Small organic matrixes are still the most commonly used ones in matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) because of their advantages of high sensitivity, convenience, and cost-effectiveness. However, due to the matrix interference in the low mass region, the direct analysis of low molecular weight amines in complex surroundings with conventional organic matrixes remains a challenge. Here, a new Brønsted–Lowry acid compound 2,3,4,5-tetrakis(3′,4′-dihydroxylphenyl)thiophene (DHPT) was designed, synthesized, and applied as a matrix for analysis of low molecular weight amines by MALDI-TOF MS. DHPT displays good selectivity in the analysis of amines without matrix-related interference and the low picomole/femtomole limit-of-detection was obtained in positive ion mode. With DHPT, the metabolites including creatinine, glycine, alloxan, allantoin, and 3-hydroxyhippuric acid in human urine were directly analyzed by MALDI-TOF MS. The identity of these metabolites was confirmed by tandem mass spectrometry. Furthermore, the urine creatinine was quantitatively determined using isotope-labeled internal standard. This DHPT-assisted LDI MS method provides a general approach for both qualitative and quantitative analysis of low molecular weight amines.
基质辅助激光解吸电离质谱(MALDI MS)具有灵敏度高、使用方便、成本低廉等优点,因此小型有机基质仍然是最常用的基质辅助激光解吸电离质谱。然而,由于低质量区的基质干扰,直接分析与传统有机基质共存的复杂环境中的低分子量胺仍然是一项挑战。本文设计、合成了一种新的布氏-洛氏酸化合物 2,3,4,5-四(3′,4′-二羟基苯基)
噻吩(
DHPT),并将其用作 MALDI-TOF MS 分析低分子量胺的基质。
DHPT 在分析
胺类化合物时具有良好的选择性,不会受到基质的干扰,而且在正离子模式下的检测限很低。利用
DHPT,MALDI-TOF MS 直接分析了人体尿液中的代谢物,包括
肌酐、甘
氨酸、阿
脲酸、
尿囊素和 3-hydroxyhippuric acid。通过串联质谱法确认了这些代谢物的身份。此外,还利用同位素标记的内标对尿
肌酐进行了定量测定。这种
DHPT 辅助 LDI MS 方法为低分子量胺的定性和定量分析提供了一种通用方法。