Method for detecting compound fertilizer by liquid chromatography

Abstract

The application discloses a method for detecting compound fertilizer by using liquid chromatography, and belongs to the technical field of fertilizer analysis and detection. In the method, hydrochloric acid solution is mixed with a fertilizer sample, ultrapure water is added, and effective phosphorus, potassium oxide, ammonia nitrogen and nitrate nitrogen are extracted after slight boiling, and the contents are determined by using liquid chromatography; meanwhile, ultrasonic waves are used to extract water-soluble phosphorus, chlorine ions and magnesium ions when the contents of the water-soluble phosphorus, the chlorine ions and the magnesium ions are determined. The liquid chromatography and the special analysis technology thereof can shorten the analysis time of the nutrients of the compound fertilizer to less than one hour, the accuracy of the single nutrient determination result basically reaches the allowable difference value specified in the national standard analysis method, and therefore, the rapid and accurate analysis of the nutrients of the compound fertilizer is realized.

Description

Technical Field

[0001] This invention belongs to the field of fertilizer analysis and detection technology, and more specifically relates to a method for detecting compound fertilizers using liquid chromatography. Background Technology

[0002] The use of compound fertilizers represents a significant new development in the fertilizer industry. Compound fertilizers, combining multiple elements, provide crops with more balanced nutrition, and are an effective way to promote crop growth, increase yield, and improve quality. Therefore, to ensure the quality of compound fertilizers and control their nutrient content, the testing and analysis of compound fertilizers is particularly important.

[0003] Currently, domestic analytical methods and equipment are configured according to the methods specified in the national standard GB / T15063-2020. Although the accuracy is high, the analysis time is as long as more than 3 hours, resulting in low work efficiency, high labor intensity, and long analysis time. Sometimes, it cannot meet the requirements of process changeover, formula adjustment, and temporary additional analysis. Research shows that liquid chromatography and its dedicated analytical techniques can shorten the analysis time of compound fertilizer nutrients to less than 1 hour, and the accuracy of single nutrient determination results basically meets the allowable difference specified by the national standard analytical methods, thus achieving rapid and accurate analysis of compound fertilizer nutrients. Although liquid chromatography has a wide range of applications, there is currently no mature technology for its direct application in the analysis of high-concentration compound fertilizers. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a method for detecting compound fertilizers using liquid chromatography. This invention combines the principles of liquid chromatography with technological development, determining optimal experimental conditions. This not only ensures instrument stability and accurate analytical results, but also reduces the analysis time from 3 hours to 1 hour, and solves the technical challenge of detecting available phosphorus.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a method for detecting compound fertilizers using liquid chromatography, comprising the following steps:

[0007] S1. Preparation of calibration solution for liquid chromatography: Take commercially available NO... 3- NH4 + PO4 3- K + Cl - Mg + Standard stock solutions, each with a concentration of 1000 mg / L, were diluted to prepare calibration stock solutions, diluted to volume with ultrapure water, and the concentrations of each ion were determined by liquid chromatography to prepare standard curve solutions.

[0008] S2. Determination of available phosphorus, potassium oxide, ammonia nitrogen, and nitrate nitrogen content:

[0009] (1) The compound fertilizer is crushed and sieved to obtain a fine powder sample;

[0010] (2) Weigh 15-21 parts of the sample, add a small amount of ultrapure water to wet it; add 10-16 parts of hydrochloric acid solution, mix well for more than 30 seconds, add 100 parts of ultrapure water, heat at 300-450℃ for 5-10 minutes, and then cool to room temperature.

[0011] (3) Take the solution, make up to volume, mix and filter to obtain the filtrate; dilute the filtrate with ultrapure water in proportion and then use liquid chromatography to perform quantitative detection to obtain the contents of available phosphorus, potassium oxide, ammonia nitrogen and nitrate nitrogen in the compound fertilizer sample.

[0012] S3. Determination of water-soluble phosphorus, chloride, and magnesium ion content:

[0013] (1) The compound fertilizer is crushed and sieved to obtain a fine powder sample;

[0014] (2) Weigh 15-21 portions of the sample, first add ultrapure water to dilute to 3 / 4 of the volumetric flask, sonicate in an ultrasonic cleaner, mix after making up to volume, filter, and obtain the filtrate.

[0015] (3) The filtrate was diluted with ultrapure water in a certain proportion and then quantitatively detected by liquid chromatography to obtain the contents of water-soluble phosphorus, chloride and magnesium ions in the compound fertilizer sample.

[0016] Compared with existing technologies, this invention uses liquid chromatography to effectively separate multiple ions simultaneously, enabling rapid detection of multiple nutrients in compound fertilizers within one hour with accurate results. Moreover, this method can solve the problem of human error in the repeatability of manual analysis of the same sample, as the machine automatically injects the sample, reducing human interference.

[0017] Furthermore, this invention creatively adds hydrochloric acid solution to the sample when detecting the content of available phosphorus, potassium oxide, ammonia nitrogen, and nitrate nitrogen. This allows for accurate determination of the available phosphorus content in compound fertilizers without interfering with other nutrients. The concentration of the added hydrochloric acid solution is low, posing no harm to the environment or human health. The inventors also discovered that hydrochloric acid solution is irreplaceable. Replacing hydrochloric acid solution with EDTA solution leads to a higher baseline, affecting the accuracy of the results; using sulfuric acid solution instead of hydrochloric acid solution results in a difference far exceeding the allowable value specified in the national standard analytical method.

[0018] Furthermore, the content percentage of each nutrient in the compound fertilizer is calculated using the formula:

[0019] The formulas for calculating available phosphorus and water-soluble phosphorus are:

[0020] In the formula, the phosphate content is expressed in mg / g, M(P) = 31, M(PO4) = 31. 3-)=95, M(P2O5)=142;

[0021] The formula for calculating potassium oxide is:

[0022] In the formula, the potassium ion content is expressed in mg / g, M(K2O) = 94, and M(K) = 39;

[0023] The formula for calculating ammonium nitrogen is:

[0024] In the formula, the ammonium content is expressed in mg / g, M(N) = 14, and M(NH4) = 18;

[0025] The formula for calculating nitrate nitrogen is:

[0026] In the formula, the nitrate content is expressed in mg / g, M(N) = 14, and M(NO) = 62;

[0027] The formula for calculating total nitrogen is: Total N / % = NH3-N / % + NO3-N / %;

[0028] The formula for calculating chloride ions is:

[0029] In the formula, the chloride ion content is expressed in mg / g, and M(Cl) = 35.5;

[0030] The formula for calculating magnesium ions is:

[0031] In the formula, the magnesium ion content is expressed in mg / g, M(MgSO4·7H2O)=246, M(Mg)=24.

[0032] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. The method of this invention can quickly extract available phosphorus, potassium oxide, ammonia nitrogen, nitrate nitrogen, water-soluble phosphorus, chloride ions and magnesium ions from compound fertilizers, and accurately detect the content of each nutrient in the compound fertilizer.

[0034] 2. Compared with the traditional national standard method, ion chromatography has simpler sample pretreatment, saves time, is green and safe, and provides accurate detection results.

[0035] 3. The sample testing has good repeatability and there is no interference from human error.

[0036] 4. Liquid chromatography was used to determine the single nutrients in compound fertilizers, and the accuracy of the results basically met the allowable difference specified in the national standard analytical method.

[0037] 5. By extracting and measuring the nutrients in compound fertilizers, we can understand the condition and nutrient content of the compound fertilizers being tested, and thus provide guidance for the rational application of compound fertilizers. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0039] Figure 1 This is a chromatogram of each ion in the mixed standard solution with the highest anion concentration in Example 1.

[0040] Figure 2 The image shows the chromatograms of each ion in the mixed standard solution with the highest cation concentration in Example 1.

[0041] Figure 3 This is a linear relationship graph of the standard curves for the calibration methods of each ion in the anion mixed standard solution of Example 1.

[0042] Figure 4 This is a linear relationship graph of the standard curves for the calibration methods of each ion in the cationic mixed standard solution of Example 1.

[0043] Figure 5 The ion chromatograms and conversion results of anionic nitrate nitrogen and available phosphorus in Example 1 are shown.

[0044] Figure 6 The images show the ion chromatograms and conversion results of cationic ammonium nitrogen and potassium oxide in Example 1.

[0045] Figure 7 The ion chromatograms and conversion results of anionic water-soluble phosphorus and chloride ions in Example 1 are shown.

[0046] Figure 8 The image shows the ion chromatogram and conversion results of the magnesium ion cation in Example 1.

[0047] Figure 9 This is a comparison of ion chromatograms of the extraction of compound fertilizer nutrients using EDTA solution at pH 12.0 and hydrochloric acid solution.

[0048] Figure 10 The image shows the ion chromatogram of available phosphorus extracted from the nutrients of compound fertilizer 12-6-24 using sulfuric acid solution.

[0049] Figure 11 This is a comparison of ion chromatograms of the extraction of compound fertilizer nutrients using EDTA solution at pH 4.5 and hydrochloric acid solution. Detailed Implementation

[0050] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0051] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0052] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0053] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0054] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this application.

[0055] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0056] Example 1

[0057] A method for detecting compound fertilizer with a 12-6-24 formulation using liquid chromatography:

[0058] (1) Preparation of calibration solution for liquid chromatography: Take commercially available NO 3- NH 4+ PO4 3- K + Cl - Mg +Standard stock solutions, all with a concentration of 1000 mg / L, were diluted separately to prepare calibration solution stock solutions (NO). 3- 500.0 mg / L, NH4 + 100.0 mg / L, PO4 3- 100.0 mg / L, K + 125.0 mg / L, Cl - 10.0 mg / L, Mg + (5.0 mg / L), diluted with ultrapure water, and the mother liquor was transferred according to the measured compound fertilizer formula concentration to prepare a standard curve solution.

[0059] (2) Adjust the instrument according to the liquid chromatography operation manual:

[0060] Main unit: Liquid chromatograph, equipped with an anion exchange eluent system and an autosampler system, built-in degassing device, and optional Thermo Fisher cationic column;

[0061] Pure water machine: resistivity 18.25MΩ.cm, conforming to GB6682-2008 Class I water standard and ASTM CAPNCLS standard;

[0062] The instrument parameter settings are shown in the table below.

[0063]

[0064] Once the instrument is ready, select the appropriate nutrient measurement method and measure the calibration solution and blank solution sequentially.

[0065] See results Figures 1-4 ,in, Figure 1 and Figure 2 This is a chromatogram of each ion in a mixed standard solution of anions and cations at their highest concentrations. Figure 1 and Figure 2 As can be seen, the chromatographic peaks of each ion in the mixed solution of six standard substances are displayed. The above method can effectively separate multiple ions simultaneously and has certain practicality. This indicates that it can effectively determine the content of available phosphorus, potassium oxide, ammonia nitrogen, nitrate nitrogen, water-soluble phosphorus, chloride ions, and magnesium ions in samples. Figure 3 and Figure 4 This is a linear relationship graph of the standard curves for each ion calibration method in a mixed standard solution of anions and cations. Figure 3 and Figure 4 It can be seen that the linearity R values ​​of each ion in the mixed standard solution are as follows: NO 3- (R = 0.999992), PO4 3- (R=0.999910), NH4 + (R=0.999668), K +(R=0.999991), Cl - (R=0.999913), Mg + (R = 0.999926), and the R value for liquid chromatography only needs to be above 0.995. The above method shows that the linear relationship of each ion in the mixed standard solution is very good, and it can accurately determine the contents of available phosphorus, potassium oxide, ammonia nitrogen, nitrate nitrogen, water-soluble phosphorus, chloride ions and magnesium ions in the sample.

[0066] (3) Weigh 20 parts of the sieved fine powder sample into a glass beaker and add a small amount of ultrapure water to moisten it; add 15 parts of hydrochloric acid solution into the beaker, mix well for more than 30 seconds, and add 100 parts of ultrapure water; place the beaker on an electric furnace and boil gently at 300℃ for 5 minutes, then remove it and cool it to room temperature; after extraction, transfer the solution into a 100mL volumetric flask, dilute to volume with ultrapure water, mix well, and filter through a 0.22um filter membrane to obtain the filtrate.

[0067] (4) The filtrate was diluted with ultrapure water in a certain proportion and then quantitatively detected by liquid chromatography to obtain the contents of available phosphorus, potassium oxide, ammonia nitrogen and nitrate nitrogen in the compound fertilizer sample.

[0068] (5) Weigh 20 portions of the sieved fine powder sample into a 100mL volumetric flask, add ultrapure water to dilute to 3 / 4 of the volumetric flask, sonicate in an ultrasonic cleaner, mix well after adjusting the volume, filter through a 0.22um filter membrane to obtain the filtrate.

[0069] (6) The filtrate was diluted with ultrapure water in a certain proportion and then quantitatively detected by liquid chromatography to obtain the content of water-soluble phosphorus, chloride and magnesium ions in the compound fertilizer sample.

[0070] Depend on Figure 5 , Figure 6 , Figure 7 , Figure 8 The results of the liquid chromatography analysis of compound fertilizer 12-6-24 are as follows: nitrate nitrogen (7.06%), available phosphorus (6.34%), ammonia nitrogen (5.44%), potassium oxide (24.53%), water-soluble phosphorus (4.53%), chloride ion (1.36%), and magnesium ion (2.41%). The results of the analysis using the method specified in the national standard GB / T15063-2020 are as follows: nitrate nitrogen (6.84%), available phosphorus (6.51%), ammonia nitrogen (5.51%), potassium oxide (24.52%), water-soluble phosphorus (4.43%), chloride ion (1.25%), and magnesium ion (2.55%).

[0071] The above results indicate that the accuracy of the measurement results basically meets the allowable difference specified by the national standard analysis method, and can realize rapid and accurate analysis of compound fertilizer nutrients.

[0072] Example 2

[0073] This invention, through experiments, has proven that adding hydrochloric acid solution can extract available phosphorus from compound fertilizer nutrients. The aim is to accurately extract the content of available phosphorus without interfering with other nutrients. The concentration of the added hydrochloric acid solution is low, posing no harm to the environment or human health. Specific experimental evidence is as follows:

[0074] (1) Prepare a 37.5 g / L EDTA solution and adjust the pH to 12.0 with sodium hydroxide solution to extract available phosphorus from the compound fertilizer. Figure 9 It can be seen that, compared with hydrochloric acid solution, EDTA solution extracts available phosphorus and has a certain impact on the determination by liquid chromatography. EDTA solution causes the baseline to be higher, affecting the accuracy of the results.

[0075] (2) Extracting available phosphorus from the nutrients in compound fertilizer 12-6-24 using sulfuric acid solution, by... Figure 10 The available phosphorus content was found to be 8.08%, while the national standard analysis showed an available phosphorus content of 6.27%, resulting in a measurement error of 1.81%, which is far greater than the allowable difference specified in the national standard analysis method. This proves that sulfuric acid solution is not suitable for extracting available phosphorus content.

[0076] (3) Prepare a 37.5 g / L EDTA solution, adjust the pH to 4.5, and extract the available phosphorus and nitrate nitrogen content from the 12-12-24 compound fertilizer. Figure 11 The results showed that the available phosphorus content was 13.51%, and the nitrate nitrogen content was 6.55%. The available phosphorus content extracted with hydrochloric acid solution was 12.60%, and the nitrate nitrogen content was 6.54%. According to national standards, the available phosphorus content was 12.57%, and the nitrate nitrogen content was 6.73%. These data indicate that the available phosphorus content extracted with EDTA solution was higher than the national standard results, with a measurement error of 0.94%. The measurement error using hydrochloric acid solution was only 0.03%, demonstrating that hydrochloric acid solution can accurately extract the available phosphorus content without interfering with other nutrients.

[0077] (4) After reviewing the literature and communicating with the instrument manufacturer, it was found that acidic solutions such as oxalic acid and citric acid could not be used to extract available phosphorus, as they would damage the chromatographic column; and phosphoric acid solution could not be used, as it would interfere with the determination of available phosphorus in compound fertilizer nutrients. The experiment ultimately proved that adding hydrochloric acid solution could extract available phosphorus from compound fertilizer nutrients, the determination of available phosphorus content was accurate, and there was no interference with other nutrients. The concentration of the added hydrochloric acid solution was not high and did not cause harm to the environment or human health.

[0078] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting compound fertilizers by liquid chromatography, characterized in that, It comprises the following steps: S1, liquid chromatography calibration solution preparation: take commercially available NO 3- , NH4 + , PO4 3- , K + , Cl - , Mg + standard stock solution, the concentration is 1000 mg / L, respectively dilute and prepare calibration solution mother liquor, use ultrapure water to constant volume, liquid chromatography determines the concentration of each ion, and prepares standard curve solution; S2, determining the content of available phosphorus, potassium oxide, ammonia nitrogen and nitrate nitrogen: (1) Pulverize the compound fertilizer, sieve, and obtain a fine powder sample; (2) Take 15-21 parts of the sample, add a small amount of ultrapure water to wet it; add 10-16 parts of hydrochloric acid solution, mix for more than 30s, add 100 parts of ultrapure water, heat at 300-450℃ for 5-10min, and then cool to room temperature; (3) Take the solution, dilute it to volume, mix well, and filter to obtain the filtrate; dilute the filtrate with ultrapure water according to the proportion, and then use liquid chromatography to quantitatively detect the content of available phosphorus, potassium oxide, ammonia nitrogen and nitrate nitrogen in the compound fertilizer sample; S3, determining the content of water-soluble phosphorus, chloride ions and magnesium ions: (1) Pulverize the compound fertilizer, sieve, and obtain a fine powder sample; (2) Take 15-21 parts of the sample, dilute to 3 / 4 of the volume of the volumetric flask with ultrapure water, ultrasonic clean in an ultrasonic cleaner, mix well after dilution to volume, and filter to obtain the filtrate; (3) Dilute the filtrate with ultrapure water according to the proportion, and then use liquid chromatography to quantitatively detect the content of water-soluble phosphorus, chloride ions and magnesium ions in the compound fertilizer sample.

2. The method for detecting compound fertilizer according to claim 1, characterized in that, The content of each nutrient in the compound fertilizer is calculated according to the formula: The calculation formula of effective phosphorus and water-soluble phosphorus is: In the formula, the phosphate content is expressed in mg / g, M(P) = 31, M(PO4) = 31. 3- )=95, M(P2O5)=142; The calculation formula of potassium oxide is: In the formula, the potassium ion content is mg / g, M(K2O)=94, and M(K)=39; The calculation formula of ammonium nitrogen is: In the formula, the ammonium content is mg / g, M(N)=14, and M(NH4)=18; The calculation formula for nitrate nitrogen is: In the formula, the nitrate content is mg / g, M(N)=14, and M(NO)=62; The total nitrogen calculation formula is total N / %=NH3-N / %+NO3-N / %; The calculation formula of chloride ion is In the formula, the chloride ion content is mg / g, M(Cl)=35.5; The formula for calculating the magnesium ions is In the formula, the magnesium ion content is mg / g, M(MgSO4·7H2O)=246, and M(Mg)=24.

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