Method for detecting contents of glycine and urotropine in glycine wastewater

Abstract

The invention provides a method for detecting the content of glycine and urotropine in glycine wastewater, and belongs to the technical field of analytical chemistry. The method comprises the following steps: firstly, obtaining a standard curve by utilizing a standard solution of glycine and urotropine, and then comparing the consistency of retention time of two main peaks of glycine and urotropine in a standard mixed solution and the retention time of a main peak in a sample to be detected, and substituting into the standard curve to obtain the content of glycine and urotropine in the sample to be detected. According to the method, when a standard mixed solution of glycine and urotropine is prepared, the weight ratio of glycine to urotropine is limited to be 1: 1, mobile phase ultrapure water and chromatographic grade methanol selected during high performance liquid chromatography testing are used as solvents, and during high performance liquid chromatography testing, an isocratic elution mode is adopted for elution, so that the content of glycine and urotropine in the mixed solution is greatly improved. Therefore, the obtained working curve prepared by using the respective chromatographic area and concentration data of glycine and urotropine has good linear correlation, and the test accuracy is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of analytical chemistry, and particularly to a method for detecting the contents of glycine and hexamethylenetetramine in glycine wastewater. Background Art

[0002] The wastewater discharged by glycine production enterprises often contains hexamethylenetetramine, a catalyst used in the synthesis of glycine, and residual glycine that has not been fully recovered. To ensure the up-to-standard discharge of glycine wastewater and reduce resource waste, it is necessary to recover hexamethylenetetramine and glycine contained in the wastewater. However, the contents of hexamethylenetetramine and glycine in the wastewater affect the selection of recovery methods, thereby affecting the treatment and disposal costs of the wastewater. Therefore, it is necessary to determine the contents of hexamethylenetetramine and glycine in the glycine wastewater that has undergone preliminary recovery to guide the selection of recovery methods, thereby reducing the treatment cost of the wastewater.

[0003] The traditional method for determining hexamethylenetetramine is the method of liquid chromatography-mass spectrometry. However, for ordinary production enterprises to detect the content of hexamethylenetetramine in the continuously discharged wastewater, the method of liquid chromatography-mass spectrometry has a high cost, is not universal, and has the problem of long detection time.

[0004] Therefore, there is an urgent need to provide a detection method that can simultaneously detect the contents of glycine and hexamethylenetetramine in glycine wastewater by using only high-performance liquid chromatography and can shorten the detection time. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for detecting the contents of glycine and hexamethylenetetramine in glycine wastewater. The method provided by the present invention has high accuracy and short detection time.

[0006] The present invention provides a method for detecting the contents of glycine and hexamethylenetetramine in glycine wastewater, including the following steps:

[0007] (1) Mix glycine, hexamethylenetetramine and a solvent to prepare a standard mixed solution of glycine and hexamethylenetetramine with a certain concentration gradient;

[0008] In the step (1), the mass ratio of glycine to hexamethylenetetramine is 1:1;

[0009] (2) Perform high-performance liquid chromatography on the standard mixed solution obtained in the step (1) to obtain a chromatogram of the standard mixed solution, and calculate by the external standard method based on the peak area to obtain a standard curve;

[0010] In the step (2), the elution method during high-performance liquid chromatography is isocratic elution; the mobile phase A during isocratic elution is ultrapure water, and the mobile phase B is chromatographic-grade methanol;

[0011] (3) Under the same test conditions of the standard mixture, perform high performance liquid chromatography (HPLC) testing on the glycine wastewater to be detected to obtain the chromatogram of the glycine wastewater to be detected;

[0012] (4) Compare the retention time consistency of the two main peaks of glycine and hexamethylenetetramine on the chromatogram of the glycine wastewater to be detected obtained in step (3) and the chromatogram of the standard mixed solution obtained in step (2), and substitute into the standard curve to obtain the contents of glycine and hexamethylenetetramine in the glycine wastewater to be detected;

[0013] In step (1), the solvent is a mixed solution of ultrapure water and chromatographic grade methanol, and the dosage ratio relationship between the two is the same as the volume ratio of mobile phase A and mobile phase B in the HPLC testing in step (2).

[0014] Preferably, the concentration gradients of the standard mixed solution in step (1) are 0.0, 0.1, 0.2, 0.3, 0.5, 1.0, 2.0 g / L in sequence.

[0015] Preferably, the volume percentage of the elution mobile phase during isocratic elution in step (2) is: mobile phase A is 55 - 60%, and mobile phase B is 45 - 40%.

[0016] Preferably, the volume percentage of the elution mobile phase during isocratic elution is: mobile phase A is 58%, and mobile phase B is 42%.

[0017] Preferably, the specification of the chromatographic column during the HPLC testing in step (2) or step (3) is: the chromatographic column uses a reversed-phase C18 chromatographic column, the model is ZORBAX SB-C18, and the column length of the chromatographic column is 250 mm.

[0018] Preferably, the column temperature of the chromatographic column during the HPLC testing is 25 - 35 °C.

[0019] Preferably, the specification of the detector during the HPLC testing in step (2) or step (3) is: an ultraviolet detector.

[0020] Preferably, the detection wavelength of the ultraviolet detector is 210 nm.

[0021] Preferably, the flow rate of the mobile phase during isocratic elution in step (2) or step (3) is 0.5 - 0.8 mL / min.

[0022] Preferably, during the HPLC testing in step (2), the injection volume of the standard mixed solution is 3 - 8 μL.

[0023] The present invention provides a method for detecting the contents of glycine and hexamethylenetetramine in glycine wastewater. By specifying that when preparing a standard mixed solution of glycine and hexamethylenetetramine with a certain concentration gradient, the weight ratio of glycine to hexamethylenetetramine is 1:1, and at the same time using ultrapure water and chromatographic-grade methanol as the solvents for the mobile phase in high-performance liquid chromatography (HPLC) testing, and the ratio of the two is the same as that in HPLC testing, the linear correlation working curve prepared from the area and concentration data of glycine and hexamethylenetetramine has good linear correlation, thus realizing the accurate determination of the contents of glycine and hexamethylenetetramine in glycine wastewater. The test results show that for the detection method provided by the present invention, the HPLC baseline is stable without drift, and the HPLC detection process can be completed in a short time; and the linear correlation working curve prepared from the chromatographic area and concentration data of glycine and hexamethylenetetramine in the measured standard mixed solution has a good linear relationship. Among them, the linear correlation coefficient R of the working curve of hexamethylenetetramine is 0.9993, and the linear correlation coefficient R of the working curve of glycine is 0.9991; and the recovery rate of hexamethylenetetramine is between 94.0% and 102.0%, and the RSD value is 2.1%; the recovery rate of glycine is between 114.0% and 119.0%, and the RSD value is 4.7%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the HPLC chromatogram of each component in the glycine wastewater sample to be tested in Example 1 of the present invention;

[0025] Figure 2 It is the HPLC chromatogram of each component in the standard mixed solution of glycine and hexamethylenetetramine when evaluating the recovery rate and relative standard deviation (RSD) of the detection method provided by the present invention;

[0026] Figure 3 It is the retention time comparison chart of each component in the glycine wastewater to be tested in Example 1 and each group in the standard mixed solution. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention provides a method for detecting the contents of glycine and hexamethylenetetramine in glycine wastewater, including the following steps:

[0028] (1) Mix glycine, hexamethylenetetramine and a solvent to prepare a standard mixed solution of glycine and hexamethylenetetramine with a certain concentration gradient;

[0029] In the step (1), the mass ratio of glycine to hexamethylenetetramine is 1:1;

[0030] (2) Perform HPLC testing on the standard mixed solution obtained in the step (1) to obtain a chromatogram of the standard mixed solution, and calculate by the external standard method based on the peak area to obtain a standard curve;

[0031] In step (2), the elution mode during the high performance liquid chromatography (HPLC) test is isocratic elution. During isocratic elution, the volume percentages of the elution mobile phase are as follows: mobile phase A is 55 - 60%, and mobile phase B is 45 - 40%. Here, mobile phase A is ultrapure water, and mobile phase B is chromatographic grade methanol.

[0032] (3) Under the same test conditions as the standard mixture solution, perform high performance liquid chromatography (HPLC) test on the glycine wastewater to be detected to obtain the chromatogram of the glycine wastewater to be detected.

[0033] (4) Compare the retention time consistency of the two main peaks of glycine and hexamine on the chromatogram of the glycine wastewater to be detected obtained in step (3) and the chromatogram of the standard mixture solution obtained in step (2), and substitute into the standard curve to obtain the contents of glycine and hexamine in the glycine wastewater to be detected.

[0034] The present invention mixes glycine, hexamine and a solvent to prepare a standard mixture solution of glycine and hexamine with a certain concentration gradient.

[0035] In the present invention, the mass ratio of glycine to hexamine is 1:1. In the present invention, the concentration gradients of the standard mixture solution are preferably 0.0, 0.1, 0.2, 0.3, 0.5, 1.0, 2.0 g / L in sequence. In the present invention, the concentration of the mixture solution refers to the total mass of glycine and hexamine. In the present invention, the solvent is a mixture of ultrapure water and chromatographic grade methanol, and the dosage ratio relationship between the two is the same as the volume percentages of mobile phase A and mobile phase B in the subsequent high performance liquid chromatography (HPLC) test. The present invention prepares the standard mixture solution of glycine and hexamine in the above manner, which is beneficial to obtaining a standard curve with better linear correlation and improving the accuracy of the test results.

[0036] After obtaining the standard mixture solution, the present invention performs high performance liquid chromatography (HPLC) test on the standard mixture solution to obtain the chromatogram of the standard mixture solution, and calculates by the external standard method with the peak area to obtain the standard curve.

[0037] In the present invention, the elution mode during the high performance liquid chromatography (HPLC) test is isocratic elution; the volume percentages of the elution mobile phases during the isocratic elution are preferably as follows: mobile phase A is 55 - 60%, and mobile phase B is 45 - 40%, more preferably: mobile phase A is 58% and mobile phase B is 42%; wherein, mobile phase A is ultrapure water and mobile phase B is chromatographic grade methanol. In the present invention, the flow rate of the mobile phase during the isocratic elution is preferably 0.5 - 0.8 mL / min, more preferably 0.8 mL / min. In the present invention, the specifications of the chromatographic column during the HPLC test are preferably as follows: the chromatographic column is a reversed-phase C18 chromatographic column, the model is preferably ZORBAX SB-C18, and the column length of the chromatographic column is preferably 250 mm. In the present invention, the column temperature of the chromatographic column during the HPLC test is preferably 25 - 35 °C. In the present invention, the specifications of the detector during the HPLC test are preferably: an ultraviolet detector; the detection wavelength of the ultraviolet detector is preferably 210 nm. In the present invention, during the HPLC test, the injection volume of the standard mixed solution is preferably 3 - 8 μL, more preferably 5 μL. The present invention performs the HPLC test under the above test conditions, and the measured HPLC baseline is stable without drift, and it is beneficial to obtain a standard curve with better linear correlation, thereby improving the accuracy of the test results.

[0038] Under the same test conditions of the standard mixed solution in the present invention, that is, under the conditions of the same instrument test parameters and the same injection volume, the glycine wastewater to be detected is subjected to HPLC test to obtain the chromatogram of the glycine wastewater to be detected.

[0039] The present invention has no special regulations on the method for performing the HPLC test on the glycine wastewater to be detected, and it can be carried out by conventional tests under the same test conditions as the standard mixed solution.

[0040] After obtaining the chromatogram of the glycine wastewater to be detected, the present invention compares the consistency of the retention times of the two main peaks of glycine and hexamine on the chromatogram of the glycine wastewater to be detected and the chromatogram of the standard mixed solution, and substitutes them into the standard curve to obtain the contents of glycine and hexamine in the glycine wastewater to be detected.

[0041] The present invention has no special regulations on the method for obtaining the contents of glycine and hexamine in the glycine wastewater to be detected by using the standard curve, and it can be compared by using the method of comparing and calculating the test results and the standard curve well-known to those skilled in the art to obtain the test results to be measured.

[0042] The present invention provides a method for detecting the contents of glycine and hexamine in glycine wastewater. By first preparing standard solutions with a certain concentration gradient and performing isocratic elution using ultrapure water and chromatographically pure methanol, a standard curve is obtained, and then the contents of glycine and hexamine in glycine wastewater are obtained using the standard curve. Under the same conditions of the present invention, the contents of glycine and hexamine in glycine wastewater can be simultaneously determined. Compared with the method of detecting hexamine by liquid chromatography-mass spectrometry, the method is simple and low-cost; compared with the method of using titration to determine glycine, this method has rapid detection and stable results.

[0043] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0044] Example 1

[0045] A method for detecting the contents of glycine and hexamine in glycine wastewater is as follows:

[0046] (1) Prepare a standard mixed solution of glycine and hexamine with a certain concentration gradient;

[0047] The specific operation is as follows: Accurately weigh 0.5000 g each of glycine and hexamine, and use a mixed solution of ultrapure water and chromatographic-grade methanol with a volume ratio of 58:42 to make up to 100 mL in a volumetric flask to prepare a stock solution with a concentration of 5 g / L; According to 7 concentration values of 0.0, 0.1, 0.2, 0.3, 0.5, 1.0, and 2.0 g / L, measure the corresponding volumes of the stock solution, and use the mobile phase of high-performance liquid chromatography to make up to 50 mL in a volumetric flask respectively to prepare a standard mixed solution for standby.

[0048] (2) Perform high-performance liquid chromatography test on the standard mixed solution obtained in step (1) to obtain the chromatogram of the standard mixed solution, and calculate by the external standard method based on the peak area to obtain the standard curve;

[0049] High-performance liquid chromatography test conditions:

[0050] The chromatographic column uses a reversed-phase C18 chromatographic column, model ZORBAX SB-C18, and the column length of the chromatographic column is 250 mm; the column temperature of the chromatographic column is 30 °C;

[0051] The detector uses an ultraviolet detector, and the detection wavelength is 210 nm;

[0052] In isocratic elution, the volume percentages of the elution mobile phase are as follows: mobile phase A (ultrapure water) is 58%, and mobile phase B (chromatographic grade methanol) is 42%; the flow rate of the elution mobile phase is 0.8 mL / min. Both mobile phase A and B are filtered, degassed, and then used on the instrument.

[0053] The injection volume of the standard mixed solution is 5 μL.

[0054] The specific operation is as follows: After all conditions of the high-performance liquid chromatography reach stability, inject the 7 prepared standard mixed solutions into the instrument in sequence according to the above chromatographic conditions, record the chromatograms, and prepare a linear correlation working curve based on the area and concentration data of glycine and hexamethylenetetramine in the 7 standard mixed solutions. Among them, the linear correlation coefficient R of the hexamethylenetetramine working curve is 0.9993, and the linear correlation coefficient R of the glycine working curve is 0.9991, indicating that the linear relationship of this working curve is good.

[0055] (3) Under the same test conditions as the standard mixed solution, perform high-performance liquid chromatography on the glycine wastewater to be detected to obtain the chromatogram of the glycine wastewater to be detected.

[0056] The specific operation is as follows: Take three 1.00 mL samples of the glycine wastewater to be detected, name them water sample 1, water sample 2, and water sample 3 respectively, dilute and make up the volume to a 100 mL volumetric flask with the solvent used to prepare the standard mixed solution, with a dilution factor of 100 times, and perform tests according to the chromatographic conditions for the determination of the standard mixed solution in step (2) to obtain the chromatogram of the glycine wastewater to be detected. The chromatogram of water sample 1 is as Figure 1 shown. It can be seen from Figure 1 that the elution times of the two main peaks are 2.808 min and 3.305 min respectively, and the peak areas are 109.392 and 214.173 respectively.

[0057] (4) Compare the consistency of the retention times of the two main peaks of glycine and hexamethylenetetramine on the chromatogram of the glycine wastewater to be detected obtained in step (3) and the chromatogram of the standard mixed solution obtained in step (2), and substitute into the standard curve to obtain the contents of glycine and hexamethylenetetramine in the glycine wastewater to be detected.

[0058] The specific operation is as follows: Obtain the chromatogram data (peak area) of the glycine wastewater to be detected during injection and substitute it into the working curve for calculation to obtain the concentration of the sample solution to be detected during injection, and multiply by the dilution factor to calculate the contents of glycine and hexamethylenetetramine in the glycine wastewater to be detected. The test results are shown in Table 1.

[0059] Table 1 Test results of the contents of glycine and hexamethylenetetramine in the glycine wastewater to be detected

[0060]

[0061] As can be seen from Table 1, the determination of the contents of glycine and hexamethylenetetramine in glycine wastewater can be completed within 4 minutes, and the test time is relatively short.

[0062] Evaluate the recovery rate and relative standard deviation (RSD) of the detection method

[0063] Accurately weigh the standard solutions of glycine and hexamethylenetetramine according to three concentration standards (0.5, 1.0, 2.0 g / L), place them in a 100 mL volumetric flask at the same time, dissolve and dilute to the scale with a mixed solution of ultrapure water and chromatographic grade methanol with a volume ratio of 58:42. Set 3 parallel samples for each concentration standard mixture, inject and detect according to the chromatographic conditions in Example 1, record the chromatogram, and determine the recovery rate and calculate the RSD value. The results are shown in Table 2.

[0064] Table 2 Recovery rates and RSD values of standard solutions of glycine and hexamethylenetetramine

[0065]

[0066] As can be seen from Table 2, the recovery rate of hexamethylenetetramine is between 94.0% and 102.0%, and the RSD value is 2.1%; the recovery rate of glycine is between 114.0% and 119.0%, and the RSD value is 4.7%.

[0067] The chromatogram of 1.0 g / L is shown in Figure 2 . From Figure 2 it can be seen that the elution times of the two main peaks are 2.805 min and 3.241 min respectively, and the peak areas are 265.537 and 693.143 respectively.

[0068] Compare the chromatograms obtained from the water sample to be tested 1 and the standard solutions of glycine and hexamethylenetetramine at three concentration standards (0.5, 1.0, 2.0 g / L). The comparison results are shown in Figure 3 , from Figure 3It can be seen that the peak emergence times at the positions of the two main peaks of the standard solution with a concentration of 1.0 g / L are 2.805 min and 3.241 min respectively, and the peak areas are 265.537 and 693.143 respectively; the peak emergence times at the positions of the two main peaks of the standard solution with a concentration of 0.5 g / L are 2.801 min and 3.249 min respectively, and the peak areas are 186.036 and 422.019 respectively; the peak emergence times at the positions of the two main peaks of the standard solution with a concentration of 2.0 g / L are 2.805 min and 3.223 min respectively, and the peak areas are 395.824 and 1193.57 respectively; the peak emergence times at the positions of the two main peaks of water sample 1 are 2.808 min and 3.305 min respectively, and the peak areas are 109.392 and 214.173 respectively. Thus, it can be seen that the difference in the peak emergence times of glycine and hexamine in the glycine wastewater and those in the standard product is not significant, and the contents of the two are proportional to the peak areas.

[0069] In summary, the detection method provided by the present invention can accurately determine the contents of glycine and hexamine in glycine wastewater in a short time under the conditions of only using high performance liquid chromatography.

[0070] 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 method for detecting the content of glycine and urotropine in glycine wastewater, comprising the following steps: (1) mixing glycine, urotropine and a solvent to prepare a standard mixed solution of glycine and urotropine with a certain concentration gradient; In the step (1), the mass ratio of glycine to hexamine is 1:1; (2) subjecting the standard mixed solution obtained in step (1) to a high performance liquid chromatography test to obtain a chromatogram of the standard mixed solution, and calculating the peak area by an external standard method to obtain a standard curve; The elution method during the high performance liquid chromatography test in step (2) is isocratic elution; the mobile phase A during the isocratic elution is ultrapure water, and the mobile phase B is chromatographic grade methanol; (3) Under the same test conditions as the standard mixed solution, the glycine wastewater to be tested is subjected to a high performance liquid chromatography test to obtain a chromatogram of the glycine wastewater to be tested; (4) comparing the consistency of the retention times of the two main peaks of glycine and urotropine on the chromatogram of the glycine wastewater to be tested obtained in step (3) and the chromatogram of the standard mixed solution obtained in step (2), and substituting them into the standard curve to obtain the contents of glycine and urotropine in the glycine wastewater to be tested; The solvent in step (1) is a mixture of ultrapure water and chromatographic grade methanol, and the ratio of the two is the same as the volume ratio of mobile phase A and mobile phase B in the high performance liquid chromatography test in step (2).

2. The detection method according to claim 1, characterized in that: The concentration gradients of the standard mixed solution in step (1) are 0.0, 0.1, 0.2, 0.3, 0.5, 1.0, and 2.0 g / L, respectively.

3. The detection method according to claim 1, characterized in that: The volume percentages of the elution mobile phases during moderate elution in step (2) are: mobile phase A is 55-60%, and mobile phase B is 45-40%.

4. The detection method according to claim 3, characterized in that: The volume percentages of the elution mobile phases during the isocratic elution are: mobile phase A is 58%, and mobile phase B is 42%.

5. The detection method according to claim 1, characterized in that: The specifications of the chromatographic column during the high performance liquid chromatography test in step (2) or step (3) are as follows: the chromatographic column adopts a reverse phase C18 chromatographic column, model ZORBAX SB-C18, and the column length is 250 mm.

6. The detection method according to claim 5, characterized in that: The column temperature of the chromatographic column during the high performance liquid chromatography test is 25-35°C.

7. The detection method according to claim 1, characterized in that: The specification of the detector during the high performance liquid chromatography test in step (2) or step (3) is: ultraviolet detector.

8. The detection method according to claim 7, characterized in that: The detection wavelength of the ultraviolet detector is 210 nm.

9. The detection method according to claim 1, characterized in that: During the isocratic elution in step (2) or step (3), the flow rate of the mobile phase is 0.5 to 0.8 mL / min.

10. The detection method according to claim 1, characterized in that: During the high performance liquid chromatography test in step (2), the injection volume of the standard mixed solution is 3 to 8 μL.

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