A simple and rapid method for determination of azinphos-methyl, parathion-methyl and ethoprofos, group of organophosphorus pesticides in wastewater matrices, is presented. A chemometric approach for the optimisation of vortex-assisted dispersive liquid-liquid microextraction experimental conditions prior to liquid chromatography-mass spectrometry detection was applied. In this method, a high-density organic solvent (chloroform) was used as the extractant, with acetone as the disperser solvent. Vortexing was applied prior to centrifugation for phase separation of the organic phase (sedimented layer of extractant) and the aqueous layer. A two-level full factorial design (2 4 ) was employed initially for the screening process, and final optimisation of the significant parameters was performed using response surface methodology based on central composite design. The method performance characteristics investigated included linear dynamic range (LDR, 5-100 µg L −1 ) with a good correlation coefficient (> 0.999). The method precision expressed as intra-day and inter-day relative standard deviation (%RSD) was in the range of 7.8-8.2% and 8.1-9.4%, respectively. The influence of matrix was found to be negligible with recoveries ranging from 99.9 to 106.7%. The proposed method was then applied in real wastewater samples. Extraction recoveries performed at two spiking levels (25 and 100 µg L −1 ) in untreated (influent) and treated (effluent) wastewater matrices ranged between 94.95 and 119.47%.
Background:
Parabens are synthetic esters used extensively as preservatives and/or
bactericides in personal care personal products.
Objective:
Development and validation of a novel robust chemometric assisted analytical technique
with superior analytical performances for the determination of ethylparaben, methylparaben and
propylparaben, using simulated wastewater matrix.
Methods:
An automated Solid Phase Extraction (SPE) method coupled with liquid chromatographymass
spectrometry was applied in this study. A gradient elution programme comprising of 0.1%
formic acid in deionised water (A) and 0.1% formic acid in Methanol (B) was employed on a 100 x
2.1 mm, 3.0 μm a particle size biphenyl column. Two-level (2k) full factorial design coupled with
response surface methodology was used for optimisation and investigation of SPE experimental
variables that had the most significant outcome of the analytical response.
Results:
According to the analysis of variance (ANOVA), sample pH and eluent volume were
statistically the most significant parameters. The method developed was validated for accuracy,
precision, Limits of Detection (LOD) and Limit of Quantification (LOQ) and linearity. The LOD and
LOQ established under those optimised conditions varied between 0.04-0.12 μgL−1 and 0.14-0.40 μgL−1
respectively. The use of matrix-matched external calibration provided extraction recoveries between
78-128% with relative standard deviations at 2-11% for two spike levels (10 and 100 μgL-1) in three
different water matrices (simulated wastewater, influent and effluent water).
Conclusion:
The newly developed method was applied successfully to the analyses of parabens in
wastewater samples at different sampling points of a wastewater treatment plant, revealing
concentrations of up to 3 μgL−1.
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