CN115452751B - Residual chlorine detection method and device - Google Patents
Residual chlorine detection method and device Download PDFInfo
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Abstract
The application discloses a residual chlorine detection method, which comprises the following steps: collecting the temperature and the pH value of a sample to be detected in real time; detecting the sample to be detected by adopting a spectrophotometry method to obtain the actually measured residual chlorine concentration of the sample to be detected; and according to the temperature and the pH value, carrying out temperature and pH compensation on the actually measured residual chlorine concentration to obtain the compensated residual chlorine concentration of the sample to be detected. Through a temperature and pH compensation algorithm, the residual chlorine detection stability is better, and the accuracy is higher.
Description
Technical Field
The application relates to the technical field of water quality detection, in particular to a residual chlorine detection method and a residual chlorine detection device.
Background
Residual chlorine is also called free residual chlorine or active free chlorine or potential free chlorine, exists in the water body in the form of hypochlorous acid, hypochlorite ions and elementary chlorine, and total chlorine is also called total residual chlorine, namely the free residual chlorine and the combined chlorine of chloramine, organic chloramines and the like. Chlorine is added into water in the form of simple substance or chlorate, and is hydrolyzed to generate free chlorine, including water molecule-containing chlorine, hypochlorous acid and hypochlorite ions, and the relative proportion of the chlorine, the hypochlorous acid and the hypochlorite ions is determined by the pH value and the temperature of the water, and under the pH value of a common water body, the chlorine is mainly hypochlorous acid and hypochlorite ions.
Residual chlorine/total chlorine is an important index for monitoring the water quality of drinking water and medical wastewater, and when the content of the residual chlorine/total chlorine is too high, secondary pollution of the water quality is easily caused, carcinogenic substances are often generated, respiratory cells are damaged, and the like, so that the residual chlorine/total chlorine has certain harm effect on human health. Therefore, it is significant in water quality detection to effectively and accurately detect the total chlorine and the residual chlorine.
In the prior art, the residual chlorine is measured by an electrode method, a residual chlorine electrode is required to be positioned in a flowing water body for measurement during measurement, the flow velocity cannot be too high, impurities are attached to the electrode due to long-time use, the working state of the electrode is changed, and the precision of residual chlorine measurement is further influenced.
Compared with an electrode method, the method for measuring the residual chlorine by using the N, N-diethyl-1,4-phenylenediamine spectrophotometry (hereinafter referred to as DPD method) has good stability and high accuracy. GB18466-2005 discharge Standard of Water pollutants for medical structures states that the determination method of total residual chlorine in medical wastewater is DPD method. However, in the actual measurement process, the pH value and the temperature in the water are found to have great influence on the measurement, and no standard interference prevention method exists at present.
Based on the above problems, it is necessary to provide a technical solution to improve the stability and accuracy of the residual chlorine detection.
Disclosure of Invention
The application aims to provide a residual chlorine detection method and a residual chlorine detection device, which are used for improving the stability and accuracy of residual chlorine detection.
Based on the above object, the present application provides a residual chlorine detection method, comprising the steps of:
collecting the temperature and the pH value of a sample to be detected in real time;
detecting the sample to be detected by adopting a spectrophotometry method to obtain the actually measured residual chlorine concentration of the sample to be detected;
and according to the temperature and the pH value, carrying out temperature and pH compensation on the actually measured residual chlorine concentration to obtain the compensated residual chlorine concentration of the sample to be detected.
Further, the residual chlorine detection method further comprises the step of performing temperature and pH compensation on the measured residual chlorine concentration through a temperature and pH compensation algorithm, wherein the temperature and pH compensation algorithm is expressed as follows:
in the formula, C represents the compensated residual chlorine concentration of the sample to be detected, C represents the actually measured residual chlorine concentration, pH represents the pH value in the colorimetric reaction, pkt represents the colorimetric reaction equilibrium constant, and the colorimetric reaction equilibrium constant pkt satisfies the following formula:
wherein T is the temperature in the colorimetric reaction, K is the slope of the colorimetric reaction equilibrium constant, and B is the intercept of the colorimetric reaction equilibrium constant.
Further, the residual chlorine detection method also comprises the step of detecting the sample to be detected by adopting the spectrophotometry, and the steps are as follows:
taking a quantitative parallel operation reference solution, continuously carrying out colorimetric measurement on the parallel operation reference solution at a certain sampling frequency to obtain a series of reference signal values, and carrying out statistics on the series of reference signal values to obtain a first reference signal value;
taking a quantitative sample to be detected, mixing a quantitative color developing agent with the sample to be detected, and carrying out colorimetric measurement on the sample to be detected after the color developing agent is mixed;
carrying out colorimetric measurement on the sample to be measured after the mixed color developing agent is mixed continuously at a certain sampling frequency to obtain a series of absorption signal values, and drawing an absorbance curve of the sample to be measured according to the absorption signal values;
according to the absorbance curve, selecting N light absorption signal values behind the inflection point of the absorbance curve, and counting the N light absorption signal values to obtain a first light absorption signal value;
and calculating to obtain the measured residual chlorine concentration according to the first reference signal value and the first light absorption signal value.
Further, the residual chlorine detection method further comprises calculating the actually measured residual chlorine concentration by the following formula:
wherein c represents the measured residual chlorine concentration, ka represents the linear slope, ba represents the linear intercept, E0 represents the first reference signal value, and E1 represents the first absorbance signal value.
Further, the residual chlorine detection method also comprises a method for counting N light absorption signal values, and the steps are as follows:
setting a first proportion, removing larger N groups of data and smaller N groups of data in the N light absorption signal values according to the first proportion, and averaging the rest N-2N groups of data to obtain a first light absorption signal value.
The application still provides a chlorine residue detection device for detect the chlorine residue concentration of the sample that awaits measuring, the device includes:
the sample chamber is used for storing a quantitative sample to be detected;
a color reagent injection unit for injecting a color reagent into the sample chamber;
the temperature sensing unit is used for detecting the temperature of the sample to be detected;
the pH sensing unit is used for detecting the pH value of the sample to be detected in real time;
the spectrophotometer is used for detecting the sample to be detected and acquiring the actually measured residual chlorine concentration;
and the data processing unit is used for carrying out temperature and pH compensation on the actually measured residual chlorine concentration according to the temperature and the pH value to obtain the compensated residual chlorine concentration of the sample to be detected.
Further, the residual chlorine detection device comprises a data processing unit for calculating the compensated residual chlorine concentration through a temperature and pH compensation algorithm, wherein the temperature and pH compensation algorithm is expressed as follows:
in the formula, C represents the compensated residual chlorine concentration of the sample to be detected, C represents the actually measured residual chlorine concentration, pH represents the pH value in the colorimetric reaction, pkt represents the colorimetric reaction equilibrium constant, and the colorimetric reaction equilibrium constant pkt satisfies the following formula:
wherein T is the temperature in the colorimetric reaction, K is the slope of the colorimetric reaction equilibrium constant, and B is the intercept of the colorimetric reaction equilibrium constant.
Further, the residual chlorine detection device also comprises a parallel operation reference solution storage chamber for storing the parallel operation reference solution.
Further, the residual chlorine detection device further comprises:
the spectrophotometer continuously carries out colorimetric measurement on the parallel operation reference solution at a certain sampling frequency to obtain a series of reference signal values, and after the color developing agent is mixed with the sample to be measured, the spectrophotometer continuously carries out colorimetric measurement on the sample to be measured after the color developing agent is mixed with the sample to be measured at a certain sampling frequency to obtain a series of absorption signal values;
the data processing unit counts the series of reference signal values to obtain a first reference signal value;
the data processing unit is also used for drawing an absorbance curve of the sample to be detected according to the absorbance signal value, selecting N absorbance signal values behind the inflection point of the absorbance curve according to the absorbance curve, and counting the N absorbance signal values to obtain a first absorbance signal value;
and the data processing unit calculates and obtains the actually measured residual chlorine concentration according to the first reference signal value and the first light absorption signal value.
Further, the residual chlorine detection device also comprises a peristaltic pump, wherein the peristaltic pump is used for pumping the sample to be detected which exceeds the part of the constant volume scale line in the sample chamber through a conduit.
The application provides a chlorine residue detection method and device, through the temperature and the pH value of gathering the sample that awaits measuring in real time, application spectrophotometry carries out the colorimetric measurement with certain sampling frequency to the sample that awaits measuring in succession to draw the absorbance curve of sample and obtain actual measurement chlorine residue concentration, further carry out temperature and pH compensation with real-time temperature and pH to actual measurement chlorine residue concentration, obtain chlorine residue concentration after the compensation of the sample that awaits measuring. The detection stability of the residual chlorine is better, and the accuracy is higher.
Drawings
FIG. 1 is a flow chart of a method for detecting residual chlorine provided in an embodiment of the present application;
FIG. 2 is a flow chart of a method of spectrophotometry as provided in an embodiment of the present application;
FIG. 3 is a graph showing the absorbance curve of a sample to be measured;
FIG. 4 is a graph of residual chlorine concentration versus absorbance provided in this example;
FIG. 5 is a schematic structural diagram of a residual chlorine detection device provided in the embodiment of the present application;
FIG. 6 is a schematic structural diagram of a spectrophotometer provided by an embodiment of the present application;
FIG. 7 is a flow chart of a method for using the chlorine residual detection device provided in the embodiments of the present application.
Detailed Description
The present application is described in detail below with reference to specific embodiments shown in the drawings, but the embodiments do not limit the present application, and structural, methodological, or functional changes made by those skilled in the art according to the embodiments are included in the scope of the present application.
As shown in fig. 1, it shows a flow chart of a method for detecting residual chlorine provided in the embodiments of the present application, comprising the following steps:
collecting the temperature and the pH value of a sample to be detected in real time;
detecting a sample to be detected by adopting a spectrophotometry method to obtain the actually measured residual chlorine concentration of the sample to be detected;
and according to the temperature and the pH value of the sample to be detected, carrying out temperature and pH compensation on the actually measured residual chlorine concentration to obtain the compensated residual chlorine concentration of the sample to be detected.
The residual chlorine detection method provided by the application carries out temperature and pH compensation on the actually measured residual chlorine concentration, and the obtained compensated residual chlorine concentration is used as the residual chlorine concentration of a sample to be detected, so that the influence of the sample temperature and the pH value on the detection of the residual chlorine concentration of the sample is avoided.
As shown in fig. 2, which illustrates a flowchart of a method of spectrophotometry provided in an embodiment of the present application, the spectrophotometry includes at least the following steps:
and S11, taking a quantitative parallel operation reference solution, continuously carrying out colorimetric measurement on the parallel operation reference solution at a certain sampling frequency to obtain a series of reference signal values, and carrying out statistics on the series of reference signal values to obtain a first reference signal value.
As an alternative implementation, taking a quantitative parallel operation reference solution to perform colorimetric measurement specifically may be: taking a quantitative parallel operation reference solution, carrying out colorimetric measurement, recording reference signal values E01 and E02 …, simultaneously recording the temperature T and the pH value, recording 200 reference signal values once every 100 milliseconds, and counting the 200 reference signal values to obtain a first reference signal value.
The parallel operation reference solution is a sample which does not contain the component to be measured and is used for being processed with the sample to be measured under the same condition, the parallel operation reference solution can have certain absorption to light, the absorption part of the parallel operation reference solution is deducted through parallel operation reference before color comparison, the measurement result is close to the absorption value of the component to be measured to the light, and therefore the concentration of the component to be measured can be obtained through correcting an absorbance curve.
In this embodiment, the sample to be measured is usually a colorless transparent liquid, and distilled water may be used as the parallel operation reference solution, and the absorption signal data of the parallel operation reference solution is recorded and used as the reference signal.
And S12, taking a quantitative sample to be measured, mixing a quantitative color developing agent with the sample to be measured, and carrying out colorimetric measurement on the sample to be measured after the color developing agent is mixed.
And S13, continuously carrying out colorimetric measurement on the sample to be detected after the color developing agent is mixed at a certain sampling frequency, obtaining a series of absorption signal values, and drawing an absorbance curve of the sample to be detected according to the absorption signal values.
As an optional implementation manner, taking a certain amount of a sample to be measured to perform colorimetric measurement specifically may be: taking a quantitative sample to be detected, adding a quantitative buffer solution into the sample to be detected to adjust the pH value (the adjusted pH value can be about 6.5), adding a color developing agent into the sample to be detected to perform a mixing reaction, and beginning to record an absorption signal value E1 1 ，E1 2 …, the temperature T and the pH value are recorded simultaneously, the recording is continuously carried out once every 100 milliseconds, the time is used as an abscissa, the signal value is used as an ordinate, and an absorbance curve is drawn.
The color developing agent and the sample to be measured are subjected to color development after mixed reaction, before full mixed reaction, the color distribution of the sample is not uniform, the measured light absorption signal value is in a continuous change stage, the light absorption signal value obtained in the stage is not stable, and if the light absorption signal value in the stage is adopted, the measurement result may have large errors.
As an alternative implementation manner, the present application finds a signal point where the derivative tends to 0 by deriving a series of obtained light absorption signal values, and takes the signal point as an inflection point where the signal value tends to be stable. After the inflection point is reached, the color developing agent and the sample to be measured are considered to be fully mixed and reacted, the color of the sample is uniformly distributed, the subsequently measured light absorption signal value tends to be stable, and the continuously collected light absorption data can accurately reflect the residual chlorine data of the sample.
For example, as shown in fig. 3, which is a graph of absorbance of a sample to be measured in an experiment, a color developing agent is added at 0 second, the color developing agent and the sample to be measured react to develop color, the measured light intensity gradually decreases, and the absorbance curve reaches an inflection point in about 20 seconds and tends to be stable.
And S14, selecting N light absorption signal values behind the inflection point of the absorbance curve according to the absorbance curve, and counting the N light absorption signal values to obtain a first light absorption signal value. Wherein, N is the natural number, represents the sample quantity that is used for the photic signal value of statistics, and the concrete numerical value of N can set up according to actual demand.
As an alternative implementation manner, step S14 may be: and finding an inflection point with stable signal value, and deriving the data, wherein the inflection point is obtained when the derivative approaches 0. 20000 milliseconds of data, i.e. 200 data, are measured continuously after the inflection point. And counting the 200 light absorption signal values to obtain a first light absorption signal value.
And S15, calculating the actually measured residual chlorine concentration according to the sum of the first reference signal and the first light absorption signal value.
Wherein, the actually measured residual chlorine concentration formula is as follows:
wherein c represents the measured residual chlorine concentration, ka represents the linear slope, ba represents the linear intercept, E0 represents the first reference signal value, and E1 represents the first absorbance signal value.
As shown in fig. 4, as an alternative implementation manner, this embodiment provides a graph of residual chlorine concentration versus absorbance, where the residual chlorine concentration and the absorbance are in a linear relationship, and the relationship is as follows: and Y = 6.094X +0.023, and substituting the first reference signal value and the first light absorption signal value into a residual chlorine concentration-light absorption curve equation according to the first reference signal value and the first light absorption signal value measured by the experiment to obtain the corresponding actually measured residual chlorine concentration.
As an alternative implementation manner, the method for counting the reference signal and the absorbance signal value may be: and setting a first proportion, removing the larger N groups of data and the smaller N groups of data in the N light absorption signal values according to the first proportion, and averaging the rest N-2N groups of data to obtain a first light absorption signal value.
For example, the first ratio may be set to 20%, and the data of the larger 20% and the data of the smaller 20% of the 200 absorbance signal values in the reference signal are removed according to the first ratio, and the remaining 120 sets of data are averaged to obtain the first absorbance signal value E0 of the reference signal; according to the first proportion, the larger 20% data and the smaller 20% data of 200 absorption signal values after the inflection point in the absorption signal are removed, and the average value of the rest 120 groups of data is obtained to obtain a first absorption signal value E1 of the absorption signal.
The first proportion is set, partial pole data are removed according to the first proportion, and then the average value is taken, so that the influence of the pole data can be eliminated.
This application improves the efficiency of adjusting pH through adding quantitative buffer solution in the sample that awaits measuring, however, to the sample that awaits measuring of difference, its self pH is different, adds quantitative buffer solution after, and the best pH range deviation that environmental pH value probably still reacts with the colour development agent is great (for example, the pH value after adding quantitative buffer solution is great with 6.5 deviations), consequently, this application gets rid of the influence of pH value to chlorine residue detection through pH compensation.
As an alternative implementation manner, after the measured residual chlorine concentration is obtained by the spectrophotometry method, the compensated residual chlorine concentration can be obtained by a temperature and pH compensation algorithm, which is expressed as follows:
in the formula, C represents the compensated residual chlorine concentration of a sample to be detected, C represents the actually measured residual chlorine concentration, pH represents the pH value in the colorimetric reaction, pkt represents the colorimetric reaction equilibrium constant, and the colorimetric reaction equilibrium constant pkt satisfies the following formula:
wherein T is the temperature in the colorimetric reaction, K is the slope of the colorimetric reaction equilibrium constant, and B is the intercept of the colorimetric reaction equilibrium constant.
To sum up, the chlorine residue detection method that this application embodiment provided, through the temperature and the pH value of gathering the sample that awaits measuring in real time, adopt spectrophotometry right the sample that awaits measuring detects, acquires actual measurement chlorine residue concentration, combines the temperature and the pH value of gained, carries out temperature and pH compensation to actual measurement chlorine residue concentration, obtains the compensation back chlorine residue concentration of the sample that awaits measuring, and the influence of temperature and pH to spectrophotometry chlorine residue concentration detection has been eliminated to a certain extent for chlorine residue detection stability is better, and the accuracy is higher.
As shown in fig. 5, it shows a schematic structural diagram of a residual chlorine detection device provided by the present application, the device is used for detecting the residual chlorine concentration of a sample to be detected, and the device includes:
the sample room 21 is used for storing a quantitative sample to be detected, and the sample room 21 is provided with a constant volume scale mark.
As an optional implementation manner, when a sample to be measured is injected into the sample chamber 21, the reference is used for referring to the amount of the injected sample, if the injected sample exceeds the constant volume scale, the reference may also be used as a reference for discharging an excessive sample, and the reference to the constant volume scale can ensure that the amount of the sample measured each time is the same, thereby avoiding errors caused thereby.
A developer injecting unit 22 for injecting a developer into the sample chamber 21.
As an optional implementation mode, the color developing agent can be N, N-diethyl-1,4-phenylenediamine, the color developing agent reacts with the chlorine-containing sample to be tested to develop red color after being combined, and the pH value of the sample to be tested needs to be adjusted to be about 6.5 before the color developing agent is added.
And the temperature sensing unit 23 is used for detecting the temperature of the sample to be detected in real time.
And the pH sensing unit 24 is used for detecting the pH value of the sample to be detected in real time.
And the spectrophotometer 25 is used for detecting the sample to be detected and acquiring the actually measured residual chlorine concentration.
According to the residual chlorine detection method provided by the application, light penetrating through a sample to be detected is measured through the spectrophotometer 25, the absorbance is detected, the absorbance is related to the residual chlorine concentration of the sample to be detected, the reference signal value and the absorption signal value are recorded by the spectrophotometer 25 once every 100 milliseconds, the time is taken as an abscissa, the signal value is taken as an ordinate, and a signal value curve is drawn. And finding an inflection point with stable signal value, and deriving the data, wherein the inflection point is obtained when the derivative approaches 0. 20000 milliseconds of data, i.e. 200 data, are measured continuously after the inflection point.
For the obtained data, a first ratio of 20% is set, and according to the first ratio, the data of the larger 20% and the data of the smaller 20% of the 200 absorbance signal values in the reference signal are removed, and the remaining 120 sets of data are averaged to obtain a first reference signal value E0. According to the first ratio of 20%, the data of the larger 20% and the data of the smaller 20% of the 200 values of the absorption signal are removed, and the remaining 120 sets of data are averaged to obtain the first absorption signal value E1.
The formula of the measured residual chlorine concentration is as follows:
wherein c represents the measured residual chlorine concentration, ka represents the linear slope, ba represents the linear intercept, E0 represents the first reference signal value, and E1 represents the first absorbance signal value.
As an alternative implementation, the spectrophotometer 25 may be configured as shown in fig. 6.
The spectrophotometer 25 includes a light source 251 and a detector 252, the light source 251 is installed on one side of the light-transmitting portion of the sample chamber 21, the light source 251 emits light to penetrate the sample chamber 21 and the sample to be measured irradiates on the detector 252. The detector 252 is installed on the other side of the light-transmitting part of the sample chamber 21, and the detector 252 measures the light transmitted by the light source 251 through the sample chamber 21 and the sample to be measured at a certain frequency to obtain an absorbance signal value.
Wherein the light source 251 may be an LED and the detector 252 may measure the light signal every 100 milliseconds.
And the data processing unit 26 is used for carrying out temperature and pH compensation on the actually measured residual chlorine concentration according to the temperature and the pH value to obtain the compensated residual chlorine concentration of the sample to be measured.
Wherein the temperature and the pH are measured, transmitted and stored in the data processing unit 26 in real time by the temperature sensing unit 23 and the pH sensing unit 24.
The data processing unit 26 calculates the compensated residual chlorine concentration by means of a temperature and pH compensation algorithm, which is expressed as follows:
in the formula, C represents the compensated residual chlorine concentration of a sample to be detected, C represents the actually measured residual chlorine concentration, pH represents the pH value in the colorimetric reaction, pkt represents the colorimetric reaction equilibrium constant, and the colorimetric reaction equilibrium constant pkt satisfies the following formula:
wherein T is the temperature in the colorimetric reaction, K is the slope of the colorimetric reaction equilibrium constant, and B is the intercept of the colorimetric reaction equilibrium constant.
As an alternative implementation manner, the residual chlorine detection device provided in the embodiment of the present application further includes a parallel operation reference solution storage chamber 27 for storing a parallel operation reference solution.
The sample to be measured is usually a colorless transparent liquid, and as an alternative implementation mode, distilled water can be selected for colorimetric measurement and recording absorption signal data to be used as a reference signal.
The parallel operation reference solution storage chamber 27 allows the parallel operation reference solution to be injected into the sample chamber 21, the colorimetric measurement to be performed, and the absorption signal data of the parallel operation reference solution to be recorded for correcting the absorbance curve of the sample to be measured.
As an optional implementation manner, the spectrophotometer 25 continuously performs colorimetric measurement on the parallel operation reference solution at a certain sampling frequency to obtain a series of reference signal values, and after the color developing agent is mixed with the sample to be measured, the spectrophotometer 25 continuously performs colorimetric measurement on the sample to be measured after the color developing agent is mixed at a certain sampling frequency to obtain a series of absorption signal values.
The data processing unit 26 performs statistics on a series of reference signal values to obtain a first reference signal value.
The data processing unit 26 also draws an absorbance curve of the sample to be measured according to the absorbance signal values, selects N absorbance signal values located after the inflection point of the absorbance curve according to the absorbance curve, and counts the N absorbance signal values to obtain a first absorbance signal value.
And the data processing unit 26 calculates and obtains the measured residual chlorine concentration according to the first reference signal value and the first light absorption signal value.
As an optional implementation manner, the residual chlorine detection device provided in the embodiment of the present application further includes a peristaltic pump 28, and the peristaltic pump 28 is configured to pump, through a conduit, a sample to be detected in the sample chamber 21 that exceeds the portion of the constant volume scale line.
As shown in fig. 7, it shows a flow chart of a method for using a residual chlorine detection device provided in the embodiment of the present application, and the using method specifically includes the following steps:
the sample chamber was filled with quantitative parallel-operating reference solutions:
the parallel operation reference solution storage chamber injects the parallel operation reference solution into the sample chamber until the scale mark is reached, and if the parallel operation reference solution exceeds the scale mark, the redundant part is pumped by a peristaltic pump.
Colorimetric measurements were taken of the reference solutions operating in parallel and the data were recorded.
As an alternative implementation, the colorimetric measurement of a reference solution is carried out in parallel, and the reference signal value E0 is recorded by a spectrophotometer 1 ，E0 2 … simultaneously records the temperature by the temperature sensing unit and the pH value by the pH sensing unit, records 200 reference signal values once every 100 milliseconds, and draws a signal value curve by taking time as an abscissa and the signal value as an ordinate.
The parallel operating reference solution was drained and the sample chamber was cleaned.
Injecting a quantitative sample to be tested into a sample chamber:
and injecting a sample to be detected into the sample chamber to the scale mark, and if the sample exceeds the scale mark, pumping the redundant part by a peristaltic pump.
Adding quantitative buffer solution to adjust the pH value, and injecting a color developing agent into a sample chamber:
the color developing agent injection unit injects quantitative color developing agent into the sample chamber, and the color developing agent is mixed with the sample to be detected for reaction.
And carrying out colorimetric measurement on the sample to be measured, and recording data.
As an optional implementation manner, colorimetric measurement is performed on a sample to be measured: after the mixing reaction starts, the spectrophotometer starts to record the light absorption signal value E1 1 ，E1 2 … simultaneously recording temperature by the temperature sensing unit and pH value by the pH sensing unit, recording once every 100 milliseconds, and drawing a signal value curve by taking time as an abscissa and signal value as an ordinate; finding an inflection point with a stable signal value, deriving data, and taking the inflection point when the derivative approaches to 0; 20000 milliseconds of data, i.e. 200 data, are measured continuously after the inflection point.
The data processing unit processes the recorded data to obtain a first reference signal value and a first absorption signal value.
As an optional implementation manner, the data processing unit processes the recording data: setting a first proportion of 20%, removing the larger 20% data and the smaller 20% data in 200 light absorption signal values after the inflection point in the reference signal according to the first proportion of 20%, and averaging the rest 120 groups of data to obtain a first reference signal value E0; according to the first ratio of 20%, the data of the larger 20% and the data of the smaller 20% of 200 values of the absorption signal after the inflection point are removed, and the remaining 120 sets of data are averaged to obtain the first absorption signal value E1.
And the data processing unit calculates the actually measured residual chlorine concentration according to the sum of the first reference signal and the first light absorption signal value. The formula is as follows:
wherein c represents the measured residual chlorine concentration, ka represents the linear slope, ba represents the linear intercept, E0 represents the first reference signal value, and E1 represents the first absorbance signal value.
And the data processing unit calculates the compensated residual chlorine concentration through a temperature and pH compensation algorithm according to the recorded temperature T and the pH value. The formula is as follows:
in the formula, C represents the compensated residual chlorine concentration of the sample to be detected, C represents the actually measured residual chlorine concentration, pH represents the pH value in the colorimetric reaction, pkt represents the colorimetric reaction equilibrium constant, and the colorimetric reaction equilibrium constant pkt satisfies the following formula:
wherein T is the temperature in the colorimetric reaction, K is the slope of the colorimetric reaction equilibrium constant, and B is the intercept of the colorimetric reaction equilibrium constant.
The sample is drained and the sample chamber is cleaned in preparation for the next test.
The residual chlorine detection method provided by the embodiment of the application continuously carries out colorimetric measurement on a sample to be detected by using a spectrophotometry at a certain sampling frequency through collecting the temperature and the pH value of the sample to be detected in real time, draws an absorbance curve of the sample to obtain the actually measured residual chlorine concentration, and further carries out temperature and pH compensation on the actually measured residual chlorine concentration by using the real-time temperature and the pH value to obtain the compensated residual chlorine concentration of the sample to be detected. The detection stability of the residual chlorine is better and the accuracy is higher.
While the present disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes, modifications, substitutions, combinations and simplifications may be made without departing from the spirit and scope of the present disclosure and the appended claims.
Claims (8)
1. A residual chlorine detection method is characterized by comprising the following steps:
collecting the temperature and the pH value of a sample to be detected in real time;
detecting the sample to be detected by adopting a spectrophotometry method to obtain the actually measured residual chlorine concentration of the sample to be detected;
according to the temperature and the pH value, carrying out temperature and pH compensation on the actually measured residual chlorine concentration to obtain the compensated residual chlorine concentration of the sample to be detected;
performing temperature and pH compensation on the measured residual chlorine concentration through a temperature and pH compensation algorithm, wherein the temperature and pH compensation algorithm is expressed as follows:
C=c*(1+10 (pH-7) /10 pkt )；
in the formula, C represents the compensated residual chlorine concentration of the sample to be detected, C represents the actually measured residual chlorine concentration, pH represents the pH value in the colorimetric reaction, pkt represents the colorimetric reaction equilibrium constant, and the colorimetric reaction equilibrium constant pkt satisfies the following formula:
lnpkt=K*1/(T-298)+B；
wherein T is the temperature in the colorimetric reaction, K is the slope of the colorimetric reaction equilibrium constant, and B is the intercept of the colorimetric reaction equilibrium constant.
2. The method for detecting residual chlorine according to claim 1, wherein the step of detecting the sample to be detected by the spectrophotometry comprises the following steps:
taking a quantitative parallel operation reference solution, continuously carrying out colorimetric measurement on the parallel operation reference solution at a certain sampling frequency to obtain a series of reference signal values, and carrying out statistics on the series of reference signal values to obtain a first reference signal value;
taking a quantitative sample to be detected, mixing a quantitative color developing agent with the sample to be detected, and carrying out colorimetric measurement on the sample to be detected after the color developing agent is mixed;
carrying out colorimetric measurement on the sample to be measured after the mixed color developing agent is mixed continuously at a certain sampling frequency to obtain a series of absorption signal values, and drawing an absorbance curve of the sample to be measured according to the absorption signal values;
according to the absorbance curve, selecting N light absorption signal values behind the inflection point of the absorbance curve, and counting the N light absorption signal values to obtain a first light absorption signal value;
and calculating to obtain the measured residual chlorine concentration according to the first reference signal value and the first light absorption signal value.
3. The residual chlorine detection method according to claim 2, wherein the formula for calculating the measured residual chlorine concentration is as follows:
c=Ka*log( E0/ E1)+Ba
wherein c represents the measured residual chlorine concentration, ka represents the linear slope, ba represents the linear intercept, E0 represents the first reference signal value, and E1 represents the first absorbance signal value.
4. The method for detecting residual chlorine according to claim 2, wherein the method for counting the N absorbance signals comprises the following steps:
setting a first proportion, removing larger N groups of data and smaller N groups of data in the N light absorption signal values according to the first proportion, and averaging the rest N-2N groups of data to obtain a first light absorption signal value.
5. The utility model provides a chlorine residue detection device for detect the chlorine residue concentration of the sample that awaits measuring, its characterized in that, the device includes:
the sample chamber is used for storing a quantitative sample to be detected;
a color reagent injection unit for injecting a color reagent into the sample chamber;
the temperature sensing unit is used for detecting the temperature of the sample to be detected;
the pH sensing unit is used for detecting the pH value of the sample to be detected in real time;
the spectrophotometer is used for detecting the sample to be detected to obtain the actually measured residual chlorine concentration;
the data processing unit is used for carrying out temperature and pH compensation on the actually measured residual chlorine concentration according to the temperature and the pH value to obtain the compensated residual chlorine concentration of the sample to be detected;
the data processing unit calculates the compensated residual chlorine concentration by a temperature and pH compensation algorithm, which is expressed as follows:
C=c*(1+10 (pH-7) /10 pkt )；
in the formula, C represents the compensated residual chlorine concentration of the sample to be detected, C represents the actually measured residual chlorine concentration, pH represents the pH value in the colorimetric reaction, pkt represents the colorimetric reaction equilibrium constant, and the colorimetric reaction equilibrium constant pkt satisfies the following formula:
lnpkt=K*1/(T-298)+B；
wherein T is the temperature in the colorimetric reaction, K is the slope of the colorimetric reaction equilibrium constant, and B is the intercept of the colorimetric reaction equilibrium constant.
6. The residual chlorine detecting device according to claim 5, further comprising a parallel operation reference solution storage chamber for storing a parallel operation reference solution.
7. The residual chlorine detecting apparatus according to claim 6,
the spectrophotometer continuously carries out colorimetric measurement on the parallel operation reference solution at a certain sampling frequency to obtain a series of reference signal values, and after the color developing agent is mixed with the sample to be measured, the spectrophotometer continuously carries out colorimetric measurement on the sample to be measured after the color developing agent is mixed with the sample to be measured at a certain sampling frequency to obtain a series of absorption signal values;
the data processing unit counts the series of reference signal values to obtain a first reference signal value;
the data processing unit is also used for drawing an absorbance curve of the sample to be detected according to the absorbance signal value, selecting N absorbance signal values behind an inflection point of the absorbance curve according to the absorbance curve, and counting the N absorbance signal values to obtain a first absorbance signal value;
and the data processing unit calculates and obtains the actually measured residual chlorine concentration according to the first reference signal value and the first light absorption signal value.
8. The residual chlorine detection device according to claim 5, further comprising a peristaltic pump for pumping the sample to be detected in the sample chamber beyond the portion of the constant volume scale line through a conduit.
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| CN117524339B (en) * | 2024-01-04 | 2024-03-19 | 攀枝花市东区生态环境监测站 | Method and system for measuring residual chlorine |
| CN117990294A (en) * | 2024-04-02 | 2024-05-07 | 江苏泷洋科技有限公司 | Chemical industry pressure vessel leak detection device |
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