Figure 1.

Response behavior of glucose. (A) Signal of 20 µM glucose in the presence of sulfate, phosphate, and gluconate at the given concentration (suppression effect); (B) Signal of 7 µM glucose in a mixture of model compounds (succinate, 2-oxoglutarate, phosphate, erythritol, ribose, fructose, inositol, mannitol, and sinapinic acid) in ascending concentrations (enhancement effect). Note that already for a glucose concentration of 10 µM, the enhancement effect decreased to a ratio of 1.0–1.4 in the same experiment (not shown). All experiments were conducted using a Trace Focus GC for compound separation.