Gas Chromatography-Mass Spectrometry Analysis of Structural Isomers of Linear Hexaamines Found in Thermophilic Bacteria

Abstract

Because of the structural similarity between long linear polyamine isomers, it is often very difficult to differentially quantify each hexaamine found in thermophilic bacteria. To quantify thermohexamine and homothermohexamine, for which separation has not been previously achieved, we analyzed a mixture of the heptafluorobutyryl derivatives of the two authentic hexaamines using gas chromatography-mass spectrometry (GC-MS). We found a correlation between the ratio of the hexaamines and the ratio of the intensities of two unique fragment ions in the MS spectra detected at m/z 774 in thermohexamine and m/z 1027 in homothermohexamine. The ratio of m/z (774/1027) vs. thermohexamine/homothermohexamine and m/z (1027/774) vs. homothermohexamine/thermohexamine calibration lines showed high linearity (r = 0.9997 and 0.9990, respectively) for hexaamine mixing ratios in the range of 0-2.33. These data indicate that the ratio of the hexaamines in a mixed solution can be determined by using the appropriate calibration line, depending on which hexaamine is present in greater quantity.