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Dionex AAA-Direct

The Thermo Scientific* Dionex* AAA-Direct* system is a highly sensitive, direct-detection type of amino acid analyzer that requires no sample derivatization. The Dionex AAA-Direct instrument uses integrated pulsed amperometry detection (IPAD)—a type of electrochemical detection—to directly detect amino acids. The Dionex AAA-Direct analyzer also provides complete separation of all common amino acids using anion-exchange chromatography (Thermo ScientificDionex AminoPac* PA10 column). Because the AAA-Direct instrument provides detection, the hydrolyzed protein sample can simply be reconstituted in water and directly injected for analysis. The Dionex AAA-Direct system has many advantages over derivatization methods for amino acid analysis. For example, the derivatized amino acid products may not be stable, depending on the derivatization method, and the reagents can cause interferences during chromatography. Lengthy sample preparation and derivatization steps are often needed. Derivatization is not always suitable for methylated, halogenated, phosphorylated, or sulfonated amino acids. Disubstitutions can occur for tyrosine and histidine when using the Fmoc chloride method. Some derivatization methods (e.g., OPA) do not allow direct analysis of secondary amino acids. For some derivatization methods, all hydrolysis reagents must be evaporated completely prior to addition of derivatization reagents. Many derivatization reagents are not stable, decompose, and have short shelf lives, adding uncertainty to the derivatization efficiency. Also, changes in response for the amino acids may occur after derivatization; amino acid response can change with sample storage. With the Dionex AAA-Direct analyzer, the absence of derivatization reagents eliminates safety hazards associated with exposure to toxic chemicals.

The Dionex AAA-Direct system provides the following advantages over traditional LC methods that require derivatization:

  • Direct detection; the hydrolyzed protein sample can simply be reconstituted in water and directly injected for analysis
  • More reliable; derivatized amino acid products may not be stable, depending on the derivatization method, and the reagents can cause interferences during chromatography
  • Derivatization is not always suitable for methylated, halogenated, phosphorylated, or sulfonated amino acids
  • Saves time
  • Allows direct analysis of secondary amino acids
  • Uses no toxic reagents