1. A method for measuring the content of potassium oxide in a fertilizer by using a flame atomic absorption spectrometer, which is characterized by comprising the following steps:

dissolving a fertilizer sample in water, setting the spectral bandwidth of a flame atomic absorption spectrometer to be 0.2nm by using air-acetylene flame, measuring the absorbance at the wavelength of 404.41nm, and calculating the content of potassium oxide by using a standard working curve method.

2. The method of claim 1, wherein the potassium oxide content of the fertilizer sample is determined in the range of 5 wt% to 20 wt%.

3. The method according to claim 1 or 2,

the method comprises the following determination steps:

preparing a standard solution, drawing a standard working curve, preparing a sample solution, measuring the sample solution and calculating the content of potassium oxide in a fertilizer sample; wherein the content of the first and second substances,

the coverage range of the potassium oxide content in each standard solution is 0-200 mug/mL;

preferably, in the step of preparing the standard solution, 0, 5, 10, 11, 13, 15mL of 1000 μ g/mL potassium chloride standard stock solutions are respectively measured, 10mL of water is added into a 100mL volumetric flask, the solution is shaken up, the volume is fixed to the scale, and the solution is kept stand for 10min, so that the potassium oxide content is respectively prepared as follows: 0. 50, 100, 110, 130, 150. mu.g/mL standard solution.

4. The method according to any one of claims 1 to 3,

in the step of drawing the standard working curve, on an air-acetylene flame atomic absorption spectrometer, according to the using method and the steps of the instrument, the peak finding is completed at the wavelength of 404.41nm, the spectral bandwidth of the instrument is adjusted to be 0.2nm, the energy balance reaches more than 99.0, after the setting is completed, the standard solution is measured, the blank solution is used for zero calibration, the potassium chloride standard solution is sequentially sucked, the clicking is stopped, and the instrument can automatically generate the standard working curve with the potassium oxide concentration as the abscissa and the absorbance as the ordinate.

5. The method according to any one of claims 1 to 4,

in the step of drawing the standard working curve, before the measurement of the standard solution, other parameters of the flame atomic absorption spectrometer are also set: the filter coefficient is 1.0, the lamp current is 2.0mA, the negative high pressure is 300v, the integration time is 1.0s, the air pressure is 0.25MPa, the acetylene pressure is 0.05MPa, the flow is 1700mL/min, and the height of the combustor is 5 mm.

6. The method according to any one of claims 1 to 5,

the calculation mode of the standard working curve in the flame atomic absorption spectrometer adopts a continuous method, and the linear correlation coefficient of the standard working curve is not less than 0.9991.

7. The method according to any one of claims 1 to 6,

in the step of preparing the sample solution, accurately weighing a fertilizer sample with the mass mark of M, adding water, boiling, cooling, transferring to a volumetric flask, and fixing the volume to the volume v, wherein the solution with the constant volume is the prepared sample solution;

preferably, in the step of preparing the sample solution, 0.2g to 0.5g of a fertilizer sample containing 20mg to 35mg of potassium oxide is accurately weighed to 0.0002g, the fertilizer sample is placed in a 250mL triangular flask, 150mL of water is added, the mixture is heated and boiled for 15min, the mixture is transferred after being cooled to room temperature and is subjected to constant volume in a 250mL volumetric flask, and the solution after constant volume is the prepared sample solution.

8. The method according to any one of claims 1 to 7,

in the step of measuring the sample solution, the same conditions as the conditions for measuring the standard solution for drawing the standard working curve are adopted, the blank zero adjustment is carried out, and the measurement of the sample solution is carried out to obtain the absorbance value of the sample solution and the numerical value m of the potassium oxide concentration.

9. The method according to any one of claims 1 to 8,

blank is water used to prepare the sample solution.

10. The method according to any one of claims 1 to 9,

in the step of calculating the content of the potassium oxide in the fertilizer sample, X represents the content of the potassium oxide in the fertilizer sample, and the content of the potassium oxide in the fertilizer sample is calculated according to a formula (1) in percentage:

wherein: m- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -measured concentration of potassium oxide in the sample solution, mu g/mL;

v- - - -diluted volume of sample, mL;

m- -the mass of the fertilizer sample weighed, g.

Background

At present, in the national standard GB/T8574-2010 compound fertilizer, the determination method of the content of potassium oxide in the fertilizer is 3, wherein a potassium tetraphenylborate gravimetric method is the most common method, the method has accurate results, but the time consumption is 4-5h, the operation procedure is complicated, and the requirement of production control cannot be well met. The plasma emission spectroscopy in the national standard GB/T15063-2020 is incapable of being borne by small and medium-sized enterprises due to the high price of plasma emission spectroscopy equipment.

The flame atomic absorption spectrometer is a common instrument in a laboratory, is used for detecting the residual quantity in a sample, and has much lower price than a plasma emission spectrum. However, the detection limit of the flame atomic absorption spectrometer is in the ppm level, which limits the application range of the instrument. At present, active element potassium is used as the residual quantity in a sample, when the active element potassium is measured on an atomic absorption spectrometer, the commonly used measuring wavelength is 766.5nm, the spectral bandwidth is 0.4nm, when the constant potassium oxide in a fertilizer sample is measured by using the bandwidth of 0.4nm, serious interference exists, and the measuring result has larger error compared with the measuring result of a gravimetric method.

If the flame atomic absorption spectrometry can be adopted to realize the measurement of the content of the constant potassium oxide in the fertilizer on the atomic absorption level, the problems can be well solved.

The spectral bandwidth in the instrument parameters is changed into 0.2nm, the slit width of the monochromator is changed, the interference of potassium as a natural active element, which is easily absorbed by other elements in the air near the resonance line is eliminated, and the detection result is accurate and stable.

Disclosure of Invention

In order to overcome the problems in the prior art, the invention provides a method for measuring the content of potassium oxide in a fertilizer by using a flame atomic absorption spectrometer, which realizes the measurement of the content of constant potassium oxide in the fertilizer on the atomic absorption level.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for determining the content of potassium oxide in a fertilizer by using a flame atomic absorption spectrometer, the method comprising:

dissolving a fertilizer sample in water, setting the spectral bandwidth of a flame atomic absorption spectrometer to be 0.2nm by using air-acetylene flame, measuring the absorbance at the wavelength of 404.41nm, and calculating the content of potassium oxide by using a standard working curve method.

In the above method, as a preferred embodiment, the content of potassium oxide in the fertilizer sample is measured in the range of 5 wt% to 20 wt%.

In the above method, as a preferred embodiment, the method comprises the following measurement steps:

preparing a standard solution, drawing a standard working curve, preparing a sample solution, measuring the sample solution and calculating the content of potassium oxide in a fertilizer sample; wherein the content of the first and second substances,

the content of potassium oxide in each standard solution covers the range of 0-200 mu g/mL;

preferably, in the step of preparing the standard solution, 0, 5, 10, 11, 13, 15mL of 1000 μ g/mL potassium chloride standard stock solutions are respectively measured, 10mL of water is added into a 100mL volumetric flask, the solution is shaken up, the volume is fixed to the scale, and the solution is kept stand for 10min, so that the potassium oxide content is respectively prepared as follows: 0. 50, 100, 110, 130, 150. mu.g/mL standard solution.

The blank solution here is: 0mL of a standard solution of 1000. mu.g/mL potassium chloride standard solution, i.e., water to formulate the standard solution or sample solution, is added, and the blank solution can also be referred to directly as a blank.

In the method, as a preferred embodiment, in the step of drawing the standard working curve, on the spectrum of the air-acetylene flame atomic absorption spectrometer, according to the using method and steps of the instrument, the peak finding of 404.41nm wavelength is completed, the spectral bandwidth of the instrument is adjusted to be 0.2nm, the energy balance reaches more than 99.0, after the setting is completed, the standard solution is measured, the blank solution is used for zero calibration, the potassium chloride standard solution is sequentially sucked, the click is stopped, and the instrument can automatically generate the standard working curve with the potassium oxide concentration as the abscissa and the absorbance as the ordinate.

In the above method, as a preferred embodiment, in the step of drawing the standard working curve, before the measurement of the standard solution is performed, other parameters of the flame atomic absorption spectrometer are further set: the filter coefficient is 1.0, the lamp current is 2.0mA, the negative high pressure is 300v, the integration time is 1.0s, the air pressure is 0.25MPa, the acetylene pressure is 0.05MPa, the flow is 1700mL/min, and the height of the combustor is 5 mm.

In the method, as a preferred embodiment, the flame atomic absorption spectrum is calculated by a continuous method using a standard working curve in a spectrometer, and the linear correlation coefficient of the standard working curve is ≧ 0.9991.

In the method, as a preferred embodiment, in the step of preparing the sample solution, a fertilizer sample is accurately weighed, the mass of the fertilizer sample is marked as M, water is added and boiled, the fertilizer sample is cooled and then transferred into a volumetric flask and the volume is determined to be v, and the solution after the volume is determined to be the prepared sample solution;

preferably, in the step of preparing the sample solution, 0.2g to 0.5g of a fertilizer sample containing 20mg to 35mg of potassium oxide is accurately weighed to 0.0002g, the fertilizer sample is placed in a 250mL triangular flask, 150mL of water is added, the mixture is heated and boiled for 15min, the mixture is transferred after being cooled to room temperature and is subjected to constant volume in a 250mL volumetric flask, and the solution after constant volume is the prepared sample solution. The potassium oxide content in the prepared sample solution is 80-140 mug/mL, which is equivalent to the potassium oxide content in the standard solution, and the absorbance is in the linear range of the standard curve.

In the above method, as a preferred embodiment, in the step of measuring the sample solution, the measurement of the sample solution is performed by blank zeroing under the same conditions as those for the test of the standard solution for drawing the standard working curve, and the absorbance value of the sample solution and the value m of the potassium oxide concentration are obtained.

In the above method, as a preferred embodiment, the blank is water for preparing the sample solution.

In the above method, as a preferred embodiment, in the step of calculating the content of potassium oxide in the fertilizer sample, X represents the content of potassium oxide in the sample, and the content of potassium oxide in the fertilizer sample is calculated according to the following formula (1):

wherein m < - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -measured concentration of potassium oxide in the sample solution, and is u g/mL.

v- -volume of sample solution, mL.

M- -the mass of the fertilizer sample weighed, g.

The invention provides a method for determining potassium oxide in fertilizer by using a flame atomic absorption spectrometer, which is characterized by comparing a detection result obtained by adopting a gravimetric method (an arbitration method), finding out an appropriate instrument parameter of the atomic absorption spectrometer, determining an absorbance value of a sample solution under the condition of the parameter, and obtaining a corresponding determined value of the potassium oxide content in a standard curve according to the absorbance value.

In the invention, the spectral bandwidth of 0.2nm and the wavelength of 404.41nm need to be used simultaneously to realize the experimental effect presented by the invention. The single use can not produce the effect of the invention, for example, when the wavelength is 766.5nm and the spectral bandwidth is selected to be 0.4nm, or when the wavelength is 766.5nm and the spectral bandwidth is selected to be 0.2nm and the wavelength is 404.41 and the spectral bandwidth is selected to be 0.4nm, the measured result has larger deviation and can not meet the requirements of national fertilizer standards.

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

1. the spectral bandwidth in the instrument parameters is changed from 0.4mm to 0.2nm, the bandwidth (namely the slit width) of the monochromator is changed, potassium element in the atomic absorption spectrum is eliminated as a natural active element, interference generated by absorption of other elements in the air around the resonance line is easy to generate, and the detection result is accurate and stable.

2. The measurement wavelength of the potassium is changed from the common 766.5nm to 404.41nm, and the influence of larger baseline fluctuation caused by higher content of the conventional potassium oxide in the fertilizer on the precision is improved by reducing the sensitivity of the instrument.

3. In the invention, the sample solution is prepared only by dissolving with water without adding other reagents, thereby avoiding the introduction of other interfering substances.

4. By adopting the method, the used reagents are simple and easy to obtain, the operation is simple and convenient, the measuring result has good stability, accuracy and reproducibility, and tests prove that the method is reliable and practical, can overcome the defects of long time consumption and complicated operation procedures of a gravimetric method, and meets the requirement of fertilizer production control.

5. The invention discloses a method for measuring the content of potassium oxide in the fertilizer and widens the application range of flame atomic absorption spectrometer equipment.

Detailed Description

The technical solutions in the embodiments of the present invention will be described below clearly and completely to enable those skilled in the art to practice and reproduce. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.

In the method for measuring the content of potassium oxide in the fertilizer by using the flame atomic absorption spectrometer, the potassium content in the fertilizer is measured by using a TAS990 air-acetylene flame atomic absorption spectrometer or other conventional air-acetylene flame atomic absorption spectrometers by using 1000ug/ml potassium chloride solution as a standard solution.

In the present invention, technical features not described in detail are adopted by conventional technical solutions in the art.

Example 1

1. Reagent and apparatus

Reagent: potassium chloride standard solution (1000. mu.g/mL).

The instrument comprises the following steps: common laboratory instruments; air-acetylene flame atomic absorption spectrometer (TAS 990); the spectrometer conditions were adjusted as follows: the wavelength is set to 404.41nm, the spectral bandwidth is set to 0.2nm, the filter coefficient is 1.0, the lamp current is 2.0mA, the negative high pressure is 300v, the integration time is 1.0s, the air pressure is 0.25MPa, the acetylene pressure is 0.05MPa, the flow is 1700mL/min, and the height of the combustor is 5 mm.

2. Measurement procedure

(1) Drawing a standard curve:

respectively weighing 0, 5, 10, 11, 13 and 15mL of 1000 mu g/mL potassium chloride standard solution, adding 10mL of water into a 100mL volumetric flask, shaking up, fixing the volume to the scale, and standing for 10 min. The content of potassium oxide in the volumetric flask is respectively as follows: 0. 50, 100, 110, 130, 150. mu.g/mL standard solution.

On an air-acetylene flame atomic absorption spectrometer, according to the using method and steps of the instrument, peak finding is completed at the wavelength of 404.41nm, the spectral bandwidth of the instrument is adjusted to be 0.2nm, the energy balance reaches more than 99.0, other parameters are set, after the setting is completed, the standard solution is measured, the blank solution is used for zero calibration, the potassium chloride standard solution is sequentially sucked, clicking is terminated, the instrument can automatically generate a standard working curve with the mass concentration as horizontal coordinate and the absorbance as vertical coordinate, the curve correlation coefficient R is not less than 0.9991, and the linearity is good. In this embodiment, the standard working curve is calculated by a continuous method.

The blank solution herein refers to a standard solution to which 0mL of a 1000. mu.g/mL potassium chloride standard solution was added.

(2) Sample solution preparation

Accurately weighing about 0.2 g-0.5 g of fertilizer sample containing 20 mg-35 mg of potassium oxide (weighing to 0.0002g), marking as M, placing in a 250mL triangular flask, adding 150mL of water, placing on an electric heating plate, heating, boiling for 15min, cooling to room temperature, transferring and fixing the volume in a 250mL volumetric flask (the diluted volume of the fertilizer sample, marked as v) to obtain the prepared sample solution.

(3) Sample solution assay

The measurement of the sample solution is carried out under the same chromatographic conditions as the curve drawn, with the blank solution being zeroed (here water), and the instrument automatically displays the absorbance value of the sample solution and the value m of the potassium oxide mass concentration.

(4) Calculating the content of potassium oxide:

x represents the potassium oxide content in the sample, calculated as a percentage according to formula (1):

wherein m is the mass concentration of potassium oxide in the sample solution measured on the instrument, mu g/mL.

v- - - -diluted volume of sample, mL.

M- -the mass of the fertilizer sample weighed, g.

3. Accuracy verification

The potassium oxide content of the compound fertilizer was measured by the above method and compared with the results of the gravimetric measurement shown in table 1.

TABLE 1 comparison of results of atomic absorption spectrometry and gravimetric determination of potassium oxide content (%)

Absolute error here means an error of a measurement result of atomic absorption spectrometry with respect to a measurement result of gravimetric method.

The data in table 1 show that when the atomic absorption spectrometry in the embodiment is used for determining the content of potassium oxide in the compound fertilizer, the absolute error between the determination result and the determination result of the gravimetric method is less than 0.3%, which indicates that the determination results of the two methods can be well matched, and the difference between the two methods meets the requirement of different laboratory determination allowable differences (0.60% when 10.0-20.0%) in the national standard GB/T8574-2010.

Therefore, the atomic absorption spectrometry in the present example can be used for the determination of the content of potassium oxide in the compound fertilizer.

4. Precision verification

The potassium oxide content in the sample was measured in parallel several times by atomic absorption photometry and verified for precision, the results are shown in table 2.

Table 2 results of parallel measurement of potassium oxide content (%). on sample solutions

The maximum absolute error here is the maximum difference between each replicate and its mean using atomic absorption spectroscopy.

As can be seen from Table 2, when the same sample solution is subjected to parallel measurement for multiple times, the maximum absolute error between the parallel measurement result and the average value is less than 0.2%, the average deviation of the parallel measurement result is less than 0.1%, the precision is high, the requirements of national standard GB/T8574-2010 are met, and the method is proved to be feasible.

Comparative example 1

The content of potassium oxide in the fertilizer is measured by adopting a conventional atomic absorption spectrometry, and the technical scheme is the same as that of the embodiment 1 except that the measurement wavelength of a flame atomic absorption spectrometer is 766.5nm, and the spectral bandwidth is 0.4nm, which is different from that of the embodiment 1. Table 3 shows the results of the experiments for determining the content of potassium oxide in the fertilizer obtained by the conventional method in this comparative example.

TABLE 3 results of experiments for determining the content of potassium oxide in fertilizers using conventional atomic absorption spectroscopy

As can be seen from Table 3, when the content of potassium oxide in the fertilizer is measured by adopting the conventional atomic absorption spectrometry, the absolute error between the measurement result and the gravimetric measurement result is large and is 0.4-1.3%, which exceeds the allowable difference (0.60% when 10.0-20.0%) measured in different laboratories in GB/T8574-2010, and the result shows that the conventional atomic absorption spectrometry in the comparative example cannot meet the requirement for measuring the content of potassium in the fertilizer.

Therefore, the conventional atomic absorption spectrometry cannot be basically applied to the determination of the fertilizer nutrient content.

It should be understood that the above description is only exemplary of the present invention, but the scope of the present invention is not limited thereto, and any changes, substitutions or improvements that may be made by those skilled in the art within the technical scope of the present invention as disclosed should be covered by the present invention.