Liquid chromatography device for simultaneously separating and quantitatively detecting potassium ions, sodium ions, nitrate radicals and nitrite radicals in solar fused salt

Abstract

The utility model relates to a liquid chromatogram device for simultaneously separating and quantitatively detecting potassium ions, sodium ions, nitrate radicals and nitrite radicals in solar fused salt, which comprises a mobile phase liquid storage device, a high-pressure pump for conveying a mobile phase, a sample injector, an Acclaim Trinity P1 liquid chromatogram column, an ultraviolet detector and an electric fog type detector, wherein the mobile phase liquid storage device is connected with the sample injector through the high-pressure pump, the sample injector is connected with the Acclaim Trinity P1 liquid chromatographic column, and the chromatographic column is sequentially connected with the ultraviolet detector and the electric fog type detector in series.

Description

Technical Field

[0001] This utility model relates to the field of molten salt detection technology, and more specifically, to a liquid chromatography apparatus for simultaneously separating and detecting potassium ions, sodium ions, nitrate ions and nitrite ions in molten salt. Background Technology

[0002] The current testing standard for solar-grade molten salt (nitro type) is GB / T 36376-2018. In this standard, the content of potassium nitrate, the main component, is estimated by titrating potassium ions with sodium tetraphenylborate, and the content of sodium nitrite is estimated by titrating nitrite with potassium permanganate, while simultaneously deducting other known impurities. This standard does not directly determine the main component, and the sodium tetraphenylborate precipitation titration method is cumbersome and easily affected by other impurity ions such as ammonium; the potassium permanganate method for determining nitrite is also easily affected by other reducing substances. All of these factors can lead to results deviating from the true value, resulting in significant errors.

[0003] Currently, inductively coupled plasma atomic emission spectrometry (ICP) is widely used for the testing of cations (sodium ions, potassium ions), and ion chromatography (IC) is widely used for the testing of anions (nitrate ions, nitrite ions). However, for the testing of the main components in molten salts, dilution of approximately 10,000 times is required. This excessive dilution factor, coupled with the inability to detect components simultaneously, results in significant systematic errors. Consequently, the ratios of nitrate ions to potassium ions and nitrite ions to sodium ions deviate considerably from the theoretical ratio of 1:1.

[0004] Currently, there are no reliable methods or devices to achieve rapid and accurate separation and detection of the main components potassium ions, sodium ions, nitrate ions, and nitrite ions in molten salt.

[0005] Therefore, this application proposes a liquid chromatography apparatus that enables the simultaneous separation and quantitative detection of the main components of solar molten salt, potassium ions, sodium ions, nitrate ions and nitrite ions, in a single sample injection using liquid chromatography. The apparatus is easy to operate and provides accurate and reliable measurement results. Utility Model Content

[0006] This application provides a liquid chromatography apparatus for the simultaneous separation and quantitative detection of potassium ions, sodium ions, nitrate ions, and nitrite ions in solar-heated molten salt. The apparatus includes a mobile phase reservoir, a high-pressure pump for delivering the mobile phase, an injector, an Acclaim Trinity P1 liquid chromatography column, and an ultraviolet detector and an electro-cavitation detector. The mobile phase reservoir is connected to the injector via the high-pressure pump, and the injector is connected to the Acclaim Trinity P1 liquid chromatography column. The column is sequentially connected to the ultraviolet detector and the electro-cavitation detector (CAD).

[0007] In one example, the ultraviolet detector is a diode array detector (DAD).

[0008] The liquid chromatography apparatus of this application is simple to operate and provides accurate and reliable measurement data. Using its Acclaim Trinity P1 liquid chromatography column and sequentially connected ultraviolet detector and electro-fogging detector, the main components of solar-powered molten salt—potassium ions, sodium ions, nitrate ions, and nitrite ions—can be simultaneously separated and quantitatively detected. Furthermore, the apparatus can simultaneously separate and detect potassium ions, sodium ions, nitrate ions, and nitrite ions in solar-powered molten salt with a single injection. Sample pretreatment is simple, requiring only a small dilution factor; a single water dilution step is sufficient for injection and detection. In addition, the standard salts used for testing are of high purity and readily available, ensuring accurate calibration calculations and avoiding errors caused by separate detections. Therefore, the apparatus of this application exhibits high resolution, good stability, high accuracy, and is simple, time-saving, and efficient to operate. Attached Figure Description

[0009] Figure 1 : A schematic diagram of the liquid chromatography apparatus of this application

[0010] Figure 2 Standard curves of sodium, potassium, nitrate, and nitrite ions in standard solutions.

[0011] Figure 3 According to Example 1, the chromatogram of the solar-powered molten salt sample was obtained by liquid chromatography separation using a DAD detector.

[0012] Figure 4 According to Example 1, the chromatogram of the solar-powered molten salt sample was obtained by liquid chromatography using a CAD detector.

[0013] Figure 5 The chromatogram obtained by liquid chromatography separation of solar-powered molten salt samples according to Comparative Example 1. Detailed Implementation

[0014] The liquid chromatography apparatus of this application and the method of using the apparatus to separate and detect the main components of solar-heated molten salt, namely potassium ions, sodium ions, nitrate ions and nitrite ions, will be described in detail below with reference to the accompanying drawings.

[0015] Figure 1 A schematic diagram of the liquid chromatography apparatus according to this application is shown. Figure 1As shown, the liquid chromatography apparatus of this application includes a mobile phase reservoir 1, a high-pressure pump 2 for delivering the mobile phase, an injector 3, an Acclaim Trinity P1 liquid chromatography column 4, and an ultraviolet detector 5 and an electro-fogging detector 6. The mobile phase reservoir 1 is connected to the injector 3 via the high-pressure pump 2, the injector 3 is connected to the Acclaim Trinity P1 liquid chromatography column 4, and the column 4 is sequentially connected to the ultraviolet detector 5 and the electro-fogging detector 6.

[0016] The method for simultaneously separating and quantitatively detecting potassium ions, sodium ions, nitrate ions, and nitrite ions in solar-heated molten salt using this liquid chromatography apparatus is as follows:

[0017] First, an aqueous solution containing potassium nitrate and sodium nitrite, a solar-grade molten salt, is prepared as the sample solution and mobile phase. The mobile phase consists of mobile phase A (pH 4-5, 10-100 mM acetate buffer), mobile phase B (acetonitrile), and mobile phase C (formic acid solution). The volume ratio of mobile phase A to mobile phase B is controlled at 40:45 to 40:50 based on the total volume of the mobile phase. Then, the mobile phase is pumped from the mobile phase reservoir 1 into the injector 3 via a high-pressure pump 2. The sample solution, along with the mobile phase, enters the chromatographic column 4 via the injector 3. The ionic components in the sample solution elute sequentially from the column and then sequentially enter the UV detector 5 and the electro-fogging detector 6. The UV detector 5 detects nitrate and nitrite, while the electro-fogging detector 6 detects sodium and potassium ions.

[0018] In this process, the steps of preparing an aqueous solution of solar molten salt containing potassium nitrate and sodium nitrite, i.e., preparing a sample solution, typically involve weighing a certain amount, usually 0.1g, of solar molten salt and diluting it with water about 1000 times to obtain the sample solution.

[0019] Before or after the sample solution preparation step, this method also includes a step of preparing a standard solution. This step involves dissolving potassium nitrate and sodium nitrite standards in water to obtain a mixed standard solution of potassium nitrate and sodium nitrite. The concentration range of the potassium nitrate and sodium nitrite standard solutions is typically 10 mg / L to 1000 mg / L, and those skilled in the art can determine the appropriate standard solution concentration according to specific circumstances.

[0020] In the liquid chromatography apparatus of this application, the chromatographic column used is an Acclaim Trinity P1 liquid chromatography column, and its stationary phase is a porous silica particle packing coated with sulfonated nanopolymer beads. The inner pore region of the porous silica particles is modified with a covalently bonded hydrophilic layer, and the outer pore region is modified with sulfonated nanopolymer beads.

[0021] The packing material is based on high-purity spherical porous silica particles, typically with a particle size of 3 μm. Using a nanopolymer-silica gel hybrid technology, the inner pore region is modified with an organic layer providing reverse-phase and anion exchange properties, while the outer pore region is modified with a sulfonated nanopolymer with cation exchange functionality. This ensures spatial separation between the anion exchange region (inner pore region) and the cation exchange region (outer pore region), allowing both retention mechanisms to function simultaneously and enabling independent control over them. Therefore, the stationary phase packing material possesses three retention mechanisms: anion exchange, cation exchange, and reverse-phase.

[0022] The mobile phase used comprises an acetate buffer solution as mobile phase A, acetonitrile as mobile phase B, and formic acid solution as mobile phase C. The acetate buffer solution is typically adjusted to pH 4-5 with acetic acid and formic acid (mobile phase C), and its concentration is typically 10-100 mM, preferably 15-50 mM, and more preferably 20-30 mM. Based on the total volume of the mobile phase, the volume ratio of mobile phase A to mobile phase B is controlled to be between 40:45 and 40:50, preferably 40:45.

[0023] When performing separation and detection using the liquid chromatography apparatus of this application, isocratic elution is preferred. The flow rate of the mobile phase is 0.7-0.9 mL / min, preferably 0.8 mL / min. The column temperature is 30-40 °C, preferably 40 °C.

[0024] The ultraviolet detector is preferably a diode array detector (DAD). The detection wavelength for detecting nitrate and nitrite in the ultraviolet detector is typically 205 nm to 230 nm, preferably 210 nm.

[0025] The contents of sodium ions, potassium ions, nitrate ions, and nitrite ions in the sample solution can be calculated using the external standard method. Specifically, using the chromatographic conditions described above, the prepared mixed standard solution is injected into the high-performance liquid chromatography (HPLC) apparatus of this application to obtain chromatograms of standard solutions at various concentrations. The corresponding peak areas are measured, and a standard curve for nitrate ions and nitrite ions is plotted with the mass concentrations of sodium ions, potassium ions, nitrate ions, and nitrite ions as the abscissa and the peak areas as the ordinate. The contents of sodium ions, potassium ions, nitrate ions, and nitrite ions in the sample solution to be tested are calculated using the external standard method based on the standard curve.

[0026] Example:

[0027] Experimental materials:

[0028] Potassium nitrate and sodium nitrite standards: purchased from Sinopharm Chemical Reagent Co., Ltd.

[0029] Solar-powered molten salt sample: purchased from Weifang Changsheng Nitrate Co., Ltd.

[0030] Example 1:

[0031] Using the liquid chromatography apparatus of this application, the chromatographic conditions are set as follows:

[0032] Washing mode: isocratic elution;

[0033] Mobile phase: Mobile phase A is 20 mM NH4OAc / 0.1% HOAc buffer solution (pH 5), mobile phase B is acetonitrile, and mobile phase C is 0.1% formic acid. The volume ratio of mobile phases A, B, and C is 40:45:15.

[0034] Flow rate: 0.8 mL / min;

[0035] Column temperature: 40℃;

[0036] Injection volume: 1.0 μL;

[0037] Detector: A DAD detector (detection wavelength: 210nm) and a CAD detector are connected in series.

[0038] Preparation of standard solution:

[0039] Weigh 250 mg of potassium nitrate standard and sodium nitrite standard respectively, dissolve them in water to prepare a series of KNO3 and NaNO2 mixed standard solutions of different concentrations.

[0040] Preparation of sample solution:

[0041] Weigh 100 mg of sample and dilute with water to 100 mL.

[0042] Under the chromatographic conditions described above, inject 1.0 μL of the sample solution into the liquid chromatography apparatus and record the chromatogram. The sample chromatogram is shown below. Figure 3 and Figure 4 .

[0043] The chromatograms showed that the retention times of sodium ions, potassium ions, nitrite ions, and nitrate ions were approximately 3.8 min, 4.5 min, 12.6 min, and 15.2 min, respectively. Their elution times differed significantly, indicating good separation.

[0044] Nitrite cannot be detected by the CAD detector in the liquid chromatography apparatus. Therefore, the inventors connected the DAD detector and the CAD detector in series in the liquid chromatography apparatus of this application. First, the DAD detector detects nitrate and nitrite, and then the CAD detector detects sodium and potassium ions, thus successfully separating and detecting sodium ions, potassium ions, nitrate, and nitrite. Figure 3 and Figure 4 As shown.

[0045] Under the chromatographic conditions described above, 1.0 μL of a mixed standard solution of KNO3 and NaNO2 was injected into the liquid chromatography apparatus for separation and detection by liquid chromatography. Quadratic linear fitting curves for sodium and potassium ions, as well as linear equation curves for nitrate and nitrite ions, were obtained. Figure 2 As shown, the linear equation for nitrite is: y = 0.0901x + 0.0947, with a correlation coefficient R. 2 =0.9992; Linear equation for nitrate: y = 0.1016x - 0.0778, correlation coefficient R 2 =0.9991; The quadratic linear equation for sodium ions is: y = -0.000019x 2 +0.0319x+0.1420, correlation coefficient R 2 =0.9987; Quadratic linear equation for potassium ions: y = -0.000014x 2 +0.0250x+0.0096, correlation coefficient R 2 =0.9991, where x represents the concentration of each ion; y represents the peak area of ​​the corresponding ion in the detection spectrum. The linear relationships of the linear equations are good, therefore they can be well used for the determination of sodium ions, potassium ions, nitrate ions, and nitrite ions.

[0046] Using the above linear equation, the contents of sodium ions, potassium ions, nitrate ions, and nitrite ions in the samples were calculated using the external standard method. Each of the three batches of samples was measured three times in parallel, and the average value was calculated for each batch. The results are shown in Table 1 below:

[0047] Table 1: Contents of sodium ions, potassium ions, nitrate ions, and nitrite ions in solar-generated molten salt samples

[0048]

[0049] The results above demonstrate that the liquid chromatography apparatus of this application can simultaneously separate and detect the contents of sodium ions, potassium ions, nitrate ions, and nitrite ions, with good repeatability and high accuracy. Furthermore, the ratios of nitrate ions to potassium ions and the ratio of nitrite ions to sodium ions deviate very little from the theoretical ratio of 1:1, both within 3%.

[0050] Accuracy test:

[0051] The spiked recoveries were determined as follows, and the results are shown in Table 2 below:

[0052] 1. Preparation of calibration curve series solutions: Weigh 500 mg each of potassium nitrate and sodium nitrite standards into 50 mL volumetric flasks, record the mass to the nearest 0.1 mg, and dissolve and dilute to volume with water. This solution is the standard stock solution with a concentration of approximately 10,000 mg / L. Prepare a series of calibration curve solutions by serial dilution and perform tests.

[0053] 2. Sample Preparation: Considering the high hygroscopicity of the solar-grade molten salt surface, its large particle size, and uneven distribution, even with the same sampling method, concentration deviations may occur. However, given its chemical composition of potassium nitrate and sodium nitrite, a simulated sample of similar concentration was prepared using potassium nitrate and sodium nitrite standards for testing. This eliminates the problem of sample inhomogeneity while still allowing for the accuracy of the method. The specific steps are as follows: Weigh approximately 0.05g of potassium nitrate and 0.045g of sodium nitrite into a 100mL volumetric flask, record the mass to the nearest 0.1mg, and prepare five parallel samples using the same steps. Two samples were directly dissolved in water and diluted to volume for testing, and the average result was used to obtain the concentration of each ion in the simulated sample. The other three samples were dissolved in 2.5mL of a 10000mg / L standard stock solution, diluted to volume with water, and tested. The recovery rate was calculated based on the ion concentration values ​​of the spiked sample solution and the average ion concentration values ​​of the simulated sample.

[0054] Table 2: Spike Recovery Rate

[0055]

[0056] As shown in the table above, the recoveries of the four ions in the molten salt samples all ranged from 95% to 100%, indicating that the apparatus of this application has high recovery rates and excellent accuracy. Therefore, the determination results of the liquid chromatography apparatus of this application are accurate and reliable.

[0057] Comparative Example 1:

[0058] Using the same chromatographic conditions as in Example 1, except that the column used in the liquid chromatography apparatus was replaced with a C18 column: Acclaim carbonyl C18 (3.0*150mm, 3μm), the sample solution was separated and detected, and the resulting chromatogram is shown below. Figure 5 As shown.

[0059] Depend on Figure 5 As can be seen, on the same C18 reversed-phase chromatographic column, according to the response signals of CAD and DAD, none of the four analytes were retained and they co-eluted directly.

[0060] The above descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A liquid chromatography apparatus for simultaneously separating and quantitatively detecting potassium ions, sodium ions, nitrate ions, and nitrite ions in a solar molten salt, characterized by comprising: a column for separating and quantitatively detecting potassium ions, sodium ions, nitrate ions, and nitrite ions in a solar molten salt; and a column oven for maintaining the column at a predetermined temperature. The liquid chromatograph device comprises a mobile phase reservoir, a high-pressure pump for conveying the mobile phase, a sample injector, an Acclaim Trinity P1 liquid chromatograph column, and an ultraviolet detector and an electrospray detector, wherein the mobile phase reservoir is connected to the sample injector through the high-pressure pump, the sample injector is connected to the Acclaim Trinity P1 liquid chromatograph column, and the chromatograph column is connected to the ultraviolet detector and the electrospray detector in sequence.

2. The liquid chromatography apparatus for simultaneously separating and quantitatively detecting potassium ions, sodium ions, nitrate ions, and nitrite ions in a solar molten salt according to claim 1, characterized by, The ultraviolet detector is a diode array detector.

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