Analysis of amino acids as DABS-derivatives with a sensitivity to the femtomole level using RP-HPLC narrow-bore columns.

In this paper we report the complete separation of amino acids as DABS-derivatives using a 3µm Supelcosil LC-18 (25 cm × 2.1 mm I.D.) narrowbore column. The system described makes it possible to perform the analysis of DABS-amino acids with a sensitivity to the femtomole level. We have also studied the conditions necessary for using the narrow-bore columns for routine analysis, paying particular attention to the problem of providing adequate protection for the analytical column. We have found it very suitable to use a (2 cm × 2.1 mm I.D.) guard column filled with a 40µm Pelliguard LC-18, pellicular packing resin, without affecting the complete resolution of the DABS-amino acids. Comparing the results obtained using conventional HPLC columns (3-5µm Supelcosil LC-18) of different lengths (15 and 25 cm × 4.6 mm I.D.) with those obtainable with the narrow-bore columns used in this work, it is possible to achieve a much greater sensitivity using the narrow-bore columns. In short, using the appropriate guard column and the "standard" HPLC apparatus used, the narrow-bore columns are very useful for routine analyses of DABS-amino acids with a sensitivity at the femtomole level.