CN113376149A - Method for detecting low-concentration free bromine by using ultra-long optical fiber flow cell-spectrophotometry phenol red method and application thereof - Google Patents
Method for detecting low-concentration free bromine by using ultra-long optical fiber flow cell-spectrophotometry phenol red method and application thereof Download PDFInfo
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- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 title claims abstract description 175
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 title claims abstract description 173
- 229910052794 bromium Inorganic materials 0.000 title claims abstract description 169
- 238000000034 method Methods 0.000 title claims abstract description 77
- BELBBZDIHDAJOR-UHFFFAOYSA-N Phenolsulfonephthalein Chemical compound C1=CC(O)=CC=C1C1(C=2C=CC(O)=CC=2)C2=CC=CC=C2S(=O)(=O)O1 BELBBZDIHDAJOR-UHFFFAOYSA-N 0.000 title claims abstract description 69
- 229960003531 phenolsulfonphthalein Drugs 0.000 title claims abstract description 69
- 239000013307 optical fiber Substances 0.000 title claims abstract description 64
- 238000002798 spectrophotometry method Methods 0.000 title description 13
- 238000001514 detection method Methods 0.000 claims abstract description 64
- 238000002835 absorbance Methods 0.000 claims abstract description 45
- UDSAIICHUKSCKT-UHFFFAOYSA-N bromophenol blue Chemical compound C1=C(Br)C(O)=C(Br)C=C1C1(C=2C=C(Br)C(O)=C(Br)C=2)C2=CC=CC=C2S(=O)(=O)O1 UDSAIICHUKSCKT-UHFFFAOYSA-N 0.000 claims abstract description 39
- 239000002957 persistent organic pollutant Substances 0.000 claims abstract description 16
- 238000006303 photolysis reaction Methods 0.000 claims abstract description 12
- 230000015843 photosynthesis, light reaction Effects 0.000 claims abstract description 12
- 238000010517 secondary reaction Methods 0.000 claims abstract description 9
- 238000005259 measurement Methods 0.000 claims abstract description 7
- 239000000243 solution Substances 0.000 claims description 51
- 238000010521 absorption reaction Methods 0.000 claims description 25
- 238000006243 chemical reaction Methods 0.000 claims description 24
- 230000007281 self degradation Effects 0.000 claims description 14
- BHZOKUMUHVTPBX-UHFFFAOYSA-M sodium acetic acid acetate Chemical compound [Na+].CC(O)=O.CC([O-])=O BHZOKUMUHVTPBX-UHFFFAOYSA-M 0.000 claims description 13
- 239000007974 sodium acetate buffer Substances 0.000 claims description 12
- 230000035484 reaction time Effects 0.000 claims description 11
- 239000011259 mixed solution Substances 0.000 claims description 10
- 239000007853 buffer solution Substances 0.000 claims description 7
- CUILPNURFADTPE-UHFFFAOYSA-N hypobromous acid Chemical compound BrO CUILPNURFADTPE-UHFFFAOYSA-N 0.000 claims description 5
- JGJLWPGRMCADHB-UHFFFAOYSA-N hypobromite Inorganic materials Br[O-] JGJLWPGRMCADHB-UHFFFAOYSA-N 0.000 claims description 2
- -1 hypobromite radical ion Chemical class 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 9
- 230000008569 process Effects 0.000 abstract description 6
- 238000011160 research Methods 0.000 abstract description 4
- 230000001590 oxidative effect Effects 0.000 abstract description 3
- RYYVLZVUVIJVGH-UHFFFAOYSA-N caffeine Chemical compound CN1C(=O)N(C)C(=O)C2=C1N=CN2C RYYVLZVUVIJVGH-UHFFFAOYSA-N 0.000 description 20
- 230000002572 peristaltic effect Effects 0.000 description 15
- LPHGQDQBBGAPDZ-UHFFFAOYSA-N Isocaffeine Natural products CN1C(=O)N(C)C(=O)C2=C1N(C)C=N2 LPHGQDQBBGAPDZ-UHFFFAOYSA-N 0.000 description 10
- 229960001948 caffeine Drugs 0.000 description 10
- VJEONQKOZGKCAK-UHFFFAOYSA-N caffeine Natural products CN1C(=O)N(C)C(=O)C2=C1C=CN2C VJEONQKOZGKCAK-UHFFFAOYSA-N 0.000 description 10
- HEFNNWSXXWATRW-UHFFFAOYSA-N Ibuprofen Chemical compound CC(C)CC1=CC=C(C(C)C(O)=O)C=C1 HEFNNWSXXWATRW-UHFFFAOYSA-N 0.000 description 9
- 239000000835 fiber Substances 0.000 description 9
- 229960001680 ibuprofen Drugs 0.000 description 9
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 7
- 229910052801 chlorine Inorganic materials 0.000 description 7
- 239000000460 chlorine Substances 0.000 description 7
- 229910052736 halogen Inorganic materials 0.000 description 7
- 150000002367 halogens Chemical class 0.000 description 7
- 239000000376 reactant Substances 0.000 description 7
- CPELXLSAUQHCOX-UHFFFAOYSA-M Bromide Chemical compound [Br-] CPELXLSAUQHCOX-UHFFFAOYSA-M 0.000 description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- 238000005406 washing Methods 0.000 description 5
- 239000000356 contaminant Substances 0.000 description 4
- 230000003287 optical effect Effects 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 239000005350 fused silica glass Substances 0.000 description 2
- QWPPOHNGKGFGJK-UHFFFAOYSA-N hypochlorous acid Chemical compound ClO QWPPOHNGKGFGJK-UHFFFAOYSA-N 0.000 description 2
- 238000012933 kinetic analysis Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 description 1
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 1
- 238000011481 absorbance measurement Methods 0.000 description 1
- 238000000862 absorption spectrum Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229940006460 bromide ion Drugs 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000005660 chlorination reaction Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 239000000645 desinfectant Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 238000012625 in-situ measurement Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000008239 natural water Substances 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 150000002989 phenols Chemical class 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000001632 sodium acetate Substances 0.000 description 1
- 235000017281 sodium acetate Nutrition 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- AAAQKTZKLRYKHR-UHFFFAOYSA-N triphenylmethane Chemical compound C1=CC=CC=C1C(C=1C=CC=CC=1)C1=CC=CC=C1 AAAQKTZKLRYKHR-UHFFFAOYSA-N 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
- G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
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- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/33—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using ultraviolet light
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Abstract
本发明属于游离溴浓度测定技术领域，具体涉及一种利用超长光纤流通池‑分光光度酚红法检测低浓度游离溴的方法及其应用，本发明以苯酚红为游离溴的捕获剂，与游离溴反应生成溴酚蓝，然后利用超长光纤流通池测定溴酚蓝在592nm处的吸光度，最后根据Lambert‑Beer定律进行计算从而得知待测体系中游离溴的浓度；同时，利用上述测定方法还可以检测游离溴的自衰减速率、检测游离溴在紫外光下的光解速率、测量有机污染物与游离溴的二级反应速率常数等；本发明的检测方法大大降低了游离溴浓度的检出下限，检测过程简单、干扰因素少、检测结果准确，同时检测成本低、精度高、范围广，对水环境中氧化物种的研究有重要价值。
The invention belongs to the technical field of free bromine concentration measurement, and in particular relates to a method for detecting low-concentration free bromine by using an ultra-long optical fiber flow cell-spectrophotometric phenol red method and its application. Free bromine is reacted to generate bromophenol blue, then the absorbance of bromophenol blue at 592 nm is measured by using an ultra-long optical fiber flow cell, and finally calculated according to Lambert-Beer's law to know the concentration of free bromine in the system to be tested; at the same time, using the above-mentioned determination The method can also detect the self-decay rate of free bromine, detect the photolysis rate of free bromine under ultraviolet light, measure the secondary reaction rate constant of organic pollutants and free bromine, etc. The detection method of the present invention greatly reduces the concentration of free bromine. The detection limit is simple, the detection process is simple, the interference factors are few, and the detection results are accurate. At the same time, the detection cost is low, the precision is high, and the range is wide, which is of great value to the research of oxidizing species in the water environment.
Description
Technical Field
The invention belongs to the technical field of free bromine concentration determination, and particularly relates to a method for detecting low-concentration free bromine by using an ultra-long optical fiber flow cell-spectrophotometry phenol red method and application thereof.
Background
Since bromide ions are ubiquitous in natural water, the commonly used disinfectants, free chlorine (HOCl and OCl-), react with bromide ions to form free bromine (also known as free bromine). Free bromine reacts with organic pollutants such as phenols and amines at a rate 1000 times higher than free chlorine and is considered to be one of the important oxides in an aqueous environment. Free bromine plays an important role in the transport conversion of pollutants in saline wastewater and offshore water.
The current methods for measuring the concentration of free bromine are less researched, and there are two main methods for measuring the concentration of free bromine reported: (1) directly measuring the absorbance of HOBr or OBr-by using an ultraviolet spectrophotometer; (2) adding phenol red to react with free bromine to generate bromophenol blue, and measuring absorbance of bromophenol blue by using an ultraviolet spectrophotometer. However, the detection limits of both methods are high, wherein the lower detection limit of the method (1) is 50mg/L, and the lower detection limit of the method (2) is 0.2mg/L, which is far higher than the concentration of free bromine generated in the actual reaction, so that the degradation contribution of the free bromine to pollutants is underestimated. Therefore, it is necessary to develop a simple and low detection limit method for detecting free bromine and performing reaction kinetic analysis.
The ultra-long fiber flow cell (LWCC) is an optical fiber flow cell, which is formed by coating a layer of polymer with low reflection index outside a fused quartz tube, a liquid sample is guided into a capillary tube and represents a waveguide core, and the signal stability is high due to the hydrophilic characteristic of the inner wall of the fused quartz capillary tube; the DH-2000 halogen lamp can provide a stable, continuous spectrum of sufficient intensity; the USB-4000 spectrometer has the advantages of wide detection range (200-1100nm), high sensitivity and high signal-to-noise ratio, converts an optical signal into an electric signal, and performs ultrasensitive absorbance measurement on a solution to be measured in the UV, VIS and NIR parts of a spectrum. During measurement, the light path is fused in a small-volume sample (3-5mL), light emitted by a light source can enter the optical fiber connection spectrometer through the rear end of liquid, and according to the Lambert-Beer law, the light absorption signal of the liquid is related to the concentration and the light path of chemical substances, so that the absorption spectrum line of the sample can be calculated. LWCC has the advantages of low sample consumption, simple operation, stable signal, high sensitivity and the like, is applied to quantitative detection of trace substances in research environment at present, but has no report of quantitative detection of free bromine by using an ultra-long optical fiber flow cell and reaction kinetic analysis.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a method for detecting low-concentration free bromine by using an ultra-long optical fiber flow cell-spectrophotometry phenol red method, the detection method greatly reduces the detection lower limit of the concentration of the free bromine, has accurate detection result and wide detection range, can be used for measuring the secondary reaction rate constant of organic pollutants and the free bromine, and the like, and has important value on the research of oxidizing species in water environment.
In order to achieve the purpose, the invention adopts the technical scheme that:
the invention provides a method for detecting low-concentration free bromine by using an ultra-long optical fiber flow cell-spectrophotometry phenol red method, which comprises the following steps: adding a solution to be detected into an ultra-long optical fiber flow cell, adjusting the pH value of the solution to be detected to 4.6-4.7 by using a buffer solution, then adding phenol red with the final concentration of 1.92-2.30mg/L into a detection system, enabling free bromine in the detection system to react with the phenol red to generate bromophenol blue, setting the maximum absorption wavelength of the ultra-long optical fiber flow cell to be 592nm, setting the ambient temperature to be 20-25 ℃, determining the absorbance of the bromophenol blue in the detection system at 592nm, and finally calculating the concentration of the free bromine according to the linear relation between the concentration of the free bromine and the absorbance determined according to Lambert-Beer law; the method can detect free bromine concentration at least as low as 0.98. mu.M.
Preferably, the super-long optical fiber flow cell comprises an LWCC-4100 super-long optical fiber flow cell (as a colorimetric tube) with the length of 1 meter, an ultraviolet and visible light detection system which is formed by combining a USB-4000 spectrometer and a DH-2000 halogen lamp, a peristaltic pump and a computer. And (3) introducing a sample to be detected into the LWCC-4100 super-long optical fiber flow cell by using a peristaltic pump, enabling the light beam emitted by the DH-2000 halogen lamp to reach the USB-4000 spectrometer through the LWCC-4100 super-long optical fiber flow cell, and connecting the spectrometer with a computer to obtain the absorbance of bromophenol blue in the sample.
The absorbance signal of a substance is related to the concentration of the compound detected, the optical path length and the concentration of the compound according to Lambert-Beer's lawThe specific molar absorption coefficient is directly proportional, so the LWCC-4100 absorbance signal using a 100cm optical path can be increased by a factor of about 100 compared to a conventional cuvette with a 1cm optical path. Meanwhile, the LWCC also has the advantages of ultra-low sample consumption (0.1-3mL), simple operation, stable signal, high sensitivity and the like. The invention takes phenol red as a trapping agent of free bromine (see formula 4 specifically), and the phenol red reacts with the free bromine to generate bromophenol blue, because the bromophenol blue has maximum absorption at 592nm, the maximum molar absorption coefficient at 592nm is 67400M-1cm-1The absorbance A of bromophenol blue at 592nm is measured by using an ultralong optical fiber flow cell, and the concentration of free bromine can be calculated according to the Lambert-Beer law.
C19H14O5S+Br2→C19H10O5SBr4+H++Br- (4)。
Preferably, the free bromine includes, but is not limited to, hypobromous acid, hypobromite ion.
Preferably, the buffer solution includes, but is not limited to, acetic acid-sodium acetate buffer solution.
Preferably, the linear relationship between free bromine concentration and absorbance is: y is 7.0467x +0.066(x is free bromine concentration and y is absorbance).
Further, the phenol red is a triphenylmethane type organic compound, and the acetic acid-sodium acetate is a buffer solution formed by mixing acetic acid and sodium acetate in a certain proportion.
Further, the linear relation between the concentration of free bromine and the absorbance is determined by the following method: respectively preparing solutions containing 0, 0.01, 0.02, 0.05, 0.1, 0.2 and 0.5mg/L of free bromine, adding the solutions into an ultralong optical fiber flow cell, adjusting the pH of the free bromine solution to 4.6-4.7 by using a buffer solution, adding phenol red with the final concentration of 1.92mg/L into a detection system, enabling the free bromine in the detection system to react with the phenol red to generate bromophenol blue, setting the maximum absorption wavelength of the ultralong optical fiber flow cell to be 592nm and the ambient temperature to be 25 ℃, measuring the absorbance of the bromophenol blue in each detection system at 592nm, and drawing by taking the concentration of the free bromine as a horizontal coordinate and the absorbance as a vertical coordinate to obtain the linear relation between the concentration of the free bromine and the absorbance.
The invention also provides the application of the method for detecting low-concentration free bromine by using the ultralong optical fiber flow cell-spectrophotometric phenol red method, wherein the application range includes but is not limited to the self-attenuation rate of free bromine detection, the photolysis rate of free bromine under ultraviolet light detection, and the secondary reaction rate constant of organic pollutants and free bromine measurement.
The invention also provides a method for detecting the self-attenuation rate of the free bromine by using the ultralong optical fiber flow cell-spectrophotometry phenol red method, which is characterized in that the method for detecting the low-concentration free bromine is adopted to determine the absorbance A of the free bromine solution after the free bromine solution is placed for different times, wherein the absorbance A is marked when the placing time is 00And the rest time is marked as AtThen calculating the self-degradation rate constant k of the free bromine according to the formula (1)1：
The invention also provides a method for detecting the photolysis rate of free bromine under ultraviolet light by using the ultralong optical fiber flow cell-spectrophotometry phenol red method, which is characterized in that the method for detecting the low-concentration free bromine is adopted to determine the absorbance A of a free bromine solution after different ultraviolet light irradiation times, wherein the absorbance A is marked when the irradiation time is 00And the other irradiation times are denoted by AtAnd determining the self-degradation rate constant k of the free bromine according to the method for detecting the self-decay rate of the free bromine1Then calculating the photolysis rate k of the free bromine according to the formula (2)2：
The invention also provides a method for measuring the secondary reaction rate constant of the organic pollutants and the free bromine by using the ultralong optical fiber flow cell-spectrophotometry phenol red method, which is characterized in that the method for detecting the low-concentration free bromine is adopted to measure the free bromine and the mixed solution of the organic pollutants in different conditionsAbsorbance A after the reaction time, wherein A denotes a reaction time of 00(i.e., no organic contaminants added) and the other reaction times are recorded as AtAnd the concentration of organic contaminants is recorded as [ T ]]And determining the self-degradation rate constant k of the free bromine according to the method for detecting the self-decay rate of the free bromine1Then calculating a reaction rate constant k of the free bromine and the organic pollutant T according to the formula (3)Bromine, T：
Preferably, the concentration of the organic contaminant is more than 20 times the concentration of free bromine.
Preferably, the organic contaminants include, but are not limited to, ibuprofen, caffeine.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a method for detecting low-concentration free bromine by using an ultralong optical fiber flow cell-spectrophotometry phenol red method, which takes phenol red as free bromine (HOBr and OBr)-) The capture agent reacts with free bromine to generate bromophenol blue, then an ultralong optical fiber flow cell is used for measuring the absorbance of the bromophenol blue at 592nm, and finally calculation is carried out according to the Lambert-Beer law so as to obtain the concentration of the free bromine in a system to be measured; meanwhile, the self-attenuation rate of the free bromine, the photolysis rate of the free bromine under ultraviolet light, the secondary reaction rate constant of the organic pollutants and the free bromine and the like can be detected by using the determination method; the detection method disclosed by the invention has the advantages that the detection lower limit of the concentration of free bromine is greatly reduced, the detection process is simple, the interference factors are few, the detection result is accurate, the detection cost is low, the precision is high, the range is wide, and the detection method has important value on the research of oxidizing species in a water environment.
Drawings
FIG. 1 is a schematic structural diagram of a detection system for an ultra-long fiber flow cell;
FIG. 2 is a graph of the linear relationship between free bromine concentration and absorbance;
FIG. 3 is a graph of the kinetics of free bromine at various times;
FIG. 4 is a graph showing the kinetics of free bromine under UV light;
FIG. 5 is a kinetic profile of free bromine after addition of the reactant ibuprofen;
figure 6 is a kinetic profile of free bromine after addition of the reactant caffeine.
Detailed Description
The following further describes the embodiments of the present invention. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The experimental procedures in the following examples were carried out by conventional methods unless otherwise specified, and the test materials used in the following examples were commercially available by conventional methods unless otherwise specified.
The ultra-long fiber optic flow cell used in the following examples included an LWCC-4100 ultra-long fiber optic flow cell (as a colorimetric cylinder) having a length of 1 meter, an ultraviolet-visible light detection system composed of a USB-4000 spectrometer and a DH-2000 halogen lamp, a peristaltic pump, and a computer. The connection relationship among the above components is shown in figure 1, a peristaltic pump is utilized to lead a sample to be measured into the LWCC-4100 super-long optical fiber flow cell, light beams emitted by the DH-2000 halogen lamp pass through the LWCC-4100 super-long optical fiber flow cell to reach the USB-4000 spectrometer, and the spectrometer is connected with a computer to obtain the absorbance of bromophenol blue in the sample.
The detection process by using the ultra-long optical fiber flow cell also comprises the following correction process:
(1) turning on a lamp: turning on the DH-2000 halogen lamp, stabilizing at normal temperature for half an hour to provide a stable, continuous spectrum of sufficient intensity;
(2) washing: firstly, washing the ultra-long optical fiber flow cell for 1min by pure water at the rate of 30mL/min, secondly, washing for 1min by methanol at the rate of 30mL/min, and finally, washing for 30s by pure water at a low rate (10mL/min) to ensure that all bubbles in the flow cell are discharged;
(3) zero setting: pulling out the optical fiber connected with the halogen lamp, sealing the flow cell in a dark place, and storing a zero point spectrum;
(4) sample introduction: the solution to be detected enters the long optical fiber flow cell at a low speed (10mL/min) under the action of the peristaltic pump, and no bubbles can enter;
(5) washing: when a sample to be detected is replaced, residual substances in the flow cell need to be flushed, bubbles and residues are flushed by pure water at a high speed (30mL/min), then the bubbles and the residues are flushed by methanol at the same speed, and finally the bubbles in the flow cell are completely discharged by flushing the residues for 30s by pure water at a low speed (10 mL/min).
Example 1 detection of Low concentration free bromine Using an ultra-Long fiber flow cell-spectrophotometric phenol Red method
Bromide ion with free chlorine (HOCl and OCl)-) The reaction will generate free bromine (HOBr and OBr)-) Thereby affecting the oxidation effect of free chlorine. Therefore, when investigating the effect of bromide ions in a chlorination system, it is generally necessary to measure the concentration of free bromine generated by oxidation of free chlorine, and the specific measurement procedure is as follows:
(1) respectively preparing reaction system solutions containing free bromine of 0, 0.01, 0.02, 0.05, 0.1, 0.2 and 0.5mg/L, adding into a super-long optical fiber flow cell, and introducing acetic acid-sodium acetate buffer solution (6.00 g of CH is weighed) into the super-long optical fiber flow cell by using a peristaltic pump3COONa was dissolved in a small dry beaker with a small amount of deionized water, and 9.00mL CH was added3CO0H, shaking up and fixing the volume to 250mL), adjusting the pH value of the free bromine solution to 4.6-4.7, and then adding phenol red to ensure that the concentration of the phenol red in the detection system reaches 1.92 mg/L; reacting free bromine with phenol red to generate bromophenol blue, setting the maximum absorption wavelength of the ultralong optical fiber flow cell at 592nm and the ambient temperature at 25 ℃, and measuring the characteristic absorption peak of bromophenol blue in a detection system at 592nm, wherein the absorbance is A1＝0.035、A2＝0.12、A3＝0.221、A4＝0.405、A5＝0.859、A61.434 (as shown in fig. 2), the linear relationship between the free bromine concentration and the absorbance was determined according to Lambert-Beer's law, plotted with the concentration of free bromine as the abscissa and the absorbance as the ordinate: y 7.0467x + 0.066.
(2) Preparing a solution to be detected containing 1 mu M of bromide ions and 70 mu M of free chlorine, adding 10mL of the solution to be detected into an ultralong optical fiber flow cell, adjusting the pH value of the solution to be detected to 4.6-4.7 by adding acetic acid-sodium acetate buffer solution by using a peristaltic pump, and then adding phenol red to ensure that the concentration of the phenol red in a detection system reaches 1.92 mg/L; reacting the generated free bromine with phenol red to generate bromophenol blue, setting the maximum absorption wavelength of the ultralong optical fiber flow cell at 592nm and the ambient temperature at 25 ℃, and measuring the characteristic absorption peak of the bromophenol blue in a detection system at 592nm, wherein the absorbance is Ax＝0.618；
(3) According to the linear relation between the concentration of free bromine and the absorbance measured in the step (1), A is measuredxThe bromine ion concentration converted from free chlorine was calculated to be 0.98. mu.M by substituting in the relational expression.
Example 2 detection of the self-decay Rate of free bromine Using an ultra-Long fiber flow cell-spectrophotometry phenol Red method
The self-degradation rate of the free bromine is measured, and the specific determination process is as follows:
(1) preparing a solution containing 50 mu M of free bromine (in-situ detection, namely standing for 0min), adding 10mL of the solution into an ultralong optical fiber flow cell, introducing an acetic acid-sodium acetate buffer solution by using a peristaltic pump to adjust the pH value of the mixed solution to 4.6-4.7, and then adding phenol red to enable the concentration of the phenol red in a detection system to reach 1.92 mg/L; reacting free bromine with phenol red to generate bromophenol blue, setting the maximum absorption wavelength of the ultralong optical fiber flow cell at 592nm and the ambient temperature at 25 ℃, and measuring the characteristic absorption peak of bromophenol blue in a detection system at 592nm, wherein the absorbance is A0＝0.236。
(2) Placing the free bromine solution obtained in the step (1) on a magnetic stirrer, respectively adding the free bromine solution after different times t (1min, 18min, 33min and 87min) into an ultra-long optical fiber flow cell, introducing an acetic acid-sodium acetate buffer solution by using a peristaltic pump to adjust the pH value of the free bromine solution to 4.6-4.7, and adding phenol red to enable the concentration of the phenol red in a detection system to reach 1.92 mg/L; reacting free bromine with phenol red to generate bromophenol blue, and measuring the characteristic absorption peak of bromophenol blue at 592nm in the detection system, wherein the absorbance is At1＝0.235、At2＝0.233、At3＝0.226、At40.213 (as shown in fig. 3).
(3) A to be measured0、AtAnd the reaction time t is substituted into the formula (1) for calculation, so that the self-degradation rate constant k of the free bromine can be obtained1：
Will k1Looking at- ρ, then the y-axis is plotted as (ln (A)t/A0) X axis is (t), and as shown in fig. 3, fitting to obtain a slope value ρ of-0.0012, that is, the self-degradation rate k of bromine is experimentally measured1＝0.0012min-1。
Example 3 detection of photolysis Rate of free bromine under ultraviolet light Using ultra-Long fiber flow cell-spectrophotometry phenol Red
The photolysis rate of free bromine under ultraviolet light is measured, and the specific determination process is as follows:
(1) preparing a reaction system solution containing 500 mu M of free bromine (in-situ measurement, namely ultraviolet irradiation time is 0min), adding 10mL of the reaction system solution into an ultra-long optical fiber flow cell, and introducing an acetic acid-sodium acetate buffer solution by using a peristaltic pump to adjust the pH value of the mixed solution to 4.6-4.7; then adding phenol red to enable the concentration of the phenol red in the detection system to reach 1.92 mg/L; reacting free bromine with phenol red to generate bromophenol blue, setting the maximum absorption wavelength of the ultralong optical fiber flow cell at 592nm and the ambient temperature at 25 ℃, and measuring the characteristic absorption peak of bromophenol blue in a detection system at 592nm, wherein the absorbance is A0＝0.255；
(2) Placing the free bromine solution obtained in the step (1) in a light intensity of 0.55mW/cm2Under an ultraviolet lamp, respectively adding free bromine solutions after different ultraviolet irradiation times t (3min, 13min, 24min, 30min and 40min) into an ultra-long optical fiber flow cell, introducing an acetic acid-sodium acetate buffer solution by using a peristaltic pump to adjust the pH of the free bromine solution to 4.6-4.7, and adding phenol red to enable the concentration of the phenol red in a detection system to reach 1.92 mg/L; reacting free bromine with phenol red to generate bromophenol blue, setting the ultra-long optical fiber flow cellThe maximum absorption wavelength is 592nm, the ambient temperature is 25 ℃, the characteristic absorption peak of bromophenol blue in the detection system at 592nm is measured, the absorbance is At1＝0.250、At2＝0.242、At3＝0.239、At4＝0.239、At50.229 (as shown in fig. 4).
(3) A to be measured0、AtSelf-degradation rate (i.e. self-decay rate) k of bromine1And the illumination time t is substituted into the formula (2) for calculation, so that the photolysis rate k of the free bromine can be obtained2：
Will k2+k1Looking at- ρ, then the y-axis is plotted as (ln (A)t/A0) X-axis (t), as shown in fig. 4, the slope value ρ of which is-0.0026, as determined by fitting, the self-degradation rate k of bromine as measured in example 21＝0.0012min-1It is substituted into the formula: k is a radical of2＝－(ρ－k1) Calculating the photolysis rate of free bromine to be 0.0014min-1。
Example 4 measurement of Secondary reaction Rate constants of ibuprofen and free bromine Using an ultra-Long fiber flow cell-spectrophotometry phenol Red method
The second order reaction rate constant of ibuprofen and free bromine was measured, and the specific determination procedure was as follows:
(1) preparing a reaction system solution containing 25.2 mu M free bromine, adding 10mL of the reaction system solution into an ultralong optical fiber flow cell, introducing an acetic acid-sodium acetate buffer solution by using a peristaltic pump to adjust the pH value of the reaction system solution to 4.6-4.7, and adding phenol red to enable the concentration of the phenol red in a detection system to reach 1.92 mg/L; reacting free bromine with phenol red to generate bromophenol blue, setting the maximum absorption wavelength of the ultralong optical fiber flow cell at 592nm and the ambient temperature at 25 ℃, and measuring the characteristic absorption peak of bromophenol blue in a detection system at 592nm, wherein the absorbance is A0＝0.083；
(2) Placing the solution obtained in the step (1) on a magnetic stirrer, and adding reactantsIbuprofen was brought to a concentration of 496.9 μ M to give a mixed solution of free bromine and ibuprofen and timing was started after addition. Respectively adding mixed solutions after different reaction times t (3min, 6min, 10min, 15min and 20min) into an ultra-long optical fiber flow cell, introducing an acetic acid-sodium acetate buffer solution by using a peristaltic pump to adjust the pH value of the mixed solution to 4.6-4.7, and adding phenol red to enable the concentration of the phenol red in a detection system to reach 1.92 mg/L; reacting free bromine with phenol red to generate bromophenol blue, setting the maximum absorption wavelength of the ultralong optical fiber flow cell at 592nm and the ambient temperature at 25 ℃, and measuring the characteristic absorption peak of bromophenol blue in a detection system at 592nm, wherein the absorbance is At1＝0.077、At2＝0.074、At3＝0.073、At4＝0.068、At50.066 (as shown in fig. 5).
(3) A to be measured0、AtThe concentration [ T ] of the reactant T in the system to be detected in the step (2)]Self-degradation rate (i.e. self-decay rate) k of bromine1And substituting the reaction time T into the formula (3) for calculation to obtain the reaction rate constant k of the free bromine and the reactant TBromine compound，T：
Will kBromine, T[T]+k1Looking at- ρ, then the y-axis is plotted as (ln (A)t/A0) X-axis (t) in a linear relationship,
as shown in fig. 5, the fitting resulted in a slope value ρ of-0.013, i.e., the ratio of the apparent reaction rate of ibuprofen and bromine to the concentration of ibuprofen added.
The concentration of ibuprofen [ T ] is known]At 496.9. mu.M, the self-degradation rate k of bromine was determined according to example 21＝0.0012min-1It is substituted into the formula: k is a radical ofBromine, T＝－(ρ－k1)/[T]Calculated reaction rate of ibuprofen and bromine was 0.396M-1s-1。
Example 5 measurement of Secondary reaction Rate constants of caffeine and free bromine Using an ultra-Long fiber flow cell-spectrophotometry phenol Red method
The second order reaction rate constant of caffeine with free bromine was measured by the following specific procedure:
(1) preparing a reaction system solution containing 50 mu M free bromine, adding 10mL of the reaction system solution into an ultralong optical fiber flow cell, introducing an acetic acid-sodium acetate buffer solution by using a peristaltic pump to adjust the pH value of the reaction system solution to 4.6-4.7, and adding phenol red to enable the concentration of the phenol red in a detection system to reach 1.92 mg/L; reacting free bromine with phenol red to generate bromophenol blue, setting the maximum absorption wavelength of the ultralong optical fiber flow cell at 592nm and the ambient temperature at 25 ℃, and measuring the characteristic absorption peak of bromophenol blue in a detection system at 592nm, wherein the absorbance is A0＝0.23；
(2) And (2) placing the solution obtained in the step (1) on a magnetic stirrer, adding the reactant caffeine to enable the concentration to reach 1000 mu M, obtaining a mixed solution of free bromine and caffeine, and starting timing after adding. Respectively adding mixed solutions after different reaction times t (1min, 5min, 11min, 17min, 21min and 25min) into an ultra-long optical fiber flow cell, introducing an acetic acid-sodium acetate buffer solution by using a peristaltic pump to adjust the pH value of the mixed solution to 4.6-4.7, and adding phenol red to enable the concentration of the phenol red in a detection system to reach 1.92 mg/L; reacting free bromine with phenol red to generate bromophenol blue, setting the maximum absorption wavelength of the ultralong optical fiber flow cell at 592nm and the ambient temperature at 25 ℃, and measuring the characteristic absorption peak of bromophenol blue in a detection system at 592nm, wherein the absorbance is At1＝0.198、At2＝0.154、At3＝0.092、At4＝0.052、At5＝0.036、At60.025 (as shown in fig. 6).
(3) A to be measured0、AtAnd (2) detecting the concentration [ T ] of the reactant T in the system to be detected]Self-degradation rate (i.e. self-decay rate) k of bromine1And substituting the reaction time T into the formula (3) for calculation to obtain a reaction rate constant k of the free bromine and the reactant TBromine, T：
Will kBromine, T[T]+k1Looking at- ρ, then the y-axis is plotted as (ln (A)t/A0) Along the x-axis, as shown in fig. 6, with a slope value ρ of-0.0878, i.e., the ratio of the apparent rate of caffeine to bromine and the concentration of caffeine added, was fitted.
Known concentration of caffeine [ T ]]At 1000. mu.M, the self-degradation rate k of bromine was determined according to example 21＝0.0012min-1It is substituted into the formula: k is a radical ofBromine, T＝－(ρ－k1)/[T]Calculated reaction rate of caffeine with bromine was 1.443M-1s-1。
The embodiments of the present invention have been described in detail, but the present invention is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, and the scope of protection is still within the scope of the invention.
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