阅读说明：本技术 一种测定甘薯中硒含量的响应面法优化原子荧光光谱法 (Response surface method optimized atomic fluorescence spectrometry for measuring selenium content in sweet potatoes ) 是由 李慧峰 陈天渊 黄咏梅 李彦青 滑金锋 范继征 银捷 于 2019-10-22 设计创作，主要内容包括：本发明公开了一种测定甘薯中硒含量的响应面法优化原子荧光光谱法,操作步骤为(1)制备待测样品溶液；(2)标准曲线的绘制；(3)原子荧光光度计测定硒含量。本发明建立了响应面优化氢化物发生-原子荧光光谱法测定甘薯薯块中总硒含量和无机硒含量,以及通过计算间接测定有机硒含量的方法,为甘薯中无机硒和有机硒的检测提供了一种快速检测的方法；本发明方法简洁、易操作、测定结果样品硒回收率为97.25％～100.68％,检出限为0.0314μg·L<Sup>-1</Sup>。(The invention discloses a response surface method optimized atomic fluorescence spectrometry for measuring selenium content in sweet potatoes, which comprises the following operation steps of (1) preparing a sample solution to be measured; (2) drawing a standard curve; (3) and (4) measuring the selenium content by using an atomic fluorescence spectrophotometer. The invention establishes a method for measuring the total selenium content and the inorganic selenium content in the sweet potato pieces by response surface optimized hydride generation-atomic fluorescence spectrometry and indirectly measuring the organic selenium content by calculation, and provides a rapid detection method for the detection of the inorganic selenium and the organic selenium in the sweet potato; the method is simple and easy to operate, the selenium recovery rate of the sample is 97.25-100.68% and the detection limit is 0.0314 mug.L ‑1 。)

1. A response surface method optimized atomic fluorescence spectrometry method for measuring selenium content in sweet potatoes is characterized by comprising the following operation steps:

(1) preparing a sample solution to be tested: weighing 0.5000g of sweet potato sample obtained after pretreatment, adding mixed acid for cold digestion overnight, dispelling acid, adding a medium hydrochloric acid aqueous solution with the volume concentration of 20% for constant volume to obtain a sample solution to be detected, and preparing a blank solution at the same time;

(2) drawing a standard curve: 100 mu L of selenium standard stock solution with the concentration of 100 mu g/mL is taken and placed in a 10mL volumetric flask, medium hydrochloric acid aqueous solution with the volume concentration of 20% is added to dilute the solution to 1.0 mu g/mL to prepare selenium standard intermediate solution, 0, 10, 20, 40, 60, 80 and 100 mu L of selenium standard intermediate solution are respectively taken and placed in the 10mL volumetric flask, medium hydrochloric acid aqueous solution with the volume concentration of 20% is used for volume to scale, and the solution is uniformly mixed to prepare a series of standard solutions with the selenium concentration of 0, 1.0, 2.0, 4.0, 6.0, 8.0 and 10.0ug/L respectively;

and (3) putting the selenium standard solution with different gradients of 0 ug/L-10.0 ug/L on a machine for testing to obtain a standard curve, wherein the equation of the selenium standard curve is as follows: fu is 69.447 × ρ -31.068, wherein: fu represents the fluorescence value, rho represents the mass concentration of selenium in the solution, the correlation coefficient R is 0.9967, and the detection limit is 0.0314 ug/L;

(3) and (3) measuring the selenium content by an atomic fluorescence photometer method: transferring 10.0mL of the sample solution to be detected and the blank solution obtained in the step (1) to an atomic fluorescence spectrophotometer sample holder, wherein the carrier liquid is a hydrochloric acid solution with the volume concentration of 5%, the reducing agent is a potassium borohydride solution with the mass concentration of 3%, reading the obtained fluorescence value, the reading time is 16.0s, the delay time is 1.0s, substituting the obtained fluorescence value into the standard curve equation obtained in the step (2), calculating the mass concentration rho of selenium in the sample solution, and then calculating the mass concentration rho of selenium in the sample solution according to the following formula,

calculating the selenium content X of the sample to be detected to obtain;

in the formula:

x: the amount of selenium in the sample in milligrams per kilogram (mg/kg);

ρ: the mass concentration of selenium in the sample solution in micrograms per liter (μ g/L);

v: total volume of sample digest in milliliters (mL);

m: sample weighing in grams (g);

1000: and (4) a conversion coefficient.

2. The response surface method optimized atomic fluorescence spectrometry for determining the selenium content in sweet potatoes as claimed in claim 1, wherein: the pretreatment in the step (1) is to clean, air-dry, shred and dry the sweet potato, then crush and screen the sweet potato through a 70-mesh sieve for standby.

3. The response surface method optimized atomic fluorescence spectrometry for determining the selenium content in sweet potatoes as claimed in claim 1, wherein: the mixed acid in the step (1) is prepared by mixing nitric acid and perchloric acid according to a volume ratio of 5: 1 mixing the components.

4. The response surface method optimized atomic fluorescence spectrometry for determining the selenium content in sweet potatoes as claimed in claim 1, wherein: when the total selenium content is determined in the step (1), the specific operation of preparing the sample solution to be detected is as follows: weighing 0.5000g of sweet potato sample powder into a polytetrafluoroethylene digestion tube, adding 10mL of mixed acid, covering the tube for overnight cold digestion, heating to 150-180 ℃ (120 ℃ for 30min, 150 ℃ for 1h, and 180 ℃ for 2h) the next day, dispelling the acid to 2mL, stopping heating when the sample is clear and transparent and white smoke is emitted, continuing heating until the solution reaches 2mL, cooling, adding 6mol/L hydrochloric acid, heating until the white smoke is emitted, stopping heating, transferring the liquid into a 10mL volumetric flask after cooling, adding 2.5mL of potassium ferricyanide with the concentration of 100g/L, and fixing the volume by using a medium hydrochloric acid aqueous solution with the volume concentration of 20% to obtain a sample solution to be detected.

5. The response surface method optimized atomic fluorescence spectrometry for determining the selenium content in sweet potatoes as claimed in claim 1, wherein: when the content of the inorganic selenium is determined in the step (1), the specific operation of preparing the sample solution to be detected is as follows: weighing 0.5000g of sweet potato sample powder, adding 45 vol% ethanol solution, extracting in 60 deg.C water bath for 30min, performing ultrasonic treatment for 30min, cooling, centrifuging for 30min to obtain supernatant, heating the extractive solution, steaming to remove most of the solution, adding mixed acid, removing acid, heating, adding 20 vol% hydrochloric acid aqueous solution, and diluting to desired volume to obtain sample solution to be measured.

Technical Field

The invention relates to a method for measuring selenium content, in particular to a response surface method optimized atomic fluorescence spectrometry method for measuring the selenium content in sweet potato blocks.

Background

Selenium is one of essential trace elements of human body, has various biological functions of eliminating in-vivo free radicals, improving immunity of the organism and the like, but can cause human diseases when being taken insufficiently or excessively. The human body can not synthesize selenium by itself, the eating of selenium-rich food is the main way for the human body to obtain selenium, and the selenium-rich sweet potatoes can be used as good carriers for supplementing selenium for the human body. At present, the method for measuring the selenium content in food is mainly based on the national standard method, but the measurement standard aiming at the selenium content in sweet potatoes is not reported. Therefore, it is necessary to develop a method for measuring the selenium content in sweet potatoes.

The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Disclosure of Invention

The method takes selenium-rich sweet potato varieties as materials, selects the proportion of mixed acid, digestion time, the concentration of a shielding agent, the concentration of carrier liquid, the concentration of a medium and the content of a reducing agent as research factors, determines the level of each factor by measuring the fluorescence value under the condition of a single factor, further establishes a detection method for quickly and accurately measuring the total selenium content of the sweet potatoes by combining a Box-Behnken design with a response surface analysis method based on an atomic fluorescence spectrometry, optimizes the types and the concentrations of extracting solutions, the extraction temperature and the extraction time for measuring the inorganic selenium content, and obtains the organic selenium content by calculation.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

a response surface method optimized atomic fluorescence spectrometry method for measuring selenium content in sweet potatoes comprises the following operation steps:

(1) preparing a sample solution to be tested: weighing 0.5000g of sweet potato sample obtained after pretreatment, adding mixed acid for cold digestion overnight, removing acid by an electric hot plate, adding a medium hydrochloric acid aqueous solution with the volume concentration of 20% for constant volume to obtain a sample solution to be detected, and preparing a blank solution at the same time;

(2) drawing a standard curve: taking 100 mu L of selenium standard stock solution 100 mu g/mL, placing the selenium standard stock solution in a 10mL volumetric flask, adding a medium hydrochloric acid aqueous solution with the volume concentration of 20% to dilute the selenium standard intermediate solution to 1.0 mu g/mL to prepare a selenium standard intermediate solution, precisely measuring 0, 10, 20, 40, 60, 80 and 100 mu L of the selenium standard intermediate solution in the 10mL volumetric flask respectively, using the medium hydrochloric acid aqueous solution with the volume concentration of 20% to hold to a scale, uniformly mixing, and preparing a series of standard solutions with the selenium concentrations of 0, 1.0, 2.0, 4.0, 6.0, 8.0 and 10.0ug/L respectively;

and (3) putting the selenium standard solution with different gradients of 0 ug/L-10.0 ug/L on a machine for testing to obtain a standard curve, wherein the equation of the selenium standard curve is as follows: fu is 69.447 × ρ -31.068, wherein: fu represents the fluorescence value, rho represents the mass concentration of selenium in the solution, the correlation coefficient R is 0.9967, the blank sample is continuously measured for 11 times, and the detection limit of the method is 0.0314ug/L by dividing 3S by the slope of the working curve;

(3) and (3) measuring the selenium content by an atomic fluorescence photometer method: the instrument is an RGF-6200 atomic fluorescence spectrometer, the lamp current of the atomic fluorescence spectrometer is set to be 80mA, the negative high pressure is set to be 280V, the carrier gas flow is 400mL/min, the shielding gas flow is 900mL/min, the carrier gas is argon with the concentration of 99.99%, the measurement mode is a standard curve method, the instrument is started to preheat for 30min, 10.0mL of the sample solution to be measured and the blank solution obtained in the step (1) are moved to the sample rack of the atomic fluorescence spectrophotometer, the carrier liquid is a hydrochloric acid solution with the volume concentration of 5%, the reducing agent is a potassium borohydride solution with the mass concentration of 3%, the obtained fluorescence value is read, the reading time is 16.0s, the delay time is 1.0s, the obtained fluorescence value is substituted into the standard curve equation obtained in the step (2), the mass concentration rho of selenium in the sample solution is calculated, and then the following,

calculating the selenium content X of the sample to be detected to obtain;

in the formula:

x: the amount of selenium in the sample in milligrams per kilogram (mg/kg);

ρ: the mass concentration of selenium in the sample solution in units of micrograms per liter (ug/L);

v: total volume of sample digest in milliliters (mL);

m: sample weighing in grams (g);

1000: and (4) a conversion coefficient.

Preferably, the pretreatment in the step (1) is to clean, air-dry, shred and dry the sweet potato, then crush and pass through a 70-mesh sieve, and transfer the sweet potato into a sealed bag for storage.

Preferably, the mixed acid in the step (1) is nitric acid and perchloric acid, wherein the volume ratio of the nitric acid to the perchloric acid is 5: 1 mixing the components.

Preferably, when the total selenium content is determined in step (1), the operation of preparing the sample solution to be tested is as follows: weighing 0.5000g of sweet potato sample powder into a polytetrafluoroethylene digestion tube, adding 10mL of mixed acid, covering the tube for overnight cold digestion, heating to 150-180 ℃ (120 ℃ for 30min, 150 ℃ for 1h, and 180 ℃ for 2h) the next day, dispelling acid to about 2mL, stopping heating when the sample is clear and transparent and white smoke is emitted, continuing heating until the solution is about 2mL, cooling, adding 5.00mL of 6mol/L hydrochloric acid, heating until the white smoke is emitted, stopping heating, transferring the liquid into a 10mL bottle after cooling, adding 2.5mL of potassium ferricyanide with the concentration of 100g/L, and carrying out volume fixing by using a medium hydrochloric acid aqueous solution with the volume concentration of 20% to obtain a sample solution to be detected, thus obtaining the sweet potato biological sample.

Preferably, when the inorganic selenium content is determined in the step (1), the preparation of the sample solution to be tested is specifically operated as follows: weighing 0.5000g of sweet potato sample powder, adding 20mL of 45 vol% ethanol solution, extracting in a water bath at 60 ℃ for 30min, then placing in an ultrasonic cleaner for ultrasonic treatment for 30min, cooling, centrifuging at 4000r/min for 30min to obtain a supernatant, namely an inorganic selenium extracting solution, heating the extracting solution to evaporate most of the solution to be used as a sample, adding mixed acid, dispelling acid, heating, adding 20 vol% medium hydrochloric acid aqueous solution, and fixing the volume to obtain a sample solution to be detected.

Compared with the prior art, the invention has the following beneficial effects:

the invention establishes a method for measuring the total selenium content and the inorganic selenium content in the sweet potato pieces by response surface optimized hydride generation-atomic fluorescence spectrometry and indirectly measuring the organic selenium content by calculation, and provides a rapid detection method for the detection of the inorganic selenium and the organic selenium in the sweet potato; the method is simple and easy to operate, the selenium recovery rate of the sample is 97.25-100.68% and the detection limit is 0.0314 mug.L ^-1。

Drawings

FIG. 1 is a graph showing the effect of various factors of the present invention on fluorescence values of a sample; wherein, fig. 1a is the influence of the concentration of the medium hydrochloric acid on the fluorescence value of the sample solution, fig. 1b is the influence of the concentration of the carrier hydrochloric acid on the fluorescence value of the sample solution, fig. 1c is the influence of the concentration of potassium borohydride on the fluorescence value of the sample solution, fig. 1d is the influence of the volume ratio of the mixed acid (nitric acid and perchloric acid) on the fluorescence value of the sample solution, fig. 1e is the influence of the content of ferric potassium chloride on the fluorescence value of the sample solution, fig. 1f is the influence of the water bath temperature on the fluorescence value of the sample solution, fig. 1g is the influence of the water bath time on the fluorescence value of the sample solution, and fig. 1h is the influence.

Detailed Description

The following detailed description is to be read in connection with the accompanying drawings, but it is to be understood that the scope of the invention is not limited to the specific embodiments. Example 100. mu.g.mL ^-1The standard stock solution of selenium (China institute of metrology science), potassium borohydride, sodium hydroxide, hydrochloric acid, nitric acid, perchloric acid, ethanol, potassium ferricyanide and the like are super-pure water, and the experimental water is ultrapure water. All glassware was treated with 20% HNO ₃Soaking for 24h, and washing with tap water and ultrapure water sequentially for later use. The sweet potato sample was collected from Guangxi agricultural academy of sciences, Mingyang, RGF-6200 atomic fluorescence photometer (Innovative photoelectric technology, Inc. of Beijing Bohui).