Water

Free amino acids (FAAs) are key components of the global nitrogen cycle and important disinfection byproduct (DBP) precursors. The knowledge gap of FAA occurrence in source and engineered water is discussed in this paper. Solid phase extraction and post column derivatization was combined with gas chromatography&ndash
mass spectrometry to simultaneously detect &mu
g/L concentrations of FAAs. This method efficiently detects alanine (Ala), threonine (Thr), serine (Ser), valine (Val), leucine (Leu), isoleucine (Ile), proline (Pro), aspartic (Asp), phenylalanine (Phe), and glutamic acid (Glu) with good linearity, accuracy, and precision. An investigation of FAAs in surface waters in Zhejiang Province found concentrations of 1.48&ndash
14.73 &mu
g/L Ala, 0.20&ndash
2.39 &mu
g/L Thr, 0.41&ndash
7.84 &mu
g/L Val, 0.21&ndash
6.86 &mu
g/L Ser, 0.11&ndash
4.16 &mu
g/L Leu, 0.57&ndash
1.54 &mu
g/L Ile, 0.24&ndash
8.06 &mu
g/L Pro, 0.42&ndash
4.73 &mu
g/L Asp, 0.30&ndash
3.01 &mu
g/L Phe, and 0.12&ndash
3.83 &mu
g/L Glu. Phe and tyrosine (Tyr) exhibited higher trichloromethane (TCM) formation (1029&ndash
1148 &mu
g/mmolAA) than dichloroacetonitrile (DCAN) formation (333&ndash
347 &mu
g/mmolAA). Asp and Glu demonstrated the opposite trend: higher DCAN (570&ndash
1106 &mu
g/mmolAA) formation than TCM (137&ndash
506 &mu
g/mmolAA).