Investigation On Ultra-high Pressure Extraction Technology For Analysis Of Pesticide Residues In Vegetables

Nowadays, food safety is a hot spot in all over the world. As one of the most important food in daily life, issues on pesticide residues in vegetables become global highlights in food safety area. There are increasing poisoning cases caused by pesticide residues superscalar in vegetables every year. Pesticide residues have gradually become a serious threat to people's health and life safety, . and constraints to the export of chinese vegetable. It is a direct and effective way to sample and analysis of pesticide residues prior to market to control pesticide residue superscalar in vegetables.The processes of previous analysis methods on pesticide residues in vegetables are complex, time non-effective, and need professionals to operate. Due to poor stability of samples, sample preparation affected accuracy of the analysis. Thus, near-infrared spectroscopy (NIR) technology based on ultra-high pressure (UHP) pre-treatment, one of detection method on pesticide residues in vegetable, is suggested in this paper.The ultrahigh isostatic hydrostatic pressure extraction (UHPE) is to put the extractible matter in the high-pressure container and extract compound by pressure of 100-1000MPa at room temperature. the course can be accomplished in several minutes. With advantages of short extraction time, high degree of automation, better stability of extracted components.Compared with the traditional detection methods, near-infrared spectroscopy (NIR) has adavantages of no complicated pre-treatment process, good speed ability, convenience for non-professionals to operate. In recent years, infrared spectroscopy was almost constantly studied on detection of pesticide residues at home and abroad.It is the first time that UHPE method is used in the samples pre-treatment and combined with NIR to analyze pesticide residues in vegetables. In accordance with the requirements of detection of NIR, reasonably conditions of extraction are choosed in order to provide appropriate samples for the latter detection. Dimetheoate, one of organophosphorus pesticides used widly in vegetable management, is taken as the first object of investigation. Cabbage is slected as the first detected vegetable sample. The affects of UHPE on the analysis of the dimetheoate residue in cabbage are studied. The effects of UHPE method on analysis of dimetheoate residue in vegetables are validated by gas chromatography-mass spectrometry(GC-MS) for uantitative analysis. Major contents are as follows:1. According to the demand of NIR, based on reference to the technology of ultra-high pressure extraction bio-active ingredients, the extracting process of pesticide residues from vegetables by UHPE (EPPRUHP) is determined. According to EPPRUHP and the detection process of GC-MS, the process of UHPE-GC-MS and its test steps are planned. By analyzing factors of UHPE, main factors of EPPRUHP in vegetables are selected, such as pressure, extraction solvent volume, and pressure time. In according to the request of NIR detection, acetone is selected as the extraction solvent.2. The pre-test is conducted prior to single factor test. To study the impact of the UHP process on the test result of GC-MS detecting dimetheoate, the stability of tested sample and extracting efficiency of UHPE are analysized. Pre-test include three parts:Dimetheoat acetone solution samples processed by different pressures are detected by GC-MS. There is no difference in detected results (retention time and solution concentration) of dimetheoat acetone solution samples processed by UHPE and the dimetheoat acetone solution without UHP treatment. Thus, UHPE does not affect the GC - MS results.Dimetheoat solution processed by different UHP are kept at 8℃for a week and detected by GC-MS. Compared with the solution without UHP treatment, the stability of solution sample processed by 200MPa is the best, whose decrease of concentration is only 3%. Followed by the samples treated by 400MPa and 500MPa, the decrease of concentration are 6.7%. The decrease of concentration of dimetheoat solution without UHP treatment is 15%. The tested results suggest that NHP treatment can improve significantly the stability of dimethoate solution.Cabbage samples with a certain concentration of dimetheoat are extracted by UHP and homogenate respectively, purified, enriched, and detected by GC– MS. The recovery rate of the former is higher than the latter by over 10%. With ultra-high pressure extraction, the stability and recovery rate of cabbage samples is promoted. The program put forwarded here is feasible.3. Affects of different factors under different experimental conditions is analyzed by single-factor test. Experiments are arranged by orthogonal design method. The experiment results is processed by the DPS software. The regression equation of recovery rate is as follows: y=76.7778+2.6833x1+2.1000x2+9.6861×10-15x3+0.0500x4 where: x1 is extraction pressure, MPa; x2 is acetone volume, ml; x3 is interactive factors; x4 is pressure time, min.The optimum UHPE condition is as follows: extraction pressure of 400MPa, extraction solvent volume of 60ml, and pressure time of 4min.4. According to the optimal UHPE condition, the effect of UHPE is verified from three aspects: adds recovery, comparing with different test methods, and verification of sample stability.Verification of adds recovery: adds recovery of sample with three concertration of dimitheoat are 92.3%,91.2%,89.6% respective, relative standard deviation (RSD) are 4.1%,5.6%and 7.8%respetive. Adds recovery is good, RSD is small. Thus, meet the requirements of analysis of pesticide residues.Compared with the other two methods (GB/T5009.20-2003 and NY/T761.1-2004), adds recovery of sample treated by UHPE with three concertration of dimitheoat are higher than GB/T5009.20-2003 by 5.3 %,7.9 % and 8.6 % respective, higher than NY/T761.1-2004 by 1.9%,1.7% and 0.9% respective.Verification of stability of samples with UHPE treatment:samples with a certain cencertration of dimitheoat are divided into five good, placed at 8℃,and detected respectively in place 1 day, 3 days, 5 days, 7 days respectively, every sample concentration decreased respectively by 1%,2.7%,5.4% and 9.1%, sample treated within 3 days does not significantly affect on test results.The NIR analysis model is established on NIR– UHPE. The related coefficient of the model of samples with pressure is 87.14%, while the related coefficient of the sample without pressure is 75.37%. The former is higher by 12% than the latter. The root mean square error of cross-validation (RMSECV) of pressure model is 0.145%, lower than the non-pressure by 0.192%, data volatility is small, derection is better than non-pressure model; in the process of data modeling, the data of pressure samples is more stable than that of non-pressure samples, outliers are less, speed of model is fast. Test results show that UHP processing promote the limit of detection of NIR by raising concentration level from 10-4 to 10-5.Due to time limit, only dimethoate residue in the cabbage is studied in this article. Pesticide residues in vegetables are generally multi-residue. Various pesticide residues in different vegetables should be studied in the future. As a new detection method, near-infrared spectroscopy detection applied in pesticide residues analysis is still in develping. Conjuncted UHPE with previous detection methods– chromatography. According to detection features of Chromatography, factors are analyzed again, sample preparation process can simplify precess of pesticide residue analysis, improve the limit of detection and stability of vegetable samples.