George O. Okonji*1, 3, Dickson Andala1 and Silvanus Shisia2
1Department of Chemistry, Multimedia University of Kenya, P.O.BOX 15653-00503, Nairobi, Kenya
2Department of Chemistry and Biochemistry, Laikipia University, P.O.BOX 1100-20300, Nyahururu, Kenya
3School of Chemistry and Material Science, Technical University of Kenya, P.O.BOX 52428-00200, Nairobi, Kenya
Abstract
Prenatal and postnatal exposure to endocrine disrupting pesticides (EDPs) is believed to cause hormonal imbalance in animals. Insufficient data on exposure levels has necessitated the need for assessments to confirm existing EDPs. Solid phase extraction (SPE) is a simple multi-residue sample preparation technique suitable for quick exposure assessments; however, extension of its application in pre-concentration of many EDPs residues in river water is largely unexplored. The method was applied in analysis of Mbagathi River water samples in Machakos County, Kenya. This study aimed to validate a SPE technique for pre-concentration of four suspected EDPs including a triazine (atrazine), a carbamate (carbaryl) and organophosphates (diazinon and dimethoate) in river water for direct liquid chromatography tandem mass spectrometric (LC-MS/MS) analysis. Precision attained was less than 2.6% RSD, while recovery was above 70% for majority of the compounds tested. Low limits of quantification and detection, below 2.5 ng/L and 0.8 ng/L respectively, indicated suitability of the method for trace exposure assessment in river waters. Samples were collected in triplicate from eighteen sampling sites at random along the river during the short rainfall season of mid-September 2019. The selected EDPs detected were in the range of: <LOQ to 3.56 μg/L for atrazine, <LOQ to 1.48 μg/L for carbaryl, <LOQ to 1.9 μg/L for diazinon and <LOQ to 0.82 μg/L for dimethoate. The quantities detected for atrazine, carbaryl, dimethoate and diazinon in a majority of sites were at levels capable of causing significant health effects to human and wildlife.
Keywords: River water, Endocrine Disrupting Pesticides, Liquid chromatography, Solid Phase Extraction, Tandem mass spectrometry
