Method for detecting levofloxacin in wastewater by ultraviolet dual-wavelength

Abstract

The invention discloses a method for detecting levofloxacin in wastewater through ultraviolet dual wavelengths. The wastewater also contains tetracycline or sulfathiazole; detecting the absorbance A of the wastewater by adopting ultraviolet dual-wavelength emission; when tetracycline is contained in the wastewater, 295 nm and 374 nm are selected for detection, the concentration of levofloxacin in the wastewater is calculated by adopting (1): # imgabs 0 # when the wastewater contains sulfathiazole, 284 nm and 302 nm are selected for detection, and the concentration of sulfathiazole in the wastewater is calculated by adopting (2): # imgabs 1 #, l is an optical path and is 1cm; epsilon is a molar absorption coefficient, and the unit is [mu] g / (mL.cm); the LZD is levofloxacin; and STZ is sulfathiazole.

Description

Technical Field

[0001] The present application relates to a method for detecting levofloxacin in wastewater using dual-wavelength ultraviolet light, and belongs to the field of wastewater detection. Background Art

[0002] Levofloxacin (LZD) is a third-generation quinolone drug with strong antibacterial effect. It is mainly used clinically for respiratory, urinary, digestive and reproductive system infections caused by Gram-negative bacteria. While the widespread use of levofloxacin benefits mankind, it also brings many problems: on the one hand, levofloxacin is widely used in humans, animals, aquaculture and agricultural applications, and inevitably enters the environment; on the other hand, the fluoroquinolone drugs to which levofloxacin belongs are too stable and cannot be completely metabolized by organisms. In the past few years, levofloxacin has been detected in wastewater treatment plant effluent, groundwater, surface water and even drinking water in many countries. More seriously, long-term exposure to levofloxacin can lead to the evolution of low-level antimicrobial resistance and increase the formation of "super bacteria" (some collectively high-level antimicrobial bacteria). And it poses a hidden threat to ecosystems and human health. (Xu, Z., et al, Environmental Pollution, 2021.272.) Therefore, there is an urgent need to develop an effective and rapid method to detect levofloxacin residues in water environments.

[0003] Currently, high performance liquid chromatography is the most studied and applied detection method. Mychelle A. Monteiro

[15] et al. used solid phase extraction-high performance liquid chromatography-tandem mass spectrometry to determine multiple antibiotics in surface water and drinking water; (Monteiro, MA, et al., Journal of the Brazilian Chemical Society, 2018. 29 (4): 801-813.) Cao Jun et al. established a high performance liquid chromatography ultraviolet / fluorescence detector tandem analysis method for simultaneous analysis and detection of 11 antibiotics. The ultraviolet detector was used to achieve complete separation and detection of 11 target antibiotics, and the tandem fluorescence detector enabled quinolone antibiotics to achieve a lower detection limit. (Liquid chromatography ultraviolet-fluorescence tandem detector method for detection of 11 common antibiotics in my country's sewage, Cao Jun et al., 2022). Although high performance liquid chromatography is accurate, the instrumentation is expensive and requires professional personnel for operation and maintenance. The detection cycle is long and the cost is high, and the scope of application is relatively limited. Therefore, it is very necessary to establish a simple, rapid and low-cost detection method. Summary of the invention

[0004] In order to improve the defects of the prior art, the present invention provides a method for rapidly detecting levofloxacin, which has the advantage of using ultraviolet light for detection, with a short detection cycle, and can replace complex and expensive chromatographic instruments, greatly saving detection costs, and can provide technical support for the construction of an unattended water body intelligent purification system intermediate treatment process.

[0005] According to one aspect of the present application, a method for detecting levofloxacin in wastewater by ultraviolet dual wavelength is provided, characterized in that:

[0006] The wastewater also contains tetracycline or sulfathiazole;

[0007] The absorbance A of the wastewater is detected by ultraviolet dual-wavelength method;

[0008] When the wastewater contains tetracycline, 295nm and 374nm are selected for detection, and (1) is used to calculate the concentration of levofloxacin in the wastewater:

[0009]

[0010] When the wastewater contains sulfathiazole, 284nm and 302nm are selected for detection, and (2) is used to calculate the concentration of sulfathiazole in the wastewater:

[0011]

[0012] in,

[0013] c is the concentration;

[0014] l is the optical path, which is 1 cm;

[0015] ε is the molar absorption coefficient, in μg / (mL·cm);

[0016] LZD is levofloxacin;

[0017] STZ is sulfathiazole.

[0018] The wastewater is pre-treated;

[0019] The pretreatment is selected from HLB solid phase extraction, C 18 At least one of the solid phase extraction methods.

[0020] The solution system of the wastewater is a methanol / water system or an acetonitrile / water system.

[0021] The molar absorption coefficient is the slope of the corresponding standard curve.

[0022] The beneficial effects of this application include:

[0023] 1. In the method of the present invention, solid phase extraction is used as a sample pretreatment method to remove impurities, thereby reducing matrix interference in wastewater.

[0024] 2. The method of the present invention adopts ultraviolet dual-wavelength detection, which shortens the detection cycle and reduces the cost of manpower and material resources.

[0025] 3. The method of the present invention is simple and easy to operate, and can provide technical support for the construction of an unattended water body intelligent purification system intermediate treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Ultraviolet absorption of sulfathiazole (STZ), levofloxacin (LZD) and tetracycline (TC). DETAILED DESCRIPTION

[0027] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0028] UV detection conditions: wavelength detection range 200-400 nm, concentration 10 μg / mL (methanol / water system), optical path l=1 cm.

[0029] Example 1

[0030] Measurements were performed on wastewater containing tetracycline and levofloxacin.

[0031] Determine the standard curve:

[0032] The solution system selected was a methanol / water system. The 1 mg / mL levofloxacin and tetracycline methanol standard solutions were diluted to 10 μg / mL with water, and the ultraviolet absorption of the two substances was measured using an ultraviolet spectrophotometer. Figure 1 , the wavelength range is: 200~400nm, and the maximum absorption wavelength of levofloxacin is 295nm. Therefore, taking the absorbance of tetracycline at 295nm as the benchmark, find the points with the same absorbance value on the ultraviolet absorption graph, that is, 308nm and 374nm. Since the difference between 308nm and 295nm is small, 295nm and 374nm are selected for subsequent research to eliminate the influence of tetracycline.

[0033] The molar absorption coefficient of levofloxacin and tetracycline at 295nm and 374nm was measured respectively. The measuring process was as follows: 1mg / mL levofloxacin and tetracycline methanol standard solutions were diluted to 3, 7, 10, 12, 15, and 20μg / mL with water, UV absorption was measured, and the absorbance values ​​of the two substances at 295nm and 374nm were recorded. The average value was obtained by repeating the measurement three times, and the concentration and absorbance were plotted. A standard curve was established according to Lambert-Beer's law (A=εlc, l=1cm). The slope of the standard curve was the molar absorption coefficient, and the molar absorption coefficient of levofloxacin and tetracycline at 295nm and 374nm was obtained respectively. To verify the stability and accuracy of the standard curve, the above experiment was repeated for three days, and the results are shown in Table 1. The relative standard deviation (RSD) value between days was small, and the stability of the standard curve was good.

[0034] Table 1 Molar absorption coefficient of levofloxacin (LZD) and tetracycline (TC) εμg / (mL·cm) (n=3)

[0035]

[0036] (Note: n is the number of repeated days, the same below)

[0037] The absorbance values ​​of mixed standard solutions of levofloxacin and tetracycline at different concentrations at 295nm and 374nm were measured to verify the feasibility of wavelength superposition. The wavelength superposition equation is:

[0038]

[0039] The process is as follows: 1 mg / mL levofloxacin and tetracycline mixed methanol standard solution is diluted with water to 3, 7, 10, 12, 15, and 20 μg / mL, respectively, ultraviolet absorption is measured, and the absorbance values ​​at 295 nm and 374 nm are recorded. The measurement is repeated three times to take the average value, and the obtained absorbance value is compared with the single-label absorbance value in Example 1. In order to verify the experimental stability and accuracy, the above experiment is repeated for three days. The results are shown in Tables 2 and 3.

[0040] Table 2 Comparison of the absorbance values ​​A of the mixed standard and the single standard at 295 nm (n = 3)

[0041]

[0042] Table 3 Comparison of the absorbance values ​​A of the mixed standard and the single standard at 374 nm (n=3)

[0043]

[0044] The ratio of the absorbance value of the mixed standard to the sum of the absorbance values ​​of the single standard is stable at about 1, and the wavelength superposition equation is feasible.

[0045] The difference between the absorbance values ​​of levofloxacin at 295 nm and 374 nm is used as the abscissa and the concentration of levofloxacin is used as the ordinate to draw a graph, that is, draw a graph according to this formula (l = 1 cm):

[0046]

[0047] The slope of the resulting curve is The results obtained by comparing the standard curve with those obtained by experimental calculation were basically consistent; to verify the stability and accuracy of the experimental method, the measurement was repeated for three days, and the results are shown in Table 4.

[0048] Table 4 The reciprocal difference of the absorption coefficient of levofloxacin at different wavelengths (n=3)

[0049]

[0050] The repeatability and stability are good, and the levofloxacin concentration can be obtained based on this standard curve later.

[0051] Since the absorbance of tetracycline at 295nm and 374nm is close, it can be eliminated in the calculation.

[0052] Detection

[0053] HLB solid phase extraction and C 18 Solid phase extraction was used to purify and enrich levofloxacin in actual wastewater. The eluate was collected, the absorbance was measured, and the formula was substituted: Eliminate the effect of tetracycline and obtain the levofloxacin concentration.

[0054] A series of actual water samples with unknown concentrations were measured and the levofloxacin concentrations were obtained from the established standard curve. The results are shown in Table 5.

[0055] Table 5 Levofloxacin concentration in actual water samples (n=3)

[0056] <![CDATA[Absorbance value difference A 295 -A 374 > <![CDATA[c LZD μg / mL]]> 0.082 1.933 0.189 3.539 0.233 4.200 0.745 11.885 0.333 5.700

[0057] (Note: n is the number of repetitions, the same below)

[0058] Example 2

[0059] Measurements were made on wastewater containing tetracycline and sulfathiazole.

[0060] Determine the standard curve

[0061] As described in Example 2, the difference is that:

[0062] The ultraviolet absorption of sulfathiazole and levofloxacin was measured, such as Figure 1 , 284nm and 302nm were selected for subsequent research to eliminate the influence of sulfathiazole.

[0063] 1 mg / mL sulfathiazole and levofloxacin methanol standard solutions were diluted with water to 0.1, 1, 3, 7, and 10 μg / mL, and the ultraviolet absorption was measured. The molar absorption coefficients of sulfathiazole and levofloxacin at 284 nm and 302 nm were obtained, respectively. The results are shown in Table 6.

[0064] Table 6 Molar absorption coefficient of sulfathiazole (STZ) and levofloxacin (LZD) εμg / (mL·cm) (n=3)

[0065]

[0066] The wavelength superposition equation is,

[0067]

[0068] The results are shown in Tables 7 and 8.

[0069] Table 7 Comparison of the absorbance values ​​A of the mixed standard and the single standard at 284 nm (n = 3)

[0070]

[0071] Table 8 Comparison of the absorbance values ​​A of the mixed standard and the single standard at 302nm (n=3)

[0072]

[0073] The repeatability and stability are good, and the levofloxacin concentration can be obtained based on this standard curve later.

[0074] Since the absorbance of levofloxacin at 284nm and 302nm is close, it can be eliminated in the calculation.

[0075] The difference between the absorbance values ​​of sulfathiazole at 284nm and 302nm is used as the horizontal axis, and the concentration of sulfathiazole is used as the vertical axis to draw a graph, that is, according to this formula,

[0076]

[0077] The slope of the resulting curve is The experimental results were compared with those obtained from the standard curve. The results are shown in Table 9. The sulfathiazole concentration was obtained and substituted into the wavelength superposition equation to obtain the levofloxacin concentration calculation formula:

[0078]

[0079] Table 9 Reciprocal difference of sulfathiazole absorption coefficient at different wavelengths (n=3)

[0080]

[0081]

[0082] Detection

[0083] HLB solid phase extraction and C 18 Solid phase extraction was used to purify and enrich levofloxacin in actual wastewater to obtain the eluate and substitute it into The effect of sulfathiazole was eliminated and the levofloxacin concentration was obtained.

[0084] Table 10 Concentrations of sulfathiazole and levofloxacin in actual water samples (n=3)

[0085] <![CDATA[Absorbance value difference A 284 -A 302 > <![CDATA[c STZ μg / mL]]> <![CDATA[c LZD μg / mL]]> 0.033 1.104 0.704 0.019 0.697 0.339 0.147 4.347 3.611 0.317 9.240 7.998 0.240 7.030 6.017

[0086] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for detecting levofloxacin in wastewater by ultraviolet dual wavelength, characterized in that: The wastewater also contains tetracycline or sulfathiazole; The absorbance A of the wastewater is detected by ultraviolet dual-wavelength method; When the wastewater contains tetracycline, 295nm and 374nm are selected for detection, and (1) is used to calculate the concentration of levofloxacin in the wastewater: When the wastewater contains sulfathiazole, 284nm and 302nm are selected for detection, and (2) is used to calculate the concentration of sulfathiazole in the wastewater: in, c is the concentration in μg / ml; l is the optical path, which is 1 cm; ε is the molar absorption coefficient, in μg / (mL·cm); LZD is levofloxacin; STZ is sulfathiazole.

2. The method according to claim 1, characterized in that The wastewater is pre-treated; The pretreatment is selected from HLB solid phase extraction, C 18 At least one of the solid phase extraction methods.

3. The method according to claim 1, characterized in that The solution system of the wastewater is a methanol / water system or an acetonitrile / water system.

4. The method according to claim 1, characterized in that: The molar absorption coefficient is the slope of the corresponding standard curve.

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