Development of Analytical Method for Detection of Some Pharmaceuticals in Surface Water

Purpose: To develop and validate a simple method using solid - phase extraction along with liquid chromatography-time of flight mass spectrometry for the analysis of pharmaceuticals in surface water of Tangkas River, Malaysia. Methods: Liquid chromatography (LC) was performed on a Dionex Ultimate 3000/LC 09115047 (USA) system equipped with a vacuum degasser, a quaternary pump, an autosampler and UV-Vis diod array detector. Chromatography was performed on a Thermo Scientific C18 (250 mm x 2.1 mm, i.d.: 5 mu m) column. The injection volume was 20 mu L. All compounds (hydrochlorothiazide, gliclazide, diclofenac-Na and mefenamic acid) were analysed in negative ion (NI) mode and eluted off the column with a mobile phase consisting of (A) 0.1% formic acid (FA) in deionised water (DIW) and (B) 40% acetonitrile (ACN) in methanol (MeOH) at 0.3 ml/min. Mass spectrometry was performed on a time of flight (TOF) instrument. Results: The linearity range, 5 - 500 ng/mL, provided a determination coefficient (R-2) > 0.99 for all compounds. The limit of detection (LOD) ranged from 65 - 136 ng/L while recovery ranged from 45 - 111.2 % in the river water. Two pharmaceutical compounds were detected in the surface water samples: diclofenac sodium and mefenamic acid at concentrations of 340 and 545 ng/L, respectively. Conclusion: The developed method is linear in the range 5 - 500 ng/mL, and precise and acceptable recoveries were obtained. In addition, this method is suitable to identify and quantify trace concentrations of diclofenac sodium and mefenamic acid in surface water.