CN103913528B - Quantitative detection method for pyrethriods pesticides in fresh tea - Google Patents
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Abstract
The invention discloses a quantitative detection method for pyrethriods pesticides in fresh tea. The quantitative detection method is characterized by comprising the following steps: ultrasonically extracting a fresh tea sample by an acetonitrile solution containing 1% of acetic acid in percentage by volume, then purifying by using an appropriate amount of mixed filler of PSA (Prostate Specific Antigen), C18 and GCB, carrying out nitrogen blowing to concentrate liquid supernatant to be nearly dry, dissolving with normal hexane and making up to volume, increasing programmed temperature and separating by using an HP-5 quartz capillary column, carrying out GC/muECD, and finally quantifying by using a matrix external standard method. Through confirmation by test, the method is wide in linear range; the technical indexes such as detection sensitivity, accuracy and precision meet the requirements of analysis of residues; the pretreatment operation is simple, convenient and quick; through the method, a reliable manner is provided for analysis and research for detecting the residues of the pyrethriods pesticides in the fresh tea.
Description
Technical field
The present invention relates to the detection method field of persticide residue, be specifically related to the quantitative detecting method of pyrethroid pesticide in a kind of tea fresh leaves, this quantitative detecting method adopts the QuEChERS method improved to extract tea fresh leaves, purify, by vapor-phase chromatography, pyrethroid pesticide is detected again, to reach quick, easy, reliable object.
Background technology
Tealeaves is one of large plant beverage in the world three, because of its uniqueness mouthfeel and there is anticancer, anti-sudden change, favor that scavenging free radicals, the health-care efficacy such as to delay senility more and more are subject to people.China is Ye Shi big export country of Tea Production big country, applying pesticides ensures tea yield, control from the most effective means that disease and pest threatens in its growth course, pyrethroid pesticide (English name: Pyrethroid pesticides) is because of wide spectrum, the preventing and controlling that efficient, cost is low, consumption is widely used in tealeaves disease and pest less.But existing research confirms that this kind of agricultural chemicals can produce toxic action to the nervous system of human body, part kind has carcinogenic, teratogenesis, mutagenesis and certain accumulative, and excessive use is likely accumulated in human body, causes chronic accumulate poisoning.Therefore, be the focal issue that people pay close attention to about residual in tealeaves of pyrethroid pesticide always.
Many countries, particularly European Union and Japan have formulated harsh Pesticide Residue regulation in the world, to limit the maximum residue limit (MRL) of Pesticides in Tea medicine.China standard GB/T 2763-2012 " Pesticide maximum residue limit " defines the MRL of 25 kinds of agricultural chemicals in tealeaves, and " The Ministry of Agriculture of the People's Republic of China, MOA announces No. 199 " defines 21 kinds of agricultural chemicals and forbid or be limited in tealeaves using.European Union has issued new Pesticide Residue Standard andRegulation (EC) No149/2008 on March 1st, 2008, have updated the MRL of Pesticide Residues in Tea, new legislation relates to the existing limit standard of Pesticide Residues in Tea 221, provisional limit standard 171, totally 392, and the agricultural chemicals employing method detection limit of more than 90% is as MRL.Japan formally implements agricultural chemicals " Positive List System " in food on May 29th, 2006, Pesticide Residue standard relevant with tealeaves in this system reaches 251, and the MRL of most of agricultural chemicals requires to be not more than 0.1mg/kg, all then " uniform limit " is performed to the agricultural chemicals not setting limit standard, namely content must not more than 0.01mg/kg, and all adopt " dry tea method " to detect.Which greatly limits the outlet of China's tealeaves, higher requirement be it is also proposed to the detection of Pesticide Residues in Tea simultaneously.
In recent years, the analytical approach about Pesticide Residues in Tea is existing much studies report, but mainly concentrates on on tea, few to the residual research in tea fresh leaves.Tea fresh leaves is as the raw material of Tea Processing, and be the material base determining tea leaf quality, its quality is directly connected to the quality of tea leaf quality.Therefore, persticide residue in direct mensuration tea fresh leaves has important practical significance, and not only can realize the Sources controlling of tealeaves agricultural chemicals, effectively guides peasant correctly to tea place medication, improve and to drink tea security, and agricultural chemicals can be reduced use unreasonably tea garden soil environment.
Contain the interfering materials such as more moisture, pigment, water-soluble ass, Tea Polyphenols because tea fresh leaves likens to tea, more easily cause extraction and cleaning difficulty, therefore the detection method of pyrethrin pesticide in existing mensuration tealeaves, is not suitable for the mensuration of tea fresh leaves matrix.There are some to report about the research work that tea fresh leaves agriculture is residual though domestic, but only relate to the detection of the organo-chlorine pesticide such as benzene hexachloride, D.D.T. (dichloro-diphenyl-trichloroethane) and a few pyrethrin pesticide, report is had no to the detection method research of the 7 kinds of pyrethrin pesticides of gamma cyhalothrin, fenvalerate etc. in tea fresh leaves simultaneously.And in tea fresh leaves residues of pesticides leaching process, existing report mainly uses the methods such as the extraction of traditional mechanical shaking extraction, homogeneous, liquid-liquid extraction, purification means are for different target agricultural chemicals many employings concentrated acid sulfonation methods and column chromatography purification method.These pre-treating methods consume that organic solvent is many, sample throughput is little, be of limited application, complex operation, expend time in, cost is high, for multiclass many residual be not simple or effective method.
Summary of the invention
The invention provides the quantitative detecting method of pyrethroid pesticide in a kind of tea fresh leaves, its object is to solve the detection method length consuming time of pyrethrin pesticide in existing mensuration tealeaves, complex operation, consumption organic solvent mainly with and the reliable and stable not problem of testing result.
For achieving the above object, the technical solution used in the present invention is: the quantitative detecting method of pyrethroid pesticide in a kind of tea fresh leaves, and described quantitative detecting method is made up of two parts:
Part I, sets up the typical curve of the tested pyrethroid pesticide of known gradient concentration respectively by vapor-phase chromatography; The foundation of described typical curve is made up of following steps:
The first step, prepare bare substrate extract, preparation method is made up of following steps:
(1) 5.0g is taken after measured not containing the blank tea fresh leaves sample of tested pyrethroid pesticide, be placed in 50mL centrifuge tube, the acetonitrile solution that 10mL is 1% acetic acid containing volume fraction is added again in centrifuge tube, mixing, ultrasonic extraction 10 ~ 15min, then add 2g anhydrous sodium acetate and 1g anhydrous magnesium sulfate, vortex 1.5min ~ 2.5min, then, with the centrifugal 3.5min ~ 4.5min of the rotating speed of 9000r/min, get supernatant and be bare substrate extract to be clean;
(2) a 10mL centrifuge tube is separately got, add 0.15g C18,0.15g N-propyl group ethylenediamine, 0.12g ketjenblack EC and 0.3g anhydrous magnesium sulfate, add bare substrate extract to be clean described in 4mL, vortex 1.5min ~ 2.5min, with the centrifugal 4.5min ~ 5.5min of the rotating speed of 9000r/min; Pipette 2.0mL supernatant after centrifugal in scale test tube, then supernatant nitrogen is slowly blown to 50 ~ 70 μ L under 50 ~ 60 DEG C of water-baths; In supernatant, add normal hexane again to be settled to 1.0mL, after crossing organic system filter membrane, obtain the bare substrate extract of pyrethroid pesticide;
Second step, with the matrix hybrid standard working solution of the bare substrate extract obtained in the described first step for solvent preparation pyrethroid pesticide, wherein, described pyrethroid pesticide refers to Fenpropathrin, gamma cyhalothrin, Permethrin, cyfloxylate, cypermethrin, fenvalerate, decis; In the matrix hybrid standard working solution of described pyrethroid pesticide, the concentration range of each pyrethroid pesticide is:
3rd step, with chromatographic peak retention time and the chromatographic peak area of each pesticide composition in the matrix hybrid standard working solution of pyrethroid pesticide described in gas chromatography determination, qualitative with chromatographic peak retention time, then being horizontal ordinate with mass concentration, take chromatographic peak area as the typical curve that ordinate draws out pyrethroid pesticide;
Wherein, the chromatographic condition measuring pyrethroid pesticide is:
Chromatographic column: model is the capillary chromatographic column of HP-5, specification is 30m × 0.32mm × 0.25 μm; Sample size: 1.0 μ L, Splitless injecting samples; Injector temperature: 220 DEG C, dottle pin purges 3mL/min; Column temperature: initial temperature 80 DEG C, keep 0.3min, 30 DEG C/min rises to 180 DEG C, and keep 5min, 20 DEG C/min rises to 260 DEG C, keeps 23min: carrier gas: high pure nitrogen, purity >=99.999%; Constant current mode, flow velocity 1mL/min; Detecting device: micro-pond electron capture detector; Detector temperature: 300 DEG C; Make-up gas: high pure nitrogen, 60mL/min;
Part II, measure 7 kinds of pyrethroid pesticide residual quantities in Part I described in tea fresh leaves sample, quantitative detecting method comprises the following steps:
The first step, extracts tea fresh leaves sample;
Take the tea fresh leaves sample pulverized, be placed in 50mL centrifuge tube, then to add containing volume fraction be the acetonitrile solution of 1% acetic acid, wherein, the input ratio of described tea fresh leaves sample and described acetonitrile solution, for drop into 1mL acetonitrile solution in every 0.5g tea fresh leaves sample, mixes, ultrasonic extraction 10 ~ 15min; Add anhydrous sodium acetate and anhydrous magnesium sulfate again, wherein, the mass ratio of described tea fresh leaves sample, anhydrous sodium acetate and anhydrous magnesium sulfate three is 5:2:1, vortex 1.5min ~ 2.5min, with the centrifugal 3.5min ~ 4.5min of the rotating speed of 9000r/min, get supernatant and be tea fresh leaves sample extracting solution to be clean;
Second step, purifies described tea fresh leaves sample extracting solution to be clean;
Separately get a 10mL centrifuge tube, add C18, N-propyl group ethylenediamine, ketjenblack EC and anhydrous magnesium sulfate, add described tea fresh leaves sample extracting solution to be clean, wherein, C18, N-propyl group ethylenediamine dropped into, ketjenblack EC and the content of anhydrous magnesium sulfate in tea fresh leaves sample extracting solution to be clean are respectively 37.5mg/mL, 37.5mg/mL, 30mg/mL and 75mg/mL, vortex 1.5min ~ 2.5min, with the centrifugal 4.5min ~ 5.5min of the rotating speed of 9000r/min; Pipette 2.0mL supernatant after centrifugal in scale test tube, supernatant nitrogen is slowly blown to 50 ~ 70 μ L under 50 ~ 60 DEG C of water-baths; In supernatant, adding normal hexane again to be settled to 1.0mL, after crossing organic system filter membrane, obtaining for measuring the residual tea fresh leaves sample extraction scavenging solution of pyrethroid pesticide;
3rd step, remain with the pyrethroid pesticide in tea fresh leaves sample extraction scavenging solution described in gas chromatography determination, record chromatographic peak retention time and chromatographic peak area, after qualitative by chromatographic peak retention time, the typical curve of the pyrethroid pesticide that the chromatographic peak area detect described tea fresh leaves sample extraction scavenging solution and described Part I obtain compares, and obtains the measured value of the often kind of pyrethroid pesticide contained in described tea fresh leaves sample extraction scavenging solution; Again described measured value is brought in quantitative computing formula, finally obtains pyrethroid pesticide residual quantity to be measured in tea fresh leaves sample;
Quantitative computing formula: ω=(ρ × v × f)/m, in formula: ω is pyrethroid pesticide residual quantity to be measured in sample, and unit is mg/kg; ρ is measured value, and unit is mg/L; M is the sample size taken, and unit is g; V is constant volume, and unit is mL; F is extension rate;
Wherein, the chromatographic condition measuring the pyrethroid pesticide in the chromatographic condition of the pyrethroid pesticide in described tea fresh leaves sample extraction scavenging solution and the 3rd step of described Part I is identical.
Related content in technique scheme is explained as follows:
1, in such scheme, the standard reserving solution mass concentration of these 7 kinds of agricultural chemicals of described Fenpropathrin, gamma cyhalothrin, Permethrin, cyfloxylate, cypermethrin, fenvalerate, decis is 1000mg/L, is purchased from Inst. of Environment Protection & Scientific Research Monitor, Ministry of Agric;
Normal hexane is HPLC level, and manufacturer is Oceanpak company of Sweden; N-propyl group ethylenediamine (English abbreviation is PSA), particle diameter is 40 ~ 60 μm, and manufacturer is Agela Technologies company of the U.S.; Ketjenblack EC (English abbreviation is GCB), particle diameter 120 ~ 400 order, manufacturer is Agela Technologies company of the U.S.; C18, aperture 6nm, granularity 40 ~ 60 μm, manufacturer is Sepax Technologies company of the U.S.; Acetonitrile, acetic acid, anhydrous sodium acetate, anhydrous magnesium sulfate, all need at 620 DEG C of calcination 4h, and be analysis pure, manufacturer is Shanghai Chemical Reagent Co., Ltd., Sinopharm Group; Experimental water is ultrapure water (18.4M Ω).
2, in such scheme, before the matrix hybrid standard working solution of preparation pyrethroid pesticide, first prepare pyrethroid pesticide hybrid standard storing solution, pestsides synthesis standard reserving solution prepares to be placed in 4 DEG C of refrigerators and preserves, during use with bare substrate extract for solvent is mixed with the agricultural chemicals matrix hybrid standard working solution of debita spissitudo;
Wherein, the compound method of pyrethroid pesticide hybrid standard storing solution is: 7 kinds of pyrethroid pesticide standard reserving solution concentration are 1000mg/L, get 1mL respectively and be placed in 5mL volumetric flask, constant volume is diluted with normal hexane, be mixed with the list mark solution that concentration is 200mg/L, preserve in-20 DEG C of lucifuge sealings.According to the response of each agricultural chemicals on μ ECD detecting device, single mark solution gamma cyhalothrin gets 0.1mL, and Fenpropathrin, cyfloxylate respectively get 0.25mL, and all the other pyrethroid pesticide list mark solution respectively get 0.5mL, be placed in 10mL volumetric flask, use normal hexane constant volume.In 7 kinds of pyrethroid pesticide hybrid standard storing solutions: gamma cyhalothrin concentration is 2mg/L, Fenpropathrin, cyfloxylate concentration are respectively 5mg/L, and Permethrin, cypermethrin, fenvalerate, decis concentration are respectively 10mg/L.
3, in such scheme, gas chromatography determination 7 kinds of pyrethroid pesticides are used, qualitative with retention time, peak area quantified by external standard method; For the pyrethroid pesticide containing more than 2 and 2 isomeride, calculate the measured value of this kind of pyrethroid pesticide with the peak area sum of Isomers.
4, in such scheme, preferably scheme be in the first step of described Part I and the first step of described Part II the condition of ultrasonic extraction be ultrasonic power between 80W ~ 100W, ultrasonic temperature is at 20 ~ 30 DEG C.
Principle of work of the present invention and beneficial effect are: 2003, the people such as the Anastassiades M at United States Department of Agriculture's Agricultural Research Service center propose one and are called as " QuEChERS " (Quick, Easy, Cheap, Effective, Rugged and Safe) novel agrochemical many residual sample preparation method.The method dirigibility is strong, applied range, can per sample with the feature of target analytes, select applicable Extraction solvent and purification filler, there is the advantages such as quick, easy, efficient, safe, be successfully applied at present the analysis and research of hundreds of residues of pesticides in food, but application report in tea fresh leaves is less." QuEChERS " method recommendation gas chromatography-mass spectrography (GC-MS) or HPLC-MS (HPLC-MS) carry out follow-up detection analysis, although GC-MS, HPLC-MS not only can be qualitative but also can be quantitative, the trend of pesticide residue analysis method development, but instrument price is expensive, require high to operative technique, thus limit its widespread use.The analytical instrument that gas chromatograph (GC) is commonly used as laboratory, it is moderate, and applied range, is equipped with the detecting device that specificity is stronger, can obtain good selectivity and lower detectability, be that testing agency of current vast basic unit applies one of the most general detection means.
Detect department for current basic unit and mostly there is no expensive gas chromatograph-mass spectrometer, only has common gas chromatograph, the deficiency of pre-treatment complex operation, the present invention adopts " QuEChERS " method of improvement to extract tea fresh leaves, purify, adopt micro-pond electron capture detector (English name GC/ μ ECD) to detect organic phosphates and pyrethrin pesticide respectively, to establish in tea fresh leaves 7 kinds pyrethroid pesticide remained fast and convenient, save time reliable analytical approach.
The ultrasonic extraction of acetonitrile solution containing volume fraction being 1% acetic acid of tea fresh leaves sample, again with appropriate PSA, C18 and GCB mixed fillers purification, supernatant liquid nitrogen blows and is concentrated near doing, use n-hexane dissolution constant volume, HP-5 quartz capillary column and programmed temperature is separated, GC/ μ ECD detects, and finally uses matrix quantified by external standard method.By test confirmation, the method range of linearity is wide, and the technical indicators such as detection sensitivity, accuracy and precision all meet the requirement of retention analysis, for analysis and research pyrethroid pesticide remained in tea fresh leaves provide reliable means.
Compare with national standard method with existing Pesticide Residues in Tea detection method, pre-treatment of the present invention is simple to operate, and extraction and cleanup only needs a few step to complete, and adopting ultrasonic method when extracting, result is stablized, reproducible, facilitate the process of follow-up batch sample, practicality is stronger; Purification process is avoided using decontaminating column and a large amount of solvent elution, and agricultural chemicals loss is few, and the recovery is high, and the time simultaneously expended and organic solvent greatly reduce, and save testing cost, environmental pollution is little, also safer to operator.Detect the gas chromatograph (being furnished with μ ECD) analyzed and adopt laboratory conventional, moderate, Operation and Maintenance is simple, and technical requirement is strict not as application of gas chromatorgraphy/mass, is more suitable for applying in testing agency of vast basic unit.Quantivative approach adopts the calibration of matrix matching standard solution quantitatively, and reduce the matrix effect of agricultural chemicals to be measured, measurement result is more accurate.Quantitative detecting method of the present invention all meets the requirement of Multi-residue analysis on the indices such as accuracy, precision, sensitivity, for tea quality controls monitoring method and the foundation of the science that provides, has certain popularizing value.
Accompanying drawing explanation
Accompanying drawing 1 is the matrix hybrid standard working solution chromatogram of 7 kinds of pyrethroid pesticides in the embodiment of the present invention;
Accompanying drawing 2 is 7 kinds of pyrethroid pesticide matrix effect figure in tea fresh leaves in the embodiment of the present invention;
Accompanying drawing 3 is add 7 kinds of pyrethroid pesticide standard colors spectrograms in the tea fresh leaves measured for the recovery and precision in the embodiment of the present invention.
Embodiment
Below in conjunction with drawings and Examples, the invention will be further described:
Embodiment: the quantitative detecting method of pyrethroid pesticide in a kind of tea fresh leaves
Take from Suzhou City's certain tea plantation local for examination tea fresh leaves, smash mixing through comminutor, load clean container, be placed in-20 DEG C of refrigerators and preserve, for subsequent use.Described quantitative detecting method is made up of two parts:
Part I, sets up the typical curve of the tested pyrethroid pesticide of known gradient concentration respectively by vapor-phase chromatography; The foundation of described typical curve is made up of following steps:
The first step, prepare bare substrate extract, preparation method is made up of following steps:
(1) 5.0g is taken after measured not containing the blank tea fresh leaves sample of tested pyrethroid pesticide, be placed in 50mL centrifuge tube, the acetonitrile solution that 10mL is 1% acetic acid containing volume fraction is added again in centrifuge tube, mixing, ultrasonic extraction 10 ~ 15min, ultrasonic power is between 80W ~ 100W, ultrasonic temperature is at 20 ~ 30 DEG C, add 2g anhydrous sodium acetate and 1g anhydrous magnesium sulfate again, vortex 2min, then, with the centrifugal 4min of the rotating speed of 9000r/min, get supernatant and be bare substrate extract to be clean;
(2) a 10mL centrifuge tube is separately got, add 0.15g C18,0.15g N-propyl group ethylenediamine, 0.12g ketjenblack EC and 0.3g anhydrous magnesium sulfate, add bare substrate extract to be clean described in 4mL, vortex 2min, with the centrifugal 5min of the rotating speed of 9000r/min; Pipette 2.0mL supernatant after centrifugal in scale test tube, then supernatant nitrogen is slowly blown to 50 ~ 70 μ L under 50 ~ 60 DEG C of water-baths; In supernatant, add normal hexane again to be settled to 1.0mL, after crossing 0.22 μm of organic system filter membrane, obtain the bare substrate extract of pyrethroid pesticide;
Second step, with the matrix hybrid standard working solution of the bare substrate extract obtained in the described first step for solvent preparation pyrethroid pesticide, wherein, described pyrethroid pesticide refers to Fenpropathrin, gamma cyhalothrin, Permethrin, cyfloxylate, cypermethrin, fenvalerate, decis; In the matrix hybrid standard working solution of described pyrethroid pesticide, the concentration range of each pyrethroid pesticide is:
3rd step, with chromatographic peak retention time and the chromatographic peak area of each pesticide composition in the matrix hybrid standard working solution of pyrethroid pesticide described in gas chromatography determination, qualitative with chromatographic peak retention time, then being horizontal ordinate with mass concentration, take chromatographic peak area as the typical curve that ordinate draws out pyrethroid pesticide;
Wherein, the chromatographic condition measuring pyrethroid pesticide is:
Chromatographic column: model is the capillary chromatographic column of HP-5, specification is 30m × 0.32mm × 0.25 μm; Sample size: 1.0 μ L, Splitless injecting samples; Injector temperature: 220 DEG C, dottle pin purges 3mL/min; Column temperature: initial temperature 80 DEG C, keep 0.3min, 30 DEG C/min rises to 180 DEG C, and keep 5min, 20 DEG C/min rises to 260 DEG C, keeps 23min: carrier gas: high pure nitrogen, purity >=99.999%; Constant current mode, flow velocity 1mL/min; Detecting device: micro-pond electron capture detector; Detector temperature: 300 DEG C; Make-up gas: high pure nitrogen, 60mL/min;
Part II, measure 7 kinds of pyrethroid pesticide residual quantities in Part I described in tea fresh leaves sample, quantitative detecting method comprises the following steps:
The first step, extracts tea fresh leaves sample;
Take the tea fresh leaves sample 5.0g pulverized, be placed in 50mL teflon centrifuge tube, add the acetonitrile solution of 10mL containing 1% acetic acid, mixing, ultrasonic extraction 10min, ultrasonic power is between 80W ~ 100W, ultrasonic temperature, at 20 ~ 30 DEG C, adds 2g anhydrous sodium acetate and 1g anhydrous magnesium sulfate, vortex 2min, with the centrifugal 4min of 9000r/min rotating speed, get supernatant and be tea fresh leaves sample extracting solution to be clean;
Second step, purifies described tea fresh leaves sample extracting solution to be clean;
Separately get a 10mL teflon centrifuge tube, add 0.15g C18,0.15g PSA, 0.12g GCB and 0.3g anhydrous magnesium sulfate, add the above-mentioned extract to be clean of 4mL, vortex 2min, with the centrifugal 5min of 9000r/min rotating speed; Pipette 2.0mL supernatant after centrifugal in scale test tube, supernatant nitrogen is slowly blown to 50 ~ 70 μ L under 50 ~ 60 DEG C of water-baths; In supernatant, adding normal hexane again to be settled to 1.0mL, after crossing 0.22 μm of organic system filter membrane, obtaining for measuring the residual tea fresh leaves sample extraction scavenging solution of pyrethroid pesticide;
3rd step, remain with the pyrethroid pesticide in tea fresh leaves sample extraction scavenging solution described in gas chromatography determination, record chromatographic peak retention time and chromatographic peak area, after qualitative by chromatographic peak retention time, the typical curve of the pyrethroid pesticide that the chromatographic peak area detect described tea fresh leaves sample extraction scavenging solution and described Part I obtain compares, and obtains the measured value of the often kind of pyrethroid pesticide contained in described tea fresh leaves sample extraction scavenging solution; Again described measured value is brought in quantitative computing formula, finally obtains pyrethroid pesticide residual quantity to be measured in tea fresh leaves sample;
Quantitative computing formula: ω=(ρ × v × f)/m, in formula: ω is pyrethroid pesticide residual quantity to be measured in sample, and unit is mg/kg; ρ is measured value, and unit is mg/L; M is the sample size taken, and unit is g; V is constant volume, and unit is mL; F is extension rate;
Wherein, the chromatographic condition measuring the pyrethroid pesticide in the chromatographic condition of the pyrethroid pesticide in described tea fresh leaves sample extraction scavenging solution and the 3rd step of described Part I is identical.
In above embodiment, instrument and equipment used has: 7890A gas chromatograph, is furnished with 63Ni micro-pond electron capture detector (μ ECD), 7693 automatic samplers and Chemstation chromatographic work station (Agilent company of the U.S.); KQ-500DE numerical control supersonic instrument (Kunshan Ultrasonic Instruments Co., Ltd.); TG16-WS table model high speed centrifuge (Hunan Xiang Yi Laboratory Instruments development corporation, Ltd.); HSC-24B Nitrogen evaporator (Tianjin Hengao Technology Development Co., Ltd.); K600 type comminutor (German Bo Lang company); VM-10 turbula shaker (Daihan Scientific company of Korea S); SX2-4-10 muffle furnace (Shanghai leap Medical Devices Co., Ltd.); EXCEED-AD-24 type ultrapure water machine (Chengdu Tangshi Kangning Science and Technology Development Co., Ltd).
Medicine used and reagent: Fenpropathrin, gamma cyhalothrin, Permethrin, cyfloxylate, cypermethrin, fenvalerate, decis, mass concentration is 1000mg/L, is purchased from Inst. of Environment Protection & Scientific Research Monitor, Ministry of Agric; Normal hexane, HPLC level (Oceanpak company of Sweden); N-propyl group ethylenediamine (PSA), 40 ~ 60 μm (Agela Technologies company of the U.S.); Ketjenblack EC (GCB), 120 ~ 400mesh (Agela Technologies company of the U.S.); C18, aperture 6nm, granularity 40 ~ 60 μm (Sepax Technologies company of the U.S.); Acetonitrile, acetic acid, anhydrous sodium acetate, anhydrous magnesium sulfate (620 DEG C of calcination 4h) are analyzes pure (Shanghai Chemical Reagent Co., Ltd., Sinopharm Group); Experimental water is ultrapure water (18.4M Ω).
The preparation of hybrid standard storing solution:
The compound method of pyrethroid pesticide hybrid standard storing solution is: 7 kinds of pyrethroid pesticide standard reserving solution concentration are 1000mg/L, get 1mL respectively and be placed in 5mL volumetric flask, constant volume is diluted with normal hexane, be mixed with the list mark solution that concentration is 200mg/L, preserve in-20 DEG C of lucifuge sealings.According to the response of each agricultural chemicals on μ ECD detecting device, single mark solution gamma cyhalothrin gets 0.1mL, and Fenpropathrin, cyfloxylate respectively get 0.25mL, and all the other pyrethroid pesticide list mark solution respectively get 0.5mL, be placed in 10mL volumetric flask, use normal hexane constant volume.In 7 kinds of pyrethroid pesticide hybrid standard storing solutions: gamma cyhalothrin concentration is 2mg/L, Fenpropathrin, cyfloxylate concentration are respectively 5mg/L, and Permethrin, cypermethrin, fenvalerate, decis concentration are respectively 10mg/L.
Above-mentioned pestsides synthesis standard reserving solution is all placed in 4 DEG C of refrigerators and preserves, and during use, bare substrate extract is the matrix hybrid standard working fluid that solvent is mixed with debita spissitudo respectively.
The test findings of the present embodiment:
1, the gas chromatography testing agricultural chemicals is separated
Adopt above-mentioned GC conditions to measure the matrix hybrid standard working solution of 7 kinds of pyrethroid pesticides, standard specimen separating effect is better, and peak shape is symmetrical, baseline stability, illustrates that instrument condition is applicable to.Under this chromatographic condition, each agricultural chemicals retention time of pyrethroid is about Fenpropathrin 16.497min, gamma cyhalothrin 17.865min, Permethrin 19.400min, 19.693min respectively; Cyfloxylate 21.499min; Cypermethrin 21.834min, 22.130min, 22.501min; Fenvalerate 25.183min, 26.086min; (shown in accompanying drawing 1, in accompanying drawing 1, label 1 is Fenpropathrin to decis 28.760min, and concentration is 0.1mg/L, label 2 is gamma cyhalothrin, and concentration is 0.04mg/L, and label 3 is Permethrin, concentration is 0.2mg/L, and label 4 is cyfloxylate, and concentration is 0.1mg/L, label 5 is cypermethrin, concentration is 0.2mg/L, and label 6 is fenvalerate, and concentration is 0.2mg/L, label 7 is decis, and concentration is 0.2mg/L).
2, matrix effect
Matrix effect refers to that other matrix components in sample except determinand is on the impact of determinand measured value.Matrix effect is different from the situation of different sample and determinand.In gas chromatographic analysis, most of agricultural chemicals shows matrix enhancement effect in various degree, namely the response of the agricultural chemicals of same concentrations in matrix is than its height in neat solvent, the existence being commonly considered as sample mesostroma composition decreases the chance of chromatographic system avtive spot and determinand molecular action, and determinand detection signal is strengthened.The method eliminating matrix effect impact has the application of matrix matching standard solution method, standard addition method, multiple purifying method, analysis protectant and statistical method correction etc.Adopt the ratio of the response of determinand in matrix hybrid standard working solution and neat solvent mixed standard solution to represent matrix effect in the present invention, ratio, more close to 1, shows that matrix effect is less.
Test findings shows, the 7 kinds of agricultural chemical compounds analyzed all exist matrix enhancement effect in various degree, and wherein the matrix enhancement effect of Fenpropathrin, Permethrin, decis is not obvious, and the matrix effect of other 4 kinds of agricultural chemicals is comparatively strong, as shown in Figure 2.So the present invention is when using quantified by external standard method, is solvent preparation standard specimen with bare substrate extract, to eliminate matrix interference, reduces error.(in fig 2, label 1 represent containing Fenpropathrin matrix hybrid standard working solution and neat solvent mixed standard solution, concentration is 0.1mg/kg; Label 2 is the matrix hybrid standard working solution and the neat solvent mixed standard solution that contain gamma cyhalothrin, and concentration is 0.04mg/kg; In like manner, label 3 represents that concentration is 0.2mg/kg containing Permethrin; Label 4 represents that concentration is 0.1mg/kg containing cyfloxylate; Label 5 represents that concentration is 0.2mg/kg containing cypermethrin; Label 6 is fenvalerate, and concentration is 0.2mg/kg; Label 7 is decis, and concentration is 0.2mg/kg; A
mrepresent the response of each agricultural chemicals in matrix matching mixed standard solution; A
srepresent the response of each agricultural chemicals in neat solvent mixed standard solution).
3, the range of linearity of method, regression equation and detection limit
Preparation mass concentration is 7 kinds of pyrethroid pesticide matrix mixed standard solutions of 0.004 ~ 2.0mg/L, measure by the chromatographic condition of the pyrethroid pesticide in the 3rd step of described Part I, (represent with ρ with mass concentration, unit is mg/L) be horizontal ordinate, with peak area (y) for ordinate drawing standard curve, 7 kinds of agricultural chemicals are good in its concentration range internal linear, related coefficient (r
2) be all greater than 0.996, be shown in Table 1.Detection limit (LOD) and the quantitative limit (LOQ) of each agricultural chemicals is calculated respectively with 3 times of noise signal in minimum Pitch-based sphere chromatogram and 10 times.As calculated, the LOD of 7 kinds of pyrethroid pesticides is between 0.0017 ~ 0.013mg/kg, and LOQ is between 0.0056 ~ 0.043mg/kg.
Table 1 is for the examination range of linearity of agricultural chemicals, regression equation, related coefficient, detection limit and quantitative limit
4, the recovery of method and precision
Blank sample mark-on method is adopted to carry out the method recovery and precision mensuration.Take 5.0g after measured not containing the some parts of blank tea fresh leaves sample for examination agricultural chemicals, add the pestsides synthesis standard working solution of 3 kinds of variable concentrations levels respectively, the Pitch-based sphere of pyrethroid pesticide is 0.01 ~ 0.5mg/kg, the parallel 3 increment product of each concentration level, after vortex mixing, standing 1h makes standard solution fully be absorbed by sample, carries out sample pre-treatments and chromatographic condition mensuration according to described Part II.Adopt matrix quantified by external standard method, calculate average recovery rate and the relative standard deviation (i.e. RSD) thereof of each agricultural chemicals, ginseng is shown in Table 2, and sample mark-on chromatogram is see accompanying drawing 3.
As shown in Table 2, in tea fresh leaves, the average recovery rate of pyrethroid pesticide is 78.3% ~ 100.2%, RSD (n=3) is 1.3% ~ 9.9%, and illustration method has good accuracy and repeatability.
Table 27 kind reclaims result (n=3) for the interpolation of examination agricultural chemicals in tea fresh leaves
Wherein, in accompanying drawing 3, label 1 is Fenpropathrin, and concentration is 0.1mg/L, label 2 is gamma cyhalothrin, and concentration is 0.04mg/L, and label 3 is Permethrin, concentration is 0.2mg/L, and label 4 is cyfloxylate, and concentration is 0.1mg/L, label 5 is cypermethrin, concentration is 0.2mg/L, and label 6 is fenvalerate, and concentration is 0.2mg/L, label 7 is decis, and concentration is 0.2mg/L.
5, actual sample analysis
Adopt this method to the tea fresh leaves sample taking from Suzhou certain tea plantation local totally 16 parts carried out 7 kinds of pyrethroid pesticide residue detection, wherein 1 part detects effective cypermethrin and cypermethrin, and content is respectively 0.248mg/kg and 0.0607mg/kg; 1 part detects gamma cyhalothrin, and content is 0.0235mg/kg; 1 part detects decis, and content is 0.0431mg/kg.Result of study shows, this method can be used for the detection that in tea fresh leaves, 7 kinds of pyrethroid pesticides are residual.
Above-described embodiment, only for technical conceive of the present invention and feature are described, its object is to person skilled in the art can be understood content of the present invention and implement according to this, can not limit the scope of the invention with this.All equivalences done according to Spirit Essence of the present invention change or modify, and all should be encompassed within protection scope of the present invention.
Claims (2)
1. the quantitative detecting method of pyrethroid pesticide in tea fresh leaves, is characterized in that: described quantitative detecting method is made up of two parts:
Part I, sets up the typical curve of the tested pyrethroid pesticide of known gradient concentration respectively by vapor-phase chromatography; The foundation of described typical curve is made up of following steps:
The first step, prepare bare substrate extract, preparation method is made up of following steps:
(1) 5.0 g are taken after measured not containing the blank tea fresh leaves sample of tested pyrethroid pesticide, be placed in 50 mL centrifuge tubes, the acetonitrile solution that 10 mL are 1% acetic acid containing volume fraction is added again in centrifuge tube, mixing, ultrasonic extraction 10 ~ 15 min, then add 2 g anhydrous sodium acetates and 1 g anhydrous magnesium sulfate, vortex 1.5min ~ 2.5min, then, with the centrifugal 3.5min ~ 4.5min of the rotating speed of 9000 r/min, get supernatant and be bare substrate extract to be clean;
(2) 10 mL centrifuge tubes are separately got, add 0.15g C18,0.15g N-propyl group ethylenediamine, 0.12 g ketjenblack EC and 0.3g anhydrous magnesium sulfate, add bare substrate extract to be clean described in 4mL, vortex 1.5min ~ 2.5min, with the centrifugal 4.5min ~ 5.5min of the rotating speed of 9000 r/min; Pipette 2.0 mL supernatants after centrifugal in scale test tube, then supernatant nitrogen is slowly blown to 50 ~ 70 μ L under 50 ~ 60 DEG C of water-baths; In supernatant, add normal hexane again to be settled to 1.0 mL, after crossing organic system filter membrane, obtain the bare substrate extract of pyrethroid pesticide;
Second step, with the matrix hybrid standard working solution of the bare substrate extract obtained in the described first step for solvent preparation pyrethroid pesticide, wherein, described pyrethroid pesticide refers to Fenpropathrin, gamma cyhalothrin, Permethrin, cyfloxylate, cypermethrin, fenvalerate, decis; In the matrix hybrid standard working solution of described pyrethroid pesticide, the concentration range of each pyrethroid pesticide is:
3rd step, with chromatographic peak retention time and the chromatographic peak area of each pesticide composition in the matrix hybrid standard working solution of pyrethroid pesticide described in gas chromatography determination, qualitative with chromatographic peak retention time, then being horizontal ordinate with mass concentration, take chromatographic peak area as the typical curve that ordinate draws out pyrethroid pesticide;
Wherein, the chromatographic condition measuring pyrethroid pesticide is:
Chromatographic column: model is the capillary chromatographic column of HP-5, specification is 30m × 0.32mm × 0.25 μm; Sample size: 1.0 μ L, Splitless injecting samples; Injector temperature: 220 DEG C, dottle pin purges 3mL/min; Column temperature: initial temperature 80 DEG C, keep 0.3min, 30 DEG C/min rises to 180 DEG C, and keep 5min, 20 DEG C/min rises to 260 DEG C, keeps 23min: carrier gas: high pure nitrogen, purity >=99.999%; Constant current mode, flow velocity 1mL/min; Detecting device: micro-pond electron capture detector; Detector temperature: 300 DEG C; Make-up gas: high pure nitrogen, 60mL/min;
Part II, measure 7 kinds of pyrethroid pesticide residual quantities in Part I described in tea fresh leaves sample, quantitative detecting method comprises the following steps:
The first step, extracts tea fresh leaves sample;
Take the tea fresh leaves sample pulverized, be placed in 50 mL centrifuge tubes, adding containing volume fraction is the acetonitrile solution of 1% acetic acid again, wherein, the input ratio of described tea fresh leaves sample and described acetonitrile solution for drop into 1mL acetonitrile solution in every 0.5g tea fresh leaves sample, mixing, ultrasonic extraction 10 ~ 15 min; Add anhydrous sodium acetate and anhydrous magnesium sulfate again, wherein, the mass ratio of described tea fresh leaves sample, anhydrous sodium acetate and anhydrous magnesium sulfate three is 5:2:1, vortex 1.5min ~ 2.5min, with the centrifugal 3.5min ~ 4.5min of the rotating speed of 9000 r/min, get supernatant and be tea fresh leaves sample extracting solution to be clean;
Second step, purifies described tea fresh leaves sample extracting solution to be clean;
Separately get 10 mL centrifuge tubes, add C18, N-propyl group ethylenediamine, ketjenblack EC and anhydrous magnesium sulfate, add described tea fresh leaves sample extracting solution to be clean, wherein, C18, N-propyl group ethylenediamine dropped into, ketjenblack EC and the content of anhydrous magnesium sulfate in tea fresh leaves sample extracting solution to be clean are respectively 37.5mg/mL, 37.5mg/mL, 30 mg/mL and 75mg/mL, vortex 1.5min ~ 2.5min, with the centrifugal 4.5min ~ 5.5min of the rotating speed of 9000 r/min; Pipette 2.0mL supernatant after centrifugal in scale test tube, supernatant nitrogen is slowly blown to 50 ~ 70 μ L under 50 ~ 60 DEG C of water-baths; In supernatant, adding normal hexane again to be settled to 1.0mL, after crossing organic system filter membrane, obtaining for measuring the residual tea fresh leaves sample extraction scavenging solution of pyrethroid pesticide;
3rd step, remain with the pyrethroid pesticide in tea fresh leaves sample extraction scavenging solution described in gas chromatography determination, record chromatographic peak retention time and chromatographic peak area, after qualitative by chromatographic peak retention time, the typical curve of the pyrethroid pesticide that the chromatographic peak area detect described tea fresh leaves sample extraction scavenging solution and described Part I obtain compares, and obtains the measured value of the often kind of pyrethroid pesticide contained in described tea fresh leaves sample extraction scavenging solution; Again described measured value is brought in quantitative computing formula, finally obtains pyrethroid pesticide residual quantity to be measured in tea fresh leaves sample;
Quantitative computing formula: ω=(ρ × v × f)/m, in formula: ω is pyrethroid pesticide residual quantity to be measured in sample, and unit is mg/kg; ρ is measured value, and unit is mg/L; M is the sample size taken, and unit is g; V is constant volume, and unit is mL; F is extension rate;
Wherein, the chromatographic condition measuring the pyrethroid pesticide in the chromatographic condition of the pyrethroid pesticide in described tea fresh leaves sample extraction scavenging solution and the 3rd step of described Part I is identical.
2. the quantitative detecting method of pyrethroid pesticide in a kind of tea fresh leaves according to claim 1, it is characterized in that: in the first step of described Part I and the first step of described Part II the condition of ultrasonic extraction be ultrasonic power between 80W ~ 100W, ultrasonic temperature is at 20 ~ 30 DEG C.
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