Integration of solid phase extraction with HILIC-MS/MS for analysis of free amino acids in source water

Amino acids (AAs) are prevalent in source water, particularly during spring run-off. Monitoring of amino acids in source water is desirable for water treatment plants (WTP) to indicate changes in source water quality. The objective of this study was to establish analytical procedures for reliable monitoring of amino acids in source water. Therefore, we examined two different methods, large volume inject (LVI) and solid phase extraction (SPE), for sample preparation prior to HILIC-MS/MS. The LVI-HILIC-MS/MS method can provide fast and sensitive detection for clean samples, but suffers from matrix effects, resulting in irreproducible separation and shortening column lifetime. We have demonstrated that SPE was necessary prior to HILIC-MS/MS to achieve reproducible and reliable quantification of AAs in source water. A natural heterocyclic amine 1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (MTCCA) was also included in the method to indicate changes in other natural nitrogenous compounds in source water. The SPE-HILIC-MS/MS method was able to achieve limits of detection from 2.6-3400 ng/L for the amino acids and MTCCA with RSDs (n=3) of 1.1%-4.8%. As well, retention times (RT) of the analytes were reproducible with variation less than 0.01 min (n=3) through the entire project. We further applied the SPE-HILIC-MS/MS method to determine AAs in authentic source water samples collected from two drinking water treatment plants (WTPs) during the 2021 spring run-off season. The results support that the SPE-HILIC-MS/MS method does not require derivatization and can provide reliable, accurate, and robust analysis of AAs and MTCCA in source water, supporting future monitoring of source water quality.     

HILIC/LC-MS直接分离测定大气颗粒物中的15种有机胺

本文建立了一种基于亲水作用液相色谱柱（HILIC）和液相色谱-质谱联用（LC-MS）的大气颗粒物有机胺的直接测定方法。颗粒物样品经甲醇提取、富集、浓缩后,对不同色谱柱与分析条件进行测试、对比,发现HILIC色谱柱可有效分离有机胺类化合物,高浓度以及低pH值的缓冲溶液可缩短大部分有机胺的保留时间,而流动相中有机相比例增加会延长保留时间。优化的HILIC/LC-MS分析方法可同时测定11种脂肪胺、2种脂环胺、1种芳香胺及1种醇胺,结合内标的有机胺标准曲线的线性相关系数R ²为0.991—0.999。本方法的检出限（S/N=3）为0.59—75.46 ng·mL⁻¹,加标回收率为59%—92%,具有较高的精密度。该方法初步应用于青岛冬季大气细颗粒物样品中有机胺的测定,为大气有机胺的深入研究提供了方法参考与技术支撑。