Detection of cytostatic drugs in municipal waste water and their transfer to surface water

Abstract

A new sensitive and selective LC-MS/MS method with positive electrospray ionization was developed to detect seven cytostatic drugs and one metabolite from municipal wastewater. The method separates the target analytes in only 16 minutes using a Hypersil Gold column (100 x 2.1 mm, 3.0 µm) kept at 20°C and a mobile phase made of aq. 0.2% HCOOH and ACN in the ratio 92/8 (v/v). A low mobile phase flow of 0.2 mL/min was used to increase MS ionization yield and hence method sensitivity. A complex two steps (10%/minute) and two plateau gradient elution program was applied for 12 minutes to achieve analyte separation from matrix and each other with highly efficient peaks. Collision energy, fragmentor and capillary voltages were optimized to increase MS sensitivity. Optimization of LC-MS parameters generated low instrumental LOQs situated in the range 0.1 ÷ 1.0 ng/mL. MS detector response was linear between 1 and 100 ng/mL with R2 coefficients > 0.997 for all eight target analytes. SPE using Oasis HLB cartridges was employed to concentrate target analytes from water samples with MeOH as elution solvent. Intraday and inter-day precision (RSD %) was situated between 5.4 ÷ 7.2% and 7.3 ÷ 10.8%, respectively. Cytostatics recovery after SPE was good due to internal standard correction with values between 70 ÷ 134%. Overall method LOQs were situated between 0.6 and 5.6 ng/L. The method was tested on four waste water samples from a WWTP plant in Bucharest, but none of the targeted cytostatic drugs were found above detection limit.