How to do Amino Acid Analysis the Quick and Easy Way

Martin Perkins

20th April 2018

Alkyl-Chloroformate, Amino Acid, Asparagine, Cereal, Chromatography, GC-FID, GC-MS, HPLC, Ion, LC-MS/MS, Nathan Hawkins, Potato, Prepstation,

Changes in food safety legislation mean that there is a need to reduce the asparagine content of potatoes and cereals to mitigate acrylamide formation in baked cereal and potato food products.

As a result, it is important to be able to routinely analyse large numbers of samples for their asparagine content.

Asparagine is, of course, an amino acid and therein lies the problem…

Widening the Options for Amino Acid Analysis

Amino acid analysis is typically performed by ion exchange chromatography and high performance liquid chromatography (HPLC) techniques, typically with post-column or pre-column derivatisation respectively.

More recently, ion chromatography with electrochemical detection has been used for the analysis of protein hydrolysates and HPLC-MS/MS has been used for the analysis of underivatised free (physiological) amino acids.

Whilst there are lots of options for amino acid analysis, most systems have been developed as dedicated analysers for the routine analysis of either free amino acids in clinical pathology or for the analysis of protein hydrolysates and are therefore optimised for the analysis of 23 standard protein amino acids in a specific matrix over a limited concentration range and to standard detection limits.

For amino acid analysis outside these two specific areas, the use of a dedicated analyser can result in limitations including:

  • Need to purchase a dedicated analyser
  • Limited dynamic range and/or detection limits
  • Matrix can adversely affect derivatisation or chromatography necessitating extensive (manual) sample clean-up
  • Matrix can cause ion suppression in LC-MS/MS
  • Throughput limited by long runtimes (post-column derivatisation)
  • Use of hazardous reagents (e.g. Ninhydrin)
  • Most analysers not designed for extended suites (e.g. non-protein amino acids or biogenic amines) or identification of non-standard amino acids

Because none of these options are ideal for this particular application, we have recently developed a new automated solution for amino acid analysis, building on some proof-of-concept work done by Dr Katja Dettmer using the alkyl-chloroformate derivatives.

Our solution offers the following benefits…

  1. Fast and easy sample prep (increased throughput and improved turnaround times)
  2. One method for all sample matrices and applications
  3. No need to invest in a dedicated analyser – GC-FID, GC-MS, LC-MS/MS

These derivatives benefit from being fast to form and robust and the derivatisation can be applied to a range of aqueous samples (plant or food extracts, beverages, plasma, urine, cell culture/broths and protein hydrolysates) without the need for either sample clean-up or urea/protein removal.

They’re also analytically useful as, depending on the application, target metabolites and required detection limits, they can be analysed by GC-FID, GC-MS or LC-MS2. The EI spectra of these derivatives are particularly valuable in 15N metabolic flux studies.

The solution is available as an offline Prepstation, complete dedicated GC-FID or GC-MS solution with online sample preparation, or can be integrated into a flexible modular multi-metabolite analysis platform.

You can learn more about this solution here.