Effect of Electrospray Ionization Source Parameters on Pharmaceuticals Analysis Using Quadrupole Time-of-Flight Mass Spectrometry

Introduction: The presence of pharmaceuticals in the environment has caused increasing concern. In the development of analytical method, selection of sensitive analytical instrument is also an important consideration. Among various analytical instruments, HPLC coupled with ESI based QTOF high resolution MS has recently emerged as a powerful analytical tool for the analysis of trace pharmaceuticals in environmental waters. This study evaluated the influence of ESI source parameters which include capillary voltage, nozzle voltage, nebulizer pressure, sheath gas temperature, sheath gas flow rate and drying gas temperature on the signal of pharmaceuticals. Methods: Cotinine, carbamazepine, atenolol, metoprolol, sotalol, ranitidine, norfloxacin, ciprofloxacin, acebutolol and ofloxacin were selected for this study. These compounds are common pharmaceutical pollutants in the environment. In general, most of the selected pharmaceuticals showed the highest response at 0 V of nozzle voltage, capillary voltage of 4500 V, sheath gas temperature and flow rate of 400 ºC and 12 L/min and drying gas of 150 ºC. For nebulizer pressure, no specific trend was observed. Conclusion: The peak area of cotinine, atenolol and sotalol was found to increase with increasing nebulizer pressure from 25 to 50 psig whereas, the signal of carbamazepine, metoprolol and acebutolol was found to decrease with increasing nebulizer pressure. The peak area of other pharmaceuticals was found to optimize at 30 or 35 psig. The result also indicated that applying nozzle voltage could largely reduce the peak area of pharmaceuticals while the peak area of selected pharmaceuticals can be significantly enhanced by increasing the sheath gas temperature. Keywords: Environmental analysis, HPLC, organic pollutants, ESI, MS, pharmaceuticals and personal care products.