الفهرس 
General IntroductionOnly 14 pages are availabe for public view
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Abstract
This thesis consists of six parts including general introduction on neonicotinoids, literature review and descriptive experimental work for the analysis of the studied neonicotinoids named acetamiprid, imidacloprid, nitenpyram, thiacloprid, flonicamid , clothianidin, dinotefuran and thiamethoxam and their metabolites 6-chloronicotinic acid and 1-methyl-3-nitroguanidine, general discussion in addition to the references and a summary in arabic.
Part I: General Introduction
This section includes a general introduction on insecticides as well as their classification, definition of neonicotinoids, their types, mode of action, uses and their toxicity.
Part II: Literature Review
This part includes a general introduction on the historical background, chemical, physical and spectral properties, environmental fate of each of the studied ten compounds and a review on different reported methods for their analysis.
Part III: Spectrophotometric and Chemometric methods for Determination of Neonicotinoids
This part consists of two sections:
Section A: Extended Derivative Ratio (EDR) method for the determination of four neonicotinoids and their metabolite in (Mixture 1) and for the determination of another four neonicotinoids and their metabolite in (Mixture 2)
In this section, an accurate, sensitive and selective univariate method named extended derivative ratio (EDR) was developed and subsequently validated for the simultaneous determination of four neonicotinoids named acetamiprid (ACT), imidacloprid (IMD), nitenpyram (NIT), thiacloprid (TCP) and their common metabolite 6-chloronicotinic acid (6-CNA) (Mixture 1) in soil and cucumber samples. The same method was developed and validated for simultaneous determination of another four neonicotinoids named flonicamid (FLO), clothianidin (CLO), dinotefuran (DIN), thiamethoxam (TMX) and their common metabolite 1-methyl 3-nitroguanidine (1-MNG) in soil and cucumber samples (Mixture 2). The method developed was applied for determination of the studied compounds, where peak amplitudes were recorded at 235.2, 291.6, 345.8, 232.2 and 233.6 nm within the linear concentration ranges 1.00-7.00, 1.00-7.00, 1.50-8.00, 1.00-7.00 and 1.00-6.00 μg/mL for ACT, IMD, NIT, TCP and 6-CNA, respectively (Mixture 1), while peak amplitudes were recorded at 280.2, 278.6, 279.8, 255.4 and 257 nm within the linear concentration ranges 1.50-7.50, 1.00-7.00, 1.00-7.00, 1.50-7.50 and 0.60-3.00 μg/ml for FLO, CLO, DIN, TMX and 1-MNG respectively (Mixture 2). The method was developed, validated according to Sanco document guidelines and successfully applied to determine the five compounds simultaneously for both mixtures in spiked cucumber and soil samples where standard deviations were less than 16.86 % for all of the recovery tests (for mixture 1) and were less than 19.36 % (for mixture 2). The limits of detection for the five compounds were in the ranges of (0.104-0.310 ppm) for mixture 1 and were in the ranges of (0.161-0.263 ppm) for mixture 2. All the results were compared to those obtained by the reported methods, where no significant difference was observed regarding both accuracy and precision. The method was successfully applied to quantify residues and calculate the disappearance rate of the four neonicotinoids for both mixtures from soil and their half-lives.
Section B: Partial Least Square (PLS) and Continuous Wavelet Transform (CWT-PLS) methods for simultaneous determination of four Neonicotinoids and their metabolite (Mixture 1) and for simultaneous determination of another four neonicotinoids and their metabolite (Mixture 2)
In this section, accurate, sensitive and selective multivariate calibration methods named partial least squares (PLS) and continuous wavelet transform coupled with PLS (CWT-PLS) were developed and subsequently validated for simultaneous determination of four neonicotinoids named acetamiprid (ACT), imidacloprid (IMD), nitenpyram (NIT), thiacloprid (TCP) and their common metabolite 6-chloronicotinic acid (6-CNA) (Mixture 1) in soil and cucumber samples and for simultaneous determination of another four neonicotinoids named flonicamid (FLO), clothianidin (CLO), dinotefuran (DIN), thiamethoxam (TMX) and their common metabolite 1-methyl 3-nitroguanidine (1-MNG) in soil and cucumber samples (mixture 2). PLS and CWT-PLS models were constructed for both mixtures where the concentration range was 1.00-7.00, 1.00-7.00, 1.50-7.50, 1.00-7.00 and 3.00-5.00 μg/mL for for ACT, IMD, NIT, TCP and 6-CNA, respectively (mixture 1) and the concentration range was 1.50-5.50, 1.00-5.00, 1.00-5.00, 1.50-5.50 and 0.60-2.20 μg/ml for FLO, CLO, DIN, TMX and 1-MNG respectively (mixture 2). The two methods were developed, validated according to Sanco document guidelines and successfully applied to determine the five compounds simultaneously for both mixtures in spiked cucumber and soil samples. All the results were compared to each other and to those obtained by the reported methods, where no significant difference was observed regarding both accuracy and precision. The methods were successfully applied to quantify residues and calculate the disappearance rate of the four neonicotinoids from soil and their half-lives.
Part IV: Simultaneous Determination of Neonicotinoids in mixture 1 and mixture 2 by High Performance Liquid chromatography with Diode Array Detection.
In this part, a sensitive, selective and a validated HPLC–DAD method was developed for the simultaneous determination of five neonicotinoid insecticides named acetamiprid (ACT), imidacloprid (IMD), nitenpyram (NIT), thiacloprid (TCP) and flonicamid (FLO) with their primary metabolite 6-chloronicotinic acid (6-CNA) (mixture 1) in cucumber and soil and for simultaneous determination of another three neonicotinoid insecticides named dinotefuran (DIN), thimethoxam (THM) and clothianidin (CLO) with their metabolite 1-methyl-3 nitroguanidine (1-MNG) (mixture 2) in cucumber and soil. Both methods were based on QuEChERS as a pretreatment procedure.
In QuEChERS procedure for both mixtures, cucumber samples were extracted with acetonitrile and cleaned using C18, while soil samples were extracted with a mixture of acetonitrile: dichloromethane (1:2). The HPLC conditions were optimized where neonicotinoids were separated using isocratic elution of acetonitrile:water (25:75) in (mixture 1) and a gradient elution of water:acetonitrile (for mixture 2) using Synergy Hydro RP C18 column. Matrix matched calibration standards were prepared in cucumber and soil to eliminate the interference of matrix. Relative standard deviations (RSDs) were less than 9 % for all of the recovery tests of mixture 1 and less than 2.08 % for all of the recovery tests of mixture 2. The limits of detection (LODs) for the neonicotinoids in mixture 1 were in the ranges of (0.006-0.122 µg/g), while LODs for the neonicotinoids in mixture 2 were in the ranges of (0.015-0.081 μg/g). The methods were applied successfully to determine residues and rate of disappearance of the neonicotinoids in both mixtures from cucumber and soil and their half-lives.
Part V: Simultaneous Determination of Eight Neonicotinoid Insecticide Residues and Two Primary Metabolites in Cucumber and Soil by Liquid chromatography-Tandem Mass Spectrometry Coupled with QuEChERS
In this part, a new, rapid, sensitive, precise and validated high performance liquid chromatography coupled to tandem mass spectrometry (HPLC–MS/MS) method was developed for the simultaneous determination of eight neonicotinoid insecticides with their two primary metabolites in cucumber and soil based on QuEChERS as a pretreatment procedure.
In QuEChERS procedure, cucumber samples were extracted with acetonitrile and cleaned using (C18 sorbent material), while soil samples were extracted with a mixture of acetonitrile:dichloromethane (8.3:16.7 v:v). The LC–MS/MS conditions were optimized to provide good selectivity and specificity of the developed method where neonicotinoids were separated using gradient elution of water and acetonitrile both containing 0.1 % formic acid with Gemini C18 column where the last compound was eluted at 9.5 minutes. Average recoveries of the eight neonicotinoids and their metabolites ranged between 81.6 % and 95.7 % in fortified cucumber samples with relative standard deviations (RSDs) lower than 13.18 % and between 80.3 % and 104 % in fortified soil samples with relative standard deviations (RSDs) lower than 8.44 %. The limits of detection (LODs) and quantification (LOQs) for the ten compounds were in the ranges of (0.08-6.06 ng/g) and (0.26-20 ng/g), respectively. The method was applied successfully to determine residues and rate of disappearance of the eight neonicotinoids from cucumber and soil and their half-lives where a safety pre-harvest interval for each neonicotinoid was suggested.
Part VI: Novel Potentiometric Sensors for Determination of Dinotefuran in Cucumber and Soil Samples
In this part, five new potentiometric membrane sensors for determination of dinotefuran have been developed. Four of them were based on the use of a newly designed molecularly imprinted polymer (MIP) material where either acrylamide or methacrylic acid was used as a functional monomer in a plasticized PVC membrane before and after elution of the template. A fifth sensor - a carboxylated-PVC based sensor plasticized with dioctyl phthalate- was also prepared and tested. Sensor 1 (acrylamide washed) and sensor 3 (methacrylic acid washed) exhibited significantly enhanced response towards dinotefuran over the concentration range of 10-7-10-2 M for both sensors with an LOD of 0.35 ppb. The response was near-Nernstian, with average slopes of 66.3 and 50.8 mV/decade for sensor 1 and sensor 3 respectively. Sensor 2 (acrylamide non washed), sensor 4 (methacrylic acid non washed) and sensor 5 (carboxylated-PVC) exhibited non-nernstian responses over the concentration range of 10-7-10-3 M with an LOD of 10.07, 6.90 4.30 ppb and average slopes of 39.1, 27.2 and 33 mV/decade respectively.
The possibility of applying the proposed sensors to dinotefuran determination in spiked soil and cucumber samples was demonstrated with average recoveries of 87.93-106.43 % and standard deviation less than 13.73 % in cucumber samples and 97.46-108.71 % with standard deviation less than 10.66 % in soil samples.
The method was applied successfully to determine residues of dinotefuran, its rate of disappearance from cucumber and soil and its half-life using the proposed sensors where a safety pre-harvest interval for dinotefuran was suggested.
Part VII: General Discussion
This part includes a comparison between the different methods for determination of the ten compounds and a comparison between the statistical analyses of the results obtained by the proposed methods and the reported method.
This thesis consists of 158 figures, 87 tables and 360 references and ends with a summary in arabic.