SIZE EXCLUSION CHROMATOGRAPHY-COMBINED NITROGEN DETECTOR AND APPLICATION METHOD

Abstract

Disclosed are a size exclusion chromatography-combined nitrogen detector and an application method thereof, which belong to the field of detection and analysis of water quality. The detector comprises an oxidation system (1), a nitrate detection system (2), a power supply system (3), and a signal processing and control system (4), wherein after being separated by size exclusion chromatography, a sample to be detected enters into the oxidation system (1) to undergo oxidation treatment, and after nitrogenous compound in the sample is converted into nitrate, the sample is detected in the nitrate detection system (2) by ultraviolet (UV) absorbance method. The power supply system (3) supplies power to the detector, and the signal processing and control system (4) is responsible for processing and controlling signals of the oxidation system (1) and the nitrate detection system (2). The detector can achieve quantitative analyses of total nitrogen, organic nitrogen, nitrate nitrogen, and ammonia nitrogen, has the advantages of easiness in operation, being rich in information, etc. and thereby effectively prevents the problems of relatively large error and negative value resulting from the subtraction calculation in conventional organic nitrogen analysis methods.

Claims

1. size exclusion chromatography-combined nitrogen detector, comprising: an oxidation system (1), a nitrate detection system (2), a power supply system (3), and a signal processing and control system (4), wherein a sample to be detected is first separated by size exclusion chromatography and then enters into the oxidation system (1) to undergo oxidation treatment, and after nitrogenous compound in the sample is converted into nitrate, the sample is detected in the nitrate detection system (2); the power supply system (3) supplies power to the detector; and the signal processing and control system (4) is configured to process and control signals of the oxidation system (1) and the nitrate detection system (2).

2. The size exclusion chromatography-combined nitrogen detector according to claim 1, wherein the oxidation system (1) comprises an ultraviolet (UV) oxidation module (101) and an UV light intensity monitoring module (103).

3. The size exclusion chromatography-combined nitrogen detector according to claim 1, wherein the oxidation system (1) comprises a leakage monitoring module (102) and a vacuum negative pressure module (104), the vacuum negative pressure module (104) being configured to remove ozone in the oxidation system (1) and vacuumize the oxidation system (1).

4. The size exclusion chromatography-combined nitrogen detector according to claim 3, wherein the UV oxidation module (101) comprises an UV lamp (111), a spiral quartz tube flow path (112), quartz adapters (113), a PEEK coupling (114), a supporting bracket (115), and a quartz sleeve (116), the supporting bracket (115) supports and secures the UV oxidation module (101) to a base, the UV lamp (111) is located inside the quartz sleeve (116), the spiral quartz tube flow path (112) is spirally wound around the quartz sleeve (116), both ends of the spiral quartz tube flow path (112) are respectively connected to one ends of the quartz adapters (113), and the other end of each of the quartz adapters (113) is connected to the PEEK coupling (114).

5. The size exclusion chromatography-combined nitrogen detector according to claim 1, wherein the nitrate detection system (2) is an UV detector, comprising a flow cell module (201) and an UV absorption optical detection module (202).

6. The size exclusion chromatography-combined nitrogen detector according to claim 2, wherein the power supply system (3) comprises an UV lamp-dedicated power supply (301) and an AC-DC power conversion module (302), the UV lamp-dedicated power supply (301) supplies power to the UV oxidation module (101), and the AC-DC power conversion module (302) supplies power to the nitrate (NO.sub.3.sup.) detection system (2), the signal processing and control system (4), and the UV light intensity monitoring module (103).

7. The size exclusion chromatography-combined nitrogen detector according to claim 4, wherein the signal processing and control system (4) comprises a single-chip microcomputer system (401), a display (402), and a communication module (403), and the single-chip microcomputer system (401) controls and processes a signal, which can be displayed on the display (402) or transmitted to a host computer by the communication module (403).

8. The size exclusion chromatography-combined nitrogen detector according to claim 1, wherein the UV light intensity monitoring module (103) monitors light intensity of the UV oxidation module (101) in real time by using an aluminum gallium nitride-based deep UV photodiode.

9. The size exclusion chromatography-combined nitrogen detector according to claim 4, wherein the UV lamp (111) is a low-pressure mercury lamp, and the spiral quartz tube flow path (112) is a quartz capillary tube with an inner diameter of 0.5-1.0 mm and an outer diameter of 1.5-3.0 mm.

10. An application method of the size exclusion chromatography-combined nitrogen detector according to claim 1, comprising the following steps: 1) separating organic nitrogen, nitrate nitrogen (NO.sub.3.sup._N), and ammonia nitrogen (NH.sub.4.sup.+_N) by using a size exclusion chromatography column (9); 2) connecting in parallel a PEEK tube of a specific length at both ends of the size exclusion chromatography column (9) to form a PEEK tube bypass (10), and adjusting the length of the PEEK tube, so that a ratio of pressure produced by the PEEK tube bypass (10) to pressure produced by the size exclusion chromatography column (9) is n:1; 3) when an automatic sampler (8) is injecting, the injected sample respectively passing through the PEEK tube bypass (10) and the size exclusion chromatography column (9) at a ratio of 1:10, and then being detected by the size exclusion chromatography-combined nitrogen detector (12), with a bypass peak area being denoted as Area_TN; after the separation by size exclusion chromatography, respectively integrating peaks of organic nitrogen, NO.sub.3.sup., and NH.sub.4.sup.+, with peak areas being respectively denoted as Area_TON, Area_NO.sub.3.sup._N, and Area_NH.sub.4.sup.+_N; and 4) establishing a linear relationship between the peak area Area_TN and nitrogen content by using NO.sub.3.sup. standard solution, calculating total nitrogen (TN) based on the bypass Area_TN of the sample, and calculating concentrations of total organic nitrogen (TON), nitrate nitrogen (NO.sub.3.sup._N), and ammonia nitrogen (NH.sub.4.sup.+_N) based on percentages of Area_TON, Area_NO.sub.3.sup._N, and Area_NH.sub.4.sup.+_N in a total peak area of the size exclusion chromatography.

11. The size exclusion chromatography-combined nitrogen detector according to claim 2, wherein the UV oxidation module (101) comprises an UV lamp (111) and a quartz microfluidic chip (117), the UV lamp (111) is mounted on a surface of the quartz microfluidic chip (117), the quartz microfluidic chip (117) is provided with an S-shaped microfluidic channel formed by etching, and preferably, the microfluidic channel has a cross-sectional width of 0.10-1.0 mm, a depth of 0.05-0.50 mm, and a flow path length of 2-10 m.

12. The size exclusion chromatography-combined nitrogen detector according to claim 2, wherein the oxidation system (1) comprises a leakage monitoring module (102) and a vacuum negative pressure module (104), the vacuum negative pressure module (104) being configured to remove ozone in the oxidation system (1) and vacuumize the oxidation system (1).

13. The size exclusion chromatography-combined nitrogen detector according to claim 12, wherein the UV oxidation module (101) comprises an UV lamp (111), a spiral quartz tube flow path (112), quartz adapters (113), a PEEK coupling (114), a supporting bracket (115), and a quartz sleeve (116), the supporting bracket (115) supports and secures the UV oxidation module (101) so a base, the UV lamp (111) is located inside the quartz sleeve (116), the spiral quartz tube flow path (112) is spirally sound around the quartz sleeve (116), both ends of the spiral quartz tube flow path (112) are respectively connected to one ends of the quartz adapters (113), and the other end of each of the quartz adapters (113) is connected to the PEEK coupling (114).

14. The size exclusion chromatography-combined nitrogen detector according to claim 5, wherein the signal processing and control system (4) comprises a (403), and the single-chip microcomputer system (401) controls and processes a signal, which can be displayed on the display (402) or transmitted to a host computer by the communication module (403).

15. The size exclusion chromatography-combined nitrogen detector according to claim 12, wherein the signal processing and control system (4) comprises a single-chip microcomputer system (401), a display (402), and a communication module (403), and the single-chip microcomputer system (401) controls and processes a signal, which can be displayed on the display (402) or transmitted to a host computer by the communication module (403).

16. The size exclusion chromatography-combined nitrogen detector according to claim 2, wherein the UV light intensity monitoring module (103) monitors light intensity of the UV oxidation module (101) in real time by using an aluminum gallium nitride-based deep UV photodiode.

17. The size exclusion chromatography-combined nitrogen detector according to claim 5, wherein the UV lamp (111) is a low-pressure mercury lamp, and the spiral quartz tube flow path (112) is a quartz capillary tube with an inner diameter of 0.5-1.0 mm and an outer diameter of 1.5-3.0 mm.

18. The size exclusion chromatography-combined nitrogen detector according to claim 12, wherein the UV lamp (111) is a low-pressure mercury lamp, and the spiral quartz tube flow path (112) is a quartz capillary tube with an inner diameter of 0.5-1.0 mm and an outer diameter of 1.5-3.0 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 is a top view of the size exclusion chromatography-combined nitrogen detector according to the present invention;

[0035] FIG. 2 is a front view of the oxidation module with spiral tube in the size exclusion chromatography-combined nitrogen detector according to the present invention;

[0036] FIG. 3 is a top view of the oxidation module with spiral tube in the size exclusion chromatography-combined nitrogen detector according to the present invention;

[0037] FIG. 4 is a flow diagram showing the application method of the nitrogen detector according to the present invention;

[0038] FIG. 5 is a diagram showing a linear relationship between the peak area Area_TN and nitrogen content, which is established by using NO.sub.3.sup. standard solution;

[0039] FIG. 6 is a chromatogram of an effluent sample after the secondary biochemical treatment of a wastewater plant as detected by the size exclusion chromatography-combined nitrogen detector according to the present invention;

[0040] FIG. 7 is a chromatogram of a water sample from Yangtze River as detected by the size exclusion chromatography-combined nitrogen detector according to the present invention;

[0041] FIG. 8 is a test diagram showing the oxidation efficiency of the size exclusion chromatography-combined nitrogen detector according to the present invention; and

[0042] FIG. 9 is a schematic diagram of the oxidation module with microfluidic chip in the size exclusion chromatography-combined nitrogen detector according to the present invention.

[0043] In the drawings: 1. oxidation system; 2. nitrate detection module; 3. power control module; 4. signal processing and control system; 5. phosphate buffered solution; 6. ultrapure water; 7. constant flow pump; 8. automatic sampler; 9. size exclusion chromatography column; 10. bypass PEEK tube; 11. syringe pump; 12. size exclusion chromatography-combined nitrogen detector; 101. UV oxidation module; 102. leakage monitoring module; 103. UV light intensity monitoring module; 104. vacuum negative pressure module; 201. flow cell module; 202. UV absorption optical detection module; 301. UV lamp-dedicated power supply; 302. AC-DC power conversion module; 401. single-chip microcomputer system; 402. display; 403. communication module; 111. UV lamp; 112. spiral quartz tube flow path; 113. quartz adapter; 114. PEEK coupling; 115. supporting bracket; 116. quartz sleeve; 117. quartz microfluidic chip.

DETAILED DESCRIPTION

[0044] The present invention is described in detail below with reference to specific examples.

Example 1

[0045] This example provides a size exclusion chromatography-combined nitrogen detector. As shown in FIG. 1, the detector includes an oxidation system 1, a nitrate detection system 2, a power supply system 3, and a signal processing and control system 4. A sample to be detected is first separated by size exclusion chromatography and then enters into the oxidation system 1 to undergo the oxidation treatment, and after nitrogenous compound in the sample is converted into nitrate, the sample is detected in the nitrate detection system 2. The power supply system 3 supplies power to the detector. The signal processing and control system 4 is configured to process and control signals of the oxidation system 1 and the nitrate detection system 2.

[0046] The basic principle of the detector of the present invention is using the oxidation system 1 to convert nitrogen contained in various compounds after separation by size exclusion chromatography into NO.sub.3.sup., and carrying out a quantitative measurement according to molar absorption coefficient or absorption coefficient per unit mass of NO.sub.3.sup. at a specific UV wavelength.

[0047] The oxidation system 1 includes an UV oxidation module 101 and an UV light intensity monitoring module 103. The UV oxidation module 101 oxidizes a compound by UV light oxidation to convert nitrogen in the compound into NO.sub.3.sup.. The UV light intensity monitoring module 103 is configured to monitor the intensity of UV light generated by the UV oxidation module 101 in real time. The signal processing and control system 4 is configured to control signals generated, so as to ensure that the UV oxidation module 101 provides enough oxidation strength.

[0048] The oxidation system 1 further includes a vacuum negative pressure module 104. The vacuum negative pressure module 104 removes ozone produced by UV irradiation in air from the detector, and vacuumizes to enhance the UV oxidation effect. The vacuum negative pressure module 104 is specifically a micro vacuum pump, which includes an activated carbon filter disposed at the suction inlet thereof to remove ozone.

[0049] The oxidation system 1 further includes a leakage monitoring module 102. The leakage monitoring module 102 is configured to monitor the leakage status of the system and is controlled by the signal processing and control system 4. The leakage monitoring module 102 uses a LeakFilm sensor strip, can respond to the liquid leakage quickly without false alarm, and can be quickly reset to enter the working state after the leakage is cleared.

[0050] As shown in FIG. 2 and FIG. 3, the UV oxidation module 101 converts nitrogen in various compounds therein into NO.sub.3.sup., the leakage monitoring module 102 is configured to monitor the leakage status, and the leakage status is displayed through the signal processing and control system 4; and the UV light intensity monitoring module 103 displays the UV light intensity through the signal processing and control system 4.

Example 2

[0051] This example is basically the same as Example 1 with differences as follows:

[0052] The nitrate detection system 2 is an UV detector, including a flow cell module 201 and an UV absorption optical detection module 202. Its working principle is using a continuous light source such as a deuterium lamp or UV_LED lamp to emit UV light having a specific wavelength, measuring UV absorbance of the mobile phase of the size exclusion chromatography over a wavelength range of 215-230 nm in a flow cell with an optical path of 10-40 nm, and quantifying NO.sub.3.sup. according to the molar absorption coefficient or absorption coefficient per unit mass of NO.sub.3.sup. at the corresponding wavelength.

[0053] The nitrate detection system 2 is the outlet of the flow path, where the flow cell module 201 carries out the quantitative measurement according to the molar absorption coefficient or the absorption coefficient per unit mass of NO.sub.3.sup. at the specific UV wavelength and emits an optical signal, and the UV absorption optical detection module 202 converts the optical signal into an electrical signal, which is then transmitted to the signal processing and control system 4.

[0054] The optical path of the flow cell module 201 is 10 mm, NO.sub.3.sup. is quantitatively measured by using UV absorbance at the wavelength of 220 nm, and the absorption coefficient per unit mass is 0.25 L/(mg*cm).

[0055] The signal processing and control system 4 includes a single-chip microcomputer system 401, a display 402, and a communication module 403. The single-chip microcomputer system 401 controls and processes a signal, which can be displayed on the display 402 or transmitted by the communication module 403 to a host computer.

[0056] The electrical signal generated by the UV absorption optical detection module 202 is processed by an amplification circuit and an analog-to-digital conversion circuit to generate a digital signal, which is transmitted to the single-chip microcomputer system 401. The single-chip microcomputer system 401 stores the digital signal in a single-chip microcomputer. The display 402 displays the digital signal and the basic status of the device in real time.

[0057] The single-chip microcomputer system 401 outputs a communication signal to the oxidation system 1, so as to control the UV oxidation module 101 in the oxidation system 1 to work in a continuous manner.

Example 3

[0058] This example is basically the same as Example 1 with differences as follows:

[0059] The UV light intensity monitoring module 103 monitors the light intensity of the UV oxidation module 101 in real time by using an aluminum gallium nitride-based deep UV photodiode, and responds only to UV light in the UVC band.

[0060] The power supply system 3 includes an UV lamp-dedicated power supply 301 and an AC-DC power conversion module 302. The UV lamp-dedicated power supply 301 supplies power to the UV oxidation module 101. The AC-DC power conversion module 302 supplies power to the nitrate (NO.sub.3.sup.) detection system 2, the signal processing and control system 4, and the UV light intensity monitoring module 103.

[0061] The reason why the UV oxidation module 101 and other modules are powered by different power supplies is that: the UV lamp used in the UV oxidation module 101 is a low-power cold-cathode lamp, which is suitable for an AC-to-DC or DC-to-AC power supply mode; while hot-cathode lamps used in other modules have high supply power, so a standard AC power supply with variable frequency and variable voltage is provide. Therefore, the use of different power supply systems for the UV oxidation module 101 and other modules can reduce power consumption and further reduce operating costs.

Example 4

[0062] This example is basically the same as Example 1 with differences as follows:

[0063] The UV oxidation module 101 includes an UV lamp 111, a spiral quartz tube flow path 112, quartz adapters 113, a PEEK coupling 114, a supporting bracket 115, and a quartz sleeve 116. FIG. 2 is a front view of the UV oxidation module 101 of this example; FIG. 3 is a top view of the UV oxidation module 101 of this example. As shown in FIG. 2 and FIG. 3, the supporting bracket 115 supports and secures the UV oxidation module 101 to a base by using a plastic retaining ring with an inner diameter of 25 mm. The UV lamp 111 is located inside the quartz sleeve 116. The quartz sleeve 116 protects the UV lamp 111 and fixes the spiral quartz tube flow path 112. The spiral quartz tube flow path 112 is a quartz capillary tube with an inner diameter of 1.0 mm and an outer diameter of 3.0 mm wound around the quartz sleeve 116 by melting. Two ends of the quartz capillary tube are connected to one ends of two quartz adapters 113 by melting, and the other end of each of the quartz adapters is provided with -28 internal threads that can be connected to a PEEK coupling 114 of the same specification. The PEEK coupling 114 and the PEEK tube connected thereto is only used for transporting liquid and have no other special function.

[0064] The sample after separation flows in the spiral quartz tube and is irradiated to be oxidized by the UV. The parts of sample, after respectively flowing through the size exclusion chromatography column and the bypass, combine into one path again. Then the influent in the oxidation module enters the spiral quartz tube flow path through a PEEK wall coupling and the quartz adapter and is oxidized therein, then enters the detection module through the quartz adapter, a PEEK wall coupling, and the PEEK tube, flows out of the detector through an effluent port of the detector after testing, and is discharged through an effluent tube.

[0065] The UV lamp 111 is a low-pressure cold-cathode lamp with a diameter of 15 mm and a length of 150 mm. The UV spectrum generated by the UV lamp 111 includes two UV rays with wavelengths of 184.9 nm and 253.7 nm, where the UV ray with the wavelength of 184.9 nm is dominant in the oxidation process of nitrogen.

Example 5

[0066] This example provides a process of sample detection by using the size exclusion chromatography-combined nitrogen detector of Example 1. FIG. 4 is a flow diagram showing the process of sample detection. As shown in FIG. 4, the entire process includes the following steps:

[0067] a) using an automatic sampler 8 to inject a sample into a phosphate buffered solution 5, which is a mobile phase driven by a multi-channel constant flow pump 7;

[0068] b) the sample entering the size exclusion chromatography-combined nitrogen detector 12 respectively through two flow paths: a size exclusion chromatography column 9 and a bypass PEEK tube 10, where the size exclusion chromatography column 9 has a length of 250 mm and an inner diameter of 20 mm, and is filled with Toyopearl HW-50S resin;

[0069] c) before the sample enters the size exclusion chromatography-combined nitrogen detector 12, introducing a potassium persulfate solution with a mass concentration of 1% as an oxidizing agent by using a syringe pump 11, where the oxidizing agent can enhance the oxidation effect for high-concentration water samples; and

[0070] d) after the sample detection is completed, washing the tubes with ultrapure water 6.

[0071] This example also provides an application method of the size exclusion chromatography-combined nitrogen detector of Example 1 for sample detection, including the following steps:

[0072] 1) separating TON, NO.sub.3.sup., and NH.sub.4.sup.+ in the sample by using a size exclusion chromatography column, with the mobile phase being a phosphate buffered solution, which is a mixture of 2.5 g/L KH.sub.2PO.sub.4 and 1.5 g/L Na.sub.2HPO.sub.4.2H.sub.2O;

[0073] 2) connecting in parallel a segment of PEEK tube at two ends of the size exclusion chromatography column by using three-way joints to form a bypass, and adjusting the length of the PEEK tube so that a ratio of pressure produced by the bypass PEEK tube 10 to pressure produced by the size exclusion chromatography column is 10:1, and therefore, a ratio of a flow rate in the bypass to a flow rate in the size exclusion chromatography column is 1:10;

[0074] 3) taking 500 L of a sample from an effluent of the secondary biochemical treatment of a wastewater plant, passing the sample respectively through the bypass and the size exclusion chromatography column at a ratio of 1:10, and then detecting the sample in the nitrogen detector, where peaks elute quickly because the bypass has no retention function, with a peak area thereof being denoted as Area_TN; after the separation by size exclusion chromatography, respectively integrating peaks of TON, NO.sub.3.sup., and NH.sub.4.sup.+, with peak areas thereof being respectively denoted as Area_TON, Area_NO.sub.3.sup._N, and Area_NH.sub.4.sup.+_N, measured in AU (Arbitrary Units); and

[0075] 4) establishing a linear relationship between the peak area Area_TN and nitrogen content by using NO.sub.3.sup. standard solution, calculating total nitrogen (TN) according to the bypass Area_ TN of the sample, and calculating concentrations of total organic nitrogen (TON), nitrate (NO.sub.3.sup._N), and ammonium (NH.sub.4.sup.+_N) according to percentages of Area_TON, Area_NO.sub.3.sup._N, and Area_NH.sub.4.sup.+_N in a total peak area of the size exclusion chromatography.

[0076] When the linear relationship is established, NO.sub.3.sup. standard solution with nitrogen concentrations of 1 mg/L, 500 g/L, 100 g/L, 10 g/L, and 5 g/L are respectively prepared and sampled, and a linear relationship between the peak area Area_TN and nitrogen content is established. FIG. 5 is a diagram showing a linear relationship between the peak area Area_TN and nitrogen content, which is established by using NO.sub.3.sup. standard solution. As can be seen from FIG. 5, in the linear equation between the peak area Area_TN and nitrogen content, R.sup.2=0.9995, which meets the criteria for linearity.

[0077] FIG. 6 is a chromatogram of an effluent sample of the secondary biochemical treatment of a wastewater plant as detected by the size exclusion chromatography-combined nitrogen detector of the present invention, where Bypass represents the peak of the TN of the bypass; TON, Area_NO.sub.3.sup._N, and Area_NH.sub.4.sup.+_N respectively represent the peaks of TON, NO.sub.3.sup._N, and NH.sub.4.sup.+_N through the size exclusion chromatography column. The calculation processes of the concentrations of

[0078] TN, TON, NO.sub.3.sup._N, and NH.sub.4.sup.+_N are as follows:

[0079] The concentration of TN is: 0.367 AU1.1 mL/min3.911 mg.Math.cm/L110.5 mL=34.735 mg/L

[0080] The concentration of TON is: 34.735 mg/L(0.2610.367 )10=2.470 mg/L

[0081] The concentration of NO.sub.3.sup._N is: 34.735 mg/L(1.3380.367 )10=12.636 mg/L

[0082] The concentration of NH.sub.4.sup.+_N is: 34.735 mg/L(2.0690.367 )10=19.582 mg/L

[0083] Table 1 shows statistics on the final test results.

TABLE-US-00001 TABLE 1 Test results Component TN TON NO.sub.3.sup._N NH.sub.4.sup.+_N Integration area 0.367 0.261 1.338 2.069 (arbitrary unit, AU) Concentration (mg/L) 34.735 2.470 12.636 19.582

Example 6

[0084] This example is basically the same as Example 5 except that: the water sample to be detected is from Yangtze River with a sampling volume of 500 L, the oxidation method is only UV oxidation and no oxidizing agent is added by using the syringe pump 11. The sum of nitrate (NO.sub.3.sup._N) and ammonium (NR.sub.4.sup.+_N) is denoted as total inorganic nitrogen (TIN). The calculation processes of the concentrations of TN, TON, NO.sub.3.sup._N, and NH.sub.4.sup.+_N are the same as those in Example 5. Table 2 shows statistics on the test results of this example.

TABLE-US-00002 TABLE 2 Test results Component TN TON TIN Integration area (AU) 0.166 0.199 1.460 Concentration (mg/L) 16.069 1.926 14.133

Example 7

[0085] This example is basically the same as Example 6 except that: in this example, the size exclusion chromatography column 9 and the bypass PEEK tube 10 are not used, and 25 L, 50 L, 12.5 L, and 6.25 L of 100 mg/L bovine serum albumin aqueous solution are respectively injected twice, for the purpose of determining the oxidation efficiency. FIG. 8 is a test diagram showing the oxidation efficiency of the size exclusion chromatography-combined nitrogen detector according to the present invention. As shown in FIG. 8, the peaks of solutions with sample volumes of 25 L and 50 L are bifurcated, indicating that the sample volume exceeds the oxidation capacity of the UV spiral tube, while the peaks of solutions with sample volumes of 12.5 L and 6.25 L have good peak shape, and the peak area of one of the solutions is 2 times that of the other, indicating that the UV oxidation module 101 can fully oxidize

[0086] TON in such sample volumes.

Example 8

[0087] In this example, the size exclusion chromatography column 9 and the bypass PEEK tube 10 are not used, and TON_N, NO.sub.3.sup._N, and NH.sub.4.sup.+_N solutions with nitrogen concentration of 10 mg/L are prepared by using bovine serum albumin, NaNO.sub.3, and NH.sub.4Cl, and respectively injected 5 times. The relative standard deviations are all less than 2% and satisfy the accuracy requirements. Table 3 shows statistics on the test results.

TABLE-US-00003 TABLE 3 Test results Relative Injected standard material 1.sup.st time 2.sup.nd time 3.sup.rd time 4.sup.th time 5.sup.th time Mean deviation TON_N 9.877 9.932 9.831 9.841 10.234 9.943 1.68% NO.sub.3.sup._N 10.031 10.053 10.042 10.073 10.043 10.048 0.16% NH.sub.4.sup.+_N 9.981 9.874 9.865 9.742 9.832 9.859 0.87%

[0088] The unit of numbers in this table is mg/L, except for the relative standard deviations.

[0089] At the same time, according to the method in Example 6, by using the size exclusion chromatography column 9 and the bypass PEEK tube 10, the prepared TON_N, NO.sub.3.sup._N, and NH.sub.4.sup.+_N solutions with the nitrogen concentration of 10 mg/L are respectively injected. The relative standard deviations are all less than 2% and satisfy the accuracy requirements. Table 4 shows statistics on the test results according to the method of the present invention.

TABLE-US-00004 TABLE 4 Test results Relative Injected standard material 1.sup.st time 2.sup.nd time 3.sup.rd time 4.sup.th time 5.sup.th time Mean deviation TON_N 9.775 9.887 9.834 10.247 9.974 9.943 1.86% NO.sub.3.sup._N 10.054 9.985 9.847 10.107 10.043 10.007 0.99% NH.sub.4.sup.+_N 9.752 10.124 9.756 9.854 9.854 9.868 1.54%

[0090] As can be seen from the results in Table 4, the method of the present invention is accurate and reliable.

Example 9

[0091] This example is basically the same as Example 5 except that: the ratio of the flow rate in the bypass 10 to the flow rate in the size exclusion chromatography column 9 is 1:5.

[0092] The spiral quartz tube flow path 112 is a quartz capillary tube with an inner diameter of 0.5 mm and an outer diameter of 1.5 mm.

Example 10

[0093] This example is basically the same as Example 5 except that the ratio of the flow rate in the bypass 10 to the flow rate in the size exclusion chromatography column 9 is 1:15.

[0094] As shown in FIG. 9, the UV oxidation module 101 includes an UV lamp 111 and a quartz microfluidic chip 117. The UV lamp 111 is mounted on a surface of the quartz microfluidic chip 117. The quartz microfluidic chip 117 is provided with an S-shaped microfluidic channel formed by etching. The microfluidic channel has a cross-sectional width of 0.40 mm, a depth of 0.10 mm, and a flow path length of 4 m.

[0095] Although the present invention and the implementations of the present invention have been schematically described above, such description is not limiting. The accompanying drawings shows only one of the implementations of the present invention, and the actual flow is not limited thereto. Therefore, any structure or embodiment similar to this technical solution designed without creative efforts by those of ordinary skill in the art based on the teaching of the present invention and without departing from the spirit of the present invention shall fall within the scope of protection of the present invention.