Xu Jiawei, Kondo Junko N, Fujino Tatsuya
Department of Applied Chemistry, Graduate School of Science and Engineering, Toyo University, 2100 Kujirai, Kawagoe, 350-8585, Japan.
Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe, 350-8585, Japan.
Anal Sci. 2020 Feb 10;36(2):177-181. doi: 10.2116/analsci.19P213. Epub 2019 Aug 30.
Nanometer-sized clay, allophane, was used as the matrix for matrix-assisted laser desorption ionization mass spectrometry (MALDI MS) and applied to the ionization of small molecules. First, the laser desorption ionization mass spectrum of cation-exchanged allophane was measured, and it was found that the cation exchange proceeded smoothly with increasing atomic number of alkali metals in the periodic table. This phenomenon was explained by considering the size of the counter anion on the allophane surface. Then, fructose was measured as the analyte using each alkali-cation-exchanged allophane as the matrix. Contrary to the measurements using allophane itself, the peak intensity of fructose decreased with increasing atomic number of alkali metals in the periodic table. This phenomenon was clarified by considering the stability of alkali cation in the presence of a surface anion, the desorption energy, and the solvation enthalpy of each alkali cation. The applicability of allophane to high molecular weight compounds was also confirmed by measuring cyclodextrin, angiotensin II, and insulin. Finally, a combination of allophane and zeolite was examined by assuming proton relay among allophane, zeolite, and analyte. As a result of proton supply from zeolite to allophane, the peak intensity of the proton sponge (1,8-bis(dimethylamino)naphthalene) was enhanced by almost 2.2 times.
纳米级黏土——水铝英石，被用作基质辅助激光解吸电离质谱法（MALDI MS）的基质，并应用于小分子的电离。首先，测量了阳离子交换水铝英石的激光解吸电离质谱，发现随着周期表中碱金属原子序数的增加，阳离子交换顺利进行。通过考虑水铝英石表面抗衡阴离子的大小来解释这一现象。然后，以每种碱金属阳离子交换的水铝英石为基质，测量了作为分析物的果糖。与使用水铝英石本身进行的测量相反，果糖的峰强度随着周期表中碱金属原子序数的增加而降低。通过考虑表面阴离子存在下碱金属阳离子的稳定性、解吸能量以及每种碱金属阳离子的溶剂化焓来阐明这一现象。通过测量环糊精、血管紧张素II和胰岛素，也证实了水铝英石对高分子量化合物的适用性。最后，通过假设水铝英石、沸石和分析物之间的质子传递，研究了水铝英石和沸石的组合。由于沸石向水铝英石供应质子，质子海绵（1,8 - 双（二甲基氨基）萘）的峰强度提高了近2.2倍。
