GC-MS identification of sympathomimetic amine drugs in urine: rapid methodology applicable for emergency clinical toxicology.

Abstract

A method was developed that permitted rapid identification in urine of the following sympathomimetic amines: amphetamine, benzphetamine, cathinone, desmethylsegiline, diethylpropion, ephedrine, fenfluramine, mazindol, methylenedioxyamphetamine, methylenedioxyethylamphetamine, methylenedioxymethamphetamine, mescaline, methamphetamine, methcathinone, methylaminorex, methylphenidate, pemoline, phendimetrazine, phenylepherine, phentermine, phenylpropanolamine, pseudoephedrine, and selegiline. In addition, two alpha-phenylethylamine-like monoamine oxidase inhibitors, phenelizine and tranylcypromine, were studied. Those sympathomimetic amines containing a primary or secondary amine, a hydrazine, and/or hydroxyl (except mazindol) functional groups were derivatized effectively using an on-column derivatization technique that used a reagent consisting of 10% fluoroanhydride in hexane, whereas the other sympathomimetic amines, including mazindol, were analyzed underivatized. Three different fluoroanhydrides, trifluoroacetic (TFAA), pentafluoropropionic (PFPA), and heptafluorobutyric (HFBA), and three different injection-port temperatures (160, 200, and 260 degrees C) were investigated. Both TFAA and PFPA gave sympathomimetic amine derivatives with essentially identical retention times, whereas HFBA gave longer retention times and better separation of individual compounds. The base fragmentation ion was noted to increase 50 amu (CF2) for each derivatized sympathomimetic amine as the length of the carbon-fluorine chain increased. Fragmentation ion abundance was maximized at an injection-port temperature of 260 degrees C, and this enhanced sensitivity coupled with the better chromatographic resolution of the individual sympathomimetic amines prompted the selection of HFBA as the derivatizing agent of choice. Assignments were made for the fragmentation ions produced by each derivatized drug. The developed method was adapted to analyze urine specimens that might be encountered in emergency toxicology testing. For identification of sympathomimetic amines requiring derivatization, 0.1 mL of the patient specimen had amphetamine-d5 and methamphetamine-d5 added as internal standard followed by adjustment of pH to 9.3 with borate buffer, extraction with 9:1 chloroform/isopropanol, centrifugation and separation of the organic phase, addition of 10% methanolic HCI and evaporation under nitrogen, reconstitution with HFBA reagent, and on-column derivatization during gas chromatographic-mass spectrometric (GC-MS) analysis. For those sympathomimetic amines not requiring derivatization, 1.0 mL of urine specimen had diazepam-d5 added as internal standard followed by the same extraction procedure and reconstitution accomplished with ethyl acetate. Because precolumn derivatization was eliminated and only 8 min was required for GC-MS analysis, complete analysis time was approximately 30 min, making the method suitable for clinical emergency toxicology purposes.