Nghiên cứu phát triển kỹ thuật QuEchERS GC MS 3 SIM để phân tích đồng thời dư lượng hoá chất bảo vệ thực vật trong đất tt tiếng anh

MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY - Pham Tuan Linh STUDY AND DEVELOPMENT OF QuEChERS GC/MS SIM TECHNIQUE TO ANALYSE MULTI PESTICIDE RESIDUES IN SOIL Major: Analytical Chemistry Code: 62.44.01.18 SUMMARY OF ANALYTICAL CHEMISTRY DOCTORAL THESIS Hanoi, 2019 This thesis is completed at: Graduate University Science and Technology – Vietnam Academy of Science and Technology Science instructor 1: Assoc.Prof.Dr Vu Duc Loi Science instructor 2: Assoc.Prof.Dr Nguyen Hong Khanh Reviewer 1: Reviewer 2: Reviewer 3: The thesis will be presented to the scientific council at Graduate University Science and Technology – Vietnam Academy of Science and Technology at … … h , date …… month …… , 2019 The thesis can be found at: - Library of Graduate University Science and Technology - National library of Vietnam INTRODUCTION The urgency of the thesis Nowadays, more than1500 different kinds of pesticides have been used, classified based on chemical structure (chlorinated, phosphorus, Carbamate, Pyrethroid ) or by application (insecticide, fungicide, herbicide ) In Vietnam, more and more different pesticides are used in agriculture (increased from 189 substances in 2003 to 437 substances in 2010) Pesticides have been known to be contaminants that persist for a long time in the environment So over time, there will be residues of many different pesticide in the soil Pesticides accumulated in the soil can be transferred to humans via the food chain, being potentially harmful to human health Thus, the level of pesticide residues in the agricultural soil needs to be monitored as farmers switch to organic farming (green and safe agriculture) Currently, pesticide residues in soil is determined separately for each substance group, with different procedures, so increasing costs, extend the analysis time and analysis process becomes more complicated Therefore, the project "Study and development of QuEChERS GC / MS SIM technique to analyze multi pesticide residues in soil" was carried out, in order to reduce the analysis time, minimize the number of analytical steps, use fewer reagents in smaller amounts and provide high recovery Scope of thesis Develop a rapid and simple method for analysis of multi-residue pesticides, including organophosphate, organochlorine, carbamate, and pyrethroid compounds in soil, with sample preparation based on QuEChERS technique and determination by GC-MS Main contents of thesis - Survey and select optimal conditions to analyze multi pesticides on GC / MS system: injection mode, temperature program, parameters for mass spectrometry - Investigate optimization of processing samples including extraction, cleaning and enrichment: solvent and extraction time, influencing factors, cleaning agents - Verification of analytical methods: determination of linear range, calibration curve, detection limit and quantitative limit, recovery coefficient and repeatability of the method - Apply the optimal procedure to analyze 30 soil samples and compare results with 04 laboratories at Vietnam and Korea New contributions of the thesis - This is the first study in Vietnam to apply the QuEChERS method for multi-residues pesticides analysis in the soil - d-SPE has been applied instead of soxhlet extraction, so the sample preparation time has been reduced from 24 h to 25 minutes, consuming only 15 ml solvent (the popular methods consume at least 300ml of solvent) - With a single run, 103 pesticides in soil have been analyzed (the latest publication, only 42 pesticides in the soil were quantified) - In quantitative step, only GC/MS is used (in publications, GC/MS/MS is analytical method usually selected) CHAPTER OVERVIEW Pesticides (herbicides, fungicides or insecticides) are environmental pollutants often found in soil, water, atmosphere and agricultural products, and may exist in harmful levels, posing an environmental threat Even low levels of pesticide can cause adverse effects on humans, plants, animals and ecosystems The application of pesticides has increased appreciably during the past few decades, resulting in a potential risk for the human health Over 95% of sprayed pesticides reach a destination other (usually soil environment) than their target So, the determination of pesticide residues in soil has been rising in demand The analysis of pesticide residues in soil consists of sample preparation and the instrumental determination The aim of the sample preparation is to isolate the trace amounts of analytes from a large quantity of complex matrices and eliminate the interferences from the soil matrix as much as possible Typical sample preparation steps include the homogenization, extraction, and clean-up Due to the low concentration levels of pesticide in soil, a technique strong enough to extract bound residues is necessary The most common of these techniques are mechanical agitation by shaking, sonication, microwave energy, and liquid-solid extraction (e.g.: Soxhlet extraction; accelerated solvent extraction, pressurized liquid extraction, and, supercritical fluid extraction) The most popular clean-up methods are based on the solid phase extraction technique using florisil cartridges These established methods are effective, yet time consuming (taking as long as 1,5day), complicated and expensive As a result, the development of new analytical methods for the determination of multi residue pesticides in soil samples is currently a high-interest research area Many innovations have occurred in analytical methods for the extraction of organic compounds from different matrices that reduce the analysis time, minimize the number of analytical steps, use fewer reagents in smaller amounts and provide high recovery In 2003, Michelangelo Anastassiades developed a method for the multiclass, multi-residue extraction of pesticides in fruits and vegetables This method was called QuEChERS, which stands for Quick, Easy, Cheap, Rugged and Safe, and it is based on dispersive solid phase extraction (d-SPE) In d-SPE, pesticides are extracted with an aqueous miscible solvent with a high amount of salt, in order to induce liquid phase separation The QuEChERS method is particularly popular for the determination of wide range of chemical residues, mostly pesticides in various food matrices, because of its simplicity, low cost, and high efficiency with a minimal number of steps QuEChERS approach is very flexible and it serves as a template for modification depending on the analyte properties, matrix composition, equipment and analytical technique available in the laboratory Unfortunately, the application of the d-SPE technique in the analysis of pesticides in agricultural soils is very rare, with a limited number of pesticides analyzed Currently, in Vietnam, QuEChERS method has only been applied for pesticide analysing in food and medicinal plant sample The level of pesticide residues in soil, still determined by GC/ECD or GC/NPD, with Shoxlet extraction CHAPTER EXPERIMENT 2.1 Materials and apparatus Stock standard solutions of 2.00 mg/g of each pesticide were prepared in MeCN, stored in −20◦C Intermediate mixture standard solution (10 mg/kg) was prepared by diluting the stock standard solutions with MeCN Gas chromatography mass spectrometry system MS-QP 2010 (Shimadzu), DB-5MS capillary column 2.2 Research content 2.2.1 Selection of pesticides 103 different group pesticides , have been widely used in agricultural cultivation in Vietnam as well as in the world and have suitable chemical and physical properties for analysis on GC / MS has been selected 2.2.2 Survey and select optimal conditions to analyze multi pesticides on GC / MS system - Survey the injection temperature and injection speed, sample volume and carrier gas - Survey temperature program - Select ion mass for quantitative 2.2.3 Investigate optimization of processing samples - Solvent and extraction time, - Influencing factors: pH, ionic strength, organic, - Absorbent agents 2.3 Develop analytical process From the research results obtained, develop an analytical procedure including: sample processing and setting on GC / MS equipment Verification of analytical methods: determination of linear range, calibration curve, detection limit and quantitative limit, recovery coefficient and repeatability of the method 2.4 Analysis of real samples Apply the optimal procedure to analyze 30 soil samples (were collected in Nam Dinh, Nghe An, and Hanoi with different pH, ion exchange and organic matter characteristics) and compare results with 04 laboratories at Vietnam and Korea CHAPTER RESULTS AND DISCUSSION 3.1 Survey and select optimal conditions to analyze multi pesticides on GC / MS system 3.1.1 Survey the injection temperature and injection speed With the slow injection mode, the sensitivity of pesticides surveyed was 50% lower than that of the fast and medium mode In addition, the stability is not high, most % RSD> 30% The sensitivity has been significantly improved, and there is not so much difference between the fast and medium sample injection modes However, the fast injection mode is more stable,% RSD is 70% 86 102 101 99 96 3.2.3 Effect of absorbents Interferences have maximum absorption in the wavelength range of 190 - 230 nm, including fats ((max = 205 - 233 nm), sugar compounds ((max = 190 nm); and triaglycerol ((max = 210 nm) Figure 3.14 Efficient removal of interferences by adsorbents (a) florisil; (b) C18; (c) PSA; and (d) GCB Experimental results (Figure 3.14) show that florisil, C18, PSA with content of 20 mg / mL and GCB with content of 10 mg / L are all capable of cleaning 13 Figure 3.16 The soil sample chromatogram is purified by various absorbents 14 However, when observing the baseline as well as the intensity of impurities in the chromatogram (Figure 3.16), we can see: - For florisil: baseline rise to 150,000 and decrease to baseline until 18 minutes Impurities are very much with high intensity - For C18 and GCB: baseline rises to 100,000 and after 11 minutes decreases to baseline - For PSA: the baseline only rises to 60,000 to the baseline (50,000) after minutes Therefore, absorbents PSA (500mg) and GCB (10mg) were selected for the cleaning of pesticides in soil samples 3.2.4 - Effect of sample matrix Effect of pH: pH can affect the chemical and physical properties of pesticides as well as the efficiency of sample extraction With agriculture soil pH ranges from 5.5 to 8.5 Experimental results show that pH from to has no significant effect on the extraction process The recovery is not much different and is in the range of 75 - 110% with % RSD ranging from - 18% - The influence of ionic strength The ionic level of the mixture, making it easier to extract pesticides However, some metals with the ability to form complexes such as Co, Cd and Cu will reduce the ability to extract some highly polarized pesticides Studies with Cu content of 1000 mg / kg showed no effect on the extraction of pesticides in soil The recovery ranges from 69 110% with % RSD from - 17% 15 - Influence of sample size and organic matter content: Studies conducted with coarse-grained (