OPO3H2

OP(=O)([O;H])[O;H]

OP(=O)([O;H])[O-]

50

PO3H2

[!O]P(=O)([O;H])[O;H]

[!O]P(=O)([O;H])[O-]

60

CO2H

C(=O)[O;H]

C(=O)[O-]

70

Arom-SH

c[S;H]

c[S-]

80

OPO3H-

OP(=O)([O;H])[O-]

OP(=O)([O-])[O-]

90

PO3H

[!O]P(=O)([O;H])[O-]

[!O]P(=O)([O-])[O-]

100

Phthalimide

O = C2c1ccccc1C(=O)[N;H]2

O = C2c1ccccc1C(=O)[N-]2

110

CO3H

C(=O)O[O;H]

C(=O)O[O-]

120

α-carbon to NO2 group

O = N(O)[C;H]

O = N(O)[C-]

130

SO2NH2

S(=O)(=O)[NH2]

S(=O)(=O)[NH-]

140

OB(OH)2

OB([OH])[OH]

OB([OH])[O-]

150

B(OH)2

[!O]B([OH])[OH]

[!O]B([OH])[O-]

160

Arom-OH

c[OH]

c[O-]

170

SH aliphatic

C[SH]

C[S-]

180

OBO2H

OB([OH])[O-]

OB([O-])[O-]

190

BO2H

[!O]B([OH])[O-]

[!O]B([O-])[O-]

200

Cyclopentadiene

[CH2]1C = CC = C1

[C-]1C = CC = C1

210

Amide

C(=O)[NH2

C(=O)[N;H;-]

220

Imidazole

c1cnc[n]1

c1cnc[n-]1

230

Aliphatic OH

[CX4][OH]

[CX4][O-]

240

H at α-carbon to carboxyl

O = C[CH]

O = C[C-]

250

H at α-carbon to acetyl

OC(=O)[CH]

OC(=O)[C-]

260

H at sp carbon

C#[CH]

C#[C-]

270

H at α -carbon of sulfone group

CS(=O)(=O)C[CH]

CS(=O)(=O)C[C-]

280

H at α-carbon of sulfoxide

C[S;D3](=O)C[CH]

C[S;D3](=O)C[C-]

290

Amine

[CX4][NH2]

[CX4][N;H;-]

300

Benzyl

c[C;D4;H]

c[C;D3;-]

310

H at sp2 carbon

[CX3;H]

[CX3;-]

320

H at sp3 carbon

[CX4;H]

[CX3-]

330