Date of Defense
14-4-2025 3:00 PM
Location
F3-036
Document Type
Dissertation Defense
Degree Name
Doctor of Philosophy in Chemistry
College
COS
Department
Chemistry
First Advisor
Prof. Mohammed Almeetani
Keywords
Pesticide residues, carbamates, food safety, MRL, UHPLC-MS/MS, camel milk, date palm fruit, COF, human health, health risk assessment, removal, phtocatalytic degradation.
Abstract
The growing global population has led to an increasing demand for food production, necessitating the widespread use of pesticides to enhance crop yield, improve quality, and protect against pests. Among the various types of pesticides, carbamates are extensively used due to their effectiveness in controlling pests. However, their residues in food products pose serious human health risks, including neurotoxicity, genetic mutations, cancer development, and immunosuppression. Therefore, the reliable detection and quantification of carbamate residues in food are paramount to ensuring food safety and regulatory compliance.
This dissertation focuses on developing and validating analytical techniques for extracting and detecting carbamate residues in two culturally and economically significant food commodities in the United Arab Emirates: camel milk and date palm fruit. The developed HPLC-MS/MS methods demonstrated high sensitivity in detecting trace levels of carbamate residues in both matrices, with detection limits ranging from 0.001 to 0.05 ng/g, well below the established maximum residue limits (MRLs). Moreover, the employed extraction techniques (liquid-liquid extraction for camel milk and QuEChERS with dispersive-solid-phase extraction (d-SPE) for date palm fruit) confirmed the methods’ reliability, accuracy, and precision, achieving recoveries and relative standard deviations within the satisfactory range set by the European SANTE/11312/2021 guidelines.
In camel milk samples, carbamate residues were detected at concentrations below the MRLs, with higher levels found in raw milk than in pasteurized milk. In contrast, carbamate residues in date palm fruit exhibited more significant variation, with some exceeding their respective MRLs, particularly carbosulfan, propoxur, and carbofuran. Given that carbosulfan was detected in all date samples, its metabolites were also analyzed, revealing exceedances of carbosulfan, carbofuran, and 3-hydroxycarbofuran in certain samples. Additionally, dibutylamine was found at high concentrations, raising critical concerns regarding date safety, especially given the absence of regulatory standards for this compound. Despite these findings, a probabilistic health risk assessment indicated that the hazard quotient (HQ) values for all studied carbamates in both camel milk and dates remained below the safety threshold of 1.0, suggesting that the consumption of these commodities does not pose significant health risks for adults or children.
Although the employed extraction and clean-up techniques were effective, conventional methods have several limitations, including a lack of selectivity, high solvent consumption, potential emulsion formation, matrix interferences, and time-consuming procedures. To overcome these drawbacks, a novel covalent organic framework (COF), named COF-RC, was synthesized and applied as a sorbent material for the solid-phase extraction (SPE) of seven carbamate residues in different fruits. The COF-based method demonstrated high selectivity and adsorption capacity for carbamates, enhanced recoveries, and reusability for at least ten extraction cycles, offering a more efficient and sustainable alternative to conventional extraction techniques.
In addition to food analysis, this dissertation explores an advanced remediation approach for carbamate pesticide removal from aqueous systems. A porphyrin-based covalent organic framework (AE-COF) was synthesized and evaluated for its dual functionality in adsorption and photocatalytic degradation of nine carbamates in water. AE-COF exhibited high removal efficiency, effectively adsorbing carbamates and facilitating their degradation under UV irradiation through reactive oxygen species (ROS) generation. The consistently high degradation rates (≥80%) for all carbamates suggest that AE-COF is an efficient and reusable material for pesticide remediation in contaminated water sources. Keywords: Pesticide residues, carbamates, food safety, MRL,
A DUAL APPROACH TO CARBAMATE PESTICIDES: EXTRACTION AND DETERMINATION IN CAMEL MILK AND DATE PALM FRUIT IN THE UAE, AND PHOTOCATALYTIC DEGRADATION IN WATER
F3-036
The growing global population has led to an increasing demand for food production, necessitating the widespread use of pesticides to enhance crop yield, improve quality, and protect against pests. Among the various types of pesticides, carbamates are extensively used due to their effectiveness in controlling pests. However, their residues in food products pose serious human health risks, including neurotoxicity, genetic mutations, cancer development, and immunosuppression. Therefore, the reliable detection and quantification of carbamate residues in food are paramount to ensuring food safety and regulatory compliance.
This dissertation focuses on developing and validating analytical techniques for extracting and detecting carbamate residues in two culturally and economically significant food commodities in the United Arab Emirates: camel milk and date palm fruit. The developed HPLC-MS/MS methods demonstrated high sensitivity in detecting trace levels of carbamate residues in both matrices, with detection limits ranging from 0.001 to 0.05 ng/g, well below the established maximum residue limits (MRLs). Moreover, the employed extraction techniques (liquid-liquid extraction for camel milk and QuEChERS with dispersive-solid-phase extraction (d-SPE) for date palm fruit) confirmed the methods’ reliability, accuracy, and precision, achieving recoveries and relative standard deviations within the satisfactory range set by the European SANTE/11312/2021 guidelines.
In camel milk samples, carbamate residues were detected at concentrations below the MRLs, with higher levels found in raw milk than in pasteurized milk. In contrast, carbamate residues in date palm fruit exhibited more significant variation, with some exceeding their respective MRLs, particularly carbosulfan, propoxur, and carbofuran. Given that carbosulfan was detected in all date samples, its metabolites were also analyzed, revealing exceedances of carbosulfan, carbofuran, and 3-hydroxycarbofuran in certain samples. Additionally, dibutylamine was found at high concentrations, raising critical concerns regarding date safety, especially given the absence of regulatory standards for this compound. Despite these findings, a probabilistic health risk assessment indicated that the hazard quotient (HQ) values for all studied carbamates in both camel milk and dates remained below the safety threshold of 1.0, suggesting that the consumption of these commodities does not pose significant health risks for adults or children.
Although the employed extraction and clean-up techniques were effective, conventional methods have several limitations, including a lack of selectivity, high solvent consumption, potential emulsion formation, matrix interferences, and time-consuming procedures. To overcome these drawbacks, a novel covalent organic framework (COF), named COF-RC, was synthesized and applied as a sorbent material for the solid-phase extraction (SPE) of seven carbamate residues in different fruits. The COF-based method demonstrated high selectivity and adsorption capacity for carbamates, enhanced recoveries, and reusability for at least ten extraction cycles, offering a more efficient and sustainable alternative to conventional extraction techniques.
In addition to food analysis, this dissertation explores an advanced remediation approach for carbamate pesticide removal from aqueous systems. A porphyrin-based covalent organic framework (AE-COF) was synthesized and evaluated for its dual functionality in adsorption and photocatalytic degradation of nine carbamates in water. AE-COF exhibited high removal efficiency, effectively adsorbing carbamates and facilitating their degradation under UV irradiation through reactive oxygen species (ROS) generation. The consistently high degradation rates (≥80%) for all carbamates suggest that AE-COF is an efficient and reusable material for pesticide remediation in contaminated water sources. Keywords: Pesticide residues, carbamates, food safety, MRL,