Table 1.

Molecular ions [M + H]⁺, retention time, correlation coefficients, limits of detection, limits of quantification, recovery, and precision values of amino acid derivatives.

Amino Acid	MS [M + H]+	Retention Time (min)	Correlation Coefficient	LODs (nmol/L)	LOQs (nmol/L)	Recovery (%)	RSD (%)
Cys	461.5	9.094	0.9981	0.60	1.45	96.4	1.56
His	441.1	9.352	0.9978	0.89	2.52	96.9	1.73
Orn	418.1	9.571	0.9992	0.22	0.58	94.5	1.65
Arg	460.1	9.798	0.9989	0.19	0.63	103.4	2.12
Lys	432.1	9.989	0.9991	1.13	3.10	98.7	2.32
Ser	391	10.355	0.9995	0.45	1.13	95.8	1.76
Asp	417.9	10.713	0.9983	0.18	0.49	97.6	2.21
Glu	433	11.394	0.9985	0.29	0.67	99.1	2.09
Thr	405	11.633	0.9987	0.15	0.53	95.4	1.87
Gly	361	12.036	0.9993	0.14	0.38	93.8	2.14
Trp	490	13.102	0.9978	0.38	1.09	98.0	2.05
Ala	375	13.403	0.9996	1.06	2.97	94.7	2.64
Tyr	466.9	13.641	0.9991	0.31	0.89	98.1	1.89
Pro	401	15.812	0.9972	0.27	0.92	101.3	1.57
Met	435.1	16.311	0.9988	0.14	0.49	95.6	1.37
Val	403	16.817	0.9979	0.23	0.58	96.9	2.27
Phe	451.1	17.205	0.9991	0.78	2.21	98.5	2.51
Ile	417.1	17.497	0.9984	0.16	0.42	95.2	1.44
Leu	417.1	17.738	0.9993	0.13	0.40	99.9	2.23