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.