title: Improving detection sensitivity of amino acids in thyroid tissues by using phthalic acid as a mobile phase additive in hydrophilic interaction chromatography-electrospray ionization-tandem mass spectrometry.
abstract: In this work, 0.08 mmol L(-1) of phthalic acid was introduced as a mobile phase additive to quantify free amino acids (AAs) by hydrophilic interaction liquid chromatography (HILIC) coupled with electrospray ionization tandem mass spectrometry (ESI-MS/MS). The addition of phthalic acid significantly increased the signal intensity of protonated AA ions, resulting from the decrease of the relative abundance of AA sodium adducts. Meanwhile, the chromatographic peak shapes of AAs were optimized. As a consequence, there was a noticeable increase in the sensitivity of detection for AAs. The limits of detection (LOD) and quantification (LOQ) of the AAs ranged from 0.0500 to 20.0 ng mL(-1) and from 0.100 to 50.0 ng mL(-1), respectively, which were 4-50 times lower compared to the values measured without the addition of phthalic acid. The enhanced detection and separation of AAs were obtained by merely adding phthalic acid to the mobile phase without changing other conditions. Eventually, this simple method was validated and successfully applied to the analysis of twenty-four kinds of free AAs in human thyroid carcinoma and para-carcinoma tissues, demonstrating a significant increase of most AAs in thyroid carcinoma tissues (p<0.05).
authors.affiliation: National Center for Organic Mass Spectrometry in Shanghai, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Wanshu
authors.initials: W
authors.lastname: Qi
authors.affiliation: Department of Head and Neck Surgery, Fudan University Shanghai Cancer Center (FUSCC), Shanghai 200032, China; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Guan
authors.affiliation: Department of Head and Neck Surgery, Fudan University Shanghai Cancer Center (FUSCC), Shanghai 200032, China; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China. Electronic address: tuanqisun@163.com.
authors.forename: Tuanqi
authors.initials: T
authors.lastname: Sun
authors.affiliation: National Center for Organic Mass Spectrometry in Shanghai, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Yanjing
authors.initials: Y
authors.lastname: Cao
authors.affiliation: National Center for Organic Mass Spectrometry in Shanghai, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China. Electronic address: zhangli7488@sioc.ac.cn.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: National Center for Organic Mass Spectrometry in Shanghai, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China. Electronic address: ylguo@sioc.ac.cn.
authors.forename: Yinlong
authors.initials: Y
authors.lastname: Guo
mesh_terms: D000596:Amino Acids / Q000032:analysis*; D002138:Calibration; D002853:Chromatography, Liquid / Q000379:methods*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D057230:Limit of Detection; D010795:Phthalic Acids / Q000737:chemistry*; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013961:Thyroid Gland / Q000737:chemistry* / Q000473:pathology; D013964:Thyroid Neoplasms / Q000473:pathology
chemical_list: D000596:Amino Acids; D010795:Phthalic Acids; C032279:phthalic acid
keywords: Amino acids; Hydrophilic interaction chromatography; Mobile phase additive; Multiple reaction monitoring; Phthalic acid; Thyroid carcinoma