Series 3 - Analytical Method

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3# What is the analytical method for amines?

In the previous section, it was clear why we must detect and quantify amines in drugs. This is possible by applying chromatography techniques, which may be preferable to spectrometry regarding specificity and selectivity. Several chromatography instruments are available for amines, including High-Performance Liquid Chromatography/Ultra-Performance Liquid Chromatography (HPLC/UPLC), Gas Chromatography (GC), and Ion Chromatography (IC), with a variety of detectors, such as Mass Spectrometry (MS), Flame Ionisation Detector (FID), and Conductivity Detector (CD).

But how can we determine which instrument to use?


First, we must investigate amines' chemical characteristics more thoroughly.

1) Amines are polar compounds due to the presence of electron lone pairs in the nitrogen; this may indicate:
  • IC may be appropriate, as it is promising to provide excellent separation.
  • Reversed-phase HPLC/UPLC and GC are also still applicable, but with caution to find the most optimum LC/GC column to enhance the amines retention, and further derivatisation may also be required.
2) Most amines are volatile compounds with a low boiling point
  • In this case, GC and IC may be more appropriate for volatile compounds than HPLC/UPLC.
3) Amines have relatively small molecular weights
  • MS detector is considerable due to its exceptional sensitivity for identifying compounds by their specific mass.

 

Figure 1. Ion Chromatography Instrumentation
(Source: https://serc.carleton.edu/microbelife/research_methods/biogeochemical/ic.html)


Then, what ...?


References:
  1. B. Tuesuwan and V. Vongsutilers, J Pharm Sci, 2021, 110, 3118–3128.
  2. G. C. Graffius, B. M. Jocher, D. Zewge, H. M. Halsey, G. Lee, F. Bernardoni, X. Bu, R. Hartman, E. L. Regardo, J Chrom A, 2017, 1518, 70-77.
  3. Z. Lewis, B. A. Jackson, A. Crampton, A. D. Ray, S. W. Holman, Rapid Commun Mass Spectrom, 2020, 34, DOI: 10.1002/rcm.8680.

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