Studies On The Form Of Pesticides In Aquatic Products And Its Analytical Application

Studies on the interaction between small– molecular drugs and biomoleculars is a hot topic among many subjects ( such as: biology, chemistry, medicine and so on). However, the importance of these studies that are of great value to the determination of the drug residue in animal food hasn't drawn the analyst'attention. Due to its endogenous fluorescence, serum albumin ( SA) has become the object used to study the interaction between small–molecular and protein. The form of the drugs in the animal can also be deduced from the interaction. The determination of the drug residue in the animal food mainly subjected to the matrix interference of protein and fat. In this paper, based on the studies of the interaction of small-molecular drug and SA, we referenced the Quick, Easy, Cheap, Effective, Rugged, Safe ( QuEChERS) sample preparation, and used the matrix eliminating and direct analysis to determine the five organophosphorus pesticides ( OPs) in the aquatic products.The paper can be divided into four sections:Section One: The function and the potential safety problems were introduced. The ways and the meanings of the interaction between small– molecular drugs and biomoleculars were reviewed. The preparation and the determination of the pesticides residue were summarized.Section Two: The fluorescence spectrometry, synchronous fluorescence spectrometry and UV-Vis spectra were used to investigate the interactions between seven OPs and bovine serum albumin ( BSA) or fish serum albumin ( FSA). The forms of the 7 OPs with serum albumin ( SA) were also analyzed. The results were as follows:1: Different OPs had different quenching modes when binding to SA. The quenching modes were showed as follows: When binding to BSA, the quenching modes of 4 OPs ( methamidophos, trichlorphon, ethyl-parathion and phoxim) were all static quenching process, while the quenching modes of another 3 OPs (dimethoate, dichlorvos and ethyl-parathion) involved predominately the static quenching and subordinately the dynamic quenching. The quenching modes of 5 OPs ( methamidophos, trichlorphon, dichlorvos, methyl-parathion and phoxim) to FSA were static quenching, and the quenching modes of the other 2 OPs ( dichlorvos and ethyl-parathion) to FSA involved predominately the static quenching and subordinately the dynamic quenching. 2: Under the same temperature, the quenching constants and the binding constants between OPs and SA increased with the increasing hydrophobicity of the OPs. It was deduced that there were a higher quenching ability and a stronger affinity of high hydrophobic OPs to SA than those of lower hydrophobic OPs;②Under the same temperature, there were higher values of the quenching constants and the binding constants of the OPs binding to BSA than those of the same OPs binding to FSA. The affinity of OPs to BSA was stronger than that to FSA, and it was more likely to form the complexes with BSA remaining in the body.3:The binding potential points of OPs to SA were at about 1, and the distances between OPs and SA were all lower than 7nm indicating that non-radiative energy transfer occurred from BSA to OPs. With the increasing hydrophobicity, the acting forces between OPs and SA increased while the distances of OPs and SA decreased.4: The synchronous fluorescence spectrometry of SA showed that the conformation of SA was changed a little by the adding of OPs. The emission peaks of SA shifted to long-wave with increasing hydrophobicity of the 7 OPs, whenΔλ=60nm.Section Three: A method employing the synchronous fluorescence spectrometry to eliminate the interference between the emission of the pyrethroids pesticides and the endogenous fluorescence of the protein was used to investigate the interactions between 4 pyrethroids pesticides and BSA.The results showed that all of the 4 Pys could regularly quench the fluorescence of BSA, and only static quenching invloved in the quenching process of tetramethrin ( TM), fenpropathrin ( Fen), deltamethrin ( DM) to BSA, and the quenching between cypermethrin ( CPM) and BSA involved predominately the static quenching and subordinately the dynamic quenching. The orders of magnitude of the equlibrum constants and the binding constants were 4 orders higher, which showed that the 4 Pys were more likely to exist in the terms of complexes with BSA. The binding potential points were also at about one. The acting forces of cypermethrin with BSA were mainly hydrogen bond and Van't Hoff forces; and the hydrophobic effect played major roles in the procedures of tetramethrin, fenpropathrin and deltamethrin binding with BSA. The distances between 4 Pys and BSA were lower than 7nm, indicating non-radiative energy transfer occurred from BSA to Pys. Nomatter in terms of quenching modes, the equilibrium constants or the binding distances, when binding to SA, the characteristics of 4 Pys were much similarly to these of the high hydrophobic OPs ( such as ethyl-parathion, methyl-parathion and phoxim). Only free drugs can be decomposed by organism, and these molecules binding to SA were much likely to stay in the body. The accumulation of these complexes in the animal bodies would lead side effects (such as, acute toxicity or dysfunction of the immune system) to the animal.Section Four: Based on the study of the form of 7 OPs pesticides binding with BSA, we referenced the QuEChERS sample preparation, the matrix eliminating and direct analysis were adapted to the determination of the OPs pesticides residue in aquatic products in which the protein was the main matrix. New method was established to determine the OPs residue in the aquatic products.The extraction efficiency of the OPs pesticides residue was low, due to the high binding interactions between OPs and protein. Studies were conducted and we found that the extract solution (V(acetonitrile): V(acetic acid): V(water) = 90:1:9) could denature the structure of protein and the OPs residue could be released. The acidic environment could reduce the decomposition of alkali sensitive Ops. Both of the denaturation of protein and the acidic environment could lead a higher recovery of drugs from the protein matrix.In this section, we used the mixture of V(acetonitrile): V(acetic acid): V(water) = 90:1:9 as the extract solution, anhydrous magnesium sulfate (MgSO4) plus sodium acetate (NaAc) was added to eliminate the moisture, and then the secondary amine (PSA) and GDX-103 was used as clean-ups. The extract was centrifuged and transferred to vials for direct analysis by gas chromatography (GC). The method was used to determinate the five organic phosphorus residues (dichlorvos, methamidophos, dimethoate, methyl-parathion and ethyl-parathion) in fish. The determination recovery ranged from 72.94% to 107.21%, and the detection limits of the five Ops (dichlorvos, methamidophos, dimethoate, methyl-parathion and ethyl-parathion) were 0.045 mg/kg, 0.024 mg/kg, 0.015 mg/kg, 0.011 mg/kg and 0.002mg/kg, respectively. Compared to the GB method, the recovery was satisfactory and the method was simple, quick and sensitive.