CN113804780A

CN113804780A - Online chromatographic analysis method for VOCs in water

Info

Publication number: CN113804780A
Application number: CN202111032860.XA
Authority: CN
Inventors: 高枝荣; 张彦俊
Original assignee: Shanghai Xuanyi Intelligent Technology Co ltd
Current assignee: Shanghai Xuanyi Intelligent Technology Co ltd
Priority date: 2021-09-03
Filing date: 2021-09-03
Publication date: 2021-12-17

Abstract

The invention discloses an online chromatographic analysis method for VOCs in water, belonging to the technical field of analytical instruments and equipment, comprising the following steps: and S1 sample collection: collecting VOCs blown out from water by adopting a flow pool with a fixed volume and a mode of blowing gas and an enrichment pipe; s2 flow path switching: the flow switching and the sample replacement of all pipelines can be thorough, and the sample collection and the flow switching are completed by the same channel; enrichment of S3 sample: by adopting a dual-channel multi-bed adsorbent, aromatic compounds and halogen compounds are respectively enriched, and meanwhile, the enrichment of components which are strong in volatility and difficult to adsorb and components which are easy to adsorb is realized. The method for analyzing the VOCs in the water by the online chromatography has the advantages of low cost, simplicity in operation and maintenance, extremely high detection sensitivity, detection limit of 0.1ug/L-0.5ug/L, detection range of 0.1ug/L-1000mg/L and no need of worrying about cross contamination of samples.

Description

Online chromatographic analysis method for VOCs in water

Technical Field

The invention relates to the technical field of analytical instruments and equipment, in particular to an online chromatographic analysis method for VOCs in water.

Background

After the drinking water standard is updated in 2021, the maximum limit content of Volatile Organic Compounds (VOCs) in the drinking water is lower and lower, the limit types are more and more, and most instrument manufacturers and testers prefer to use a mass spectrometer for detection. However, the mass spectrometer detector has high manufacturing cost and use cost, is a semi-quantitative detector and needs to be calibrated by adopting an internal standard; leading to complex operation and maintenance, extremely high technical requirements on operation and maintenance personnel and poor field actual use condition.

Disclosure of Invention

This section is for the purpose of summarizing some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. In this section, as well as in the abstract and the title of the invention of this application, simplifications or omissions may be made to avoid obscuring the purpose of the section, the abstract and the title, and such simplifications or omissions are not intended to limit the scope of the invention.

To solve the above technical problem, according to an aspect of the present invention, the present invention provides the following technical solutions:

an on-line chromatographic analysis method for VOCs in water, which comprises the following steps:

and S1 sample collection: collecting VOCs blown out from water in a mode of a flow pool with a fixed volume and a blowing gas enrichment pipe;

s2 flow path switching: the flow switching and the sample replacement of all pipelines can be thorough, and the sample collection and the flow switching are completed by the same channel;

enrichment of S3 sample: adopts a dual-channel multi-bed adsorbent, simultaneously takes account of the simultaneous enrichment of components with strong volatility and difficult adsorption and components with easy adsorption,

s4 thermal desorption-chromatography: the sample enrichment and the thermal desorption-chromatographic analysis are two parallel independent channels, the aromatic hydrocarbon compound and the halogen compound are respectively and independently analyzed by adopting two channels, one channel adopts a polar chromatographic column and an FID detector to separate and detect the aromatic hydrocarbon compound, and the other channel adopts a medium-polarity chromatographic column and an ECD detector to separate and detect the halogen compound.

As a preferred scheme of the on-line chromatographic analysis method for VOCs in water, the method comprises the following steps: in the step S1, a sample collection system is adopted, which comprises a water outlet, a water inlet, a flow cell and a collector;

the water outlet and the water inlet are respectively arranged at the top end of one side and the bottom end of the other side of the flow-through pool, and the collector is arranged inside the flow-through pool.

As a preferred scheme of the on-line chromatographic analysis method for VOCs in water, the method comprises the following steps: in step S2, a flow path switching system is adopted, which includes,

electronic switch valve assembly: an electronic switch valve A, an electronic switch valve B, an electronic switch valve C, an electronic switch valve D, an electronic switch valve E, an electronic switch valve F and an electronic switch valve G;

a pipeline;

flow line assembly: flow line a, flow line B, flow line C, flow line D, flow line E, flow line F, flow line G, flow line H, flow line I, flow line J, flow line K, flow line L, flow line M, flow line N, flow line O, flow line P;

the carrier gas, the pipeline, the flowmeter, the flow pipeline A, the tee joint A, the flow pipeline B, the electronic switch valve A, the flow pipeline C, the tee joint B, the flow pipeline D, the electronic switch valve B and the flow pipeline E are connected with one another, the tee joint A, the electronic switch valve E, the flow pipeline M and the collector are connected with one another, the collector, the flow pipeline P, the electronic switch valve G, the flow pipeline O, the tee joint D and the flow pipeline N are connected with one another, the tee joint B and the tee joint D are connected with one another through the flow pipeline H, the electronic switch valve C, the tee joint C, the electronic switch valve F, the flow pipeline J and the flow pipeline K, and the tee joint C, the flow pipeline G, the electronic switch valve D, the flow pipeline F and the evacuation port are connected with one another.

As a preferred scheme of the on-line chromatographic analysis method for VOCs in water, the method comprises the following steps: the step S3 employs a sample enrichment system, including,

the valve port component: valve port A, valve port B, valve port C, valve port D, valve port E, valve port F, valve port G, valve port H, valve port I, valve port J, valve port K, valve port L, valve port M and valve port N;

enrichment line assembly: an enrichment pipeline A, an enrichment pipeline B, an enrichment pipeline C, an enrichment pipeline D, an enrichment pipeline E, an enrichment pipeline F, an enrichment pipeline G, an enrichment pipeline H, an enrichment pipeline I, an enrichment pipeline J, an enrichment pipeline K, an enrichment pipeline L and an enrichment pipeline M;

a tee E and a tee F;

a water removal pipe A and a water removal pipe B;

a collecting pipe A and a collecting pipe B;

carrier gas B and carrier gas C;

the valve port A is connected with a valve port B, the valve port C, the valve port D, an enrichment pipeline G, a water removal pipe A, an enrichment pipeline H, a collecting pipe B, the valve port G, the valve port H, a tee joint E, the enrichment pipeline A, the valve port N, the valve port M, the enrichment pipeline B, the valve port I, the enrichment pipeline C, the enrichment pipeline D, the enrichment pipeline J, the enrichment pipeline E and the tee joint F are connected with one another, and the carrier gas C, the enrichment pipeline I, the valve port F, the valve port E, the carrier gas B, the enrichment pipeline M, the valve port K, the valve port L and the enrichment pipeline B are connected with one another through the valve port E.

As a preferred scheme of the on-line chromatographic analysis method for VOCs in water, the method comprises the following steps: in the step S4, a chromatography system is adopted, which includes a chromatography column a, a chromatography column B, FID detector, and an ECD detector;

the chromatographic column A is connected with an FID detector and an enrichment pipeline B, and the chromatographic column B is connected with an ECD detector and a valve port L.

As a preferred scheme of the on-line chromatographic analysis method for VOCs in water, the method comprises the following steps: the flow cell volume was 2L and the internal sample flowed.

As a preferred scheme of the on-line chromatographic analysis method for VOCs in water, the method comprises the following steps: the sample enrichment system has a heating function and can resist high temperature of 150-180 ℃.

As a preferred scheme of the on-line chromatographic analysis method for VOCs in water, the method comprises the following steps: the chromatographic column and the chromatographic column can respectively separate hydrocarbon compounds and halogen compounds, and the FID detector and the ECD detector respectively detect benzene series and chloride; the detection limits of the benzene series and the chloride can reach below 0.5ug/L and 0.1ug/L respectively.

Compared with the prior art: purging by adopting a large-volume flow cell, performing primary enrichment on VOCs samples in water by adopting a dynamic headspace, selectively performing secondary enrichment on hydrocarbon compounds and halogen compounds by adopting a dual-channel enrichment system, separating by adopting special separation columns respectively after heating desorption, and detecting by using FID and ECD detectors respectively. Thereby ensuring extremely high detection sensitivity of the entire analysis system. Meanwhile, the sample injection amount is accurately controlled by adopting high-precision flow control and an integrated purging pipeline, linear calibration is carried out by adopting a volume sample injection mode, and the analysis range of the sample covers 0.1ug/L-1000 mg/m3, so that the adaptability of the instrument is greatly improved;

the method for online chromatographic analysis of the VOCs in the water adopts conventional detectors FID and ECD, the cost of the instrument is much lower than that of a mass spectrometer, the operation and maintenance are simple, the method is more suitable for on-site online analysis, the quantification is accurate, the large-volume flow cell purging, the dynamic headspace, the two-channel enrichment tube secondary enrichment and the special separation column separation are realized, the detection sensitivity of the whole analysis system is ensured to be extremely high, meanwhile, the high-precision flow control is realized, the volume sampling mode is adopted for linear calibration, the sample analysis range is expanded from 0.01ppb to 1000ppm, and the integrated valve purging system ensures that the pipeline is clean without worrying about sample cross contamination.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail with reference to the accompanying drawings and detailed embodiments, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise. Wherein:

FIG. 1 is a schematic structural diagram of an on-line chromatographic analysis method for VOCs in water according to the present invention;

FIG. 2 is a typical chromatogram for high concentration sample analysis according to the present invention;

FIG. 3 is a typical chromatogram for low concentration sample analysis according to the present invention.

In the figure: chromatography system 1, sample enrichment system 2, port A211, port B212, port C213, port D214, port E215, port F216, port G217, port H218, port I219, port J2110, port K2111, port L2112, port M2113, port N2114, enrichment line A221, enrichment line B222, enrichment line C223, enrichment line D224, enrichment line E225, enrichment line F226, enrichment trap A251, trap B252, carrier gas B261, carrier gas C262, flow path switching system 3, electronic switch valve A311, electronic switch valve B312, electronic switch valve C313, electronic switch valve D314, electronic switch valve E315, electronic switch valve F316, electronic switch valve G317, line 321, flow path line A322, flow path line B323, flow path C324, flow path line D325, flow path line E, flow path F327, flow path line G326, flow path G328, flow path H329, flow path I3210, flow path J3211, flow path L3212, flow path L3213, flow path L3214, and flow path C312, A channel line M3214, a channel line N3215, a channel line O3216, a channel line P3217, a sample collection system 4, a drain 41, a water inlet 42, a flow cell 43, and a collector 44.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described herein, and it will be apparent to those of ordinary skill in the art that the present invention may be practiced without departing from the spirit and scope of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.

Next, the present invention will be described in detail with reference to the drawings, and in the detailed description of the embodiments of the present invention, the cross-sectional views illustrating the structure of the device are not enlarged partially according to the general scale for convenience of illustration, and the drawings are only examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, the invention provides an online chromatographic analysis method for VOCs in water, which comprises four steps of sample collection, flow path switching, sample enrichment and thermal desorption-chromatographic analysis.

In this embodiment, the sample collection comprises: the water sample flows into a sample pool 43 with fixed volume through a sample inlet 42 and is discharged from a water outlet 41; the carrier gas 36 purges the VOCs in the water sample in the sample cell 43 through the pipe 321, the flow meter 34, the pipe 322, the tee 331, the pipe 3213, the electronic switch valve 315, and the pipe 3214.

In this embodiment, the sample gas replacement includes: the carrier gas 36 displaces the air and the pipeline gas above the sample cell 43 through the pipeline 321, the flow meter 34, the pipeline 322, the tee joint 331, the pipeline 3213, the electronic switch valve 315 and the pipeline 3214, and enters the electronic switch valve integration box 3 after being collected by the collector 44, and is discharged through the exhaust port 35 through the pipeline 3217, the electronic switch valve 317, the tee joint 334, the pipeline 3212, the electronic switch valve 316, the pipeline 3211, the tee joint 333, the pipeline 326, the electronic switch valve 314 and the pipeline 327.

In this example, sample enrichment includes: the carrier gas 36 purges the VOCs in the water through a pipeline 321, a flow meter 34, a pipeline 322, a tee joint 331, a pipeline 3213, an electronic switch valve 315 and a pipeline 3214, collects the VOCs in the water through a collector 44, enters the electronic switch valve integration box 3, and enters the enrichment system 2 through a pipeline 3217, an electronic switch valve 317, a tee joint 334 and a pipeline 3216; the enrichment system 2 is divided into two paths by a tee joint 232, wherein one path enters a water removal module 241 through a valve port 213 of a pipeline 226, a valve port 214 and a pipeline 227, enters an enrichment pipe 252 through a pipeline 228 after water removal, and is collected in the tee joint 231 through a pipeline 2211, a valve port 217, a valve port 218 and a pipeline 2210 after coming out; the other path enters the water removal module 242 through the pipeline 225, the valve port 219, the valve port 2110 and the pipeline 224, enters the enrichment pipe 251 through the pipeline 223 after water removal, and is collected in the tee joint 231 through the pipeline 222, the valve port 213, the valve port 214 and the pipeline 221; the gas collected by the tee joint 231 finally reaches the exhaust port 35 for exhaust through a pipeline 326, an electronic switch valve 312, a pipeline 325, a tee joint 332, a pipeline 329, an electronic switch valve 313, a pipeline 3210, a tee joint 333, a pipeline 328, an electronic switch valve 314 and a pipeline 327.

In this embodiment, the in-line sample gas capture includes: after the sample is enriched, the carrier gas 36 blows and traps the residual sample gas in the system into respective enrichment tubes through a pipeline 3215, a tee joint 232 and subsequent pipelines in sequence through a pipeline 321, a flow meter 34, a pipeline 322, a tee joint 331, a pipeline 323, an electronic switch valve 311, a pipeline 324, a tee joint 332, a pipeline 329, an electronic switch valve 313, a tube 3210, a tee joint 333, a pipeline 3211, an electronic switch valve 316, a pipeline 3212 and a tee joint 334.

In this embodiment, the thermal desorption-chromatography analysis includes: the aromatic hydrocarbon compounds enriched from the enrichment pipe 251 enter the enrichment pipe 251 to blow out the hydrocarbon compounds by heating the enrichment pipe 251 and the carrier gas 261 through a line 2213, a valve port 2111, a valve port 2110 and a line 224, and enter the chromatographic column 111 for separation through a line 223, a water removal module 242, a line 222, a valve port 2113, a valve port 2112 and a line 132, and are detected by an FID detector 121; the halogen compounds enriched in the enrichment pipe 252 are heated by the enrichment pipe 252, the carrier gas 262 enters the enrichment pipe 252 through the line 229, the valve port 216, the valve port 217 and the line 2211 to blow out the hydrocarbon compounds, and enters the chromatographic column 112 through the line 228, the water removal module 241, the line 227, the valve port 214, the valve port 213 and the line 134 to be separated, and the separation is carried out through the ECD detector 122.

In this embodiment, the purge aging includes: the carrier gas 36 enters the sample trapping system 2 through a pipeline 321, a flow meter 34, a pipeline 322, a tee 331, a pipeline 323, an electronic switch valve 311, a pipeline 324, a tee 332, a pipeline 325, an electronic switch valve 312 and a pipeline 326, and is divided into two paths through the tee 231, wherein one path passes through a pipeline 221, a valve port 2114, a valve port 2113, a pipeline 222 and a purging aging trapping pipe 251, the purging object simultaneously purges and ages the dewatering pipe 242 through the pipeline 223 through gas flow, and the waste gas is collected in the tee 232 through the pipeline 224, the valve port 2110, the valve port 219 and the pipeline 225; the other path is through a pipeline 2210, a valve port 218, a valve port 217, a pipeline 2211 and a purging aging collecting pipe 252, purging objects pass through a pipeline 228 through gas flow and simultaneously purge and age a water removing pipe 241, and waste gas is collected to a tee joint 232 through a pipeline 227, a valve port 214, a valve port 213 and a pipeline 226; the gas collected by the tee 232 is exhausted to the outside through the pipeline 3215, the tee 316, the pipeline 3211, the tee 333, the pipeline 328, the electronic switch valve 314 and the pipeline 327, and finally reaches the exhaust port 35, and the purging and aging steps are performed to ensure the cleanness of the whole system.

By adopting the online chromatographic analysis method for the VOCs in the water, the VOCs of a high-concentration sewage sample and low-concentration drinking water are respectively analyzed, and typical chromatograms of aromatic compounds and halogen compounds are respectively shown in fig. 2 and fig. 3.

While the invention has been described above with reference to an embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the various features of the disclosed embodiments of the invention may be used in any combination, provided that no structural conflict exists, and the combinations are not exhaustively described in this specification merely for the sake of brevity and resource conservation. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. An on-line chromatographic analysis method for VOCs in water is characterized by comprising the following steps:

enrichment of S3 sample: the method adopts a dual-channel multi-bed adsorbent, and simultaneously integrates the enrichment of components which are strong in volatility and difficult to adsorb and components which are easy to adsorb;

2. The on-line chromatographic analysis method for VOCs in water according to claim 1, wherein the step S1 employs a sample collection system (4) comprising a water outlet (41), a water inlet (42), a flow cell (43), and a collector (44);

the water outlet (41), the water inlet (42), the circulation pool (43) and the collector (44), wherein the water outlet (41) and the water inlet (42) are respectively arranged at the top end of one side and the bottom end of the other side of the circulation pool (43), and the collector (44) is arranged inside the circulation pool (43).

3. The on-line chromatographic method for VOCs in water according to claim 1, wherein the step S2 employs a flow path switching system comprising,

electronic switch valve assembly: an electronic on-off valve a (311), an electronic on-off valve B (312), an electronic on-off valve C (313), an electronic on-off valve D (314), an electronic on-off valve E (315), an electronic on-off valve F (316), and an electronic on-off valve G (317);

a conduit (321);

flow line assembly: flow line a (322), flow line B (323), flow line C (324), flow line D (325), flow line E (326), flow line F (327), flow line G (328), flow line H (329), flow line I (3210), flow line J (3211), flow line K (3212), flow line L (3213), flow line M (3214), flow line N (3215), flow line O (3216), and flow line P (3217);

the carrier gas (36), the pipeline (321), the flowmeter (34), the flow line A (322), the tee joint A (331), the flow line B (323), the electronic switch valve A (311), the flow line C (324), the tee joint B (332), the flow line D (325), the electronic switch valve B (312) and the flow line E (326) are connected with each other, the tee joint A (331), the electronic switch valve E (315), the flow line M (3214) and the collector (44) are connected with each other, the collector (44), the flow line P (3217), the electronic switch valve G (317), the flow line O (3216), the tee joint D (334) and the flow line N (3215) are connected with each other, and the tee joint B (332) and the tee joint D (334) are connected with each other through a flow line H (329), an electronic switch valve C (313), a tee joint C (333), an electronic switch valve F (316), a flow line J (3211) and a flow line K (3212), the three-way valve C (333), the flow line G (328), the electronic switch valve D (314), the flow line F (327) and the drain port (35) are connected with each other.

4. The on-line chromatographic analysis method for VOCs in water of claim 1, wherein the step S3 employs a sample enrichment system comprising,

the valve port component: valve port a (211), valve port B (212), valve port C (213), valve port D (214), valve port E (215), valve port F (216), valve port G (217), valve port H (218), valve port I (219), valve port J (2110), valve port K (2111), valve port L (2112), valve port M (2113), and valve port N (2114);

enrichment line assembly: enrichment line a (221), enrichment line B (222), enrichment line C (223), enrichment line D (224), enrichment line E (225), enrichment line F (226), enrichment line G (227), enrichment line H (228), enrichment line I (229), enrichment line J (2210), enrichment line K (2211), enrichment line L (2212), enrichment line M (2213);

a tee E (231) and a tee F (232);

a water removal pipe A (241) and a water removal pipe B (242);

a collection pipe A (251), a collection pipe B (252);

carrier gas B (261), carrier gas C (262);

the valve port A (211) is connected with a valve port B (212), the valve port C (213), the valve port D (214), an enrichment pipeline G (227), a water removal pipe A (241), an enrichment pipeline H (228), a collecting pipe B (252), the valve port G (217), the valve port H (217), a tee joint E (231), the enrichment pipeline A (221), the valve port N (2114), the valve port M (2114), the enrichment pipeline B (222), the valve port I (219), the enrichment pipeline C (223), the enrichment pipeline D (224), the enrichment pipeline J (2210), (225), the enrichment pipeline E (225) and the tee joint F (232) are connected with each other, the carrier gas C (262), the enrichment line I (229), the valve port F (216), the valve port E (215), the carrier gas B (261), the enrichment line M (2213), the valve port K (2111), the valve port L (2112), the enrichment line B (222) are connected to each other with the valve port E (215).

5. The on-line chromatographic method for VOCs in water according to claim 1, wherein the step S4 employs a chromatographic system comprising a chromatographic column A (111), a chromatographic column B (112), a FID detector (121), an ECD detector (122);

the chromatographic column A (111) is connected with an FID detector (121) and an enrichment pipeline B (222), and the chromatographic column B (112) is connected with an ECD detector (122) and a valve port L (2112).

6. An on-line chromatographic analysis method for VOCs in water according to claim 1, characterized in that the volume of the flow cell (43) is 2L and the internal sample flows.

7. The on-line chromatographic analysis method for VOCs in water according to claim 1, characterized in that the sample enrichment system (2) has a heating function and can resist high temperature of 150-180 ℃.

8. The on-line chromatographic analysis method for VOCs in water according to claim 1, characterized in that the chromatographic column A (111) and the chromatographic column B (112) can separate hydrocarbon compounds and halogen compounds respectively, and the FID detector (121) and the ECD detector (122) detect benzene series and chloride respectively; the detection limits of the benzene series and the chloride can reach below 0.5ug/L and 0.1ug/L respectively.