Instrument for synchronously characterizing soluble organic matter structure/physicochemical/concentration characteristics of water sample

Abstract

The invention relates to an instrument for synchronously characterizing soluble organic matter structure / physicochemical / concentration characteristics of a water sample, and belongs to the technical field of environment detection. All instruments are in single-flow-path connection, and the purpose is that (1) the synchronism and the stability of the whole multi-detector detection system are ensured; and (2) the influence of nitrate ions in the water sample to be detected is removed on the organic nitrogen distribution of the water sample to realize the accurate detection of the organic nitrogen distribution with different molecular weights. According to the invention, ultraviolet absorption / fluorescence characteristics / organic carbon concentration / organic nitrogen concentration of organicmatters with different molecular weights in the water sample can be synchronously detected, and the comprehensive characterization of the structure / physicochemical / concentration characteristics of thewater sample to be detected is realized. Rich quantitative / qualitative information provided by the instrument and the method can be used for research and application of rapid water quality scanning,accurate identification of drinking water disinfection by-product precursors, membrane pollution mechanism and water treatment process optimization and the like in the field of water treatment.

Description

technical field [0001] The present invention relates to the technical field of environmental detection, in particular to a single-channel UV / fluorescence / organic carbon / organic nitrogen multi-detector based on size exclusion chromatography to simultaneously characterize the structure / physicochemical / concentration characteristics of dissolved organic matter in water samples Instruments and methods. Background technique [0002] Dissolved organic matter (dissolved organic matter, DOM) widely exists in various natural water bodies, and it is one of the main concerns in drinking water treatment. The existence of DOM will make the water body show bad color and odor. In addition, DOM will also affect the treatment effect of ozone activated carbon and membrane filtration process, and may breed microorganisms in the water transmission and distribution network. DOM can also reduce the performance of oxidants and disinfectants, produce harmful oxidation and disinfection by-products,...

AI Technical Summary

Problems solved by technology

Patent CN201810480719.8 discloses an instrument and method for detecting dissolved organic nitrogen. Although the method can accurately detect the concentration distribution of DON with different molecular weights and avoid the influence of inorganic nitrogen ions such as nitrate on the detection results, the detection instrument It is more complicated, and more color reagents need to be added, which reduces the stability of the detection system and increases the analysis cost

[0005] For the combined detection of size exclusion chromatography and DOC and DON, the mainstream detection instrument in the world is the LC-OCD-OND system developed by the German DOC-Labor laboratory (that is, the combined size exclusion chromatography-organic carbon detector-organic nitrogen detector). system), the system reflects the water quality characteristics of the water sample by detecting the distribution of DOC and DON of different molecular weight components of the sample after separation by size exclusion chromatography. It is a milestone in water quality detection, but its shortcoming is : (1) using multi-flow path parallel mode to detect DOC and DON respectively has reduced the synchronism and the stability of multi-detector system; The current mainstream separation chromatographic column, because it is used in conjunction with the entire detection system, replacing the chromatographic column is equivalent to redesigning the entire separation and detection system) has a low separation limit (0.1-10KDa), and cannot separate macromolecular proteins and macromolecular polysaccharides. There is a literature "Three -dimensional excitation and emission matrix fluorescence (3DEEM) for quick and pseudo-quantitative determination of protein and humor-like substances in full-scale membrane bioreactor (MBR)" pointed out that due to the low separation limit of the chromatographic column and the interference of macromolecular polysaccharides, the use of this The correlation between the protein fluorescence obtained by the detection system and the protein fluorescence characterized by three-dimensional fluorescence is not good, which further shows that it cannot meet the current analysis requirements of heavily polluted surface water samples; (3) the detection system can only reflect the The structure / concentration information of dissolved organic matter is still lacking for the characterization of physical and chemical characteristics; (4) For the detection of DOC, the instrument uses an infrared carbon dioxide detector (NDIR) to detect the CO generated after the DOC is digested by ultraviolet light. 2 , and used nitrogen for CO 2 Blow off, the device occupies too much space, the operation is complicated, and it is very cumbersome. In addition, the detection limit of the NDIR detector is relatively high; (5) the system detects NO produced by DON through ultraviolet oxidation 3 - To characterize the DON concentration, this method is susceptible to the interference of inorganic nitrogen ions, and cannot accurately reflect the distribution information of DON with molecular weight; (6) Due to the monopoly position, the price of each equipment is extremely expensive

[0006] Patent CN201811466516.X discloses an organic nitrogen-organic carbon tandem online detection method and device. The device has the disadvantages of: (1) the thioproducts produced after activation of the pre-added oxidant (potassium persulfate) such as sulfuric acid ions, persulfate ions, etc. will absorb in the low ultraviolet wavelength region, which will have a greater impact on the subsequent DON detection results; (2) the higher content of nitrate inorganic nitrogen ions in surface water will The ion repulsion of the ion repulsion effect of the nitrate goes out of the peak ahead of time, which has a great impact on the detection of organic nitrogen. Therefore, it is necessary to further eliminate the influence of nitrate inorganic nitrogen ions on small molecule organic nitrogen substances; (3) because the mobile phase needs to be transported at a flow rate of 1.0mL / min to CO 2 selectively permeable to the CO 2 The pressure of the selective permeation membrane is relatively high, causing membrane damage and other problems. It is proposed to modify the pipeline of the organic nitrogen detection system so that the design of the pipeline back pressure of the organic nitrogen detector is less than 5bar, which has a great impact on the flow path and may interfere with the multi-detector Synchronization and stability; (4) The Toyopearl HW-50S gel resin-filled chromatographic column used with the instrument (also the current mainstream separation chromatographic column) has a low separation limit (0.1-10KDa), and cannot separate macromolecular proteins and large Molecular polysaccharides cannot meet the current analysis needs of heavily polluted surface water samples

Common fluorescence detectors currently on the market have three detection modes: (1) fixed excitation and emission wavelengths, that is, a single wavelength pair detection mode, which is not enough to fully characterize the physical and chemical properties of substances; (2) fixed excitation or emission wavelengths , scan a certain range of emission and excitation wavelength detection mode, that is, half-scan mode, the data acquisition frequency in this detection mode is generally 1 ~ 20HZ, too high data detection frequency will inevitably lead to too fast scanning speed and too long scanning step (generally 5-10nm), this will make the accuracy of the excitation light scanning data collected within a certain wavelength range not high; (3) scan the excitation and emission wavelength detection mode within a certain range, that is, the full scan mode, the detection mode A large amount of useless data will be generated in the separation and characterization of size exclusion chromatography, which will bring difficulties to the later data processing

[0009] Patents CN201410502662.9 and CN201510738667.6 disclose fluorescent signal water quality monitoring devices using LED light-emitting diodes as light sources. The shortcomings of these two patents lie in the fact that the invented fluorescent signal detection devices are used in online detection of water quality and detect actual mixed water bodies. The fluorescence of humic substances and proteins in the medium, the thickness of the internal pipeline, the design of the flow cell, the matching detection frequency and scanning speed determine that it cannot be used with the liquid phase

[0010] Therefore, there are still the following problems in the characterization of DOM at present: (1) The detection information is not comprehensive enough, which is reflected in the fact that the selection of supporting chromatographic columns cannot meet the current water sample analysis requirements, and the stability and synchronization of the multi-detector coupling system cannot be guaranteed, resulting in It cannot comprehensively reflect the structure / physicochemical / concentration characteristics of DOM

(3) Fluorescence detectors suitable for use with size exclusion chromatography are not accurate, which is reflected in the fact that the detection mode, parameter settings, hardware configuration, etc. are not suitable for the entire detection system

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