Supplier tra [min] r12b MW ion Target ion Confirmation ions LOD [ng] formic acid Flukac 2.8 0.1 118 103 73, 45 0.2 acetic acid Fisherd 3.9 0.2 132 117 75, 45 0.3 lactic acid Sigma-Aldriche 12.3 0.5 230 191 147, 117 0.2 oxalic acid Sigma-Aldrich 13.6 0.6 230 190 219, 147 0.2 3-hydroxybutyric acid Sigma-Aldrich 13.8 0.6 244 191 233, 117 0.04 butanediol Sigma-Aldrich 13.9 0.6 234 177 147, 116 0.02 benzoic acid Sigma-Aldrich 15.3 0.7 192 179 135, 105 0.4 glycerol Fisher 15.7 0.7 308 205 218, 117 0.2 proline Sigma-Aldrich 15.9 0.7 259 142 216, 73 0.1 malic acid Sigma-Aldrich 18.5 0.8 344 233 245, 147 0.04 phthalic acid Sigma-Aldrich 20.8 0.9 310 295 147,73 0.1 xylitol Supelcof 21.0 0.9 502 307 319, 217 0.04 arabitol Supelco 21.1 0.9 502 307 319, 217 0.02 ribitol Supelco 21.2 0.9 502 319 307, 217 0.06 citric acid Sigma-Aldrich 22.2 1.0 480 273 465, 73 0.03 glucose Supelco 23.1 1.0 530 204 191, 147 0.02 sucrose Supelco 29.8 1.3 902 361 217, 73 19 a Retention time b Relative retention time (retention time/IS retention time) c Fluka – St. Louis, MO, USA d Fisher – Waltham, MA, USA e Sigma-Aldrich – St. Louis, MO, USA f Supelco – St. Louis, MO, USA

Table 1: List of acids, saccharides and polyalcohols studied, their suppliers, the GC–MS retention times, target and confirmation ions (used for quantification) of their trimethylsilyl derivatives used for data processing, and limits of detection (LODs).