Instrument and method for simultaneously testing molecular weight distribution and organic nitrogen level of water sample

Patent metadata

Field	Value
Publication number	US-11796525-B2
Application number	US-201817056425-A
Country	US
Kind code	B2
Filing date	Aug 29, 2018
Priority date	May 18, 2018
Publication date	Oct 24, 2023
Grant date	Oct 24, 2023

Abstract

An instrument and a method for simultaneously testing a molecular weight distribution and an organic nitrogen level of a water sample are provided. The instrument comprises: a tail-end injection valve, a chromatographic column, a pressure relief valve, an acid-adding injection valve, an oxygen-adding injection valve, a helical tube for an acid-oxygen reaction, a CO2 remover, a UV digester, a second gas-water separator membrane, a buffer solution injection valve, a helical tube for a buffer solution reaction, a cadmium column, a chromogenic agent injection valve, a helical tube for a chromogenic agent reaction, and a UV detector, sequentially connected via a pipeline. The tail-end injection valve is for receiving a fluid phase and a sample. The second gas-water separator membrane is connected to an electrical conductivity-based CO2 detector. The UV detector and the electrical conductivity-based CO2 detector are connected to a data processing computer.

First claim

What is claimed is:

1. An instrument for simultaneously testing a molecular weight distribution and an organic nitrogen of water samples, comprising a tail-end injection valve, a chromatographic column, a pressure relief valve, an acid-adding injection valve, an oxygen-adding injection valve, an helical tube for an acid-oxygen reaction, a carbon dioxide (CO 2 ) remover, a ultraviolet digester, a second gas-water separation membrane, a buffer solution injection valve, a helical tube for a buffer solution reaction, a cadmium column, a chromogenic agent injection valve, a helical tube for a chromogenic agent reaction and a ultraviolet detector, sequentially connected via a pipeline, the tail-end injection valve is configured to receive a fluid phase and a sample, the second gas-water separation membrane is connected to an electrical conductivity-based CO 2 detector, the ultraviolet detector and the electrical conductivity-based CO 2 detector are both connected to a data processing computer.

2. The instrument for simultaneously testing the molecular weight distribution and the organic nitrogen of the water samples according to claim 1 , wherein the tail-end injection valve is connected with a sampling pump and a sample bottle, and the tail-end injection valve is further connected with a fluid phase infusion pump and a fluid phase reagent bottle,
the acid-adding injection valve is connected with an acid injection pump and an acid bottle,
the oxygen-adding injection valve is connected with an oxygen liquid injection pump and an oxygen liquid bottle,
the buffer solution injection valve is connected with a buffer solution injection pump and a buffer solution reagent bottle,
the chromogenic agent injection valve is connected with a chromogenic agent injection pump and a chromogenic agent reagent bottle.

3. The instrument for simultaneously testing the molecular weight distribution and the organic nitrogen of the water samples according to claim 1 , wherein the CO 2 remover comprises a first gas-water separation membrane, a gas collecting coil, a purge pump and a diaphragm, the first gas-water separation membrane, the gas collecting coil and the diaphragm are connected in sequence, and the first gas-water separation membrane is connected to an acid-oxygen reaction spiral pipe through a pipeline, the diaphragm is connected with the ultraviolet digester ( 16 ) through a pipeline, the blow-off pump is connected to the gas collecting coil.

4. The instrument for simultaneously testing the molecular weight distribution and the organic nitrogen of the water samples according to claim 3 , wherein the ultraviolet digester comprises a heating wire, a transparent quartz spiral tube and an ultraviolet lamp, the transparent quartz spiral tube is connected between the diaphragm and the second gas-water separation membrane through a pipeline, the ultraviolet lamp is located above the transparent quartz spiral tube ( 30 ), the heating wire is located under the transparent quartz spiral tube.

5. The instrument for simultaneously testing the molecular weight distribution and the organic nitrogen of the water samples according to claim 1 , wherein the electrical conductivity-based CO 2 detector comprises an ultra-pure water tank and an ultra-pure water pump and a conductivity cell, which are connected in sequence, the sample oxidized by the ultraviolet digester passes through a gas-water separation membrane, the CO 2 separates and dissolves in ultra-pure water driven by the ultra-pure water pump and purifies by ion purification resin, then passes into the conductivity cell, the amount of CO 2 is measured by detecting the change of liquid conductivity in the conductivity cell, and a specific conversion relationship characterizes a concentration of TOC.

6. A method of using the instrument for simultaneously testing the molecular weight distribution and the organic nitrogen of the water samples according to claim 1 , comprising the following steps:
a sample is collected into a pipeline, mixed with a fluid phase, and then separated by a chromatographic column, components of the sample flow out in sequence according to a different molecular weight, and then a pressure is reduced by a pressure relief valve, the different molecular weight of the components of the separated sample pass through an acid-adding injection valve and an oxygen-adding injection valve, injecting an acid liquor into the acid-adding injection valve, injecting an oxygen liquor into the oxygen-adding injection valve, and fully reacting the components to be detected, the fluid phase, the acid liquor and the oxygen liquor in an acid-oxygen reaction spiral tube;
inorganic carbon in the components to be detected is acidified by the acid liquor to produce CO 2 , which is blown off into the air through the back remover of CO 2 ;
the components to be detected removed from inorganic carbon reach in a ultraviolet digester through a pipeline, TOC of the components is oxidized to CO 2 and DON is oxidized to nitrate nitrogen, the oxidized sample passes through a gas-liquid separation membrane to separate the generated CO 2 into an electrical conductivity-based CO 2 detector, the electrical conductivity-based CO2 detector detects an amount of CO 2 , and a specific conversion relationship characterizes a concentration of TOC, after that, the remaining components without TOC are added to a buffer solution through a buffer solution injection valve, then after a reduction of a cadmium column, nitrate nitrogen is reduced to nitrite nitrogen, then a reagent is added through a chromogenic agent injection valve, and a mixing reaction is carried out in a helical tube for a chromogenic agent reaction, finally as an amount of nitrate-nitrogen is detected at 540 nm in a UV detector and a specific conversion relationship characterizes a concentration of DON.

7. The method according to claim 6 , wherein the fluid phase is selected as phosphate buffer solution, a ionic strength is 0.1-0.4 M, a pH value is 6.8±0.2, a flow rate of a fluid phase infusion pump is selected to be 0.4-1.0 mL/min, a pressure of the fluid phase infusion pump is selected to be 1.8±0.2 MPa, a maintaining temperature of a chromatographic column is 30-60° C., a pressure is 1.8±0.2 MPa before the chromatographic column, a pressure after the chromatographic column passes through a pressure relief valve is 1 bar, a flow state is free flow, in the ultraviolet digester, a wavelength of a UV lamp is 190 nm, and a heating temperature is set to be 95±2° C.

8. The method according to claim 6 , wherein the sampling pump adopts a microinjection pump, a pump's working pressure is higher than 1500 psi, and a highest precision is less than 0.1%, a sampling volume is 50-500 μL, an acid injection pump and an oxygen liquid injection pump adopt the microinjection pump, a working pressure is higher than 1500 psi, a highest precision is less than 0.1% and pulse-free transportation, a flow rate of the acid oxygen injection pump and the oxygen liquid injection pump is 1.0-4.0 μL/min, and a flow rate of a chromogenic agent injection pump is 1.0-4.0 μL/min.

9. The method according to claim 6 , wherein a tail-end injection valve, the acid-adding injection valve, the oxygen-adding injection valve, the buffer solution injection valve, and the chromogenic agent injection valve are all stable to add one liquid to another liquid slowly and stably for mixing without having a back suction.

10. The method according to claim 6 , wherein the acid-oxygen reaction spiral tube, a helical tube for a buffer solution reaction and a chromogenic agent reaction spiral tube are all made of stainless steel PEEK tubes in a spiral manner, and the stainless steel PEEK tubes are selected as the

Assignees

• Univ Tongji

Inventors

• Li Lei
• Zhang Wenjun
• Wang Shichong

Classifications

• G01N33/182 Primary

  Specific anions in water · CPC title

• G01N21/78

  producing a change of colour · CPC title

• G01N30/14

  by elimination of some components · CPC title

• G01N30/64

  Electrical detectors · CPC title

• G01N30/88 Primary

  Integrated analysis systems specially adapted therefor, not covered by a single one of the groups G01N30/04 - G01N30/86 · CPC title