CN105929016A - Value determination method for selenium content of quality control sample of tobacco leaf - Google Patents

Value determination method for selenium content of quality control sample of tobacco leaf Download PDF

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Publication number
CN105929016A
CN105929016A CN201610255547.5A CN201610255547A CN105929016A CN 105929016 A CN105929016 A CN 105929016A CN 201610255547 A CN201610255547 A CN 201610255547A CN 105929016 A CN105929016 A CN 105929016A
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quality
control sample
nicotiana tabacum
solution
content
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朱书秀
斯文
林垦
陆明华
许高燕
洪梨梨
潘力
陆扬
苏燕
陈晓水
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China Tobacco Zhejiang Industrial Co Ltd
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China Tobacco Zhejiang Industrial Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
    • G01N27/64—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using wave or particle radiation to ionise a gas, e.g. in an ionisation chamber
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/44—Sample treatment involving radiation, e.g. heat

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Abstract

The invention discloses a value determination method for the selenium content of a quality control sample of a tobacco leaf. The value determination method comprises the following steps: step (1) separately preparing a quality control tobacco leaf sample solution, a blank solution and a standard solution; step (2) carrying out tuning on ICP-MS by using a dynamic reaction tank mode, then determining a standard solution and drafting a standard work curve; step (3) determining the blank solution under testing conditions mentioned in step (2), and then determining selenium content of the quality control tobacco leaf sample solution many times; and step (4) carrying out uniformity and stability examination on each measured value of the quality control tobacco leaf sample solution, and after examination results are qualified, calculating the mean value of the measured values so as to obtain the selenium content of the quality control sample of the tobacco leaf. The method provided by the invention has good applicability, operability and uniformity and high stability, can scientifically and effectively monitor analysis process and ensures accuracy of determination results.

Description

A kind of valued methods of Nicotiana tabacum L. quality-control sample Se content
Technical field
The invention belongs to the physical and chemical inspection technical field of Nicotiana tabacum L., relate generally to the trace element determination techniques field of Nicotiana tabacum L., The specifically valued methods of a kind of Nicotiana tabacum L. quality-control sample Se content.
Background technology
Selenium is the trace element of needed by human, is mainly used in participating in the synthesis of enzyme, has anti-lipid peroxidation, removes and live Change oxygen-derived free radicals function, can play anticancer, detoxify, protect the liver, protect cell membrane and improve body immunity physiological function.But with Time, selenium element has duality, and picked-up too much can be diseases induced, and serious even can cause selenosis.From toxicology, no Having different toxicity with the selenium of form, inorganic states selenium toxicity is relatively strong, and biological activity and the utilization rate of Organic Selenium are higher.
The raising day by day to smoking Yu health problem attention rate along with domestic and international consumer and research institution, Nicotiana tabacum L. safety, Health, environmental issue increasingly obtain society's attention.Research shows, Nicotiana tabacum L. is when burning, and the part selenium contained can produce and turn Move and move fortune, being entered in smoker's body by main flume and side-stream smoke, affect the healthy of consumer.
Tobacco business height self-discipline always, deeply and carefully studies in terms of quality safety.Industry was put into effect in 2010 and is promulgated Standard YC/T 380-2010 " Nicotiana tabacum L. and tobacco product chromium, nickel, arsenic, selenium, cadmium, the mensuration inductivity coupled plasma mass spectrometry of lead Method ".Meanwhile, the heavy metal limit of Nicotiana tabacum L. and tobacco product is carried out military pre-research project by State Bureau, and this project is by large sample amount Analysis measure, make the reference Limited Doses of Se content in Nicotiana tabacum L..
For to look for novelty dynamically immediately following industry product quality safety, it is best understood from resting in the security performance using Nicotiana tabacum L., I Department active response State Bureau call, synchronize follow-up Nicotiana tabacum L. Analysis of Heavy Metal detection work, wherein selenium be listed in Testing index it One.In real work, find also have the space improved further, mainly have:
1, in YC/T 380-2010, Se content selection standard pattern measures82Se.Nicotiana tabacum L. is a kind of plant sample, and matrix is relatively For complexity, especially a large amount of carbon containings of origin, sulphur compound can produce the most serious mass spectrum interference.Therefore, certain is being measured During a little Selenium In Some Selenium-rich Biological Samples content, the phenomenons such as interference cannot thoroughly be eliminated, measurement result is higher occur.
2, during analyzing mensuration, it is often necessary to by Quality control samples (hereinafter referred to as quality-control sample) assessment side Method, tester, the precision of monitor and detection process and stability, it is ensured that the accuracy of analytical data and credibility.At present, cigarette Grass industry lacks the quality-control sample measured for Nicotiana tabacum L. content of beary metal, does not makes quality-control sample clearly in recommended industry standard Regulation, and the domestic literature report of relevant content of selenium in tobacco leaf quality-control sample definite value also has no and addresses.
Summary of the invention
The invention provides the valued methods of a kind of Nicotiana tabacum L. quality-control sample Se content.Have an advantage in that the assay method suitability And strong operability, possess certain novelty；Nicotiana tabacum L. quality-control sample uniformity is good, and stability is high, can scientific and effective monitoring analysis Process, it is ensured that the accuracy of measurement result.
A kind of valued methods of Nicotiana tabacum L. quality-control sample Se content, including:
Step (1): preparation Nicotiana tabacum L. quality-control sample solution, blank solution and standard solution respectively；
Step (2): use dynamic response pool mode that ICP-MS is tuned；Bioassay standard solution subsequently, and make mark Quasi-working curve；
Step (3): measure blank solution under the test condition of step (2)；Subsequently Nicotiana tabacum L. quality-control sample solution is carried out The repeatedly mensuration of Se content；
Step (4): each measured value of Nicotiana tabacum L. quality-control sample solution is carried out uniformity and stability test, and it is qualified to check After, the meansigma methods trying to achieve each measured value is the Se content of Nicotiana tabacum L. quality-control sample.
When using inductively coupled plasma mass spectrometry to measure the heavy metal element in complicated substrate, exist the tightest The isobar of weight and Polyatomic ion, these interference may result in the deviation of measurement result.Tobacco sample matrix Complex, especially a large amount of origin carbon containings, the existence of sulphur compound can produce interference to the mensuration of selenium.YC/T 380- 2010 recommend to measure in mode standard82Se.Selenium belongs to more difficult ionizing element,82The abundance of Se is only 8.73%, therefore,82Se exists Test process does not ensures that a higher instrumental response value, easily produces counting statistics error.The present invention selects dynamically Reaction tank (DRC) pattern, utilizes chemical reaction mechanism, and introduce oxygen reacting generation mass number with the selenium in determinand is 9680Se16O.The difficult problem that selenium is disturbed by low signal value and multi-atomic ion can be effectively evaded by measuring selenium oxide.
The valued methods of the present invention, carries out uniformity horizontal survey repeatedly to Nicotiana tabacum L. quality-control sample solution, to each measurement number According to being analyzed, after the assay was approved, more each measured value is carried out stability test, thus verify the reliability of valued methods, carry The accuracy of high-set setting.Additionally, use dynamic response pool mode to be measured, the selenium in Nicotiana tabacum L. is converted into the shape being suitable for analysis State (80Se16O), it is more conducive to selenium is carried out quantitative analysis.By investigating the uniformity of Nicotiana tabacum L. quality-control sample test result and stablizing Property, thus verify the reliability of valued methods.
In step (1), first prepare each detection solution, including Nicotiana tabacum L. quality-control sample solution, blank solution and standard solution Preparation.
Obtain standard solution with 5% nitric acid dilution standard storing solution, as dilution obtain concentration be 0.5ug/L, 1ug/L, The standard solution of 2ug/L, 5ug/L, 10ug/L.For improving the drafting accuracy of standard curve, standard solution is now with the current, and dense Degree covers Nicotiana tabacum L. quality-control sample solution and estimates the Se content of detection.
In the process for preparation of Nicotiana tabacum L. quality-control sample solution, according to tobacco business standard YC/T 31-1996 " Nicotiana tabacum L. and Nicotiana tabacum L. The preparation of product sample and determination of water Oven Method " prepare tobacco powder sample, and measure the moisture of tobacco powder sample. Accurately weigh sample, be placed in micro-wave diminishing pot, add digestion solution, screwing hermetic.Disappear by the micro-wave digestion program arranged Solve, to clearing up completely,
As preferably, Nicotiana tabacum L. quality-control sample, after micro-wave digestion, prepares Nicotiana tabacum L. quality-control sample solution through water dilution.
During micro-wave digestion, the digestion solution used be volume ratio be nitric acid and the mistake of 30wt% of the 65wt% of 3:1 Hydrogen oxide；Wherein, every gram of Nicotiana tabacum L. quality-control sample adds the digestion solution of 30-35mL.
Micro-wave digestion process carries out following program of clearing up successively:
(a): clearing up power is 1600W, and rank rise to 100 DEG C, clear up 5min；
(b): clearing up power is 1600W, and rank rise to 130 DEG C, clear up 5min；
(c): clearing up power is 1600W, and rank rise to 160 DEG C, clear up 5min；
(d): clearing up power is 1600W, and rank rise to 190 DEG C, clear up 20min.
As preferably, step (a) at room temperature rank rise to 100 DEG C, wherein, and step (a), step (b), the rank of step (c) The time of liter is 5min, and the rank liter time of step (d) is 10min.
After having cleared up, system is water white transparency shape liquid, with ultra-pure water dilution digestion solution to required concentration, is Nicotiana tabacum L. quality-control sample solution.
Use same method prepare blank solution, blank solution and Nicotiana tabacum L. quality-control sample solution be uniquely distinguished as do not add Add tobacco powder sample.
The present invention uses internal standard method to measure.As a rule, during internal mark method determination, internal standard substance requires thing in the choice Reason and chemical property are similar to analyte, and its signal can not disturb analyte, is not disturbed by other components in sample, and There is the signal being prone to measure.The internal standard substance testing selenium in YC/T 380-2010 is recommended as72Ge.But find through exploratory development, Ge is relatively vulnerable at amu7240Ar32The Polyatomic ion of S.Sulfur is one of important element of Nicotiana tabacum L., and content is generally 0.2% 0.7%.Therefore,72Ge generally can be detected higher signal value by instrument in tobacco sample.
As preferably, the internal standard substance of interpolation is103Rh standard solution.
After solution has been prepared, opening ICP-MS, be tuned ICP-MS, the tuning liquid used by ICP-MS is 10ug/L Ba, Cd, Ce, Cu, In, Mg, Pb, Rh, U tune liquid.
Instrument tunes by rear, under selected instrument parameter, uses internal standard method to be measured standard solution.And with mark Quasi-solution concentration is abscissa, and it is vertical coordinate mapping that instrument records selenium oxide counting rate with rhodium count rate ratio, sets up work bent Line.Each data point is carried out linear regression, and matching obtains the regression equation of selenium oxide concentration relationship.
After standard curve determination, measure blank solution.After mensuration completes, then measure Nicotiana tabacum L. quality-control sample solution, survey Each instrument parameter when determining blank solution and Nicotiana tabacum L. quality-control sample solution is equal to instrument parameter during tuning.
The selenium oxide obtaining Nicotiana tabacum L. quality-control sample solution to be measured is substituted into, with rhodium count rate ratio, the mark that institute's step (2) tries to achieve Directrix curve, tries to achieve selenium oxide concentration in sample solution.
Computing formula is
In formula:
The content of selenium oxide in X sample, unit is mg/kg；
C sample solution concentration, unit is ug/L；
C0Sample blank solution concentration, unit is ug/L；
V sample solution volume, unit is mL；
M sample quality, unit is g；
W sample moisture, unit is %.
In ICP-MS running, it is the most anti-that reaction gas flow speed (Cell Gas A) and low quality intercept threshold value (RPQ) Answer the running parameter that pond is important.By the size between both regulations, control the extent of reaction, improve reaction efficiency, select to close Suitable dynamic " band is logical ".
As preferably, in step (2) and step (3), during the tuning of ICP-MS, mensuration, reaction gas flow speed is 0.85mL/min, it is 0.60 that low quality intercepts threshold value.
The present invention uses dynamic response pool mode, and the target of measurement is80Se16O, with standard recommendation82Se compares ionization energy There occurs change, thus the time of integration is studied by the present invention.By fixed to Nicotiana tabacum L. quality-control sample measured result and addition The response rate after amount mark liquid selects the best total of points time.As preferably, in step (2) and step (3), the mensuration of ICP-MS Cheng Zhong, the time of integration is 4000ms.
Taking multiple measurements Nicotiana tabacum L. quality-control sample solution, pendulous frequency is preferably 10-20 time.The result of repetitive measurement Meansigma methods is the Se content in Nicotiana tabacum L. quality-control sample solution.But, before this, each measured value need to be carried out uniformity and stablize Property inspection, after uniformity testing is qualified, it was demonstrated that between characteristic value and another part characteristic value of this quality-control sample a portion Difference is the least, it is believed that consistent；After stability test is qualified, it was demonstrated that this quality-control sample in predetermined time interval, component energy It is maintained within the scope of regulation.Reliable and stable by two inspection rear these quality-control samples provable, next step definite value mistake Journey result is effective.Any one disqualified upon inspection, illustrates that this sample does not possess the primary condition making Quality control samples.
As preferably, in step (4), by SPPS software, described measured value is carried out statistical analysis, check each measured value Uniformity, if each measured value does not exist significant difference, described meansigma methods is as Se content in described Nicotiana tabacum L. quality-control sample Actual value；If each measured value exists significant difference, then terminate to measure.
As preferably, the significance condition of described uniformity testing is: level of significance α=0.05.
After uniformity testing is qualified, the measured value of step (4) is carried out ADF and verifies its stability, utilize Eviews software carries out ADF inspection to described measured value, if the time series of described measured value is stable, then explanation definite value becomes Merit；If the time series of described measured value is non-stable, then terminate to measure.
Chemical analysis field, the statistical method that stability test is commonly used includes that t method of inspection, method franchise method, concordance are examined Test method, stardard uncertairty method.ADF inspection is then the time series method of inspection in a kind of more practical macroeconomics field, The method specifically involves mathematical modeling, and the method that more above-mentioned chemical field is conventional more can reflect, describe dynamic structure.ADF examines Test in chemical field application few, do not retrieve pertinent literature or research report, belong to the frontier of knowledge migration infiltration, possess Certain creativeness.Being all random owing to weighing the position of quality-control sample every time, therefore this process is preferably with being good at dynamically The method of inspection that structure describes judges the stability of measurement data, verifies whether whole process is in the optimal shape of mensuration with this State, it is to avoid some unnecessary error impacts on measurement data, thus improve the accuracy of measurement.
ADF inspection selects three below model to carry out:
Model 1:
Model 2:
Model 3:
Wherein, α is constant term, εtFor residual error item, Δ XtFor time series, t is time variable, t=1,2,3 ..., βtFor Trend term, βi, δ be coefficient.
During practice examining from the beginning of model 3, then model 2, model 1.When null hypothesis H is refused in inspection0: δ=0, immediately Between sequence there is not unit root, when stop inspection, now can be determined that former data stabilization.Otherwise it is necessary to continue inspection, until Till having inspected model 1.When the assay of three models all can not refuse null hypothesis, it is possible to think time series right and wrong Stable.
As preferably, the significant level of described ADF inspection is 1%.
The inventive method also includes step (5): Nicotiana tabacum L. quality-control sample is carried out uncertainty evaluation.
Identified analysis, the uncertainty of Nicotiana tabacum L. quality-control sample definite value result mainly has sample to prepare, standard curve fit, The five elementses such as repetition measurement, sample inhomogeneities, sample unstability are constituted.The mathematical model setting up uncertainty evaluation can It is expressed as:
x = x ‾ ± x ‾ μ 1 2 + μ 2 2 + μ 3 2 + μ 4 2 + μ 5 2
In formula:
X Selenium In Some Selenium-rich Biological Samples content, unit: mg/kg
The definite value result of Nicotiana tabacum L. quality-control sample selenium, unit: mg/kg
μ1The partial uncertainty that sample preparation introduces
μ2The partial uncertainty that standard curve fit introduces
μ3The partial uncertainty that repetition measurement introduces
μ4The partial uncertainty that sample inhomogeneities introduces
μ5The partial uncertainty that sample unstability introduces
Present invention additionally comprises the Nicotiana tabacum L. quality-control sample that the valued methods described in employing prepares.
It addition, present invention additionally comprises the application in the mensuration of Se content in Nicotiana tabacum L. of described Nicotiana tabacum L. quality-control sample.
Successful for Se content definite value Nicotiana tabacum L. quality-control sample is applied in real work, Se content in tobacco product is checked Carry out quality control.Se content is a meter characteristic value, therefore can be selected for based on normal distribution, highly sensitiveFigure.
Measurement process is launched monitoring by the quality-control sample utilizing embodiment, collects data, the preliminary date then will collected Rationally it is divided into 20 subgroups and calculates the average of each group of sampleWith extreme difference Ri。
The inventive method suitability and strong operability, uniformity is good, and stability is high, energy scientific and effective monitoring analysis process, Guarantee the accuracy of measurement result.
Accompanying drawing explanation
Fig. 1 is under Cell GasA difference value, selenium oxide sensitivity and the changing trend diagram of detection limit (LOD)；
Fig. 2 is under RPQ difference value, selenium oxide sensitivity and the changing trend diagram of background equipotent concentration (BEC).
Detailed description of the invention
Below in conjunction with specific embodiment, the present invention is further elaborated.
The present embodiment launches narration mainly for the foundation of method, specifically sets up a kind of inductivity coupled plasma mass spectrometry Method measures the Se content in tobacco sample.
1. reagent
1.1 water, ultra-pure water (resistivity >=18.2M Ω cm)
1.2 concentrated nitric acids, mass fraction 65% (Merck KGaA company)
1.2.1 standard blank solution: 5% nitric acid
1.3 hydrogen peroxide, mass fraction 30% (Merck KGaA company)
1.4 tunings liquid 10 μ g/L:Ba, Cd, Ce, Cu, In, Mg, Pb, Rh, U tuning liquid (1% nitric acid medium)
1.5 1000ug/mL selenium standard reserving solutions
1.5.1 selenium standard working solution (standard solution)
With 5% nitric acid, selenium standard reserving solution is diluted to successively the mark of 0.5ug/L, 1ug/L, 2ug/L, 5ug/L, 10ug/L Quasi-working solution, now with the current, concentration should cover the Se content of anticipated detection in sample.
1.6 1000mg/L rhodium standard reserving solutions
1.6.1 rhodium inner mark solution
Rhodium standard reserving solution is diluted to 1ug/L as inner mark solution with 5% nitric acid, now with the current.
1.7 liquid argons (purity is more than 99.999%)
2. instrument and equipment
2.1 analytical balances (MettlerXS204 type, sensibility reciprocal 0.0001g)
2.2 ultra-pure-water treatment systems (Milli-Q Synthesis type, Millipore company of the U.S.)
2.3 airtight microwave digestion instrument (Mars Xpress type, U.S. CE M company),
2.4 icp ms (PE company, DRC-e model)
3. testing sample:
Sample is selected from producing region at county level, Fuzhou Shi Lean, Jiangxi Province in 2013, and K326 kind, through the upper leaf of deciding grade and level.
Embodiment 1
Step (1): configuration solution:
(1-1): sample pre-treatments:
According to tobacco business standard YC/T 31-1996 " Nicotiana tabacum L. and the preparation of tobacco product sample and determination of water baking oven Method " prepare tobacco powder sample, and measure the moisture of tobacco powder sample.Accurately weigh sample 0.2500g (to be accurate to 0.0001g), being placed in micro-wave diminishing pot, (30% mass is dense for addition 6mL nitric acid (65% mass concentration) and 2mL hydrogen peroxide Degree), screwing hermetic.Micro-wave digestion program as shown in table 1 is cleared up, and to clearing up completely, solution is water white transparency shape liquid. Sample blank is prepared by same method.
Table 1
Constant volume:
Clear up complete, after temperature is down to room temperature, takes out counteracting tank；Directly sample solution is transferred to 50mL plastic sample In Ping, with ultrapure water counteracting tank 3～4 times, cleanout fluid is transferred in sample bottle in the lump, then with ultra-pure water constant volume and shake up Obtain test liquid；
(1-2): standard solution is prepared:
With 5% nitric acid, 1000ug/mL selenium standard reserving solution is diluted to ρ=1000ug/L selenium one-level and uses liquid.Standard respectively The selenium one-level really pipetting 0.5mL, 1mL, 2mL, 5mL, 10mL uses liquid to be transferred in 1000mL volumetric flask, with 5% nitric acid constant volume To scale, the concentration obtained is respectively 0.5ug/L, 1ug/L, 2ug/L, 5ug/L, 10ug/L.Standard working solution needs now with the current, Concentration should cover the Se content of anticipated detection in sample.
(1-3): inner mark solution is prepared
Rhodium standard reserving solution is diluted to 1ug/L as inner mark solution with 5% nitric acid, now with the current.
Step (2): bioassay standard solution, and draw standard curve:
(2-1): icp ms running parameter
Use tuning liquid tuning coil couple plasma mass spectrometer to best effort environment, inductively coupled plasma matter Spectrometer main working parameters is as shown in table 2:
Table 2
(2-2): Specification Curve of Increasing
After instrument tuning, being inserted in 1ug/L rhodium inner mark solution by internal standard sample feeding pipe, sample feeding pipe is sequentially inserted into standard null White solution, the selenium standard solution of variable concentrations.Under the parameter that instrument is selected, promote sample introduction with peristaltic pump, inject inductive In plasma mass spectrograph, record the counting rate (CPS) of respective selenium oxide and rhodium.With concentration of standard solution as abscissa, instrument Recording selenium oxide counting rate with rhodium count rate ratio is vertical coordinate mapping, sets up working curve.Each data point is linearly returned Returning, it is Y=0.1032X+0.0026, R=0.9994 that matching obtains the regression equation of selenium oxide concentration relationship；
Step (3): sample determination:
Pipette samples blank solution respectively, sample solution injects in icp ms, at selected instrument Under device parameter, obtain element oxide selenium to be measured and the regression equation made by the substitution of rhodium count rate ratio, try to achieve sample blank molten Selenium oxide concentration in liquid and sample solution.
Computing formula is:
In formula:
The content of selenium oxide in X sample, unit is mg/kg
C sample solution concentration, unit is ug/L
C0Sample blank solution concentration, unit is ug/L
V sample solution volume, unit is mL
M sample quality, unit is g
W sample moisture, unit is %
Sample definite value:
Under the same conditions, accurately weigh Nicotiana tabacum L. quality-control sample 20 parts, carry out sample preparation and solely by technique scheme Vertical measurement.
Step (4): uniformity and stability test:
(4-1): uniformity testing:
The sampling mode of uniformity testing follows strictly the position extraction being likely to occur difference from characteristic magnitude undetermined, sampling The distribution of point should make taken sample have enough representativenesses for Bulk Samples.Owing to this quality-control sample is powdered substance, because of This respectively from top, middle part, bottom respectively weigh 6 parts of samples sample as uniformity testing, by same operator by above-mentioned side Method, uses identical test equipment, METHOD FOR CONTINUOUS DETERMINATION in short time interval, and every part of sample is repeated 3 times, and uniformity testing result is shown in Table 3.
Table 3
All level of significance α=0.05 of value difference
In level of significance α=0.05 time, by SPSS17.0 software, use F method of inspection that upper table data are added up Analyze.By calculating probit P=0.071 together, more than 0.05, the Se content of this explanation Nicotiana tabacum L. quality-control sample is at significance Significant difference is there is not, it is believed that selenium is uniformly distributed in the sample under the conditions of horizontal α=0.05.
(4-2): stability test:
Owing to Nicotiana tabacum L. powder has hygroscopicity, therefore need to take white beeswax to seal in stability test sample, insert exsiccator In keep in Dark Place at shady and cool.Within the time of December, the quality-control sample of different storage periods is carried out stability test.Monitoring is pressed Dredge principle after first close, respectively the 1st, 2,4,6,9, within 12 months, implement.From sample, weigh 6 parts at random, by same operation every time Member as stated above, uses identical test equipment, METHOD FOR CONTINUOUS DETERMINATION in short time interval, and every part of sample is repeated 3 times.
Chemical analysis field, the statistical method that stability test is commonly used includes that t method of inspection, method franchise method, concordance are examined Test method, stardard uncertairty method.ADF inspection is then the time series method of inspection in a kind of more practical macroeconomics field, The method specifically involves mathematical modeling, and the method that more above-mentioned chemical field is conventional more can reflect, describe dynamic structure.The present invention Why take this method, be based primarily upon following some consider:
1. this method of inspection is few in chemical field application, does not retrieves pertinent literature or research report, belongs to knowledge migration The frontier of infiltration, possesses certain creativeness.
2. being all random owing to weighing the position of quality-control sample every time, therefore this process is preferably with being good at dynamic structure The method of inspection described judges the stability of measurement data, verifies whether whole process is in the optimum state of mensuration with this, Avoid the impact on measurement data of error that some are unnecessary, thus improve the accuracy of measurement.
ADF inspection selects three below model to carry out:
Model 1:
Model 2:
Model 3:
Wherein, the t in model 3 is time variable, represents time series certain trend time dependent, and β t is trend ?.The null hypothesis of three models is all H0: δ=0, i.e. there is a unit root, time series is random walk sequence, say, that Time series is non-stable.Additionally, α is constant term, εtFor residual error item.Whether model 1 is with the difference of another two model Comprise constant term and trend term.
During practice examining from the beginning of model 3, then model 2, model 1.When null hypothesis H is refused in inspection0: δ=0, immediately Between sequence there is not unit root, when stop inspection, now can be determined that former data stabilization.Otherwise it is necessary to continue inspection, until Till having inspected model 1.When the assay of three models all can not refuse null hypothesis, it is possible to think time series right and wrong Stable.
Utilizing Eviews software that measured value is carried out ADF inspection, it is as shown in table 4 that Eviews software specifically exports result:
Table 4
As shown in Table 4, the ADF test value of selenium is-5.483916, is the marginal value of 1% less than significance level.Therefore, It is believed that the selenium of quality-control sample is reliable and stable under the significant level of 1%, meet stability requirement.
In sum: this valued methods uniformity is good, stability is high, and the average result of 20 parallel laboratory tests is: Se content 0.152mg/kg.This definite value result is i.e. as the target value of Nicotiana tabacum L. quality-control sample.
Principle analysis:
Embodiments of the invention are newly-built, and a kind of inductively coupled plasma mass spectrometry measures the Se content in tobacco sample. According to the physicochemical property of tobacco sample, it is optimized comparison to measuring thing, reaction pattern, internal standard substance, instrument parameter etc., and this A little the technical program just possess prominent substantive distinguishing features and significance progress, specifically include:
(1) selection of mensuration thing:
Eliminating the effect of interference for investigating checking DRC further, experiment selection standard pattern and DRC pattern are respectively to sample Launch to measure, and use certified reference material GBW07602 bush branch and leaf to carry out the magnitude tracing of accuracy, carry out accuracy survey Fixed, the results are shown in Table 5:.
Table 5
Known by table 5, use the selenium in DRC pattern mensuration bush branch and leaf compared with mode standard closer to the central value assert, Illustrating that DRC pattern capacity of resisting disturbance is relatively strong, measurement result is more accurately and reliably
(2) selection of internal standard substance:
Reasonably selecting internal standard substance for more scientific, the present invention adds semi-quantitative analysis test.With 10ug/L tuning liquid for mark Standard sets up curve, and on the basis of this curve, different producing area, different parts, 9 tobacco samples of different cultivars is carried out semidefinite Component analysis, selects to scan all elements in full spectral limit, gathers element and the relevant information of concentration in sample.Compared by experiment Right, look for signal value in Nicotiana tabacum L. low, disturb the factors such as less element, and bond quality number, ionization degree, operability, the suitability, Finally determine use103Rh is80Se16The internal standard element of O.
(3) optimization reaction gas flow speed and low quality intercepting number:
Reaction gas flow speed (Cell Gas A) and low quality intercepting threshold value (RPQ) are the work ginsengs that Dynamic Reaction Cell is important Number.By the size between both regulations, control the extent of reaction, improve reaction efficiency, select the most dynamically " band is logical ".
For obtaining optimal working condition, need that reaction gas flow speed and low quality are intercepted threshold value and carry out condition test.This Test determination reaction gas flow speed is from 0.1mL/min to 2.0mL/min, and low quality intercepts threshold value from 0.1 to 0.9 graded, Selenium standard solution (10ppb) and the sensitivity of standard blank solution under different condition, result is shown in Fig. 1, Fig. 2.Wherein, in Fig. 1, real Line 1 represents that standard solution, solid line 3 represent that standard is blank, and solid line 2 is synthesis gained.In Fig. 2, blue solid lines 1 represents that standard is molten Liquid, solid line 3 represents that standard is blank, and solid line 2 is synthesis gained.Wherein, BEC is background equipotent concentration, refers to element quality to be measured The concentration of element value that background absolute counting value at Shuo is suitable, eliminates interference application aspect at dynamic response pool technology, and BEC is table The important indicator of balancing method power of test of seeking peace.BEC is the least, illustrates that the sensitivity of the method is the highest.
Fig. 1,2 show, along with Cell GasA and RPQ is gradually increased, the sensitivity of standard solution and standard blank solution in Existing same trend, is the process declined after first rising arrival summit.This is because when flow is less, reaction gas be not enough to Selenium is completely combined；Secondary side reaction then it is susceptible to time bigger.And dynamically " band is logical " arranges unreasonable, may result in target from Son loss or interfering ion together enter level Four bar with object ion.Therefore, for different elements, can exist one optimal Cell Gas A and RPQ.With this understanding, BEC and LOD is minimum, and the sensitivity of method is the highest.When selenium oxide is measured in this test, Take oxygen flow be 0.85mL/min, RPQ be 0.60.
(4) select the time of integration:
Under normal circumstances, the data acquisition of ICP-MS selects to jump peak measurement pattern.YC/T 380-2010 recommends to measure82Se The required time of integration is 2000ms, and i.e. residence time (Dwell time) is 100ms, often place's scanning 20 times.But due to this reality Test amount be80Se16O, ionization energy there occurs change, thus the time of integration is studied by the present invention.By to Nicotiana tabacum L. matter The response rate after control sample measured result and addition quantitatively mark liquid selects the best total of points time.The time of integration is to test result The results are shown in Table 6, as shown in Table 6, along with the increase of the time of integration, test result and the response rate index of sample all gradually rise. This is owing to using longer time of integration, can have that more to analyze ion collected, but may introduce simultaneously non-targeted from Son.Considering accuracy, analysis efficiency and testing cost, the present invention will be defined as 4000ms the time of integration, i.e. residence time For 200ms, improve the counting statistics error of high ionization energy with this.
Table 6
(5) monitoring element is increased13C:
There are some researches show, add a small amount of methanol when measuring selenium element, signal intensity can be improved 2-3 times.This signal At the middle section of plasma, the selenium strengthening carbon species and high ionization energy that phenomenon is probably positively charged there occurs that electric charge shifts Reaction, thus promote the ionization of analyte.Therefore, the present invention, when method sets, adds13C as monitoring element, closely with The ionizing usefulness of track selenium.When sample solution13C signal value can not remain stable in certain level well, occurs that moment is rapid Situation about so increasing or drastically shake, may infer that the selenium in sample it may happen that enhancement effect, and ripple easily occurs in measurement result Dynamic deviation, affects accuracy and the precision of definite value result.
Uncertainty evaluation is carried out for Nicotiana tabacum L. quality-control sample:
Identified analysis, the uncertainty of Nicotiana tabacum L. quality-control sample definite value result mainly has sample to prepare, standard curve fit, The five elementses such as repetition measurement, sample inhomogeneities, sample unstability are constituted.The mathematical model setting up uncertainty evaluation can It is expressed as:
x = x ‾ ± x ‾ μ 1 2 + μ 2 2 + μ 3 2 + μ 4 2 + μ 5 2
In formula:
X Selenium In Some Selenium-rich Biological Samples content, unit: mg/kg
The definite value result of Nicotiana tabacum L. quality-control sample selenium, unit: mg/kg
μ1The partial uncertainty that sample preparation introduces
μ2The partial uncertainty that standard curve fit introduces
μ3The partial uncertainty that repetition measurement introduces
μ4The partial uncertainty that sample inhomogeneities introduces
μ5The partial uncertainty that sample unstability introduces
(1) uncertainty that sample preparation introduces
The uncertainty source of Sample Preparation Procedure includes that baking oven wind speed and the temperature inside the box introduce μ1T (), balance weigh and draw Enter μ1M (), liquid-transfering gun sample-adding introduces μ1(Va), clear up rear constant volume introduce μ1(Vb), standard solution preparation introduce μ1(s) etc..Therefore,
u 1 = μ 1 ( t ) 2 + μ 1 ( m ) 2 + μ 1 ( V a ) 2 + μ 1 ( V b ) 2 + μ 1 ( s ) 2 = 0.0105
(2) uncertainty that standard curve fit introduces
The technical program uses internal standard method to carry out the quantitative of selenium.By each data point is carried out linear regression, matched curve. Owing to matched curve itself has uncertainty, therefore use Bezier, experimental standard deviation is converted and obtains standard song The uncertainty that line matching introduces.It is computed, tries to achieve μ2=0.0185
(3) sample repeatability measures the uncertainty introduced
Under the conditions of repeatability, accurately weigh Nicotiana tabacum L. quality-control sample 6 parts, carry out sample preparation and solely by technique scheme Vertical measurement, the relative standard uncertainty of computation and measurement result.It is computed, tries to achieve μ3=0.0097
(4) uncertainty that sample inhomogeneities introduces
Use the uncertainty that method of analysis of variance assessment introduces because of sample inhomogeneities.Above-mentioned uniformity testing result is entered Row between group variable and the calculating of intra-class variance, try to achieve μ4=0.0198
(5) uncertainty that sample unstability introduces
μ5The same μ of calculating process4, it is calculated μ5=0.0361
Because each component is separate uncorrelated, the standard uncertainty of Nicotiana tabacum L. quality-control sample Determination of Selenium result
Take confidence probability when being 95%, Coverage factor K=2, expanded uncertainty U=K × μ=0.014
To sum up, Nicotiana tabacum L. quality-control sample Se content uncertainty expression formula is (0.152 ± 0.014) mg/kg, K=2.

Claims (10)

1. the valued methods of a Nicotiana tabacum L. quality-control sample Se content, it is characterised in that including:
Step (1): preparation Nicotiana tabacum L. quality-control sample solution, blank solution and standard solution respectively；
Step (2): use dynamic response pool mode that ICP-MS is tuned；Bioassay standard solution subsequently, and make standard work Make curve；
Step (3): measure blank solution under the test condition of step (2)；Subsequently Nicotiana tabacum L. quality-control sample solution is carried out repeatedly The mensuration of Se content；
Step (4): each measured value of Nicotiana tabacum L. quality-control sample solution is carried out uniformity and stability test, after the assay was approved, asks The meansigma methods obtaining each measured value is the Se content of Nicotiana tabacum L. quality-control sample.
2. the valued methods of Nicotiana tabacum L. quality-control sample Se content as claimed in claim 1, it is characterised in that Nicotiana tabacum L. quality-control sample warp After micro-wave digestion, prepare Nicotiana tabacum L. quality-control sample solution through water dilution；
During micro-wave digestion, the digestion solution used be volume ratio be nitric acid and the peroxidating of 30wt% of the 65wt% of 3:1 Hydrogen；Wherein, every gram of Nicotiana tabacum L. quality-control sample adds the digestion solution of 30-35mL.
3. the valued methods of Nicotiana tabacum L. quality-control sample Se content as claimed in claim 1, it is characterised in that micro-wave digestion process depends on Secondary carry out following program of clearing up:
(a): clearing up power is 1600W, and rank rise to 100 DEG C, clear up 5min；
(b): clearing up power is 1600W, and rank rise to 130 DEG C, clear up 5min；
(c): clearing up power is 1600W, and rank rise to 160 DEG C, clear up 5min；
(d): clearing up power is 1600W, and rank rise to 190 DEG C, clear up 20min.
4. the valued methods of Nicotiana tabacum L. quality-control sample Se content as claimed in claim 1, it is characterised in that step (2) and step (3) using internal mark method determination, the internal standard substance of interpolation is103Rh standard solution.
5. the valued methods of Nicotiana tabacum L. quality-control sample Se content as claimed in claim 1, it is characterised in that in step (4), by SPPS software carries out statistical analysis to described measured value, checks the uniformity of each measured value, if each measured value does not exist significance Difference, described meansigma methods is as the actual value of Se content in described Nicotiana tabacum L. quality-control sample；If it is poor to there is significance in each measured value Different, then terminate to measure.
The valued methods of Nicotiana tabacum L. quality-control sample Se content the most according to claim 1, it is characterised in that described uniformity is examined The significance condition tested is: level of significance α=0.05.
7. the valued methods of Nicotiana tabacum L. quality-control sample Se content as claimed in claim 5, it is characterised in that uniformity testing is qualified After, the measured value of step (4) is carried out ADF and verifies its stability, utilize Eviews software that described measured value is carried out ADF checks, if the time series of described measured value is stable, then and explanation definite value success；If the time series of described measured value It is non-stable, then terminates to measure.
The valued methods of Nicotiana tabacum L. quality-control sample Se content the most according to claim 7, it is characterised in that described ADF checks Significant level be 1%.
The valued methods of Nicotiana tabacum L. quality-control sample Se content the most according to claim 1, it is characterised in that step (2) and step Suddenly, in (3), during the tuning of ICP-MS, mensuration, reaction gas flow speed is 0.85mL/min, and it is 0.60 that low quality intercepts threshold value.
The valued methods of Nicotiana tabacum L. quality-control sample Se content the most according to claim 1, it is characterised in that step (2) and step Suddenly, in (3), during the mensuration of ICP-MS, the time of integration is 4000ms.
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