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. Author manuscript; available in PMC: 2015 Jun 24.
Published in final edited form as: Anal Chem. 2015 Mar 17;87(7):3800–3805. doi: 10.1021/ac504435b

Figure 6.

Figure 6

Regions of 800 MHz 1H NMR spectra of the same pooled intact human serum: (a) serum before spiking with pyroglutamic acid (pGlu); (b–d) serum spiked with standard solution of pyroglutamic acid so that the added concentration is 86, 172 and 1032 μM, respectively. Virtually no pyroglutamic acid peaks were seen even after the addition of up to 172 μM pyroglutamic acid solution (see spectra in panels b and c); only at very high concentration are broad peaks for pyroglutamic acid seen (spectrum in panel d).