CN105241829B - A kind of circulation type original position high-precision seawater pH measuring device and measurement method - Google Patents
A kind of circulation type original position high-precision seawater pH measuring device and measurement method Download PDFInfo
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Abstract
The present invention provides a kind of circulation type original position high-precision seawater pH measuring device and measuring method, and device includes fluid communication means and signal supervisory instrument；The fluid communication means, including indicator bag, the first triple valve, the second triple valve, third triple valve, flow cell, peristaltic pump, pulse pump and fluid circuit；When the second triple valve is connected to third triple valve, second triple valve, third triple valve, peristaltic pump and flow cell form closed circuit；The light path detecting device, including LED light group, filter set, fiber optic splitter, optical fiber and photodiode；The light that LED light issues is propagated after filter set filters by optical fiber and fiber optic splitter；Fiber optic splitter exports two-beam, and a branch of to be imported after flow cell by optical fiber into photodiode, another light beam directly imports photodiode by optical fiber.The device of the invention forms CIRCULATION ANALYSIS, and seawater and indicator can be thoroughly mixed in closed loop, to improve the precision of measuring system.
Description
Technical field
The invention belongs to Marine Chemistry monitoring technical fields, concretely relate to photometry and the measurement of CIRCULATION ANALYSIS technology
The method of seawater pH value.
Background technique
PH is the positive evidence of one of important parameter of seawater carbonate system and Ocean acidification.Using photometry as base
The high-precision seawater pH sensor accuracy class in situ of plinth can reach 0.001, can satisfy Ocean acidification and carbon cycle research
It needs.Its working principle is that mixing seawater with indicator in measurement system, counted by measuring the absorbance of mixed solution
Calculate seawater pH.The seawater pH sensor in situ for being mostly based on photometry both at home and abroad at present is in laboratory development phase, only two
Money the type sensor realizes commercialization.To find out its cause, mainly due to the generally existing cost power consumption of the type sensor compared with
It is high, caused by structure is complicated, volume is big, integrated level is low, stability is poor.
Most of seawater pH measuring systems do light source using xenon lamp or deuterium-tungsten halogen lamp, and spectrometer makees detector, power compared with
Greatly, it is chiefly used in boat-carrying and walks aerial survey amount, is not suitable for the application of in-situ measurement system.In addition, measuring system generallys use flow injection
Analysis, indicator are injected into seawater flow path, and the liquid when measuring absorbance in flow path is not thoroughly mixed, can be to measurement
Stability generate certain influence.
Summary of the invention
In order to solve the above technical problems, the high-precision sea that present invention discusses a kind of based on photometry and CIRCULATION ANALYSIS
Water pH measuring device and measuring method, signal supervisory instrument are mainly made of LED light and photodiode, and cost is low in energy consumption, surely
It is qualitative good；Fluid communication means are mainly made of triple valve and peristaltic pump, and structure is simple, and dead volume is small, are suitable for scene in situ
Monitoring.In CIRCULATION ANALYSIS, seawater and indicator can be thoroughly mixed in closed loop, to improve the essence of measuring system
Density.
A kind of circulation type original position high-precision seawater pH measuring device of the invention, including fluid communication means and signal detection
Device；
The fluid communication means, including indicator bag, the first triple valve, the second triple valve, third triple valve, circulation
Pond, peristaltic pump, pulse pump and fluid circuit；First triple valve respectively with seawater water inlet pipe, pulse pump and the second triple valve
Connection, the indicator bag are connect by pulse pump with the first triple valve；Second triple valve respectively with the first triple valve,
Three triple valves and flow cell connection；The third triple valve is connect with the second triple valve, sewer pipe and peristaltic pump respectively；When second
When triple valve is connected to third triple valve, second triple valve, third triple valve, peristaltic pump and flow cell formation are closed back
Road；
The signal supervisory instrument, including LED light group, filter set, fiber optic splitter, optical fiber and photodiode；LED
The light that lamp issues is propagated after filter set filters by optical fiber and fiber optic splitter；Fiber optic splitter exports two beams
Light, a branch of to be imported after flow cell by optical fiber into photodiode, another light beam directly imports photodiode by optical fiber.
Further, filtering head is arranged in the water inlet of the seawater water inlet pipe, and the filtering head is stainless steel or plastics, hole
Diameter is 0.45-5.0 μm.
Further, the indicator bag and fluid circuit are the polytetrafluoroethylene material for completely cutting off air, the indicator
Bag body product is 200-1000ml, and fluid circuit outer diameter is 1-4mm, internal diameter 0.5-2mm.
Further, fluid extra heavy pipe, outer diameter 3-8mm are set between the peristaltic pump and third triple valve, and internal diameter is
2-6mm。
Further, the flow cell is Z-type, and material is PMMA or PEEK；The flow cell is equipped with fluid inlet and the
The connection of two triple valves, fluid outlet and peristaltic pump connection and optical entrance connect with fiber optic splitter, optical emission exit and photoelectricity
Diode connection；Optical path length is 1-5cm in the flow cell.
Further, the half-wave of the optical filter is wide within ± 5nm, using 14 or more A/D when acquiring signal
Converter, signal-to-noise ratio are higher than 800:1.
Further, the filter set includes three optical filters, and the central wavelength of the optical filter is respectively indicator
Wavelength at acid-state maximum absorption band, at indicator alkali state maximum absorption band wavelength and indicator acid-state and alkali state etc. absorb
Wavelength.
A kind of measurement method of circulation type original position high-precision seawater pH measuring device of the invention, comprising the following steps:
1) cleaning and sample introduction are carried out to fluid communication means, at this time by the ac of the first triple valve, the ac of the second triple valve, the
Peristaltic pump is opened in the bc connection of three triple valves, and filtered seawater is extracted into flow path and carries out cleaning and sample introduction, extra liquid
Body is discharged from waste-solution line；
2) cleaning and sample introduction are carried out to the pipeline between the second triple valve and third triple valve, at this time by the second triple valve
Peristaltic pump is opened in the ac connection of bc, third triple valve, and seawater sample is full of the pipeline between the second triple valve and third triple valve
Step 1) is repeated afterwards, by bubble or residual liquid discharge line；It is repeated several times step 1) and operation 2), completes the cleaning of flow path
And sample introduction；
3) light intensity for measuring blank seawater, successively opens three LED light at this time, and two photodiodes detect simultaneously respectively
The light intensity of three LED light, record main optical path signal are I0, reference light paths signal is I0 reference；
4) light intensity for measuring mixed solution, calculate absorbance and pH, at this time by the bc of the first triple valve, the second triple valve
The bc connection of ac, third triple valve, unbalanced pulse pump, indicator is extracted into pipeline, closes pulse pump, then the second threeway
The ac connection of the bc, third triple valve of valve, fluid circuit formed a closed circuit, open peristaltic pump, drive seawater sample and
Indicator mixes in the closed circuit, then successively opens three LED light, the detection three simultaneously respectively of two photodiodes
The light intensity of LED light, record main optical path signal are I, and reference light paths signal is IReference；Calculate the absorbance and pH of mixed solution；
5) indicator is added again, measures the absorbance and pH of mixed solution, it is mixed for the first time in indicator and seawater sample
After conjunction, by the bc connection of the bc of the first triple valve, the ac of the second triple valve, third triple valve, unbalanced pulse pump is continuously added
Enter pipeline with the indicator of the medium volume of step 4)；Then it by the ac connection of the bc of the second triple valve, third triple valve, opens
Peristaltic pump, indicator and seawater mix in pipeline, then successively open three LED light, two photodiodes difference are simultaneously
Detect the light intensity of three LED light；Calculate the absorbance and pH of mixed solution；
6) correction of indicator interference, using absorbance as x-axis, pH is y-axis, waits suction for what is measured in step 4) and step 5)
The pH for receiving the absorbance at wavelength and measuring twice does straight line, and the y value obtained as x=0 is seawater pH value itself.
Further, the concentration of the indicator is 0.5-10mmol/L.
Further, the mixed volume ratio of seawater and indicator is 20:1-1000:1 in the step 4).
Compared with prior art, the advantages and positive effects of the present invention are: seawater pH measuring system of the present invention with
Based on photometry and CIRCULATION ANALYSIS technology, precision is high, stability is good, can be realized the detection of long-term seawater pH in situ.It is excellent
Point is that 1) the present invention is especially suitable for fixed point monitorings in situ, forms CIRCULATION ANALYSIS system using triple valve and peristaltic pump, group
Simple at structure, dead volume is small, and indicator and seawater sample can be realized and be thoroughly mixed, and improves the stability of long term monitoring；
Light path system is formed using LED light and photodiode, greatly reduces cost and power consumption.2) present invention is measuring it every time
Afterwards, live the interference of indicator can be corrected, to effectively increase the accuracy of measurement.
Detailed description of the invention
A kind of structural schematic diagram of circulation type original position high-precision seawater pH measuring device Fig. 1 of the invention.
Specific embodiment
The technical scheme of the present invention will be explained in further detail With reference to embodiment.
The present invention provides one kind based on photometry and CIRCULATION ANALYSIS, can be realized long-term high precision monitor sea in situ
The measuring system and analysis method of water pH value.The measuring system forms power consumption, light at low cost using LED light and photodiode
Electricity detecting system, using triple valve and peristaltic pump composition, dead volume is small, the simple CIRCULATION ANALYSIS system of structure, can in indicator and
Seawater detects absorbance and calculates pH value after being thoroughly mixed, to improve precision of measurement, can be widely applied to sensor.
High-precision seawater pH measuring device in situ of the invention, including fluid communication means and signal supervisory instrument.
The fluid communication means, for the circulation of seawater sample and indicator, including filtering head 1, seawater water inlet pipe 2,
Indicator bag 3, pulse pump 4, the first triple valve 5, the second triple valve 6, third triple valve 10, flow cell 7, peristaltic pump 8, fluid are thick
Pipe 9, sewer pipe 11；The triple valve is two-bit triplet solenoid valve, can pass through the stream of the channel selecting fluid of change triple valve
Road.A, b, c port of first triple valve 5 are connect with seawater water inlet pipe 2, pulse pump 4 and the second triple valve 6 respectively；It is described
Indicator bag 3 is connect by pulse pump 4 with the first triple valve 5, and the pulse pump enters the volume in circuit for control instructions agent；
A, b, c port of second triple valve 6 are connect with the first triple valve 5, third triple valve 10 and flow cell 7 respectively；Described
A, b, c port of three triple valves 10 are connect with the second triple valve 6, sewer pipe 11 and peristaltic pump 8 respectively.When the second triple valve and
When three triple valves connect, i.e., when the b of the second triple valve is connected with c, while a of third triple valve is connected with c, the described 2nd 3
Port valve, third triple valve, peristaltic pump and flow cell form closed circuit.
The water inlet of the seawater water inlet pipe 2 is arranged filtering head 1, the filtering head 1 can with particulate matter in filtering sea, with
Exempt from particulate matter blocking pipeline or influence the measurement of absorbance, filtering head is stainless steel or plastic material, and aperture is 0.45-5.0 μm.
Between the peristaltic pump 8 and third triple valve 10, fluid extra heavy pipe 9 is set, the fluid extra heavy pipe can be improved two
The mixing efficiency of kind of liquid, increases the mixed proportion of seawater and indicator, and material is polytetrafluoroethylene (PTFE), outer diameter 3-8mm, interior
Diameter is 2-6mm.
The indicator bag and fluid circuit are made of the polytetrafluoroethylene material of isolation air, the indicator bag
Volume is 200-1000ml, and fluid circuit outer diameter is 1-4mm, internal diameter 0.5-2mm.
The flow cell is designed as Z-type, can reduce the generation of bubble, and material is organic glass PMMA or polyether-ether-ketone
PEEK；It is connect equipped with fluid inlet with the second triple valve 6, the connection of fluid outlet and peristaltic pump 8 and optical entrance and optical fiber divide
The connection of beam device 15, optical emission exit and photodiode 16 connect.Optical path length is 1-5cm in flow cell.
The signal supervisory instrument, for in fluid communication means seawater sample or seawater sample and indicator it is mixed
It closes liquid and carries out light-intensity test, including LED light group 12, filter set 13, fiber optic splitter 14, optical fiber 15, photodiode 16.Institute
Stating LED light group preferably includes three LED light, issues three kinds of monochromatic light respectively, filters by filter set；The optical filtering
Piece group preferably includes three optical filters, and the central wavelength of the optical filter is respectively indicator wave at acid-state maximum absorption band
Long, indicator wavelength and equivalent absorbance point of indicator acid-state and alkali state at alkali state maximum absorption band.To indicator acid-state
PH value can be calculated in measurement with alkali state maximum absorption wave strong point absorbance, the measurement for absorbance at equivalent absorbance point
It can indicate concentration of indicator in mixed solution.The light of three kinds of wavelength after optical filtering is passed by optical fiber and fiber optic splitter
It broadcasts；Wherein a branch of two-beam derived from the fiber optic splitter is main optical path, enters photodiode after importing flow cell by optical fiber,
Another light beam directly imports photodiode by optical fiber as reference, for the fluctuation bring error of calibration light source light intensity.
In order to guarantee measurement accuracy, the half-wave of optical filter is wide to use 14 or more when acquiring signal within ± 5nm
A/D converter, signal-to-noise ratio be higher than 800:1.It, should be by adjusting concentration of indicator or flow cell light path when measuring absorbance
Length, so that absorbance data is between 0.2-1.0.
Detection method includes the following steps for circulation type original position high-precision seawater pH measuring system of the invention:
1) cleaning and sample introduction are carried out to fluid communication means, at this time by the ac of the first triple valve, the ac of the second triple valve, the
Peristaltic pump is opened in the bc connection of three triple valves, will be extracted through the filtered seawater of filtering head into flow path and be carried out cleaning and sample introduction,
Extra liquid is discharged from waste-solution line.
2) cleaning and sample introduction are carried out to the pipeline between the second triple valve and third triple valve, at this time by the second triple valve
Peristaltic pump is opened in the ac connection of bc, third triple valve, and seawater sample is full of the pipeline between the second triple valve and third triple valve
Step 1) is repeated afterwards, by bubble or residual liquid discharge line；It is repeated several times step 1) and operation 2), completes the cleaning of flow path
And sample introduction.
3) light intensity for measuring blank seawater, successively opens three LED light at this time, and two photodiodes detect simultaneously respectively
The light intensity of three LED light, record main optical path signal are I0, reference light paths signal is I0 reference。
4) light intensity of mixed solution is measured, at this time by the bc of the first triple valve, the ac of the second triple valve, third triple valve
Bc connection, unbalanced pulse pump, the indicator of certain volume is extracted into pipeline, closes pulse pump, then the second triple valve
The ac connection of bc, third triple valve, fluid circuit form a closed circuit, open peristaltic pump, drive seawater sample and instruction
Agent mixes in the closed circuit.After mixing completely, three LED light, the detection three simultaneously respectively of two photodiodes are successively opened
The light intensity of a LED light, record main optical path signal are I, and reference light paths signal is IReference。
5) absorbance, method are as follows: A=-log (I '/I are calculated0'), I '=I/IReference, I0'=I0/I0 reference.Wherein I0For detection
Main optical path light intensity, I when blank seawater0 referenceReference light paths light intensity when to measure blank seawater, I0' it is the two ratio；I is that measurement is mixed
Main optical path light intensity when closing solution, IReferenceReference light paths light intensity when to measure mixed solution, I ' are the two ratio.Process is utilized in formula
The I of reference corrected0' and I ' calculating absorbance A, error caused by light source intensity fluctuation can be eliminated.
PH meter calculates formula are as follows:
It is also writeable are as follows:
Wherein K2For indicator second level dissociation constant, R is absorbance ratio, e1, e2, e3It is indicator different shape not
The ratio of the molar absorption coefficient of co-wavelength:
λ1And λ2Maximum absorption wavelength for indicator in acid-state and alkali state, λ2A and λ1A is in λ2、λ1The lower measurement of wavelength
Sample absorbance,WithFor I2 -In λ1And λ2Absorptivity when wavelength,WithFor HI-In λ1With
λ2When absorptivity.e1,e2And e3The function of temperature, salinity and pressure, thus in situ measure when also need to measure simultaneously
Ocean temperature, salinity and pressure data.
6) pH obtained in step 5) is the pH of seawater Yu indicator mixed solution, but indicator is as a kind of binary acid
Meeting generates interference to the pH of seawater, it is therefore desirable to eliminate the interference of indicator.It is as follows for the bearing calibration of indicator interference:
After the mixing of the first time of indicator and seawater sample, by the bc of the first triple valve, the ac of the second triple valve, the
The bc connection of three triple valves, unbalanced pulse pump, continuously adds and enters pipeline with the indicator of the medium volume of step 4), then by the
Peristaltic pump is opened in the ac connection of the bc, third triple valve of two triple valves, and indicator and seawater mix in pipeline.Mixing is complete
Afterwards, three LED light are successively opened, two photodiodes detect the light intensity of three LED light simultaneously respectively.Calculate mixed solution pH
Value.
Equivalent absorbance point λ3The absorbance λ at place3A can represent concentration of indicator size.Using absorbance as x-axis, pH is y-axis,
The absorbance λ that will be measured in step 4) and step 6)3A and the pH measured twice do straight line, and the y value obtained as x=0 is sea
Water pH value itself.
Indicator in the present invention can choose m-cresol purple, thymol blue, phenol red or cresol red etc..
Preferably, the concentration of indicator is 0.5-10mmol/L in the indicator bag.
Preferably, the mixed volume ratio of seawater and indicator is adjustable as 20:1 to 1000:1 in the step 4).
Below by embodiment to the circulation type original position high-precision seawater pH measuring system of the present invention based on valve body system
Structure and on-line operation method of the present invention be further explained.
Embodiment 1
The present embodiment analyzes seawater pH, and using seawater pH measuring device in situ of the invention, indicator is selected between purifying
Cresol-purple, but the present invention is not limited to the indicator, flow cell light path is 1cm, and the central wavelength of three optical filters is respectively
434nm, 578nm and 478.6nm.
1. the preparation of indicator
M-cresol purple and sodium chloride mixed solution are prepared, m-cresol purple concentration is 5mmol/L, and sodium chloride concentration is
0.7mol/L, and the pH value of mixed solution is adjusted to about 7.9 with the hydrochloric acid of 1.0mol/L and sodium hydroxide solution.2. live in situ
The measurement of seawater pH
1) peristaltic pump 8 is opened in the bc connection of the ac of the first triple valve 5, the ac of the second triple valve 6, third triple valve 10, will
The seawater filtered through filtering head 1 extract into flow path carry out cleaning and sample introduction, extra liquid be discharged from waste-solution line 11.
2) in order to complete the cleaning of pipeline and sample introduction between the second triple valve 6 and third triple valve 10, by the second triple valve 6
Bc, third triple valve 10 ac connection, open peristaltic pump 8, seawater sample is full of step 1) is repeated after this section of pipeline, by bubble
Or residual liquid discharge line.
3) step 1) and operation 2) is repeated several times, completes cleaning and the sample introduction of entire flow path.Successively open three LED light
12, blank seawater light intensity is detected, main optical path signal is denoted as I0, reference light paths signal is denoted as I0 reference。
4) the bc connection of the bc of the first triple valve 5, the ac of the second triple valve 6, third triple valve 10, unbalanced pulse pump 4 will
For 20 μ L m-cresol purple solution extractions into pipeline, the volume ratio of seawater and indicator is about 500:1, closes pulse pump 4, then
The ac connection of the bc, third triple valve 10 of second triple valve 6, fluid circuit form a closed circuit, open peristaltic pump 8, drive
Dynamic two kinds of liquid mix in the closed circuit.After mixing completely, successively opens three LED light 12 and detect mixed solution light intensity, it is main
Optical path signal is denoted as I, and reference light paths signal is denoted as IReference, calculate mixed solution pH.
5) the bc connection of the bc of the first triple valve 5, the ac of the second triple valve 6, third triple valve 10, opens compacted pulse pump 4,
It will be again introduced into pipeline with the m-cresol purple indicator of same volume in step 4).Then the bc of the second triple valve 6, the three or three
Peristaltic pump 8 is opened in the ac connection of port valve 10, and liquid mixes in pipeline.It is same to detect three waves of mixed solution after mixing completely
Long light intensity calculates mixed solution pH.
6) with absorbance λ at 478.6nm478.6A is x-axis, and solution ph is y-axis, the λ of two mixed solutions478.6A and pH
Make straight line, obtains the pH value that y value is seawater itself when x is 0.
The calculation method of absorbance are as follows: A=-log (I '/I0'), I '=I/IReference, I0'=I0/I0 reference
Wherein I0And I0 referenceMain optical path and reference light paths light intensity, I when respectively measuring blank seawater0' it is the two ratio；I and
IReferenceMain optical path and reference light paths light intensity when respectively measuring mixed solution, I ' are the two ratio.
PH meter calculates formula are as follows:
Wherein K2For m-cresol purple indicator second level dissociation constant, R is absorbance ratio, e1, e2, e3For indicator difference
Ratio of the form in the molar absorption coefficient of different wave length:
λ578A and λ434A is the absorbance of the sample measured under 578nm and 434nm wavelength,WithFor I2 -
In the absorptivity of 434nm and 578nm wavelength,WithFor HI-In the absorptivity of 434nm and 578nm wavelength.
e1, e2, e3For the function of temperature, salinity and pressure.Have the m-cresol purple parameters of purifying with temperature, salinity and pressure at present
The formula changed by force:
-log(k2e2)=(a+b/T+c lnT-dT)-(0.05645/T) × P
A=246.64209+0.315971S+2.8855 × 10-4S2
B=7229.23864-7.098137S-0.057034S2
C=44.493382-0.052711S
D=0.0781344
e1=-0.007762+4.5174 × 10-5T+1.7×10-6P
e3/e2=-0.020813+2.60262 × 10-4T+1.0436×10-4(S-35)+4.6×10-6P
The scope of application of wherein salinity (S), temperature (T) and pressure (P) is respectively as follows: 20≤S≤40, and 278.15≤T≤
308.15K, 0≤P≤827bar.When the optical filter half-wave that measuring system is selected is wide is less than 2nm, e1, e2And e3Value it is available
The above-mentioned formula delivered is calculated, and is needed voluntarily beyond the range in order to guarantee measurement accuracy if optical filter half-wave is wide
Measure e1,e2And e3Numerical value.
Above embodiments are only several in the several preferred embodiment of the present invention, it is noted that the present invention is not limited to
Above-described embodiment；It for those of ordinary skill in the art, still can be to technical solution documented by previous embodiment
It modifies or equivalent replacement of some of the technical features；And these modifications or substitutions, do not make relevant art side
The essence of case is detached from the spirit and scope of claimed technical solution of the invention.
Claims (5)
1. a kind of circulation type original position high-precision seawater pH measurement method, which is characterized in that the measurement method is in a kind of circulation type
It is carried out in high-precision seawater pH measuring device in situ, the measuring device includes fluid communication means and signal supervisory instrument；
The fluid communication means, including it is indicator bag, the first triple valve, the second triple valve, third triple valve, flow cell, compacted
Dynamic pump, pulse pump and fluid circuit；First triple valve is connect with seawater water inlet pipe, pulse pump and the second triple valve respectively,
The indicator bag is connect by pulse pump with the first triple valve；Second triple valve respectively with the first triple valve, the three or three
Port valve and flow cell connection；The third triple valve is connect with the second triple valve, sewer pipe and peristaltic pump respectively；When the second threeway
When valve is connected to third triple valve, second triple valve, third triple valve, peristaltic pump and flow cell form closed circuit；
The signal supervisory instrument, including LED light group, filter set, fiber optic splitter, optical fiber and photodiode；LED light group
Including three LED light, photodiode is two, and the light that LED light issues passes through optical fiber and optical fiber after filter set filters
Beam splitter is propagated；Fiber optic splitter exports two-beam, and a branch of imported after flow cell by optical fiber enters photodiode, another
Beam light directly imports photodiode by optical fiber；
Fluid extra heavy pipe, outer diameter 3-8mm, internal diameter 2-6mm, the circulation are set between the peristaltic pump and third triple valve
Pond is Z-type, and material is PMMA or PEEK；The flow cell be equipped with fluid inlet connect with the second triple valve, fluid outlet with it is compacted
Dynamic pump connection and optical entrance are connect with fiber optic splitter, optical emission exit and photodiode connect；Light in the flow cell
Cheng Changdu is 1-5cm；
The measurement method the following steps are included:
1) cleaning and sample introduction are carried out to fluid communication means, at this time connected a port of the first triple valve with c port, the two or three
The a port of port valve is connected with c port, the b port of third triple valve is connected with c port, peristaltic pump is opened, by filtered seawater
Extraction carries out cleaning into flow path and sample introduction, extra liquid are discharged from waste-solution line；
2) cleaning and sample introduction are carried out to the pipeline between the second triple valve and third triple valve, at this time leads to the b of the second triple valve
Mouth is connected with c port, a port of third triple valve is connected with c port, opens peristaltic pump, and seawater sample is full of the second triple valve
Step 1) is repeated after pipeline between third triple valve, by bubble or residual liquid discharge line；Be repeated several times step 1) and
2) cleaning and the sample introduction of flow path are completed in operation；
3) light intensity for measuring blank seawater successively opens three LED light, the detection three simultaneously respectively of two photodiodes at this time
The light intensity of LED light, record main optical path signal are I0, reference light paths signal is I0 reference；
4) light intensity for measuring mixed solution, calculates absorbance and pH, at this time connects the b port of the first triple valve with c port, the
The a port of two triple valves is connected with c port, the b port of third triple valve is connected with c port, and unbalanced pulse pump takes out indicator
It takes into pipeline, closes pulse pump, then the b port of the second triple valve is connected with c port, a port of third triple valve and c lead to
Mouth connection, fluid circuit form a closed circuit, open peristaltic pump, and seawater sample and indicator is driven to mix in the closed circuit
It closes, then successively opens three LED light, two photodiodes detect the light intensity of three LED light simultaneously respectively, record main optical path
Signal is I, and reference light paths signal is IReference；The concentration of the indicator is 0.5-10mmol/L, the mixture of seawater and indicator
Product ratio is 20:1-1000:1, calculates the absorbance and pH of mixed solution；
5) indicator is added again, measures the absorbance and pH of mixed solution, mixes it for the first time in indicator and seawater sample
Afterwards, the b port of the first triple valve is connected with c port, a port of the second triple valve is connected with c port, the b of third triple valve
Port connects connection with c port, and unbalanced pulse pump continuously adds and enters pipeline with the indicator of the medium volume of step 4)；Then
The b port of second triple valve is connected with c port, a port of third triple valve is connected with c port, unlatching peristaltic pump, indicator
It is mixed in pipeline with seawater, then successively opens three LED light, two photodiodes detect three LED light simultaneously respectively
Light intensity；Calculate the absorbance and pH of mixed solution；
6) correction of indicator interference, using absorbance as x-axis, pH is y-axis, the equal absorption wave that will be measured in step 4) and step 5)
The absorbance of strong point and the pH measured twice do straight line, and the y value obtained as x=0 is seawater pH value itself.
2. a kind of circulation type original position high-precision seawater pH measurement method according to claim 1, which is characterized in that the sea
Filtering head is arranged in the water inlet of water water inlet pipe, and the filtering head is stainless steel or plastics, and aperture is 0.45-5.0 μm.
3. a kind of circulation type original position high-precision seawater pH measurement method according to claim 1, which is characterized in that the finger
Show agent bag and fluid circuit is the polytetrafluoroethylene material for completely cutting off air, the indicator bag body product is 200-1000ml, fluid
Pipeline outer diameter is 1-4mm, internal diameter 0.5-2mm.
4. a kind of circulation type original position high-precision seawater pH measurement method described in any one of -3 according to claim 1, special
Sign is that the filter set includes three optical filters, and the central wavelength of the optical filter is respectively that indicator acid-state maximum is inhaled
Receive wavelength at peak, wavelength and the equivalent absorbance point of indicator acid-state and alkali state at indicator alkali state maximum absorption band.
5. a kind of circulation type original position high-precision seawater pH measurement method described in any one of -3 according to claim 1, special
Sign is that the half-wave of the optical filter is wide within ± 5nm, using 14 or more A/D converters, noise when acquiring signal
Than being higher than 800:1.
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| CN108872214A (en) * | 2018-05-04 | 2018-11-23 | 大连理工大学 | Part CO is measured using absorbance2The experimental system visualizing and method of concentration of ordinary dissolution |
| CN109164731B (en) * | 2018-08-18 | 2024-09-03 | 中国海洋大学 | High-precision in-situ seawater pH sensor control system and control method |
| 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 |
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