The EZ:Faast Family of Amino Acid Analysis Kits: Application of the GC-FID Kit for Rapid Determination of Plasma Tryptophan and Other Amino Acids

  • Abdulla A.-B. Badawy
Part of the Methods in Molecular Biology book series (MIMB, volume 2030)


Plasma tryptophan (Trp) and other amino acids (AA) can be determined rapidly by gas (GC) or liquid (LC) chromatography using the Phenomenex EZ:Faast™ family of kits. Three kits are available: (1) GC-FID or -NPD, (2) GC-MS, and (3) LC-MS. The two GC kits can determine 32 AA, whereas the LC-MS can determine 5 additional AA. All three kits, however, share the same experimental procedure up to and including the preparation of derivatized AA. The method is based on solid-phase extraction (SPE), thus saving time on prior removal of plasma or other proteins and interfering substances and can be applied to other body fluids and experimental media and to supernatants of extracts of solid material. Briefly, SPE is performed using a proprietary cation-exchange mechanism. The acid solution of the internal standard ensures that the free amino acids are in an anionic form suitable for cationic binding. The alkaline nature of the elution medium ensures that the AA cations are released prior to derivatization. The latter involves production of chloroformate derivatives of both the amino and carboxylic acid groups. With experience, six plasma samples can be so processed within 12 min. The shortest analytical run is <7 min per sample using the GC-FID/NPD kit. Despite its many steps, the procedure becomes second nature and an enjoyable task. I have now used the GC-FID kit with manual injection to process >1600 plasma and other samples. Limit of detection of AA is 1 μM or less. The procedure has been validated and optimized for Trp and its main five brain uptake competitors.

Key words

Amino acids EZ:Faast™ Kits Gas chromatography Liquid chromatography Plasma Solid-phase extraction Tryptophan Amino acid analysis 



This work was funded by the Wellcome Trust (069301). I thank Chris Morgan and Jennifer Turner for technical assistance and Ben Atkins and Lindsey Starr (Phenomenex UK) for helpful discussions and useful technical information. The author held an honorary professorial appointment at Cardiff Metropolitan University (previously University of Wales Institute, Cardiff) during the period September 2006 to September 2016.


  1. 1.
    Walker V, Mills GA (1995) Quantitative methods for amino acid analysis in biological fluids. Ann Clin Biochem 32:28–57CrossRefGoogle Scholar
  2. 2.
    Deng C, Li N, Zhang X (2004) Rapid determination of amino acids in neonatal blood samples based on derivatisation with isobutyl chloroformate followed by solid phase microextraction and gas chromatography/mass spectrometry. Rapid Commun Mass Spectrom 18:2558–2564CrossRefGoogle Scholar
  3. 3.
    Phenomenex EZ:faast [easy fast] amino acid sample testing kit (2003) User guide, Phenomenex, 411 Madrid Avenue, Torrance, CA 90501–1430, USA (
  4. 4.
    Badawy AA-B, Morgan CJ, Turner JA (2008) Application of the Phenomenex EZ:faast™ amino acid analysis kit for rapid gas-chromatographic determination of concentrations of plasma tryptophan and its brain uptake inhibitors. Amino Acids 34:587–596CrossRefGoogle Scholar
  5. 5.
    AA-B B et al (2007) The acute tryptophan depletion and loading tests: specificity issues. Int Congr Series 1304:159–166CrossRefGoogle Scholar
  6. 6.
    Dougherty DM et al (2008) Comparison of 50- and 100-g L-tryptophan depletion and loading formulations for altering 5-HT synthesis: pharmacokinetics, side-effects, and mood states. Psychopharmacology (Berl) 198:431–445CrossRefGoogle Scholar
  7. 7.
    Badawy AA-B et al (2009) Activation of liver tryptophan pyrrolase mediates the decrease in tryptophan availability to the brain after acute alcohol consumption by normal subjects. Alcohol Alcohol 44:267–271CrossRefGoogle Scholar
  8. 8.
    Badawy AA-B, Dougherty DM, Richard DM (2010) Specificity of the acute tryptophan and tyrosine plus phenylalanine depletion and loading tests Part II. Normalisation of the tryptophan and the tyrosine plus phenylalanine to competing amino acid ratios in a new control formulation. Int J Tryptophan Res 3:35–47PubMedPubMedCentralGoogle Scholar
  9. 9.
    Kagan IA et al (2008) A validated method for gas chromatographic analysis of gamma-aminobutyric acid in tall fescue herbage. J Agric Food Chem 56:5538–5543CrossRefGoogle Scholar
  10. 10.
    Mohabbat T, Drew B (2008) Simultaneous determination of 33 amino acids and dipeptides in spent cell culture media by gas chromatography-flame ionisation detection following liquid and solid phase extraction. J Chromatogr B Analyt Technol Biomed Life Sci 862:86–92CrossRefGoogle Scholar
  11. 11.
    Cowley DS et al (1996) Effect of diazepam on plasma γ-aminobutyric acid in sons of alcoholic fathers. Alcohol Clin Exp Res 20:343–347CrossRefGoogle Scholar

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© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  • Abdulla A.-B. Badawy
    • 1
  1. 1.School of Health SciencesCardiff Metropolitan UniversityCardiffUK

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