Figure 3.

Sensitivity of ¹H NMR Analysis for Salivary Metabolomics Experiments. Partial (3.06–3.56 ppm regions of) 600 MHz ¹H NMR spectra acquired on phosphate-buffered (10.00 mmol./L, pH 7.00) aqueous solutions of choline chloride (only 100, 200 and 500 nmol./L). Spectra were acquired on a Jeol JNM-ECZ600R/S1 600 MHz spectrometer operating at a frequency of 600.17 MHz for ¹H, with a probe operating temperature of 25 °C. Solutions also contained 10% (v/v) ²H₂O, 330 µmol./L TSP as a chemical shift reference and quantitative internal standard, and 0.03% (w/v) sodium azide as a microbicide. Spectra were acquired at an operating frequency of 600.17 MHz and 298 K, and with suppression of the very intense H₂O/HOD resonance (δ = 4.80 ppm) by use of the WASTED-II pulse sequence. Pulsing conditions were: sweep width 11,218 Hz; 16,384 datapoints; acquisition time 1.81 s; relaxation delay 1.00 s; and 1024 transients. STN values for each spectrum were estimated using Jeol Delta-5 software.