Determination system of octadecylamine in potassium chloride and its application

Abstract

The present invention discloses a determination system for octadecylamine in potassium chloride and its application. The determination system includes a water-soluble indicator solution, a buffer solution, and an octadecylamine standard stock solution. Among them, the water-soluble indicator solution is prepared by the following steps: Weigh a water-soluble indicator and make up the volume with distilled water to obtain a water-soluble indicator solution with a concentration of 0.1 - 20 g / L; the pH of the buffer solution is 4.5 - 6.0; the octadecylamine standard stock solution includes a plurality of octadecylamine standard solutions with different concentrations, and the concentrations of the plurality of octadecylamine standard solutions vary in a gradient manner. It is prepared by the following steps: Accurately weigh a predetermined mass of octadecylamine, dissolve it in a long-chain alkane and make up the volume, and then dilute it respectively to obtain octadecylamine standard solutions with different concentrations. The determination system of the present invention can improve the accuracy of the determination of the octadecylamine content in potassium chloride.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical detection, and particularly relates to a determination system for octadecylamine in potassium chloride and its application. Background Art

[0002] Octadecylamine is an impurity introduced in the production process of potassium chloride. The existing methods for determining octadecylamine are as follows:

[0003] Hu Jiayuan et al. (CN102062728B) provided a method for determining the concentration of octadecylamine without adding a chromogenic agent. Glacial acetic acid was added to the solution to be measured, and the absorbance in the ultraviolet region was directly measured, which could effectively measure octadecylamine in the content range of 10 - 50 mg / L. Octadecylamine has low solubility in water, and its solubility is even smaller in high-concentration potassium chloride due to the salting-out effect. This method is not suitable for determining low-content octadecylamine.

[0004] Evtushenko et al. used methyl orange as a chromogenic agent at pH = 2.5 to directly measure the absorbance value to obtain the concentration of octadecylamine in water. Sun Deshun et al. first added salicylaldehyde to react with octadecylamine to form salicylaldimine, and then added bromocresol green for color development to measure the absorbance value to obtain the content of octadecylamine. For the above two methods without using an extractant, chromogenic agents were added. Since the chromogenic agent itself has absorbance, an excessive and inaccurate amount is usually added during the measurement, which easily causes background interference to the absorbance measurement of the complex, resulting in a decrease in measurement precision, especially for low-content samples, with a large measurement error.

[0005] Ronald M. Silverstein used methyl orange as a chromogenic agent and chloroform, dichloroethane, and diethyl ether as extractants to determine the amine content in the water of the boiler system. The national standard for the power industry in China, "Determination of Alkyl Octadecylamine in Water" (DL / T1042.2007), also recommends using methyl orange as a complexing chromogenic agent. At pH = 3 - 4, chloroform extraction and spectrophotometry are used to determine octadecylamine in the wastewater of power plant boilers.

[0006] When determining octadecylamine as a flotation reagent for potash fertilizers, Liang Huibin used gas chromatography and aurin - 2 spectrophotometry to determine the content of octadecylamine hydrochloride in a saturated potassium chloride solution. When using gas chromatography, after chloroform extraction, solvent evaporation and concentration are still required, and the measurement process is cumbersome and chloroform volatilization causes air pollution; when using aurin - 2 spectrophotometry, the detection limit is low and it is suitable for determining the content of octadecylamine hydrochloride in a pure potassium chloride solution. In an actual potassium chloride system, magnesium and calcium ions are often present, and aurin - 2 will form precipitates with magnesium and calcium ions in the solution, affecting its complexation and color development with octadecylamine, resulting in inaccurate measurement and being not suitable for the actual system.

[0007] Diao Xiangrui et al. used bromocresol green spectrophotometry to determine the content of octadecylamine in potassium chloride. When drawing the standard curve, the amount of color reagent added to different concentrations of octadecylamine solutions was different, and the ratio of the organic phase to the aqueous phase in the chloroform extraction step was not fixed. If this method is used to determine unknown samples, the amount of color reagent used cannot be determined, nor can the influence on the extraction efficiency and the entire analysis process be determined, and the accuracy cannot be guaranteed when measuring actual samples. Since octadecylamine is highly soluble in chloroform, chloroform is used as the extractant in the above methods. However, chloroform is highly volatile and carcinogenic, sensitive to light, can be decomposed into highly toxic phosgene, and is controlled by dangerous chemicals and precursor chemicals.

[0008] Li Bing used methyl orange as the color reagent and ethyl acetate instead of chloroform as the extractant to determine the content of octadecylamine in water. Ethyl acetate has low toxicity, but ethyl acetate has a certain solubility in water (0.1 mL / mL) and will undergo a certain degree of hydrolysis. When used to extract the methyl orange-octadecylamine complex, the recovery rate may not be high and the measurement result may be on the low side.

[0009] At present, when using spectrophotometry to determine low-content octadecylamine, chloroform is mainly used as the extractant. Chloroform is highly volatile and will quickly volatilize in each step of the measurement operation, resulting in affected measurement accuracy and low measurement precision. In addition, chloroform is carcinogenic, sensitive to light, can be decomposed into highly toxic phosgene, posing a health threat to the measurement experimenters, and chloroform is controlled by dangerous chemicals and precursor chemicals, with strict requirements for purchase, use and storage. When using ethyl acetate instead of chloroform as the extractant, ethyl acetate has low toxicity, but ethyl acetate has a certain solubility in water (0.1 mL / mL). When used to extract the methyl orange-octadecylamine complex, the recovery rate may not be high and the measurement result may be on the low side.

[0010] When using bromocresol green as the indicator, since bromocresol green has low solubility in water, ethanol is usually used for dissolution and preparation. The present invention uses a water-soluble indicator as the color reagent and uses distilled water for dissolution and preparation, avoiding the introduction of ethanol into the measurement system, reducing the solubility of the octadecylamine complex in the aqueous phase, and further improving the accuracy of the measurement method.

[0011] When usually determining the content of components or impurities in soluble solids, the solid sample is first dissolved and then the content of the components in the aqueous solution is determined. When producing potassium chloride by the cold crystallization - positive flotation method, the flotation agent octadecylamine adsorbs on the surface of potassium chloride particles and is separated from the liquid phase in the form of foam through hydrophobic interaction. If the potassium chloride sample to be measured is directly dissolved in water, since octadecylamine has low solubility in water and even lower solubility in high-concentration potassium chloride due to the salting-out effect, the octadecylamine in potassium chloride cannot be completely dissolved, but is adsorbed on the container wall through hydrophobic interaction and cannot be completely transferred into the measurement system, which may result in a low measurement result. Summary of the Invention

[0012] The object of the present invention is to address the technical deficiencies existing in the prior art. The present invention provides a determination system for octadecylamine in potassium chloride, which uses a water-soluble indicator as a chromogenic agent and a long-chain alkane for extraction and color development.

[0013] On the other hand, the present invention provides the application of the said determination system, which is used in conjunction with ultraviolet-visible spectrophotometry to determine the content of octadecylamine in potassium chloride, providing a low-toxicity, reliable, and convenient analysis method for the quality evaluation and purification of potassium chloride.

[0014] The technical solution adopted to achieve the object of the present invention is as follows:

[0015] A determination system for octadecylamine in potassium chloride includes a potassium chloride standard (preferably of analytical reagent grade), a water-soluble indicator solution, a buffer solution, and an octadecylamine standard stock solution, which are independent of each other. Among them,

[0016] The water-soluble indicator solution is prepared through the following steps: Weigh the water-soluble indicator and make up the volume with distilled water to obtain a water-soluble indicator solution with a concentration of 0.1 - 20 g / L;

[0017] The pH of the buffer solution is 4.5 - 6.0;

[0018] The octadecylamine standard stock solution includes multiple octadecylamine standard solutions with different concentrations, and the concentrations of the multiple octadecylamine standard solutions vary in a gradient. It is prepared through the following steps: Accurately weigh a predetermined mass of octadecylamine, dissolve it in a long-chain alkane and make up the volume, and then dilute it respectively to obtain octadecylamine standard solutions with different concentrations;

[0019] The volume ratio of the buffer solution to the water-soluble indicator solution is (5 - 100):1, and the volume ratio of the organic phase (each octadecylamine standard solution) to the aqueous phase (including the water-soluble indicator solution and the buffer solution) is (0.05 - 9):1. The water-soluble indicator is in excess relative to octadecylamine for complete color development.

[0020] In the above technical solution, the water-soluble indicator is sodium bromocresol green, potassium bromocresol green, sodium bromophenol blue, or potassium bromophenol blue.

[0021] In the above technical solution, the long-chain alkane is C n H 2n+2 , where n is a natural number from 7 to 14, and the long-chain alkane is a single substance or a mixture of two or more substances.

[0022] In the above technical solution, the buffer solution is an acetic acid - sodium acetate buffer solution.

[0023] In the above technical solution, the acetic acid-sodium acetate buffer solution is prepared by the following steps: weighing anhydrous sodium acetate and dissolving it in distilled water, adding acetic acid to adjust the pH of the solution, and obtaining an acetic acid-sodium acetate buffer solution with a pH of 4.5-6.0.

[0024] In the above technical solution, the concentration of the octadecylamine standard solution is 0.5 mg / L-100 mg / L.

[0025] In the above technical solution, the standard curve is drawn by the following method:

[0026] Step 1.1, accurately weigh a potassium chloride standard, accurately measure a predetermined volume of a buffer solution, a water-soluble indicator solution, and distilled water and add them to the potassium chloride standard, and then add an octadecylamine standard solution according to a volume ratio of an organic phase to an aqueous phase of (0.05-9): 1; fully react and extract, after standing for stratification, use a long-chain alkane as a blank, use a quartz cuvette, and scan the organic phase layer for absorption spectrum within a wavelength range of 800-200nm, select a measurement wavelength, preferably, the wavelength corresponding to the peak value of the absorbance is the measurement wavelength, more preferably, the wavelength corresponding to the absorbance maximum value of the symmetrical absorption peak is selected as the measurement wavelength, and steps 1.2-1.3 are performed. If the obtained standard curve is linear, the measurement wavelength is used. If the obtained standard curve is not linear, then other absorption values ​​corresponding to the measurement wavelengths are selected to perform steps 1.2-1.3 until the standard curve is linear;

[0027] Step 1.2, accurately weigh the same mass of potassium chloride standard as in step 1.1, accurately measure the same volume of buffer solution, water-soluble indicator solution, and distilled water as in step 1.1, add to the potassium chloride standard, and then add octadecylamine standard solutions with gradient concentrations, preferably equal volumes of octadecylamine standard solutions, according to the same volume ratio of organic phase to aqueous phase as in step 1.1, fully react and extract, stand for stratification, and use a long-chain alkane as a blank, using a quartz colorimetric dish, at a selected measurement wavelength, respectively, to measure the absorbance of the organic phase layer;

[0028] Step 1.3, using the concentration of each octadecylamine standard solution as the abscissa and the corresponding absorbance as the ordinate to draw a standard curve.

[0029] Another aspect of the present invention is the use of the determination system in combination with UV-visible spectrophotometry in determining the content of octadecylamine in potassium chloride solid particles.

[0030] In another aspect of the present invention, the determination system is used in combination with UV-visible spectrophotometry to determine the content of octadecylamine in potassium chloride flotation slurry.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. For the determination of the content of low-content substances in a complex system, the accuracy of the determination method determines the quality of the determination method. In the present invention, long-chain alkanes are used as extractants, which have good solubility in octadecylamine and the octadecylamine complex of the chromogenic agent, are insoluble in water, and will not cause loss of octadecylamine extraction. Moreover, long-chain alkanes have low volatility and low toxicity, high determination accuracy, and little harm to the human body and the environment; ethanol is not introduced, and it will not cause loss of the octadecylamine complex of the chromogenic agent in water.

[0033] 2. During the determination process of the present invention and the process of drawing the standard curve, potassium chloride samples are directly added to the chromogenic determination system, which avoids the loss of octadecylamine adsorbed on the container wall due to hydrophobicity during the sample dissolution process. At the same time, when using this determination system, the dissolution, extraction, and chromogenesis are all carried out in the same closed container, further improving the accuracy of the determination of octadecylamine content.

[0034] 3. The present invention selects a liquid long-chain alkane with low volatility and low toxicity and a carbon chain length as close as possible to that of octadecylamine. The better the similarity solubility with octadecylamine, the better the extraction chromogenicity, sensitivity, and accuracy.

[0035] 4. The chromogenic agent molecules and octadecylamine molecules complex to form macromolecules, which are extracted into the organic phase for chromogenesis by the "similar solubility" principle. The chromogenic agent itself cannot be extracted due to insufficient hydrophobicity (as shown by the scanning curve when the octadecylamine concentration is 0). Due to the salting-out effect of the complex molecules, the salt concentration in the solution will promote the complexation of the chromogenic agent molecules and octadecylamine molecules to form macromolecules and be extracted. The higher the potassium chloride concentration, the greater the absorbance and the higher the determination sensitivity. Description of the Drawings

[0036] Figure 1 It is the spectral scanning curve of different contents of octadecylamine in the sodium bromocresol green-heptane system in Example 1.

[0037] Figure 2 It is the standard curve for the determination of octadecylamine in the sodium bromocresol green-heptane system in Example 1.

[0038] Figure 3 It is the spectral scanning curve of different contents of octadecylamine in the potassium bromocresol green-tetradecane system in Example 2.

[0039] Figure 4 It is the standard curve for the determination of octadecylamine in the potassium bromocresol green-tetradecane system in Example 2.

[0040] Figure 5 It is the spectral scanning curve of different contents of octadecylamine in the sodium bromophenol blue-dodecane system in Example 3.

[0041] Figure 6 It is the standard curve for the determination of octadecylamine in the sodium bromophenol blue-dodecane system in Example 3. Detailed Embodiments

[0042] The present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0043] Example 1 1.1

[0045] A determination system for octadecylamine in potassium chloride includes a water-soluble indicator solution, an acetic acid-sodium acetate buffer solution, and an octadecylamine standard stock solution. Among them,

[0046] The water-soluble indicator solution is prepared by the following steps: Weigh sodium bromocresol green and make up the volume with distilled water to obtain a water-soluble indicator solution with a concentration of 20 g / L;

[0047] The acetic acid-sodium acetate buffer solution is prepared by the following steps: Weigh anhydrous sodium acetate and dissolve it in distilled water, add acetic acid to adjust the pH of the solution to obtain an acetic acid-sodium acetate buffer solution with pH = 6.0;

[0048] The octadecylamine standard stock solution is prepared by the following steps: Accurately weigh 0.5000 g of octadecylamine, dissolve it in C7H 16 and make up the volume to 1 L, and obtain an octadecylamine standard stock solution with a concentration gradient by dilution, and the concentrations are 4, 8, 16, 24, 32, and 40 mg / L respectively. 1.2

[0050] Using the determination system described in Example 1.1, the content of octadecylamine in the potassium chloride sample is determined, including the following steps:

[0051] Step 1, drawing the standard curve:

[0052] Step (1), accurately weigh 29.9997 g of potassium chloride standard product of superior grade and add it to a volumetric flask. Then, accurately measure 75.00 mL of acetic acid-sodium acetate buffer solution, 0.75 mL of water-soluble indicator solution, and 24.25 mL of distilled water and add them to the volumetric flask in sequence. The volume ratio of the buffer solution to the water-soluble indicator solution is 100:1; after shaking and dissolving, the concentration of potassium chloride is 300 g / L.

[0053] According to the volume ratio of the organic phase to the water phase of 0.05:1, add 5.00 mL of octadecylamine standard solution with a concentration of 16 mg / L. Cover the volumetric flask and shake it well. After sufficient reaction and extraction, let it stand for layering, and use C7H 16 as the blank, use a quartz cuvette, and perform spectral scanning on the organic phase layer in the wavelength range of 800 - 200 nm, and select the measurement wavelength as 624 nm.

[0054] Step (2): Using the same method as in step (1), add 5.00 mL of octadecylamine standard solutions with concentrations of 4, 8, 16, 24, 32, and 40 mg / L respectively, measure the absorbance at 624 nm, plot the standard curve, as shown in the figure.

[0055] Step 3: Determination of octadecylamine content:

[0056] Accurately weigh 29.9998 g of the potassium chloride sample to be tested and add it to a volumetric flask. Then, accurately measure 75.00 mL of the buffer solution, 0.75 mL of the water-soluble indicator solution, and 24.25 mL of distilled water and add them to the volumetric flask. The volume ratio of the buffer solution to the water-soluble indicator solution is 100:1; after shaking and dissolving, the concentration of potassium chloride is 300 g / L.

[0057] According to the phase ratio of 0.05:1, add 5.00 mL of C7H 16 ; After covering the volumetric flask and shaking, fully extract and shake well, then let it stand for layering. Using C7H 16 as the blank, measure the absorbance of the organic phase layer. The absorbance is 1.002. Calculate the octadecylamine content in the sample as 6.27 mg / kg through the standard curve.

[0058] Example 2 2.1

[0060] A determination system for octadecylamine in potassium chloride, including a water-soluble indicator solution, an acetic acid-sodium acetate buffer solution, and an octadecylamine standard stock solution. Among them,

[0061] The water-soluble indicator solution is prepared by the following steps: Weigh potassium bromocresol green and make up the volume with distilled water to obtain a water-soluble indicator solution with a concentration of 0.1 g / L;

[0062] The acetic acid-sodium acetate buffer solution is prepared by the following steps: Weigh anhydrous sodium acetate and dissolve it in distilled water, add acetic acid to adjust the pH of the solution to obtain an acetic acid-sodium acetate buffer solution with pH = 4.5;

[0063] The octadecylamine standard stock solution is prepared by the following steps: Accurately weigh a predetermined mass of octadecylamine, dissolve it in C 14 H 30 and make up the volume to obtain the octadecylamine standard stock solution. Specifically, accurately weigh 0.2000 g of octadecylamine, use C 14 H 30 to make up the volume to 500 mL, and obtain octadecylamine standard solutions with gradient concentrations through dilution, with concentrations of 8, 16, 32, 64, 80, and 96 mg / L respectively. 2.2

[0065] Using the measurement system described in Example 2.1, the octadecylamine content in the potassium chloride sample was measured, including the following steps:

[0066] Step 1, Standard curve plotting:

[0067] Step (1), Accurately weigh 3.0283 g of potassium chloride standard of superior grade and add it to a volumetric flask. Then, accurately measure 5.00 mL of acetic acid-sodium acetate buffer solution, 1.00 mL of water-soluble indicator solution, and 4.00 mL of distilled water and add them to the volumetric flask. The volume ratio of the buffer solution to the water-soluble indicator solution is 5:1; after shaking and dissolving, the potassium chloride concentration is 303 g / L.

[0068] According to the volume ratio of the organic phase to the aqueous phase of 9:1, add 90.00 mL of octadecylamine standard stock solution with a concentration of 32 mg / L; cover the volumetric flask and shake it well. After sufficient reaction and extraction, let it stand for stratification, and use C 14 H 30 as the blank. Using a quartz cuvette, perform an absorption spectrum scan of the organic phase layer from 800 - 200 nm, and select the symmetric absorption peak wavelength of 394 nm in the ultraviolet absorption region as the measurement wavelength;

[0069] Step (2), Using the same method as in Step (1), add 90.00 mL of octadecylamine standard stocks with concentrations of 8, 16, 32, 64, 80, and 96 mg / L respectively. Measure the absorbance at 394 nm and plot the standard curve.

[0070] Step 3, Octadecylamine content determination:

[0071] Accurately weigh 3.0279 g of the potassium chloride sample to be tested and add it to a volumetric flask. Then, accurately measure 5.00 mL of acetic acid-sodium acetate buffer solution, 1.00 mL of water-soluble indicator solution, and 4.00 mL of distilled water and add them to the volumetric flask. The volume ratio of the buffer solution to the water-soluble indicator solution is 5:1; after shaking and dissolving, the potassium chloride concentration is 303 g / L.

[0072] According to the volume ratio of the organic phase to the aqueous phase of 9:1, add 90.00 mL of C 14 H 30 ; cover the volumetric flask and shake it. After sufficient extraction and shaking, let it stand for stratification, and use C 14 H 30 as the blank. Measure the absorbance of the organic phase layer. The absorbance is 0.013. Calculate the octadecylamine content in the sample to be 251.43 mg / kg through the standard curve.

[0073] Example 3 3.1

[0075] A determination system for octadecylamine in potassium chloride, comprising a water-soluble indicator solution, an acetic acid-sodium acetate buffer solution, and an octadecylamine standard stock solution, wherein,

[0076] The water-soluble indicator solution is prepared by the following steps: Weigh sodium bromophenol blue and make up the volume with distilled water to obtain a water-soluble indicator solution with a concentration of 10 g / L;

[0077] The acetic acid-sodium acetate buffer solution is prepared by the following steps: Weigh anhydrous sodium acetate and dissolve it in distilled water, add acetic acid to adjust the pH of the solution to obtain an acetic acid-sodium acetate buffer solution with pH = 5.0;

[0078] The octadecylamine standard stock solution is prepared by the following steps: Accurately weigh a predetermined mass of octadecylamine, dissolve it in C 12 H 26 and make up the volume to obtain an octadecylamine standard stock solution. Specifically, accurately weigh 0.5000 g of octadecylamine, use C 12 H 26 to make up the volume to 500 mL, and dilute it to obtain octadecylamine standard solutions with concentration gradients of 2, 4, 8, 16, 20, and 24 mg / L. 3.2

[0080] Using the determination system described in Example 3.1, the content of octadecylamine in the potassium chloride sample is determined, including the following steps:

[0081] Step 1, Standard curve drawing:

[0082] Step (1), Accurately weigh 5.9011 g of potassium chloride standard of superior grade and add it to a volumetric flask. Sequentially and accurately measure 12.00 mL of acetic acid-sodium acetate buffer solution, 0.50 mL of water-soluble indicator solution, and 7.50 mL of distilled water and add them to the volumetric flask. The volume ratio of the buffer solution to the water-soluble indicator solution is 24:1; After shaking and dissolving, the potassium chloride concentration is 295 g / L.

[0083] According to the volume ratio of the organic phase to the aqueous phase of 0.2:1, add 4.00 mL of octadecylamine standard stock solution with a concentration of 16 mg / L; Cover the volumetric flask and shake it well. After sufficient reaction and extraction, let it stand for layering, and use C 12 H 26 as the blank, use a quartz cuvette to perform an absorption spectrum scan on the organic phase layer from 800 - 200 nm, and select the measurement wavelength to be 568 nm;

[0084] Step (2): Using the same method as in step (1), add 4.00 mL of octadecylamine standard stock solutions with concentrations of 2, 4, 8, 16, 20, and 24 mg / L respectively, measure the absorbance respectively, plot the standard curve as shown in the figure. Both bromophenol blue and bromocresol green are chromogenic agents, and their sodium salts are soluble in water. The difference is that there is an additional methyl group at the ortho position of bromine in the molecular structure of bromocresol green. Therefore, the colors they display are different, and the absorption spectra are different.

[0085] To determine the detection limit, measure the absorbance of the blank solution 20 times continuously, and obtain the standard deviation of the absorbance σ = 4.12×10 -4 , According to the detection limit formula D.L. = 3σ / r (r is the slope of the standard curve) recommended by IUPAC, calculate that the detection limit of this standard curve is 3.09×10 -2 mg / L (dodecane). Combining the phase ratio (0.2:1) and the potassium chloride concentration (295 g / L), calculate that the detection limit of this determination standard curve for the octadecylamine content in potassium chloride products is 2.09×10 -2 mg / kg.

[0086] Step 3: Determination of octadecylamine content:

[0087] Accurately weigh 5.9002 g of the potassium chloride sample to be tested and add it to a volumetric flask. Then accurately measure 12.00 mL of acetic acid-sodium acetate buffer solution, 0.50 mL of water-soluble indicator solution, and 7.50 mL of distilled water and add them to the volumetric flask. The volume ratio of the buffer solution to the water-soluble indicator solution is 24:1; after shaking and dissolving, the potassium chloride concentration is 295 g / L.

[0088] According to the volume ratio of the organic phase to the aqueous phase of 0.2:1, add 4.00 mL of C 12 H 26 ; After covering the volumetric flask and shaking, fully extract and shake well, then let it stand for layering. Using C 12 H 26 as the blank, use a quartz cuvette to measure the absorbance of the organic phase layer. The absorbance is 0.401. Calculate the octadecylamine content in the sample to be 20.13 mg / kg through the standard curve.

[0089] Example 4

[0090] This example is the application of the determination system in Example 1 to the determination of the octadecylamine content in potassium chloride flotation slurry.

[0091] A method for determining octadecylamine in potassium fertilizer flotation slurry, comprising the following steps:

[0092] (1) Solution preparation: Weigh sodium bromocresol green and dissolve it in distilled water, then make up the volume to a volumetric flask to prepare a 20 g / L sodium bromocresol green solution; Weigh anhydrous sodium acetate and dissolve it in distilled water, add acetic acid to adjust the pH of the solution to prepare an acetic acid - sodium acetate buffer solution with pH = 6.0; Accurately weigh 0.5000 g of octadecylamine and dissolve it in C7H 16 , and make up the volume to 1 L in a volumetric flask. After dilution, obtain octadecylamine standard stock solutions with concentration gradients of 4, 8, 16, 24, 32, and 40 mg / L respectively.

[0093] (2) Determination of salt concentration in the slurry liquid phase: Use the mercuric nitrate titration method to determine the chlorine content in the slurry liquid phase, and convert it to the equivalent concentration of potassium chloride as 300 g / L.

[0094] (3) Standard curve drawing:

[0095] Step 3.1, accurately weigh 29.9997 g of potassium chloride of superior grade pure and add it to a volumetric flask. Then, accurately measure 75.00 mL of acetic acid - sodium acetate buffer solution, 0.75 mL of water - soluble indicator solution, and 24.25 mL of distilled water and add them to the volumetric flask. The volume ratio of the buffer solution to the water - soluble indicator solution is 100:1; After shaking and dissolving, make the potassium chloride concentration in the aqueous solution 300 g / L.

[0096] According to the volume ratio of the organic phase to the water phase of 0.05:1, add 5.00 mL of the octadecylamine standard stock solution with a concentration of 16 mg / L; Cover the volumetric flask and shake it well. After full reaction and extraction, let it stand for layering, and use C7H 16 as the blank, use a quartz cuvette to perform absorption spectrum scanning on the organic phase layer in the wavelength range of 800 - 200 nm, and select the measurement wavelength as 624 nm;

[0097] Step 3.2, use the same method as in Step 3.1, add 5.00 mL of octadecylamine standard stock solutions with concentrations of 4, 8, 16, 24, 32, and 40 mg / L respectively, measure the absorbance at 624 nm, and draw the standard curve as shown in the figure.

[0098] (4) Slurry sample treatment: According to 20 mL / L of slurry, add silicone defoamer to the slurry. After the bubbles are eliminated and the solid phase is deposited, centrifuge to separate the solid - liquid two - phase. The solid phase is freeze - dried for later use.

[0099] (5) Determination of octadecylamine content: Use the same conditions as in step (3):

[0100] ① Accurately measure the liquid phase solution, buffer solution, and water - soluble indicator solution in step (2) and add them to a volumetric flask. The volume ratio of the buffer solution to the water - soluble indicator solution is 100:1; According to the volume ratio of the organic phase to the water phase of 0.05:1, add C7H16 ; After covering the volumetric flask and shaking it well, after fully reacting and extracting, let it stand for layering. Using C7H 16 as the blank, use a quartz cuvette to measure the absorbance of the organic phase layer. Calculate the octadecylamine content in the liquid phase to be 0.394 mg / L through the standard curve.

[0101] ②Accurately weigh the solid phase sample in step (4) and add it to a volumetric flask. Sequentially and accurately measure buffer solution, water-soluble indicator solution, and distilled water and add them to the volumetric flask. The volume ratio of the buffer solution to the water-soluble indicator solution is 100:1; after shaking and dissolving, make the potassium chloride concentration in the aqueous solution 300 g / L. According to the volume ratio of the organic phase to the aqueous phase of 0.05:1, add C7H 16 ; After covering the volumetric flask and shaking it well, after fully reacting and extracting, let it stand for layering. Using C7H 16 as the blank, use a quartz cuvette to measure the absorbance of the organic phase layer. Calculate the octadecylamine content in the solid phase to be 6.27 mg / kg through the standard curve.

[0102] The contents of the flotation reagents in both the solid and liquid phases are relatively small, and there are fewer foams. It is necessary to increase the dosage of the reagents.

[0103] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A determination system for octadecylamine in potassium chloride, characterized in that, It includes independent potassium chloride standard, water-soluble indicator solution, buffer solution and octadecylamine standard stock solution, wherein: The water-soluble indicator solution is prepared by the following steps: weighing the water-soluble indicator and diluting the volume with distilled water to obtain a water-soluble indicator solution with a concentration of 0.1-20 g / L; The pH of the buffer solution is 4.5-6.0; The octadecylamine standard stock solution comprises a plurality of octadecylamine standard solutions of different concentrations, the concentrations of the plurality of octadecylamine standard solutions are gradiently changed, and are prepared by the following steps: accurately weighing a predetermined mass of octadecylamine, dissolving it in a long-chain alkane to a fixed volume, and then diluting them respectively to obtain octadecylamine standard solutions of different concentrations; The volume ratio of the buffer solution to the water-soluble indicator solution is (5-100):1, and the volume ratio of the organic phase to the aqueous phase is (0.05-9):1; The long-chain alkane is C n H 2n+2 , where n is a natural number from 7 to 14, and the long-chain alkane is a mixture of one kind or two or more kinds.

2. The determination system for octadecylamine in potassium chloride according to claim 1, characterized in that, The water-soluble indicator is bromocresol green sodium salt, bromocresol green potassium salt, bromophenol blue sodium salt or bromophenol blue potassium salt.

3. The determination system for octadecylamine in potassium chloride according to claim 1, characterized in that, The buffer solution is an acetic acid-sodium acetate buffer solution.

4. The determination system for octadecylamine in potassium chloride according to claim 3, characterized in that, The acetic acid-sodium acetate buffer solution is prepared by the following steps: weighing anhydrous sodium acetate and dissolving it in distilled water, adding acetic acid to adjust the pH of the solution, and obtaining the acetic acid-sodium acetate buffer solution with a pH of 4.5-6.

0.

5. The determination system for octadecylamine in potassium chloride according to claim 1, characterized in that, The concentration of the octadecylamine standard solution is 0.5 mg / L-100 mg / L.

6. The determination system for octadecylamine in potassium chloride according to claim 1, characterized in that, The standard curve was drawn by the following method: Step 1.1, accurately weigh a potassium chloride standard, accurately measure a predetermined volume of a buffer solution, a water-soluble indicator solution, and distilled water and add them to the potassium chloride standard, and then add an octadecylamine standard solution according to a volume ratio of an organic phase to an aqueous phase of (0.05-9):1; fully react and extract, stand for stratification, use a long-chain alkane as a blank, use a quartz cuvette, scan the organic phase layer for absorption spectrum within a wavelength range of 800-200nm, select a measurement wavelength, and perform steps 1.2-1.

3. If the obtained standard curve is linear, use the measurement wavelength. If the obtained standard curve is not linear, select a measurement wavelength corresponding to other absorption values ​​to perform steps 1.2-1.3 until the standard curve is linear; Step 1.2, accurately weigh the same mass of potassium chloride standard as in step 1.1, accurately measure the same volume of buffer solution, water-soluble indicator solution, and distilled water as in step 1.1, add to the potassium chloride standard, and then add octadecylamine standard solutions with gradient concentrations according to the same volume ratio of organic phase to aqueous phase as in step 1.1, fully react and extract, stand for stratification, and use a long-chain alkane as a blank, using a quartz colorimetric dish, and at a selected measurement wavelength, respectively measure the absorbance of the organic phase layer; Step 1.3, using the concentration of each octadecylamine standard solution as the abscissa and the corresponding absorbance as the ordinate to draw a standard curve.

7. The determination system for octadecylamine in potassium chloride according to claim 6, characterized in that, The wavelength corresponding to the peak value of the absorbance is the measurement wavelength.

8. The determination system for octadecylamine in potassium chloride according to claim 6, characterized in that, The wavelength corresponding to the absorbance maximum of the symmetrical absorption peak is selected as the measurement wavelength.

9. Application of the determination system according to any one of claims 1-8 in combination with ultraviolet-visible spectrophotometry in the determination of the content of octadecylamine in potassium chloride solid particles.

10. Application of the determination system according to any one of claims 1-8 in combination with ultraviolet-visible spectrophotometry in the determination of the content of octadecylamine in potassium chloride flotation slurry.

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