PARENT SESSION
PS12 - Applications of LC-MS in Environmental Analysis
Sunday, 17 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P127) Analysis of 11 Pharmaceuticals by Solid-Phase Extraction and LC/MS.
Chen, Chia-Yang1, O'Keefe, Patrick*,1,2, Aldous, Kenneth1,2, 1 Wadsworth Center, New York State Department of Health, Albany, NY, USA2 School of Public Health, State University of New York at Albany, Albany, NY, USA
ABSTRACT- A method for the analysis of 11 pharmaceuticals in water was developed using solid-phase extraction and LC/MS techniques. Estrone, 17
-ethynylestradiol, 17
-estradiol, ibuprofen and valproic acid were extracted from water (adjusted to pH 2.5) by 3M SDB-XC Empore disks. The elution solvent was pH 8.5 methanol (adjusted with N-methylmorpholine) and the eluate was concentrated to 100 
L (in 12% methanol/88% water). The recoveries were 47-68% with RSD 2.5-8.5%. Twenty L of the final extract were injected onto LC/MS-APCI in negative ion mode and the mobile phase was 10 mM N-methylmorpholine aqueous solution (pH 9.4)/acetonitrile. Amoxicillin, atenolol, caffeine, cephalexin, sulfamethoxazole, and trimethoprim were also extracted using SDB-XC disks. Over 95% of the analytes were retained except for amoxicillin (45-55%). The recoveries were stable when the water pH was between 5 and 7.5. Disks were eluted with 90% dimethyl sulfoxide/10% pH 3.5 water. The eluate was diluted with two volumes of water and loaded on a dual-cartridge system composed of weak (carboxypropyl, CBA) and strong (propylsulfonic, SCX-2) cation exchangers. The CBA cartridge retained 40% of caffeine but 88-100% of the other five analytes. Increased dilution with water did not improve the retention of caffeine. The SCX-2 adsorbent caught the breakthrough caffeine from the CBA. Each cartridge was eluted separately. The eluates were combined and analyzed by LC/MS-ESI in the positive ion mode using pH 3.5 buffer (8.7 mM ammonium formate and 10 mM formic acid)/acetonitrile mobile phases. The sensitivities were estimated to be 0.3-14 ng/L for the six analytes.
Key words: pharmaceuticals, water, solid-phase, LC/MS