Papers by Keyword: Pesticide Residue

Abstract: This experiment was conducted to study the new shoot, bud and leaf of Fuding Dabai Tea, which was picked and purchased from Zhongfeng Tea Garden in Ya'an famous mountain area. The sensory quality, contents, pesticide residues and heavy metals of fresh leaves and green tea were studied and compared. The total soluble solids content and turbidity of water samples before and after the cleaning process were determined. The results showed that: (1) the weighted total score of sensory evaluation of finished tea added with fresh leaf cleaning technology was 91.15, which was 2.45 points higher than that of the control (without fresh leaf cleaning), and increased by 2.76%. (2) Fresh leaf cleaning process can significantly reduce the content of tea polyphenols, caffeine and water extract, and the ratio of phenol to ammonia, but has no significant effect on the content of amino acid and soluble sugar. (3) The total soluble solids of Q 2 are 4.3 times as much as Q1, and the turbidity of Q2 is 37.2 times as much as Q1. Cleaning process of fresh leaves can significantly reduce the indexes of agricultural residues and heavy metals. In conclusion, the cleaning process of fresh tea leaves can improve the sensory quality of tea to a certain extent, significantly reduce the content of bitter and astringent substances in tea leaves, effectively clean the surface impurities of fresh tea leaves, reduce pesticide residues and heavy metal content.

Abstract: According to the national food inspection standards,research a new inspection system of pesticide residues combine with fluorescence detection method. Integration with photoelectric technology, sensor technology and micro processing technology ,First ,analysis of fluorescence detection mechanism of pesticide, adopting the light-emitting diode and a photoelectric device as the core to design the fluorescence detection system and using photomultiplier tube design microprocessor control system, System can rapid determination of food pesticide residues.

Abstract: With the improvement of life quality, the people attach more importance to health, and have higher requirements on residue detection of harmful substance in foods. The existing traditional detection methods not only have complicated procedures, but also are very expensive, so it is urgent to develop an intelligent rapid residue detector of harmful substances. The paper researches the portability design of intelligent pesticide residue detector. It applies embedded system design method which implements control and processing functions of detector on a Xilinx-FPGA chip, which not only reduces system volume, but also reduces power consumption and cost. So it has great significance to develop rapid food safety testing instrument.

Abstract: The existing methods of detecting pesticide residue include gas chromatography, high performance liquid chromatography, gas chromatograph-mass, liquid chromatograph-mass, capillary electrophoresis, radioimmunoassay, biosensor and rapid detection on the spot. The paper analyzes the comparison of gas chromatography and liquid chromatogram detecting pesticide residue, for achieving the development tendency and the future goal of analyzing pesticide residue.

Abstract: The inclusion complex formation between fluorescent sensor 3, 3’-benzidine/β-cyclodextrin derivative (BDCD) and pesticide carbaryl was studied and characterized by TEM, XRD and fluorescence spectroscopy. The stability constant and the stoichiometry of complex were determined. Based on the enhancement of the fluorescence intensity of carbaryl produced through complex formation, a new sensitive method for the determination of carbaryl was established. The linear relationship between the fluorescence intensity and carbaryl concentration was obtained in the range of 0.60-3.00 μmol/L with a correlation coefficient of 0.9946. The detection limit was 5.12 nmol/L. This method has been successfully applied to the determination of carbaryl pesticide residue in water, fruit and vegetable samples with satisfactory results, recoveries in the range of 94.12 % to 105.88 % were obtained. The method is rapid, simple, direct, economical, sensitive and useful for carbaryl analysis.

Abstract: The host-guest inclusion complex formation between 3, 3’-benzidine/β-cyclodextrin derivative (BDCD) and pesticide carbendazim was studied and characterized by TEM and XRD. The result showed that inclusion complex had hydrophobic small-molecule fluorophores. The fluorescence titration was performed to calculate binding constant, sensitivity factor and limit of detection of the resulting complex. Based on the enhancement of the fluorescence intensity of carbendazim produced throught complex formation, a new sensitive method for the determination of carbendazim was established. A linear relationship was obtained between the fluorescence intensity and carbendazim concentration in the range of 3.57 and 17.83 μmol/L. The correlation coefficient, the lowest limit of detection and RSD were 0.9916, 15.51 nmol/L and 2.13%, respectively. This method has better anti-interference ability and stability. The proposed method have been successfully applied to the determination of carbendazim pesticide residues in water, vegetable and fruit samples with satisfactory results, recoveries in the range of 87.56 % to 104.04 % were obtained.

Abstract: In order to ensure the healthy safety of edible lettuce, an identification way of pesticide residues of lettuce leaves is studied. Soilless cultivation of lettuce sample was adopted. At tillering stage, various levels of fenvalerate were sprayed to different groups of lettuce, lettuce leaves accompanied by a collection of pesticide residues and lettuce leaves not sprayed pesticide residues were collected, Hyperspectral Information of each blade leaf were collected and lettuce leaves sample spectral library was set up. Randomly 90 samples were selected as training samples, and the classification models based on BP neural network and LVQ neural network were set up. The remaining samples were taken to forecast classification test. Results showed that, the prediction identification correct rate of LVQ neural network model is 98.3607%. The algorithm is suitable for pesticide residues diagnosis of lettuce leaves.

Abstract: A method was developed for simultaneous determination of imidacloprid,acetamiprid, thiabendazole and carbendazim in lentinus edodes, straw mushroom and oyster mushroom by HPLC. Acetonitrile was edded in the sample for extraction solvent, the sample was purified by NH₂ solid phase extraction cartridge,then detected by HPLC.The results showed that a good linearity in the range of 0.05~5.0μg/mL with the linear correlation coefficients of 0.9991~0.9997, the detection limits of imidacloprid, acetamiprid, thiabendazole and carbendazim were respectively 0.002 mg/kg,0.005mg/kg, 0.003 mg/kg and 0.003 mg/kg.Tests for recovery were made by addition of four pesticidess standards at three different concentration levels (0.1, 0.5 and 1.0 mg/kg) to the blank sample.The mean recovery rates were 86.0%~105.0% , the relative standard deviations were less than 3.5%.The sensitivity, accuracy and precision of this method were able to meet the requirements for pesticide residue analysis.

Abstract: Nowadays, public concern over food safety, especially the potential health risk to humans cause by the high levels of pesticide residues, has increased. In general, people usually refrigerate fresh vegetable in order to keep their freshness intact for longer duration of time. Very few research studies have investigated the correlation between refrigerated vegetables and degradation of pesticide residue. Gas chromatography was used to conduct dynamic analysis of pesticide degradation in off-season vegetables, which are kept in cold storage conditions. Cowpea and balsam pear samples were extracted with acetonitrile. The resultant extracts were purified in SPE column filled with cleanert pesticarb. Thereafter, the eluant extracts were determined through gas chromatography coupled with μECD. Matrix-matched calibrations were analyzed through GC-ECD, where in the limits of quantification varied between 0.0005 and 0.0026mg/kg. The linear coefficients of correlation varied between 0.9916 and 0.9997. Recoveries on cowpea and balsam pear were in the range 74.7%~98.8%. Based on the residue dynamics study, the half-lives of the five pesticides in cowpea were as follows: chlorpyrifos: 247d, chlorfenapyr: 407d, bifenthrin: 462d, cyhalothrin: 346d, and cis-cypermethrin: 315d. In balsam pear samples, the half-lives of the five pesticides were as follows:chlorpyrifos: 150d, chlorfenapyr: 187d, bifenthrin: 433d, cyhalothrin: 266d, and cis-cypermethrin: 210d. The residue of five pesticides in cowpea and balsam pear underwent slow degradation in cold storage conditions. In this study, the findings serve as important reference data, which can be used by the concerned state authorities in formulating the limit of pesticide residue in food.

Abstract: Pesticide residue grade solvents have the characteristic of ultra high purity, low UV value, low pH value, low moisture content and low evaporation residue, which do not have those controlled impurity peak in pesticide chromatographic detection. This project is funded by the China government to develop the industrialization process of pesticide residue grade n-hexane, in which the industrial n-Hexane is used as crude purified by decoloration, distillation and filtration process. The products are validated by National Research Center for Environmental Analysis and Measurement (CNEAC), National Research Center for Geoanalysis, Chinese Academy of Inspection and Quarantine (CAIQ), Chinese Academy of Agricultural Sciences (CAAS) and other government originations for polychlorinated biphenyls, organochlorine pesticide or chiral pesticides analysis and further confirmed that it’s competitive to all others imported n-Hexane currently occupied in China. The optimized process parameters are: firstly utilizing 2% of silicon dioxide as decoloration agent then rinsed with distillation water before distillation. The heating temperature of two distillation towers is 88°C with reflux ratio of 15:1 and 4:1 respectively, the discharge rate of heavy component is 20 mL/min, the yield of this process is approximately 70%. This patented technique will meet pesticide residue grade n-Hexane market in China and seek for cooperation globally.