Pahokee泥炭腐殖酸的电喷雾质谱特征研究

CHARACTERIZATION OF HUMIC ACID FROM PAHOKEE PEAT BY ELECTROSPRAY IONIZATION MASS SPECTROMETRY

采用电喷雾质谱(ESI-MS)技术,对水溶态Pahokee泥炭腐殖酸的ESI MS特征进行了研究。ESI MS质谱扫描图中,离子峰连续分布,m/z值主要集中在低于1 500 的范围内,在质谱图低质荷比端形成相差2 amu的奇数系列峰,可能为复杂分子峰[M-1]的系列中性丢失的结果;在m/z约250,350,500 和700 处有类似“波”的离子峰分布,可能暗示不同来源的木质素单体形成的二聚体、三聚体、四聚体结构等。对木质素17 种模型化合物的电喷雾二级质谱碎片机理进行了较为详细的研究,以此来推断腐殖酸m/z200以内离子峰的结构。m/z 70 110为Pa hokee泥炭腐殖酸的“核结构”,m/z 110 200主要为三种木质素来源的单体结构及其衍生物,总体上可看出Pahokee泥炭腐殖酸的母源为裸子植物和被子植物。该方法对腐殖酸样品具有重现性,可用于腐殖酸的结构研究。

The characterization of aqueous humic acid from Pahokee peat was conducted by electrospray ionization mass spectrometry. The ion peaks were distributed continuously with mass charge ratios, with most ion fragments below m/z 1500. The two atomic mass unit difference of the odd ion peaks in the low mass charge ratios resulted from neutral mass loss of complex molecules. The strength of ion peaks was characterized by 'wave pattern' maxima at m/z 250, 350, 500 and 700, representing the dimeric, trimeric and tetrameric structures of lignin degraded products. Based on the ESI-MS/MS mechanism of 17 model compounds of lignin monomers, the structures of ion fragments between m/z70 and 110 were deduced. m/z70-110 represents the 'core structure' of Pahokee humic acid, while m/z110-200 mainly the monomer of p-hydroxy phenols, vanillyl phenols, syringyl phenols and their derivations. Results showed that the ESI-MS method is of duplicity for humic acid samples and can be used to study the structure of humic acid.