Table 1.

LC-MS/MS method development and validation

AA	Linear dynamic range (LLOQa–HLOQb)	R2	Retention time (min)	LOD (μM)	LOQ (μM)
Alanine	7.3 nM–750 μM	0.992	3.11	0.002	0.007
Arginine	16.0 nM–750 μM	0.989	4.67	0.006	0.016
Asparagine	0.76 μM–500 μM	0.998	2.52	0.250	0.760
Aspartic acid	0.45 μM–375 μM	0.998	3.09	0.150	0.450
Citrulline	7.0 nM–250 μM	0.989	3.55	0.002	0.007
Cysteine	0.23 μM–250 μM	0.981	3.66	0.076	0.230
Cystine	66.0 nM–312.5 μM	0.999	4.16	0.022	0.066
Glutamic acid	66.0 nM–750 μM	0.992	3.37	0.022	0.066
Glutamine	49.0 nM–500 μM	0.996	3.13	0.016	0.049
Glycine	0.14 μM–375 μM	0.989	2.72	0.049	0.140
Histidine	99.0 nM–750 μM	0.995	4.47	0.033	0.099
Hypotaurine	0.67 μM–5,000 μM	0.990	1.81	0.220	0.670
Isoleucine	27.0 nM–375 μM	0.988	4.74	0.009	0.027
Leucine	70.0 nM–750 μM	0.983	4.89	0.023	0.070
Lysine	75.0 nM–375 μM	0.996	4.39	0.025	0.075
Methionine	0.44 μM–750 μM	0.993	4.44	0.144	0.440
Ornithine	0.18 μM–500 μM	0.995	4.52	0.059	0.180
Phenylalanine	0.10 μM–750 μM	0.991	5.16	0.033	0.100
Proline	80.0 nM–375 μM	0.993	3.79	0.026	0.080
Putrescine	1.42 μM–250 μM	0.978	4.77	0.470	1.420
Sarcosine	0.10 μM–250 μM	0.990	3.44	0.033	0.100
Serine	0.20 μM–750 μM	0.983	2.60	0.070	0.200
Spermidine	4.26 μM–250 μM	0.983	5.21	1.410	4.260
Spermine	53.0 nM–250 μM	0.991	5.76	0.017	0.053
Taurine	67.0 nM–150 μM	0.980	1.51	0.022	0.067
Threonine	22.0 nM–750 μM	0.996	3.32	0.007	0.022
Tryptophan	0.39 μM–500 μM	1.000	5.51	0.130	0.390
Tyrosine	0.47 μM–750 μM	0.992	4.31	0.150	0.470
Valine	48.0 nM–750 μM	0.984	4.19	0.016	0.048

External calibration standards were analyzed for each compound to determine dynamic range, R², retention time, LOD, and LOQ of unlabeled compounds

^aLower limit of quantitation

^bHigher limit of quantitation