Determination of Low Activity of Tritium-Labeled Amino Acids Using Simultaneously Flow Scintillation and Amino Acid Analyzers

Abstract

The possibility of measuring a low activity of tritium-labeled amino acids in the eluate from Amino Acid Analyzer 835 (Hitachi, Japan) using a Radiomatic 150TR Flow Scintillation Analyzer (Packard Instrument Co., USA) was studied. Due to stepped variations of pH, ionic strength, and salt concentration in eluting solutions during amino acid separation and utilization of ninhydrin reagent in spectrophotometric measurements of amino acids, special selection of scintillation liquids was necessary. Six scintillation cocktails were tested: ZhS-8 (Reakhim, Ukraine), OptiPhase “HiSafe” 3 (Wallac Oy, EGGgr; Co., Finland), Hionic-Fluor, Ultima-Flo AP, Ultima-Flo M, and Ultima Gold (Packard Instrument Co., USA). It was found that Hionic-Fluor and Ultima-Flo AP cocktails are the most appropriate for flow measurements of tritium activity. Under optimal conditions the detection limit with Hionic-Fluor and Ultima-Flo AP was 150 and 100 decays min- 1 in the peak of amino acid, respectively. Such a high sensitivity allows utilization of the above analytical system for measurements of amino acid radioactivity to study the structure of proteins and protein complexes by tritium planigraphy.