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Figure 1: Evaluation of metabolite quantification. Two data sets, synthetic and urine samples, are plotted in this figure to give a measure for accuracy and precision, respectively: (1) nominal and measured concentrations for synthetic samples were measured to determine accuracy and (2) data of first and repeated measurements of urine samples were compared to determine precision. The synthetic samples (grey) were composed of a set of 4 metabolites (glucose, citrate, lactate, creatinine) in aqueous solution at arbitrarily varying concentrations ranging from 10 to 10,000 μg/mL ( , glucose: ). The nominal metabolite concentration is plotted against the metabolite concentration measured with 1D 1H NMR spectroscopy. Urine samples from rats treated with natrosol (black), furosemide (green), or HCBD (blue) with or without pH or salt modifications (“stability test” dataset) were measured repeatedly. Eight repeated measurements per sample (performed over 14 days with refrigerating at about 4°C) are plotted against the first measurement to show reproducibility ( except for glucose: , other values are missing since they were below LOD; 3 treatments 18 modifications (“original” + 9 pH changes + 8 salt modifications) = 54, for definition of pooled samples see Section 2.4). Equations for linear regression curves are given for all data fromsynthetic and urine samples, which were above LLOQ nominally/with first themeasurement. Dashed lines represent the LLOQ, dotted lines thee LOD (glucose only).