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. Author manuscript; available in PMC: 2019 Oct 2.
Published in final edited form as: Soil Biol Biochem. 2018 Dec 7;130:73–81. doi: 10.1016/j.soilbio.2018.12.005

Fig. 2.

Fig. 2

Concentration and isotope calibration of the method based on purge-and-trap isotope ratio mass spectrometry (PT-IRMS) method. (a) Increment of N2O peak area (Vs) with concentration of nitrite (slope = 1.76, r2 = 0.997, n = 2), glycine (slope = 0.85, r2 = 0.995, n = 2) and amino acid mix (slope = 0.58, r2 = 0.998, p < 0.001, n = 2) and isotope calibration for (b) nitrite (20 μM, slope = 0.51, r2 = 0.994, n = 2). (c) 10 μM FAA-mix (slope = 0.56, r2 = 0.995, n = 2, dashed line) and 20 μM FAA-mix (0.53, r2 = 0.9974, n = 2, solid line). (d) Isotope calibration for 10 μM FAA-mix (slope = 0.59, r2 = 0.997, n = 2, dashed line) and spiked 1 μM FAA-mix (slope = 0.60, r2 = 0.995, n = 2, solid line).