Use of UPLC-ESI-MS/MS to quantitate free amino acid concentrations in micro-samples of mammalian milk

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Table 3 Calibration data, dynamic range and human milk reproducibility of FAA (n = 6)

Free amino acid	Linear regression data	Dynamic range	CV (%)^b
	r²	pmol/μL^a
L-Histidine	0.9998	0.10 – 133.3	2.8
Taurine	0.9993	0.05 – 100	1.8
L-Serine	0.9994	0.05 – 26.7	2.3
L-Glutamine	0.9982	0.05 – 100	8.3
L-Arginine	0.9956	0.1 – 6.7	10.0
Glycine	0.9991	0.05 – 26.7	2.3
L-Aspartic acid	0.9980	0.05 – 26.7	2.9
L-Glutamic acid	0.9986	0.05 – 200	1.6
L-Citrulline	0.9974	0.05 – 5	8.6
L-Threonine	0.9990	0.05 – 26.7	2.8
L-Alanine	0.9953	0.05 – 53.3	2.2
L-Proline	0.9984	0.2 – 53.3	7.1
L-Cystine	0.9948	0.05 – 53.3	15.5
L-Tyrosine	0.9958	0.05 – 26.7	2.7
L-Lysine	0.9954	0.1 – 6.7	8.5
L-Methionine	0.9973	0.05 – 26.7	2.7
L-Valine	0.9973	0.05 – 26.7	2.5
L-Isoleucine	0.9947	0.05 – 13.3	4.4
L-Leucine	0.9968	0.05 – 13.3	2.9
L-Phenylalanine	0.9982	0.05 – 26.7	7.0
L-Tryptophan	0.9986	0.05 – 5	7.5

^aassay concentration of AQC amino acid derivatives, 1 μL injected.
^bcoefficient variation of reproducibility, calculated on 6 independent milk samples tested on 2 days with 2 operators.