Abstract
Damaging the environmental population suggests the population-level effects of NSAIDs. However, there is currently no evidence for population-level effects. As such the occurrence of NSAIDs is considered an issue of concern. The aim of the study was to implement an analytical method that permits the extraction and detection of selected NSAIDs in water samples using solid phase extraction and high-performance liquid chromatography coupled to a diode array detector (SPE-HPLC-DAD).
SPE-HPLC-DAD was optimized using both univariate and multivariate optimisation procedures. The separation of of ibuprofen (IBU), naproxen (NAP), diclofenac (DCF), and indomethacin (INDO) was optimized using central composite design to determine the optimum flow rate and percentage of formic acid in the mobile phase. The optimum HPLC-DAD conditions were 72:28 (v/v) acetonitrile: 0.2% formic acid in water, 200 and 230 nm as wavelength, a flow rate of 1.031 mL/min, and 10 min run time. The SPE optimization showed that a combination of 2% formic acid in acetonitrile was proven to be the most appropriate eluent for the extraction of all target compounds from LC-SCX sorbent (liquid chromatography-strong cation exchanger) with recoveries ranging from 79.3% for NAP, 91.6% for INDO, 92.4% for DCF, and 93.2% for IBU. The multivariate optimization showed that the optimum conditions for the extraction of the analytes were as follows (ionic strength = 0.125 % m/v, pH= 5, sample flow rate = 2.00mL/min, eluent volume = 883 μL and eluent flow rate = 1.10 mL/min).
In chapter 4, HPLC-DAD has been developed and it was validated for different water samples namely upstream, downstream, and influent wastewater treatment. Solid phase extraction one of the most approaches for sample preparation was used to clean up and preconcentrate target compounds (IBU, NAP, DCF, and INDO) from water matrices. The developed method allowed detection limits in the low concentration micrograms per litre (μg/L) level. Due to the sensitivity and selectivity of the optimized method, all target compounds were detected from water samples at a concentration of up to 2.72±0.12 μg/L. The environmental risk assessment for each target compound was measured using the risk quotient (RQ). The RQ values of NSAIDs were classified as low risk (RQ, 0.01-0.1), medium risk (RQ, 0.1-1), and high risk (RQ>1).