Quantification of multiple compounds containing heterogeneous elements in the mixture by one-dimensional nuclear magnetic resonance spectroscopy of different nuclei using a single universal concentration reference.

ABSTRACT

One-dimensional (1D) quantitative NMR (qNMR) is a useful tool for concentration determination due to its experimental simplicity and the direct proportionality of the integrated signal area to the number of nuclei spin. For complex mixtures, however, signal overlapping often in one-dimensional quantitative (1) H NMR (1D (1) H qNMR) spectrum limits the accurate quantification of individual compound. Here, we introduced employing joint 1D qNMR methods of different nuclei, such as (1) H and (31) P (or/and (19) F), to quantify multiple compounds in a complex mixture using a single universal concentration reference. When the concentration ratio of several compounds containing different elements in a complex mixture is of interest, the result calculated from measured intensities from 1D qNMR of different nuclei is independent of the gravimetric error from the reference. In this case, the common reference also serves as a 'quantitative bridge' among these 1D qNMR of different nuclei. Quantitative analysis of choline, phosphocholine, and glycerophosphocholine mixture is given as an example using trimethylphosphine oxide ((CH(3))(3) P(O)) as concentration reference. Compounds containing multiple elements, such as tetramethylammonium hexafluorophosphate (N(+) (CH(3))(4 PF6 (-) are proposed as the common concentration reference for (1) H, (13) C, (15) N, (31) P, and (19) F qNMR for the quantitative analysis of complex mixture containing these different elements. We anticipate that the proposed joint 1D qNMR approach using a universal concentration reference will be a valuable alternative for simultaneous quantification of multiple compounds in a complex mixture due to its accuracy and single and simple sample preparation.