CN210071669U - High-precision seawater pH in-situ measurement system based on integrated valve island device - Google Patents
High-precision seawater pH in-situ measurement system based on integrated valve island device Download PDFInfo
- Publication number
- CN210071669U CN210071669U CN201920695433.1U CN201920695433U CN210071669U CN 210071669 U CN210071669 U CN 210071669U CN 201920695433 U CN201920695433 U CN 201920695433U CN 210071669 U CN210071669 U CN 210071669U
- Authority
- CN
- China
- Prior art keywords
- seawater
- valve island
- integrated valve
- solenoid valve
- valve
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Landscapes
- Investigating Or Analysing Materials By Optical Means (AREA)
- Optical Measuring Cells (AREA)
Abstract
The utility model belongs to the technical field of the ocean monitoring, concretely relates to high accuracy sea water pH normal position measurement system based on but integrated valve island device multi-reagent detects. The measuring system comprises a flow path module, a light path module and a circuit module; the flow path module comprises an integrated valve island for controlling the flow path direction, and is used for sampling seawater samples, reagents and mixing; through the integrated valve island control flow path, when the pH value of the seawater is measured in situ, firstly, the seawater is injected into the flow path to measure blank light intensity, then, the indicator is injected into the flow path, the flow path is closed to form a loop, the seawater and the indicator are mixed in the loop, the light intensity of the mixed solution is detected after the seawater and the indicator are completely mixed, the absorbance is calculated, and then the pH value of the seawater is obtained through calculation. The utility model provides a flow path structure adopts the valve island device, has characteristics that dead volume is little, compact structure, low power dissipation, can realize mixing completely of sea water and indicator, can improve the stability of instrumental survey.
Description
Technical Field
The utility model belongs to the technical field of the ocean monitoring, concretely relates to high accuracy sea water pH normal position measurement system based on but integrated valve island device multi-reagent detects.
Background
At present, the pH value of surface seawater is continuously reduced at the speed of 0.002/a, the deep research of a marine carbonate system puts higher requirements on the pH measuring technology, and a stable and reliable high-precision pH measuring instrument is urgently needed. The seawater pH measurement technology based on the photometric method has the advantages of high precision (up to 0.001), good stability and the like, and becomes a mainstream method for accurately observing pH in the fields of seawater acidification, carbon cycle and the like. The high-precision seawater pH in-situ measurement system is based on a photometric method and a flow injection analysis technology, and the pH value of seawater can be obtained by measuring the light absorption values of indicators in different forms after a sample and the indicators are mixed.
The flow path composition and control, the flow cell selection, the light source coupling module, the signal acquisition detection, the indicator correction and the like are core technologies for constructing a high-precision seawater pH in-situ measurement system and are also the key for determining whether the whole system is accurate and stable.
The existing flow path design of the in-situ pH sensor mostly adopts a three-way valve combination or a multi-position selection valve and the like, and has the defects of large volume, high power consumption and the like; the light source and the signal detection are combined by an LED lamp and a photodiode, only a single indicator is used for determination, and the defects of low resolution, poor accuracy and the like exist, so that the determination precision and the measurement range of an instrument are directly influenced.
SUMMERY OF THE UTILITY MODEL
In view of the above technical problem, the utility model provides a but high accuracy sea water pH in situ measurement system of many reagents detection based on integrated valve island device; the flow path structure of the high-precision seawater pH in-situ measurement system is based on an integrated valve island device, so that the dead volume is small, and the stability is good; and the light path structure takes an LED coupling light source and a micro spectrometer as a light source and a detector, and can use various indicators for measurement, thereby widening the measurement range and improving the measurement accuracy.
The utility model discloses a realize through following technical scheme:
high accuracy sea water pH normal position measurement system based on integrated valve island device includes: the device comprises a flow path module, a light path module and a circuit module;
the flow path module comprises an integrated valve island, a flow cell and a reagent bag connected with the integrated valve island through a pulse pump; one end of the flow cell is connected with the integrated valve island through a peristaltic pump, and the other end of the flow cell is connected with the integrated valve island; the integrated valve island is also provided with a seawater sample introduction pipeline, a seawater waste liquid discharge pipeline and an indicator waste liquid discharge pipeline;
the light path module is used for measuring the absorbance of the sample at the characteristic wavelength; the system comprises a light source coupling module, a micro spectrometer and optical fibers, wherein the light source coupling module comprises three LED lamps with different wavelengths arranged in a light source coupler, the three LED lamps with different wavelengths form a coupling light source, and light emitted by the coupling light source is transmitted through the optical fibers, enters the micro spectrometer after passing through a flow cell and is detected for signal intensity;
the peristaltic pump, the pulse pump, the integrated valve island and the micro spectrometer are all connected with the circuit module; the circuit module is used for controlling the opening or closing of the peristaltic pump, the pulse pump, the integrated valve island and the micro spectrometer and is used for data acquisition.
Further, the integrated valve island comprises four two-position three-way electromagnetic valves, namely a first electromagnetic valve, a second electromagnetic valve, a third electromagnetic valve and a fourth electromagnetic valve; the first electromagnetic valve, the second electromagnetic valve, the third electromagnetic valve and the fourth electromagnetic valve respectively comprise three interfaces, namely a normally closed port a, a normally open port b and a third interface;
the seawater sampling pipeline with the normally open b of first solenoid valve connects, the third interface of first solenoid valve with the normally open b of second solenoid valve connects, the normally closed a of second solenoid valve with the reagent bag passes through the pulse pump and connects, the third interface of second solenoid valve with the third interface connection of third solenoid valve, the normally open b of third solenoid valve pass through the peristaltic pump with the one end of flow-through cell is connected, the normally closed a of third solenoid valve with indicator waste liquid discharge tube connects, the normally closed a of fourth solenoid valve with the normally closed a of first solenoid valve connects, the normally open b of fourth solenoid valve and seawater waste liquid discharge tube connect, the third interface of fourth solenoid valve with the other end of flow-through cell connects.
Further, the integrated valve island also comprises a valve island, and the valve island comprises a substrate and a bottom plate; the bottom plate is arranged at the lower part of the substrate, and the four electromagnetic valves are all arranged at the lower part of the bottom plate;
the substrate and the bottom plate are made of high-transparency acrylic materials and are bonded in a glue joint and a seamless mode in a dust-free clean environment; and liquid channels are arranged in the substrate and the bottom plate and are used for communicating the electromagnetic valve and an external fluid pipeline connected to the integrated valve island.
Further, the external fluid pipeline connected to the integrated valve island comprises a fluid pipeline between the peristaltic pump and the integrated valve island, a fluid pipeline between the pulse pump and the integrated valve island, the indicator waste liquid discharge pipeline, the seawater sample injection pipeline, a fluid pipeline between the flow cell and the integrated valve island, and a fluid pipeline between a third interface of the first electromagnetic valve and a normally open port b of the second electromagnetic valve;
the liquid channel is also used for connection between the first solenoid valve and a fourth solenoid valve and between the second solenoid valve and the third solenoid valve;
the inner diameters of the liquid channels inside the substrate and the bottom plate are the same as the inner diameter of the external fluid pipeline connected into the integrated valve island.
Furthermore, the flow cell is made of plastic materials and is of a cross structure, fluid flows from bottom to top, optical signals are transmitted in the horizontal direction, and bubbles generated in the fluid can float to the top of the flow cell to avoid the influence of bubble accumulation on absorbance measurement;
the length of the light path of the flow cell is 0.5-4cm, and the flow cell is placed in seawater outside the instrument cabin so as to keep the temperature of a sample in the flow cell consistent with that of the seawater; and a temperature probe is arranged beside the flow cell and used for measuring the temperature of the seawater in real time.
Further, the three LED lamps having different wavelengths include: warm white LED lamp with center wavelength of 580nm, LED lamp with center wavelength of 435nm and LED lamp with center wavelength of 490 nm.
Furthermore, the spectrum detection range of the micro spectrometer is 300nm-800nm, a 25 μm slit is arranged, and the wavelength resolution is 1.5nm.
The device adopts three LED lamps with different wavelengths to form a coupling light source as a light source and adopts the micro spectrometer as a detector, and can be suitable for measuring the pH value of seawater of three indicators of m-cresol purple, thymol blue and cresol red, wherein the pH measuring range is 6.8-8.6.
The utility model has the advantages of:
the utility model provides a high accuracy sea water pH in situ measurement system's flow path structure has characteristics small, compact structure, low power dissipation based on integrated valve island device, can realize the complete mixing of sea water and indicator, can improve the stability of instrument survey.
The utility model provides a high accuracy sea water pH normal position measurement system's light path structure uses LED coupling light source and miniature spectrum appearance as light source and detector, can use multiple indicator to measure, has widened measuring range, has improved the measurement accuracy.
Drawings
Fig. 1 is a structural composition and a flow chart of a high-precision seawater pH in-situ measurement system based on an integrated valve island in the embodiment of the present invention;
fig. 2 is a schematic perspective view of an integrated valve terminal device according to an embodiment of the present invention
Reference numerals: 1. a reagent bag; 2. a pulse pump; 3. an integrated valve island; 4. a first solenoid valve; 5. a second solenoid valve; 6. a third electromagnetic valve; 7. a fourth solenoid valve; 8. a seawater sample introduction pipeline; 9. a seawater waste liquid discharge pipeline; 10. an indicator waste liquid discharge pipeline; 11. a peristaltic pump; 12. a light source coupling module; 13. a flow-through cell; 14. a micro spectrometer; 3-1. substrate base; 3-2. a baseplate base body; 3-3. normal opening b; 3-4. a third interface; 3-5, normally closed port a; 3-6, cleaning and cleaning holes of the electromagnetic valve; 3-7, fixing the screw hole; 3-8, a threaded hole; 3-9. a substrate liquid channel; 3-10, a bottom plate liquid channel; 3-11. internal liquid channel of valve island.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
On the contrary, the invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in order to provide a better understanding of the present invention to the public, certain specific details are set forth in the following detailed description of the invention. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details.
Aiming at the defects of large volume, high power consumption and the like of the prior art that the flow path design of an in-situ pH sensor mostly adopts a three-way valve combination or a multi-position selection valve and the like; the light source and the signal detection are combined by an LED lamp and a photodiode, only a single indicator is used for determination, and the defects of low resolution, poor accuracy and the like exist, so that the determination precision and the measurement range of an instrument are directly influenced. The embodiment of the utility model provides a high-precision seawater pH in-situ measurement system based on an integrated valve island device and capable of detecting multiple reagents; based on a photometric method and circulation analysis, the determination principle is that the pH value is obtained by the change of absorbance after the indicator is completely mixed with seawater.
As shown in fig. 1, the measuring system includes: the device comprises a flow path module, a light path module and a circuit module;
the flow path module comprises an integrated valve island, a flow cell and a reagent bag connected with the integrated valve island through a pulse pump; one end of the flow cell is connected with the integrated valve island through a peristaltic pump, and the other end of the flow cell is connected with the integrated valve island; the integrated valve island is also provided with a seawater sample introduction pipeline, a seawater waste liquid discharge pipeline and an indicator waste liquid discharge pipeline; the flow path module also comprises flow path pipelines, and the reagent bag is connected with the pulse pump, the pulse pump is connected with the integrated valve island, the peristaltic pump is connected with the flow cell, and the flow cell is connected with the integrated valve island by the flow path pipelines;
the light path module is used for measuring the absorbance of the sample at the characteristic wavelength; the micro spectrometer comprises a light source coupling module, a micro spectrometer and optical fibers, wherein the light source coupling module comprises three LED lamps with different wavelengths, the three LED lamps with different wavelengths are arranged in a light source coupler, a coupling light source is formed by the three LED lamps with different wavelengths, light emitted by the coupling light source is transmitted through the optical fibers and enters the micro spectrometer after passing through a flow cell to detect the signal intensity.
The peristaltic pump, the pulse pump, the integrated valve island and the spectrometer are all connected with the circuit module; the circuit module is used for controlling the peristaltic pump, the pulse pump, the integrated valve island, the spectrometer to be turned on or off and used for data acquisition. Preferably, the circuit system adopts a modular design concept, and corresponding circuit modules are turned on or turned off according to the working process in the measurement process, so that static working power consumption is reduced. Based on the consideration of the working environment of the measuring system, a leakage detection circuit is designed and used for carrying out leakage power-off protection on some parts of the measuring system and uploading leakage early warning information.
In this embodiment, the integrated valve island includes four two-position three-way solenoid valves, namely a first solenoid valve, a second solenoid valve, a third solenoid valve and a fourth solenoid valve; the first electromagnetic valve, the second electromagnetic valve, the third electromagnetic valve and the fourth electromagnetic valve respectively comprise three interfaces, namely a normally closed port a, a normally open port b and a third interface;
the seawater sampling pipeline with the normally open b of first solenoid valve connects, the third interface of first solenoid valve with the normally open b of second solenoid valve connects, the normally closed a of second solenoid valve with the reagent bag passes through the pulse pump and connects, the third interface of second solenoid valve with the third interface connection of third solenoid valve, the normally open b of third solenoid valve pass through the peristaltic pump with the one end of flow-through cell is connected, the normally closed a of third solenoid valve with indicator waste liquid discharge tube connects, the normally closed a of fourth solenoid valve with the normally closed a of first solenoid valve connects, the normally open b of fourth solenoid valve and seawater waste liquid discharge tube connect, the third interface of fourth solenoid valve with the other end of flow-through cell connects.
In this embodiment, the integrated valve island further comprises a valve island, wherein the valve island comprises a substrate and a bottom plate; the bottom plate is arranged at the lower part of the substrate, and the four electromagnetic valves are all arranged at the lower part of the bottom plate;
the substrate and the bottom plate are made of high-transparency acrylic materials and are bonded in a glue joint and a seamless mode in a dust-free clean environment; liquid channels are arranged in the substrate and the bottom plate and are used for communicating the electromagnetic valve with external fluid pipelines connected to the integrated valve island;
the external fluid pipeline connected into the integrated valve island comprises a fluid pipeline between the peristaltic pump and the integrated valve island, a fluid pipeline between the pulse pump and the integrated valve island, the indicator waste liquid discharge pipeline, the seawater sample injection pipeline, a fluid pipeline between the flow cell and the integrated valve island, and a fluid pipeline between a third interface of the first electromagnetic valve and a normally open port b of the second electromagnetic valve;
the liquid channel is also used for connection between the first solenoid valve and a fourth solenoid valve and between the second solenoid valve and the third solenoid valve;
the inner diameters of the liquid channels in the base plate and the bottom plate are the same as the inner diameter of the external fluid pipeline connected into the integrated valve island, so that the change of the flow speed state of fluid entering the integrated valve island is avoided, and the measurement precision is ensured. In this embodiment, the inner diameters of the liquid channels inside the substrate and the bottom plate and the outer fluid pipeline connected to the integrated valve island are both 0.1-3 mm.
Specifically, as shown in fig. 2, the specific structure of the integrated valve island is as follows:
the liquid channels arranged inside the substrate and the bottom plate comprise bottom plate liquid channels 3-10, substrate liquid channels 3-9 and valve island internal liquid channels 3-11,
a bottom plate liquid channel communicated with the electromagnetic valves is arranged on the bottom plate in a penetrating manner, three bottom plate liquid channels respectively connected with the electromagnetic valve normal opening b3-3, the third interface 3-4 and the normally closed port a3-5 are arranged above each electromagnetic valve, namely, 12 bottom plate liquid channels are arranged on the valve island;
the upper part of the substrate is provided with 3-8 threaded holes, and a fluid pipeline between the peristaltic pump and the integrated valve island, a fluid pipeline between the pulse pump and the integrated valve island, the indicator waste liquid discharge pipeline, the seawater sample introduction pipeline, a fluid pipeline between the flow cell and the integrated valve island, and a fluid pipeline between the third interface of the first electromagnetic valve and the normally open port b of the second electromagnetic valve are all connected with the threaded holes on the integrated valve island substrate, wherein the number of the threaded holes is 8 in the embodiment;
the lower part of the substrate is provided with substrate liquid channels 3-9, the substrate liquid channels correspond to the threaded holes 3-8 one by one, and the number of the substrate liquid channels is 8; and the upper end of the substrate liquid channel is communicated with the threaded hole, and the lower end of the substrate liquid channel 3-9 is connected with the corresponding bottom plate liquid channel 3-10 on the bottom plate, so that the connection between the external fluid pipeline of the integrated valve island and the electromagnetic valve is realized. Wherein, each threaded hole is provided with a joint for clamping, fixing and clamping the fixed fluid pipeline; in particular, the threaded hole is a flat-bottom threaded hole.
Forming valve island internal liquid channels 3-11 after the lower end surface of the substrate and the upper end surface of the bottom plate are simultaneously subjected to groove bonding, wherein the valve island internal liquid channels comprise a first internal liquid channel and a second internal liquid channel;
two ends of the first internal liquid channel are respectively connected with a second electromagnetic valve third interface and a bottom plate liquid channel corresponding to the third electromagnetic valve third interface so as to realize the connection of the second electromagnetic valve third interface and the third electromagnetic valve third interface; two ends of the second internal liquid channel are respectively connected with a fourth electromagnetic valve normally-closed port a and a bottom plate liquid channel corresponding to the first electromagnetic valve normally-closed port a, so that the fourth electromagnetic valve normally-closed port a is connected with the first electromagnetic valve normally-closed port a;
specifically, 4 groups of bright and clean holes 3-6 for installing and fixing four electromagnetic valves are arranged at the lower end of the bottom plate; the lower end of the bottom plate is simultaneously provided with fixing screw holes 3-7 for fixing the whole integrated valve island device. The solenoid valve 8 all can choose for use two three-way valves on the market, and the PEEK material is chooseed for use to the material, can prevent high salt and acid-base erosion. Under the drive of a peristaltic pump or a pulse pump, fluid enters a liquid channel in the valve island through an external fluid pipeline connected into the integrated valve island and then enters the electromagnetic valve, and the flow direction of the fluid is controlled.
The whole integrated valve island device enables a flow path system to be compact in structure, and reduces the dead volume of the flow path and the power consumption of an instrument.
In this embodiment, the flow cell is made of a plastic material and has a cross-shaped structure, the fluid flows from bottom to top, the optical signal is transmitted in the horizontal direction, and bubbles generated in the fluid can float up to the top of the flow cell, so as to avoid the influence of bubble accumulation on the absorbance measurement;
the length of the light path of the flow cell is 0.5-4cm, and the flow cell is placed in seawater outside the instrument cabin so as to keep the temperature of a sample in the flow cell consistent with that of the seawater; and a temperature probe is arranged beside the flow cell and used for measuring the temperature of the seawater in real time.
In this embodiment, the three LED lamps having different wavelengths include: the LED lamp comprises a warm white LED lamp with a wider peak width and a central wavelength of 580nm, an LED lamp with a central wavelength of 435nm and an LED lamp with a central wavelength of 490 nm;
the spectrum detection range of the spectrometer is 300nm-800nm, a slit with the wavelength resolution of 1.5nm is arranged, and the size of the slit is 25 mu m;
the device adopts three LED lamps with different wavelengths to form a coupling light source as a light source and adopts the spectrometer as a detector, and can be suitable for measuring the pH value of seawater of three indicators of m-cresol purple, thymol blue and cresol red, wherein the measurement range is 6.8-8.6.
In this embodiment, the choice of LED lamp depends on the characteristic wavelengths of the indicator used, including the wavelength at the maximum absorption peak in the acid state, the wavelength at the maximum absorption peak in the base state, and the wavelengths at the absorption peaks in the acid and base states. At present, indicators commonly used in seawater pH measurement comprise m-cresol purple, thymol blue, cresol red and the like, the wavelength of the three indicators at the maximum absorption peak of an acid state is 430-440 nm, the wavelength of the three indicators at the maximum absorption peak of an alkali state is 550-600 nm, and the wavelength of the equal absorption peak is mostly concentrated in 480-500 nm along with the temperature change. Therefore, the utility model discloses in adopt above-mentioned three LED lamp that has different wavelengths to constitute the coupling light source and can satisfy the survey demand of three kinds of indicators between cresol purple, thymol blue and cresol red simultaneously, can accomplish the sea water pH of three kinds of indicators and measure.
Furthermore, in the embodiment of the present invention, a micro spectrometer with small volume and low power consumption is used as the signal detection unit, the spectrum detection range is 300nm-800nm, a 25 μm slit is provided, and the wavelength resolution is 1.5nm. When the wavelength resolution of a signal detection unit selected by the measuring system is higher than 2nm, the pH value can be calculated according to published related data of the indicator, and if the wavelength resolution is lower than 2nm, all characteristic coefficients of the indicator need to be automatically determined to ensure the measuring precision. The micro spectrometer can accurately measure the absorbance at the characteristic wavelength of the indicator, can simultaneously measure the absorbance values at a plurality of wavelengths, is not interfered by other circuits in the using process, has stable performance, can realize the measurement of various indicators while meeting the high-precision detection requirement, and thus widens the application range of the instrument.
The indicator is mainly used for measuring the pH value of the seawater in a range of a second-order dissociation constant K2The optimum range of PK was determined and also influenced by the molar absorption coefficient2-1≤pH≤pK2. Commonly used indicators for measuring seawater are m-cresol purple, thymol blue and cresol red, according to the prior art, the measurement range of the m-cresol purple is 7.2-8.2, the measurement range of the thymol blue is 7.6-8.6, the measurement range of the cresol red is 6.8-7.8, according to the current seawater pH distribution, the m-cresol purple is suitable for section and near-shore seawater, the thymol blue is suitable for ocean surface seawater, and the cresol red is suitable for seawater in a low pH region.
In this embodiment, through the integrated valve island control flow path, when the pH of seawater is measured in situ, seawater is first introduced into the flow path to measure blank light intensity, then an indicator is introduced into the flow path, the flow path is closed to form a loop, the seawater and the indicator are mixed in the loop, after complete mixing, the light intensity of the mixed solution is detected, absorbance is calculated, and then the pH of the seawater is obtained by calculation.
The structure that the flow path is closed to form a loop has the characteristics of small dead volume, compact structure and low power consumption, can realize the complete mixing of seawater and the indicator, and can improve the stability of the measurement of the instrument. In this embodiment, the fluid pipeline is made of polytetrafluoroethylene, and the inner diameter is 0.1-3 mm; the reagent bag is made of aluminum foil material and has the characteristics of light resistance and air impermeability; the concentration of the indicator is 0.1-5 mmol/L; the pulse pump is a micro pump, and the pulse volume is 10-500 μ L.
The process of high-precision seawater pH in-situ measurement by adopting the measurement system in the embodiment comprises the following steps:
sampling seawater: controlling the first electromagnetic valve 4, the second electromagnetic valve 5, the third electromagnetic valve 6 and the fourth electromagnetic valve 7 to be in a normal open b position, starting the peristaltic pump, enabling a seawater sample to enter from a seawater sample introduction pipeline 8 and fill a flow path, and discharging redundant samples from a seawater waste liquid discharge pipeline 9;
blank light intensity detection: the peristaltic pump is closed, the LED lamp is turned on, and the spectrometer is used for detecting the blank sample of the seawater in the selected indicatorBlank light intensity at the characteristic wavelength, wherein the characteristic wavelength of the selected indicator comprises the wavelength at the maximum absorption peak of an acid state, the wavelength at the maximum absorption peak of an alkali state and the wavelengths at the absorption peaks of the acid state, the alkali state and the like; recording the optical signal as λ I0λ is the wavelength;
taking thymol blue as an example, the wavelengths at the maximum absorption peak of the acid state, the maximum absorption peak of the alkali state and the absorption peaks of the acid state and the alkali state are 435nm, 596nm and 494nm respectively, and the optical signals are recorded as lambda435I0，λ596I0，λ494I0。
Reagent sample introduction: switching the second electromagnetic valve 5 and the third electromagnetic valve 6 to a normally closed port a position, starting the pulse pump 2, pumping the indicator into the reagent flow path from the reagent bag, discharging the redundant indicator from the indicator waste liquid discharge pipeline 10, and closing the pulse pump;
mixing samples: switching a second electromagnetic valve 5 and a third electromagnetic valve 6 to a normally open b position, switching a first electromagnetic valve 4 and a fourth electromagnetic valve 7 to a normally closed a position to form a closed loop, integrating a valve island, a peristaltic pump, a flow cell and other pipelines to form a circulation system, starting the peristaltic pump, fully mixing a seawater sample and an indicator, wherein the mixing time is 20-180s, selecting the mixing time according to the pump speed and the pipelines, and closing the peristaltic pump after uniform mixing;
detecting the light intensity of the mixed solution, and calculating the absorbance: after the mixture is completely mixed, the LED lamp is turned on, the light intensity of the mixed solution is detected, the light signal is recorded as lambda I, and the absorbance lambda A is calculated to be-log10(λI/λI0) (ii) a The spectrometer can accurately measure the light intensity of each wavelength in the whole measuring range, the spectrometer can measure the light intensity in the wavelength of 300-800nm, and the wavelength required to be output is selected during output. When the indicator is replaced, a proper output wavelength is selected, and the pH is calculated according to the measurement result of the spectrometer.
Specifically, the method for calculating the pH specifically comprises the following steps:
the pH value of the seawater is measured by a photometric method and a secondary dissociation equilibrium reaction of an acid-base indicator, and the calculation formula is as follows:
pHTexpressed as pH, K, on the total hydrogen ion scale2 TIs the secondary dissociation constant of the indicator, [ I2-]And [ HI-]The concentrations of the indicator in the alkali state and the acid state; in [ HI ]-]And [ I2-]Respectively measuring the absorbance lambda of the sample at the maximum absorption wavelengths lambda 1 and lambda 21A and lambda2A；
According to lambert beer's law, the calculation formula can be written as:
K2 Tthe measuring range of the indicator is determined, and the pH of the seawater can be measured by adopting the applicable seawater pH measuring indicator;
wherein:
e1，e2，e3the ratio of molar absorption coefficients of different forms of the indicator at different wavelengths is shown, and R is an absorbance ratio; lambda [ alpha ]1εI 2-And λ2εI 2-Is I2-At λ1And λ2The absorption coefficient at the time of wavelength,
and
is HI-At λ1And λ2The extinction coefficient of time is related to temperature and salinity.
In this embodiment, the method further includes a step of correcting the indicator, specifically:
the indicator is used as a dibasic acid, the addition of the indicator can interfere the measurement of the pH value of the seawater, and the pH value of the seawater is calculated by adopting the concentration change and the pH value change of a mixed solution in the indicator dilution process so as to eliminate the interference of the indicator, so that the real-time correction is realized.
Detecting the light intensity of the mixed solution, after the step of calculating the absorbance is completed, switching the first electromagnetic valve 4 and the fourth electromagnetic valve 7 to a normally open b position, starting the peristaltic pump, enabling the seawater sample to enter the pipeline, continuously diluting the indicator in the pipeline, continuously collecting the light intensity of the mixed solution in the dilution process by adopting a spectrometer, and calculating the absorbance and the pH value, wherein the dilution time is 20-180 s; the absorbance of the indicator at the absorption wavelengths of the acid state, the alkali state and the like is only related to the concentration of the indicator, the absorbance value of the indicator at the absorption wavelengths of the acid state, the alkali state and the like is measured for multiple times as an x axis, the corresponding pH value is a straight line with the y axis, and the obtained y value is the pH value of the seawater after the interference of the indicator is eliminated when the x is 0.
The method also comprises the steps of flushing the pipeline: switching the first electromagnetic valve 4 and the fourth electromagnetic valve 7 to a normally open a position, reversely rotating the peristaltic pump for 1-10s, connecting the normally closed a position of the first electromagnetic valve 4 with the normally closed a position of the fourth electromagnetic valve 7, flushing a sample in the pipeline to a position between the fourth electromagnetic valve 7 and the flow cell, reasonably controlling the reverse rotation time, and avoiding the sample from flowing into the flow cell while completely flushing the sample; and (3) switching the first electromagnetic valve 4 and the fourth electromagnetic valve 7 to a normally open b position, and starting the peristaltic pump to continuously flush the pipeline for 20-180 s.
Interference correction of the indicator is accomplished during the mixing of the seawater and the indicator: the indicator itself is a dibasic acid, the addition of which causes a change in the pH of the seawater. The traditional correction method is applied to the calculation of the pH value of the seawater after a correction model is obtained in a laboratory, and the correction accuracy needs to be improved. The utility model discloses a method that indicator disturbed can be rectified to quick normal position can carry out indicator interference correction to the measurement of sea water pH at every turn, and this method is applicable to the normal position instrument very much, has improved the degree of accuracy of correction.
The following examples are used to analyze the process of determining the pH of seawater, and the seawater pH in-situ measuring device of the present invention is used, wherein thymol blue (but the present invention is not limited to the indicator) is used as the indicator, and the optical length of the flow cell is 1 cm. The determination method comprises the following steps:
and (3) preparing an indicator: 0.1954g of thymol blue sodium salt is weighed and dissolved in 200mL of high-purity water, and after complete dissolution, the pH value of the solution is adjusted to 7.9 +/-0.1 by using 1.0mol/L hydrochloric acid and sodium hydroxide solution. Wherein the concentration of the thymol blue sodium salt is 2 mmol/L.
Measuring the pH value of the seawater:
a. controlling the first electromagnetic valve, the second electromagnetic valve, the third electromagnetic valve and the fourth electromagnetic valve to be in a normal opening b position, starting the peristaltic pump, enabling a seawater sample to enter from the seawater sample introduction pipeline and fill the flow path, and discharging redundant samples from the seawater waste liquid discharge pipeline to finish seawater sample introduction;
b. closing the peristaltic pump, starting an LED coupling light source, detecting the light intensity of a hollow white sample in the flow cell by using a spectrometer, and recording blank light intensities at characteristic wavelengths of thymol blue (including the wavelength (435nm) at the maximum absorption peak in an acid state, the wavelength (596nm) at the maximum absorption peak in an alkali state and the wavelength (494nm) at the absorption peaks in the acid state and the alkali state), wherein the blank light intensities are respectively lambda435I0，λ596I0，λ494I0；
c. Switching the second electromagnetic valve and the third electromagnetic valve to a normally closed port a position, starting the pulse pump, enabling the indicator to enter a flow path, pumping the indicator into the reagent flow path from the reagent bag, discharging the redundant indicator from an indicator waste liquid discharge pipeline, finishing the sample introduction of the indicator, and closing the pulse pump;
d. switching the second electromagnetic valve 5 and the third electromagnetic valve 6 to a normally open b position, switching the first electromagnetic valve 4 and the fourth electromagnetic valve 7 to a normally closed a position to form a closed loop, starting the peristaltic pump, fully mixing the seawater sample and the indicator for 60s, and closing the peristaltic pump;
e. detecting the light intensity of the mixed solution in the flow cell by using a micro spectrometer, and recording the light intensity at the characteristic wavelength of thymol blue, wherein the light intensity is lambda435I，λ596I，λ494I; the absorbance is calculated by the formula λ A ═ log (λ I/λ I)0) Recording the absorbance respectively as lambda435A，λ596A，λ494A；
Calculation of seawater pH:
the seawater pH calculation formula is as follows:
wherein the pH isTExpressed as pH, K, on the total hydrogen ion scale2 TIs the second order dissociation constant of indicator thymol blue, [ I2-]And [ HI-]Is the concentration of indicator thymol blue in both the alkaline and acid states.
According to lambert beer's law, the formula can be written as:
wherein e1，e2，e3The ratio of the molar absorption coefficients of different forms of thymol blue at different wavelengths is:
λ435a and lambda596A is the absorbance of the sample measured at wavelengths of 435nm and 596nm,andis I2-Absorption coefficients at wavelengths of 435nm and 596nm,
and
is HI-Absorption coefficients at wavelengths of 435nm and 596 nm. Since the wavelength resolution of the spectrometer used for the measurement in this example is 1.5nm, the calculation can be performed by directly using the published literature values in the prior art, and the secondary dissociation constant and molar absorption coefficient formulas of the indicator thymol blue in the prior art are as follows:
-log10(KT 2)＝4.706S/T+26.3300-7.17218logT-0.017316×S
e1＝-0.00132+1.600×10-5T
e2＝7.2326-0.0299717T+4.600×10-5T2
e3＝0.0223+0.0003917T
wherein the application ranges of the temperature (T) and the salinity (S) are respectively as follows: t is more than or equal to 278.15 and less than or equal to 308.15K, and S is more than or equal to 20 and less than or equal to 40.
The method also includes the following steps of indicator calibration and line cleaning:
f. and (3) correcting the indicator: switching the first electromagnetic valve and the fourth electromagnetic valve to a normally open b position, starting the peristaltic pump, enabling the seawater sample to enter the pipeline, continuously diluting the indicator thymol blue for 60s, and continuously collecting the light intensity lambda of the mixed solution in the dilution process by adopting a spectrometer435Ii，λ596Ii，λ494IiCalculating the absorbance lambda435Ai，λ596Ai，λ494Ai。
Respectively calculating the pH value of the mixed solution in the indicator thymol blue dilution process according to a seawater pH calculation formula, and recording as the pH valuei(ii) a Measurement of absorbance. lambda. with the Mixed solution494And A is an x axis, the corresponding pH value is a y axis, a straight line is made, and when x is 0, the obtained y value is the pH value of the seawater after the interference of the thymol blue is eliminated.
g. Cleaning a pipeline: switching the first electromagnetic valve 4 and the fourth electromagnetic valve 7 to a normally closed port a position, and reversely rotating the peristaltic pump for 5 s; and (3) closing the peristaltic pump, enabling the first electromagnetic valve 4 to be normally closed at the position a and the fourth electromagnetic valve 7 to be normally opened at the position b, starting the peristaltic pump to continuously flush the pipeline for 60s, and finishing pipeline cleaning.
Claims (7)
1. High accuracy sea water pH normal position measurement system based on integrated valve island device which characterized in that includes: the device comprises a flow path module, a light path module and a circuit module;
the flow path module comprises an integrated valve island, a flow cell and a reagent bag connected with the integrated valve island through a pulse pump; one end of the flow cell is connected with the integrated valve island through a peristaltic pump, and the other end of the flow cell is connected with the integrated valve island; the integrated valve island is also provided with a seawater sample introduction pipeline, a seawater waste liquid discharge pipeline and an indicator waste liquid discharge pipeline;
the light path module is used for measuring the absorbance of the sample at the characteristic wavelength; the system comprises a light source coupling module, a micro spectrometer and optical fibers, wherein the light source coupling module comprises three LED lamps with different wavelengths arranged in a light source coupler, the three LED lamps with different wavelengths form a coupling light source, and light emitted by the coupling light source is transmitted through the optical fibers, enters the micro spectrometer after passing through a flow cell and is detected for signal intensity;
the peristaltic pump, the pulse pump, the integrated valve island and the micro spectrometer are all connected with the circuit module; the circuit module is used for controlling the opening or closing of the peristaltic pump, the pulse pump, the integrated valve island and the micro spectrometer and is used for data acquisition.
2. The high-precision seawater pH in-situ measurement system based on the integrated valve island device according to claim 1, wherein the integrated valve island comprises four two-position three-way electromagnetic valves, namely a first electromagnetic valve, a second electromagnetic valve, a third electromagnetic valve and a fourth electromagnetic valve; the first electromagnetic valve, the second electromagnetic valve, the third electromagnetic valve and the fourth electromagnetic valve respectively comprise three interfaces, namely a normally closed port a, a normally open port b and a third interface;
the seawater sampling pipeline with the normally open b of first solenoid valve connects, the third interface of first solenoid valve with the normally open b of second solenoid valve connects, the normally closed a of second solenoid valve with the reagent bag passes through the pulse pump and connects, the third interface of second solenoid valve with the third interface connection of third solenoid valve, the normally open b of third solenoid valve pass through the peristaltic pump with the one end of flow-through cell is connected, the normally closed a of third solenoid valve with indicator waste liquid discharge tube connects, the normally closed a of fourth solenoid valve with the normally closed a of first solenoid valve connects, the normally open b of fourth solenoid valve and seawater waste liquid discharge tube connect, the third interface of fourth solenoid valve with the other end of flow-through cell connects.
3. The integrated valve island device-based high-precision seawater pH in-situ measurement system according to claim 2, wherein the integrated valve island further comprises a valve island, the valve island comprises a substrate and a bottom plate; the bottom plate is arranged at the lower part of the substrate, and the four electromagnetic valves are all arranged at the lower part of the bottom plate;
the substrate and the bottom plate are made of high-transparency acrylic materials and are bonded in a glue joint and a seamless mode in a dust-free clean environment; and liquid channels are arranged in the substrate and the bottom plate and are used for communicating the electromagnetic valve and an external fluid pipeline connected to the integrated valve island.
4. The integrated valve island device-based high-precision seawater pH in-situ measurement system according to claim 3, wherein the external fluid pipeline connected to the integrated valve island comprises a fluid pipeline between the peristaltic pump and the integrated valve island, a fluid pipeline between the pulse pump and the integrated valve island, the indicator waste liquid discharge pipeline, the seawater sample injection pipeline, a fluid pipeline between the flow cell and the integrated valve island, and a fluid pipeline between a third interface of the first solenoid valve and a normally open port b of the second solenoid valve;
the liquid channel is also used for connection between the first solenoid valve and a fourth solenoid valve and between the second solenoid valve and the third solenoid valve;
the inner diameters of the liquid channels inside the substrate and the bottom plate are the same as the inner diameter of the external fluid pipeline connected into the integrated valve island.
5. The high-precision seawater pH in-situ measurement system based on the integrated valve island device according to claim 1, wherein the flow cell is made of plastic and has a cross-shaped structure, fluid flows from bottom to top, optical signals are transmitted in the horizontal direction, and bubbles generated in the fluid can float to the top of the flow cell to avoid the influence of bubble accumulation on absorbance measurement;
the length of the light path of the flow cell is 0.5-4cm, and the flow cell is placed in seawater outside the instrument cabin so as to keep the temperature of a sample in the flow cell consistent with that of the seawater; and a temperature probe is arranged beside the flow cell and used for measuring the temperature of the seawater in real time.
6. The integrated valve island device-based high-precision seawater pH in-situ measurement system according to claim 1, wherein the three LED lamps with different wavelengths comprise: warm white LED lamp with center wavelength of 580nm, LED lamp with center wavelength of 435nm and LED lamp with center wavelength of 490 nm.
7. The high-precision seawater pH in-situ measurement system based on the integrated valve island device according to claim 1 or 6, wherein the micro spectrometer has a spectral detection range of 300nm-800nm, is provided with a 25 μm slit, and has a wavelength resolution of 1.5nm.
The device adopts three LED lamps with different wavelengths to form a coupling light source as a light source and adopts the micro spectrometer as a detector, and can be suitable for measuring the pH value of seawater of three indicators of m-cresol purple, thymol blue and cresol red, wherein the pH measuring range is 6.8-8.6.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201920695433.1U CN210071669U (en) | 2019-05-16 | 2019-05-16 | High-precision seawater pH in-situ measurement system based on integrated valve island device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201920695433.1U CN210071669U (en) | 2019-05-16 | 2019-05-16 | High-precision seawater pH in-situ measurement system based on integrated valve island device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN210071669U true CN210071669U (en) | 2020-02-14 |
Family
ID=69452131
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201920695433.1U Active CN210071669U (en) | 2019-05-16 | 2019-05-16 | High-precision seawater pH in-situ measurement system based on integrated valve island device |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN210071669U (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110057814A (en) * | 2019-05-16 | 2019-07-26 | 山东省科学院海洋仪器仪表研究所 | High-precision seawater pH in-situ measurement system and method based on integrated valve terminal device |
| CN112032362A (en) * | 2020-08-31 | 2020-12-04 | 石家庄瑞祥电子科技有限公司 | Valve terminal base |
-
2019
- 2019-05-16 CN CN201920695433.1U patent/CN210071669U/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110057814A (en) * | 2019-05-16 | 2019-07-26 | 山东省科学院海洋仪器仪表研究所 | High-precision seawater pH in-situ measurement system and method based on integrated valve terminal device |
| WO2020228507A1 (en) * | 2019-05-16 | 2020-11-19 | 山东省科学院海洋仪器仪表研究所 | High-precision seawater ph in-situ measurement system and method based on integrated valve-terminal apparatus |
| EP3819631A4 (en) * | 2019-05-16 | 2021-11-17 | Institute of Oceanographic Instrumentation, Shandong Academy of Sciences | High-precision seawater ph in-situ measurement system and method based on integrated valve-terminal apparatus |
| CN112032362A (en) * | 2020-08-31 | 2020-12-04 | 石家庄瑞祥电子科技有限公司 | Valve terminal base |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| WO2020228507A1 (en) | High-precision seawater ph in-situ measurement system and method based on integrated valve-terminal apparatus | |
| CN210071669U (en) | High-precision seawater pH in-situ measurement system based on integrated valve island device | |
| AU597168B2 (en) | Sensor and method for detecting the presence of air bubbles in liquid | |
| CN106556598B (en) | Automatic in-situ nutritive salt analysis device for seawater monitoring | |
| CN103439258B (en) | A kind of water nutrition in situ detection instrument based on integrated valve terminal device and detection method | |
| CN105067542A (en) | Photometric method based boat-carrying pH and pCO2 measuring device and measuring method | |
| US20120275958A1 (en) | Determination method and instruments of hexavalent chromium | |
| CN105241829B (en) | A kind of circulation type original position high-precision seawater pH measuring device and measurement method | |
| CN106198532A (en) | The dual wavelength autocontrol method of a kind of quick photometric titration and device | |
| KR20150106493A (en) | Microfluidic chips having flow cells using standard addition method and absorbance measurement apparatus having thereof | |
| CN111678966A (en) | Electrochemical sensing-based ocean carbon dioxide on-line monitoring method and device | |
| CN209247625U (en) | A kind of micro-fluidic NH 3 flow path system | |
| CN101187637B (en) | Automatic analysis method for seawater phenols compounds | |
| CN208091910U (en) | A kind of device for analyzing on-line checking Nitrate In Sea Water content based on optofluidic | |
| CN214011063U (en) | Nutritive salt analyzer | |
| CN203310744U (en) | Liquid core waveguide food detector | |
| CN105115913A (en) | High precision absorbance detection apparatus | |
| CN212301399U (en) | Ocean carbon dioxide on-line monitoring system based on electrochemical sensing | |
| CN111458319A (en) | Device and method for online determination of ammonia nitrogen concentration in water body | |
| CN101231248B (en) | Non-contact type photoelectricity pH value detection method and used sensor | |
| CN114878531A (en) | Device and method for online monitoring of content of multiple oil types in water based on oil type judgment | |
| CN109060697A (en) | Automatically select the water quality parameter analyzer of Detection wavelength | |
| CN108444994B (en) | Automatic analysis device and method for formaldehyde in water | |
| CN209055454U (en) | Automatically select the water quality parameter analyzer of Detection wavelength | |
| CN208795642U (en) | A kind of microflow control technique original position NH 3 device and its flow cell |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| GR01 | Patent grant | ||
| GR01 | Patent grant |