DIRECT INTRODUCTION OF LARGE-VOLUME URINE SAMPLES INTO AN ONLINE IMMUNOAFFINITY SAMPLE PRETREATMENT CAPILLARY GAS-CHROMATOGRAPHY SYSTEM

An immunoaffinity precolumn containing immobilized antibodies raised against the synthetic steroid hormone beta-19-nortestosterone, has been used for the automated sample pretreatment of urine samples containing beta-19-nortestosterone or the related steroids norethindrone and norgestrel. The sample pretreatment system was coupled on-line to a capillary GC. The on-line connection between the immunoaffinity precolumn and the capillary GC was realized with an interface that consisted of a 10 mm X 2 mm i.d. reversed-phase precolumn and a diphenyltetramethyldisilazane-deactivated GC retention gap. After preconcentration on the immunoaffinity precolumn the analytes were eluted and reconcentrated on the reversed-phase precolumn. Subsequently, this precolumn was desorbed with 75-mu-L of ethyl acetate, which was directly introduced into the retention gap by using partially concurrent solvent evaporation. The system allows the automated pretreatment and GC analysis of 5-25-mL urine samples for the ppt-level determination of 19-norsteroids. The general applicability and potential of on-line immunoaffinity-capillary GC systems are discussed.