Analysis of the Alcohol Amine Mixtures by 1D Selective COSY

Abstract

Proton nuclear magnetic resonance (¹H-NMR) is one of the most commonly used techniques for structure identification in the field of chemical warfare convention (CWC) because of its strong ability in aiding structure assignment of chemicals. However, due to the lack of separation function coupled with chromatograph, the greatest disadvantage of ¹H-NMR in the analysis of environmental and biological samples is that the resonances can be easily covered or interfered. One-dimensional NMR selective excitation technology can effectively remove background interference and reveal the hidden spectral peak information. In this paper, three schedule chemicals of Chemical Weapons Convention (CWC), triethanolamine, N-methyldiethanolamine and 2-diisopropylaminoethanol, were selected as model chemicals. Homonuclear 1D COSY NMR selective excitation analysis method was established with these chemicals to solve the problem of resonances covered in ¹H-NMR. Key experiment parameters of 1D COSY were optimized. The optimized experimental conditions of 1D COSY are as follows: pulse sequence is selcogp, shaped pulse is G3, relaxation delay of d1 is 4 s, the excitation width of <i>d<SUB>H</SUB></i> 0.91 (a), 2.51 (g), 2.62 (e) and 3.44 (d) is 39.16, 35.34, 20.00 and 26.03 Hz respectively. The established 1D COSY method was used to analyze 1~10 μg/mL alcohol amine mixtures with 2 mg/mL quinuclidinol as the background interference and the LOD was 5 μg/mL. This method is simple, fast and can wipe off the interference effectively in the ¹H NMR spectrum without proceeding complex sample pretreatment. 1D selective COSY reflects the more accurate position of hydrogen atom, and can be used as a reliable auxiliary technology for structural identification.