CN112798585A - Color development tube for on-site determination of ferrous concentration in water and detection method - Google Patents
Color development tube for on-site determination of ferrous concentration in water and detection method Download PDFInfo
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Abstract
The invention relates to a color development tube for on-site determination of ferrous concentration in water and a detection method, belonging to the field of water quality detection and monitoring. The color developing tube comprises a glass color developing tube and a color developing tube cover, wherein a reagent groove is arranged in the cover, the reagent groove and the cover are integrally formed, a solid mixed color developing agent is filled in the reagent groove, and a plastic sealing film capable of being torn is arranged at the opening of the reagent groove. Adding 1:1 hydrochloric acid into a glass color development tube, and then injecting a water sample into the glass color development tube to a position of a 20mL scale mark; tearing a plastic sealing film of a reagent notch in a cover of the color development tube, pouring the solid mixed color development agent in the reagent groove into the sampled glass color development tube, screwing the cover, repeatedly oscillating to fully and uniformly mix the solid mixed color development agent with a water sample, dissolving, and then standing to finish color development reaction; and (4) carrying out on-site detection by adopting a portable spectrophotometer to obtain the concentration of the ferrous iron in the water sample. The color development tube has low cost and can be produced in batch; the on-site detection method has the advantages of high accuracy, good stability and strong timeliness.
Description
Technical Field
The invention relates to a color development tube for on-site determination of ferrous concentration in water and an on-site detection method, which are mainly applied to the field of water quality detection and monitoring.
Background
The iron element is a common element in nature, the iron ions in the water environment mainly exist in a ferrous form and a ferric form, and different valence states of iron determine the environmental behavior, the bioavailability and the biotoxicity of the iron ions in an ecological system, so that the accurate determination of the valence states of the iron ions in the water environment has very important significance. In the process of collecting, storing and transporting a water sample, the valence state of iron ions is easy to change, and ferrous iron in the water is easy to be oxidized into ferric iron when contacting with air; under the action of microorganisms and other redox substances, ferrous iron and ferric iron are also easy to be mutually converted in the process of storing and transporting a water sample, so that the accurate determination of the ferrous iron concentration in water is influenced.
The published journal literature and standard specification mainly measure the ferrous content in water in a laboratory, the buffer solution and the color developing agent used in each technical method are slightly different, but water samples need to be collected and transported back to the laboratory, and meanwhile, the liquid color developing agent and the buffer solution need to be prepared in the laboratory, and finally, a desktop instrument in the laboratory is used for completing analysis and test. However, the liquid color developing agent is prepared from a high-purity solid medicine and a solvent, the concentration is low, and the solvent contains water or an acid-base reagent, so that the chemical components of the color developing agent/buffer solution are easy to change, the normal color developing reaction is influenced, and the accuracy of a detection result is further influenced. In addition, the effective period of the liquid reagent is about one week, even some liquid reagents are required to be prepared at present, and individual liquid reagents are also required to be stored in a dark place, so that the liquid reagents are difficult to store. Therefore, the laboratory tests for ferrous content in water have the following disadvantages: firstly, a water sample needs to be transported back to a laboratory for analysis, and valence state change easily occurs between ferrous iron and ferric iron in water in the processes of sample collection, storage and transportation, so that the ferrous iron concentration is difficult to accurately determine; secondly, the liquid color developing agent used in the laboratory test is not easy to store and needs to be prepared regularly, and the reagent consumption is large; sample collection, storage and transportation need sample bottles, protective agents, transportation cost and other related expenses, and the comprehensive cost of laboratory testing is high; and thirdly, after the sample is collected, the transportation time and the laboratory sample sending analysis period are longer, and the analysis and test timeliness is poorer.
Some journal literatures report on-site rapid detection methods for ferrous iron in water, mainly adopt visual colorimetry, the method does not need instruments and equipment, the detection speed is high, but the graduation value of the color scale of the visual colorimetry established in the literature is 1/2 color scale units, and the resolution and the accuracy of the method are poor.
Disclosure of Invention
The invention provides a color developing tube for measuring ferrous concentration in water and a field detection method, which aim to quickly and accurately measure the ferrous ion content in water and solve the problems that the valence state of the ferrous ions in water is easy to change in the sampling, storing and transporting processes and the ferrous content is difficult to accurately measure.
The invention discloses a color development tube for on-site testing of ferrous concentration in water containing a solid mixed color development agent, wherein the adopted solid mixed color development agent is a high-purity solid medicine, and the quality guarantee period is more than 12 months.
A color developing tube for on-site measuring the ferrous concentration in water is composed of a glass color developing tube with a reagent tank, a cover for said color developing tube, and a torn plastic sealing film in the mouth of said reagent tank.
The glass color developing tube is made of transparent hard glass, the cross section of the glass color developing tube can be round, rectangular or square and the like, and the shape of the glass color developing tube is determined according to the shape of the cell groove of the portable spectrophotometer.
The diameter of the glass developing tube is 24mm, the wall thickness is 1.2mm, and the height is 95 mm.
The mouth of the glass color developing tube is a spiral mouth, so that the cover can be screwed or opened conveniently.
The diameter of the spiral opening of the glass developing tube is smaller than that of the glass developing tube, and the height of the spiral opening of the glass developing tube is 9 mm.
The glass color development tube is provided with 20mL of scale marks.
The color development tube cover is circular, is made of plastic, has the outer diameter consistent with the diameter of the glass color development tube, and has the height of 10 mm.
The color development tube is characterized in that a cylindrical solid mixed color development agent reagent groove is arranged in the center of the inner part of the cover of the color development tube, the reagent groove and the cover are integrally formed, and the material of the reagent groove is plastic.
The diameter of the reagent groove is 5mm, the height of the reagent groove is 4mm, a plastic sealing film which can be torn is arranged on a reagent groove opening, and a solid mixed color developing agent is arranged in the reagent groove.
The solid mixed color developing agent comprises the following components: 0.012g of phenanthroline hydrochloride monohydrate, 0.075g of glycine and 0.005g of aminotriacetic acid.
The invention also discloses a technical method for carrying out field detection by adopting the color development tube for measuring the ferrous concentration in water on site.
A field detection method for the concentration of ferrous iron in water adopts the color development tube for the field detection of the concentration of ferrous iron in water, which is mainly divided into four steps of calibration curve preparation (including 'detection method establishment'), sampling, color development reaction and field test, and comprises the following specific operation steps:
(1) sampling: adding 4 drops of 1:1 hydrochloric acid (1 volume of concentrated hydrochloric acid (mass concentration is 36-38%) and 1 volume of water mixed hydrochloric acid) into a glass color development tube, and then injecting a water sample into the glass color development tube to a 20mL scale mark position;
(2) and (3) color development reaction: tearing a plastic sealing film of a reagent notch in a cover of the color development tube, pouring the solid mixed color development agent in the reagent groove into the sampled glass color development tube, screwing the cover, oscillating repeatedly to fully and uniformly mix the solid mixed color development agent with a water sample, dissolving, and standing for 4-6 minutes to complete color development reaction;
(3) and (3) field test: and (4) carrying out on-site detection by adopting a portable spectrophotometer to obtain the concentration of the ferrous iron in the water sample.
In the step (1), when the water sample is turbid, the water sample is firstly filtered through a 0.45-micrometer filter membrane.
In the step (2), the frequency of repeated oscillation is more than 3 times, for example, 3-5 times, the water sample can fully dissolve the residual solid mixed color developing agent in the reagent tank in the oscillation process, the oscillation time is 8-15 seconds each time, so that the water sample in the glass color developing tube and the solid color developing agent are fully mixed and dissolved, and then the time is waited for 4-6 minutes, so that the color developing reaction is completed.
In the step (3), the method for carrying out on-site detection by adopting the portable spectrophotometer comprises the following steps:
1) preparing a calibration curve, and establishing a detection method:
firstly, preparing a series of ferrous standard solutions, taking a standard solution sample according to the step (1) and the step (2) in the method, carrying out color development reaction, then testing by adopting a portable spectrophotometer to generate a calibration curve and a linear equation, storing a test program, and establishing a detection method;
2) on-site detection of a water sample: sampling a water sample and carrying out a color reaction according to the step (1) and the step (2) in the method; and (3) carrying out field test on the water sample which finishes the color reaction after the blank reagent is used for zero adjustment by adopting a detection method stored in the portable spectrophotometer.
In the step 1), a calibration curve is prepared, and a field detection method is established, wherein the specific process comprises the following steps:
step one, preparing a standard solution: preparing a series of standard solutions with ferrous concentration of 0.00, 0.025, 0.05, 0.10, 0.20, 0.50 and 1.00mg/L by using ammonium ferrous sulfate hexahydrate (super pure);
step two, transferring a standard solution: adding 4 drops of 1:1 hydrochloric acid into a glass color development tube, and then respectively injecting 20mL of standard solutions with different concentrations;
step three, color reaction: tearing a plastic sealing film of a reagent notch in a cover of the color development tube, pouring the solid mixed color development agent in the reagent groove into the sampled glass color development tube, screwing the cover, oscillating repeatedly to fully and uniformly mix the solid mixed color development agent with a water sample, dissolving, and standing for 4-6 minutes to finish color development reaction;
fourthly, field test: a user program is newly established in a portable spectrophotometer, a mode selects a single wavelength, an analysis wavelength is 515nm, then a standard measurement or reading step is carried out, a blank sample of 0.00mg/L is taken as a reference solution to carry out instrument zero setting, then series standard solution samples of ferrous concentration of 0.00, 0.025, 0.05, 0.10, 0.20, 0.50 and 1.00mg/L are sequentially placed in a colorimetric hole to carry out absorbance measurement, the concentration value of the standard solution is firstly input into the program before each standard solution sample is placed, a calibration curve is automatically generated by the instrument after the absorbance measurement is finished, a linear equation is calculated, and finally a test program is stored.
When the water sample is tested in a short time (generally within 2 days) after the detection method is established, only the detection method stored in the portable spectrophotometer needs to be directly called, and the step of preparing the calibration curve is not needed again.
When the test is carried out for the first time or the test is not carried out again for a long time (generally more than 3 days), the calibration curve needs to be prepared again to establish a detection method.
In the step 2), the field detection of the water sample comprises the following specific steps:
first step, sampling: adding 4 drops of 1:1 hydrochloric acid into a glass color development tube, and then injecting 20mL of water sample to be detected;
and step two, color reaction: tearing a plastic sealing film of a reagent notch in a cover of the color development tube, pouring the solid mixed color development agent in the reagent groove into the sampled glass color development tube, screwing the cover, oscillating repeatedly to fully and uniformly mix the solid mixed color development agent with a water sample, dissolving, and standing for 4-6 minutes;
step three, field detection: a newly established detection method is called out from a user program of the portable spectrophotometer, a blank sample (a 0.00mg/L standard solution sample) is used as a reference for instrument zero setting, then a glass color developing tube of a water sample to be detected which finishes color development reaction is placed in a color comparison hole of the portable spectrophotometer, and the concentration of ferrous iron in the water sample to be detected is read.
The technical design characteristics and the functions of the invention are as follows:
the cover structure of the glass developing tube has unique design. The inside of the cover of the invention is designed with a solid reagent storage groove with the diameter of 5mm and the height of 4mm, and the reagent notch is provided with a plastic sealing film which can be torn open, so that the solid mixed color developing agent can be effectively preserved, and the solid mixed color developing agent can be conveniently released when in use.
Secondly, the invention adopts proper solid mixed color developing agent components and proportion. Different color developing agents have different color developing sensitivity to ferrous ions in water and different influence degrees by other elements in the water; the different proportions of the solid mixed color developing agent influence the accuracy and sensitivity of the determination of ferrous ions in water. The solid mixed color developing agent component and the proportion of each component of the solid mixed color developing agent have sensitive response to ferrous ions in water, the color is stable within 4 hours after color development, the interference of other common elements in water can be effectively masked in the color development process, and the solid mixed color developing agent is sealed in a reagent groove in the cover of the color development pipe, can be stored for a long time, and is very suitable for rapidly and quantitatively determining the ferrous concentration in water on site.
And thirdly, the release mode (color reaction) of the solid mixed color developing agent in the field detection method of the concentration of the ferrous iron in the water is the technical key point of the invention. According to the invention, a plastic sealing film of a reagent notch in a cover of a color development tube needs to be torn, a solid mixed color development agent in a reagent tank is poured into a glass color development tube which is subjected to sampling, the cover is screwed, the cover is forcefully and repeatedly oscillated for 3-5 times, each oscillation time is 8-15 seconds, and a water sample can fully dissolve the residual solid mixed color development agent in the reagent tank in the oscillation process, so that the color development effect is ensured. If the oscillation is insufficient, the solid mixed color developing agent may remain in the reagent tank, or the color development reaction of the solid mixed color developing agent may be insufficient, which may affect the accuracy of the detection of the ferrous iron concentration in water.
If the solid mixed developer is released in the reagent tank without using the solid mixed developer arranged in the color developing tube cover, the solid mixed developer is released in a powder pillow bag mode, namely, the prepared solid mixed developer is filled into the powder pillow bag, the powder pillow bag is torn when the powder pillow bag is used, and the solid mixed developer in the powder pillow bag is poured into the glass color developing tube; the defect that when the powder pillow package is torn open to release the solid mixed color developing agent, the solid mixed color developing agent is difficult to be completely poured into the glass color developing tube, and a part of the solid mixed color developing agent remains in the powder pillow package, so that the release of the solid mixed color developing agent is incomplete, and the color developing effect of a water sample to be detected and the accuracy of a detection result are influenced.
The method for pretreating the sample in the step of detecting the concentration of the ferrous iron in the water on site is the original design of the invention. 4 drops of 1:1 hydrochloric acid are added into the glass color developing tube in advance before a water sample is injected into the glass color developing tube, and if the hydrochloric acid is not added, the mixed color developing agent can not effectively mask the interference of other common elements in water. When the water sample is turbid, the water sample is firstly filtered by a 0.45-micrometer filter membrane, and if the turbid sample is not filtered, the concentration of the ferrous iron in the water sample cannot be accurately determined.
The invention adopts a portable spectrophotometer to carry out on-site detection, has high sensitivity and accuracy, and has small error in measuring the concentration of the ferrous iron in the water sample. If the portable spectrophotometer is not used, the standard colorimetric card is used instead, namely: carrying out color development reaction on the series of standard solutions, and then manufacturing the concentration of the standard solutions and the color depth of the developed solutions into a standard colorimetric card so as to complete the field measurement of the ferrous concentration in water; the defects are that the sensitivity and the accuracy are not enough, and the error of the ferrous concentration in the water sample is judged by visual colorimetry is larger.
The existing laboratory detection technology has the defects of high cost, long detection period and difficulty in ensuring accuracy. According to the invention, the water sample does not need to be transported back to a laboratory, and after the water sample is developed on site, a test result can be issued in a few minutes, so that the detection efficiency and the accuracy are high. The invention directly pre-loads various solid medicaments in a reagent tank according to the proportion without secondary preparation when in use, and the pre-loaded solid mixed color developing agent in each color developing tube is 0.092g in total, the pre-loading amount is very small, and the cost of the used medicament is very low.
The disclosed on-site detection technology mainly adopts a visual colorimetry, compares with a standard color scale tube, subjectively judges the ferrous concentration in a water sample by naked eyes, and has larger error and lower sensitivity. The on-site detection method disclosed by the invention is in the range of 0.02-1.00 mg/L, the linear correlation coefficient of a calibration equation is 0.9998, the detection limit is 0.007mg/L, the different concentration standard addition recovery rate is 93.33% -104.76%, and the method is high in sensitivity and good in accuracy, and can be used for on-site rapid quantitative detection of the ferrous concentration in water.
The technical scheme of the invention has the beneficial effects that:
(1) the method for detecting the concentration of the ferrous iron in the water on site is high in accuracy and good in stability (the recovery rate and the precision of the method both meet the requirements of relevant standard specifications), does not need to carry out water sample collection protection (adding a protective agent), storage and transportation, and effectively avoids the conversion of valence states (bivalent and trivalent) of the iron in the water in the processes of sampling storage and transportation.
(2) The timeliness of the ferrous concentration in the test water is far higher than that of the laboratory analysis method. The field detection and analysis only need 6-7 minutes per sample, the water sample is collected, protected, stored and transported to a laboratory in the field, and the laboratory generally needs about two days for completing the steps of sample receiving, sample dispatching, analysis and test and the like. In comparison, the timeliness of the invention is very high.
(3) The ferrous concentration field test color development tube designed by the invention can be produced in batches, has complete commodity attributes, and can be prepared by injecting a sample to be tested according to the test steps, developing and carrying out field test by an operator. The testing steps are simple and easy to understand, secondary reagent preparation is not needed, operating personnel do not need professional qualification, the operation is very simple and convenient, and the method is very suitable for popularization and application in the field of water quality and environment field monitoring.
(4) The field detection method for the concentration of the ferrous iron in the water, which is established by the invention, has low test cost. The invention only needs to inject 20ml of water sample on site, does not need to collect a large amount of samples and add a protective agent, only needs to pre-load a very small amount of chemical agent (0.092g) in the ferrous concentration test color development tube in water, has the cost of the pre-loaded chemical agent of a single color development tube of less than 1 yuan, has no storage and transportation cost, does not need to use a large-scale laboratory analytical instrument, and has very low test cost on the whole.
The invention is further illustrated by the following figures and detailed description of the invention, which are not meant to limit the scope of the invention.
Drawings
Fig. 1 is a schematic view of the overall structure of the ferrous iron developing tube in water (including parameters).
Fig. 2 is a schematic structural diagram (including parameters) of a glass color developing tube in the ferrous color developing tube in water of the invention.
Fig. 3 is a side sectional view of a developing tube cover in the ferrous developing tube in water of the present invention.
Fig. 4 is a front plan view of the cover of the developing tube in the ferrous developing tube in water of the present invention.
Description of the main reference numerals:
1 glass color development tube 2 color development tube cover
320 mL graduation line 4 screw mouth
5 reagent tank 6 Plastic sealing film
Detailed Description
The specific structure and parameters of the color development tube for on-site determination of the ferrous concentration in water are shown in figures 1-4. The ferrous iron color developing tube mainly comprises a glass color developing tube 1 and a color developing tube cover 2 (a cover contains a solid mixed developer reagent groove). The color development tube cover 2 is provided with a reagent tank 5, the reagent tank 5 and the color development tube cover 2 are integrally formed, the reagent tank 5 is internally provided with a solid mixed color development agent, and the opening of the reagent tank is provided with a tearable plastic sealing film 6.
The parameters of each part of the color development tube for measuring the ferrous concentration in water on site and the composition of the solid developer are detailed as follows:
as shown in fig. 1-2, the glass developing tube 1 is made of transparent hard glass and is round, rectangular or square; the method is particularly determined according to the cuvette groove of the portable spectrophotometer, and if the cuvette groove of the portable spectrophotometer is circular, the glass color development tube 1 is circular; if the cuvette groove of the portable spectrophotometer is a square or rectangular strip, the glass color development tube 1 is square or rectangular. The diameter of the glass color developing tube 1 is 24mm, the parameter is set mainly because the diameter of a colorimetric hole of a general portable spectrophotometer is about 25mm at most, so the diameter of the color developing tube is less than or equal to the diameter of the colorimetric hole of the portable spectrophotometer, and simultaneously, in order to improve the detection limit of the method, the diameter of the color developing tube is designed to be close to the maximum value of the diameter of the colorimetric hole; the thickness of the glass developing tube 1 is 1.2mm, the thickness of the wall cannot be too thin and is easy to break, and the thickness cannot be too thick, so that the absorbance is influenced, and therefore the commonly used thickness of 1.2mm is selected. The specific diameter depends on the size of the cuvette groove of the portable spectrophotometer, and the diameter of the glass color developing tube 1 shown in the figure 1 is suitable for the portable spectrophotometer with a circular color comparison hole, such as the U.S. Hash DR2800 portable spectrophotometer. The height of the glass color development tube 1 is 95mm, and the height of the tube body not only ensures that the liquid level of a sample in the tube body is higher than the light path of the light source, but also ensures that a certain distance is exposed outside the colorimetric hole, so that the colorimetric tube is convenient to insert and take out; the specific height depends on the colorimetric hole structure of the portable spectrophotometer, and the glass developing tube 1 shown in the figure 1 is highly suitable for the U.S. hash DR2800 portable spectrophotometer. The pipe orifice of the glass color developing pipe 1 is a spiral orifice 4, the height of the spiral orifice 4 of the glass color developing pipe is 9mm, the height is the conventional height, and the screw orifice is too long, unnecessary and high in cost; too short can result in the cap not being screwed firmly. The glass developing tube 1 was provided with 20mL of scale lines 3.
As shown in fig. 3-4, the color development tube cover 2 is made of circular plastic, the outer diameter of the color development tube cover is consistent with the diameter of the glass color development tube 1, the height of the color development tube cover is 10mm, and the cover can be conveniently screwed and opened. The inside central point of lid has a circular plastics solid to mix colour development agent reagent groove 5, and reagent groove 5 and lid integrated into one piece, 5mm of diameter in reagent groove, high 4mm, and the reagent notch has a plastic seal membrane 6 that can tear, is equipped with the solid mixed colour development agent of having prepared in the reagent groove 5, and the solid mixed colour development agent component becomes: 0.012g of phenanthroline hydrochloride monohydrate, 0.075g of glycine and 0.005g of aminotriacetic acid.
The invention also discloses a field detection technical method, which comprises all the factors of medicine reagent preparation (formula), detection device preparation, instrument parameters, analysis steps and the like.
The method for detecting the ferrous concentration in water on site established by the color development tube mainly comprises four steps of calibration curve preparation (including 'detection method establishment'), sampling, color development reaction and site test. The specific operation method of each step is detailed as follows: when the method is established for the first time (or the method is not used for a long time and the ferrous concentration in water is tested again), the preparation of the standard solution is needed to be carried out firstly, then the sampling is carried out (the standard solution is taken), then the color reaction is carried out, and then the field test is carried out, thereby completing the preparation of the calibration curve, preserving the calibration curve and completing the establishment of the 'field detection method for the ferrous concentration in water'. When the water sample is tested in a short time, only the 'in-water ferrous concentration field detection method' stored in the instrument needs to be taken, and a calibration curve preparation step is not needed to be carried out again, namely, the calibration curve can be continuously used for 1-2 days once, the 'calibration curve preparation' is not needed to be carried out once every sample is tested, and then after reagent blank zero setting, the steps of actual sample sampling, color reaction and field test are directly carried out, so that a sample test is completed. The next sample is still a repeat of the "sample-color reaction-field test" procedure. When the samples are continuously measured, zero setting is carried out once.
Sampling: 4 drops of 1:1 hydrochloric acid are added into a glass color development tube 1, and then a water sample is directly injected into the position of a scale mark 3 of the glass color development tube 1-20 mL. If the water sample is turbid, the water sample should be filtered through a 0.45 μm filter membrane.
② color reaction: tearing a plastic sealing film 6 of a reagent notch in a cover of the color development tube by hand, pouring the solid mixed color developing agent in the reagent tank 5 into the glass color development tube 1 which is sampled, screwing the cover, oscillating repeatedly for 3 times, fully dissolving the residual solid mixed color developing agent in the reagent tank 5 by a water sample in the oscillation process, oscillating for 10 seconds each time, fully and uniformly mixing the water sample in the glass color development tube 1 and the solid color developing agent, dissolving, and waiting for 5 minutes to finish color development reaction.
Preparing a calibration curve, including 'establishing a field detection method': the process comprises four steps of standard solution preparation, standard solution transferring, color reaction and field test.
Step one, preparing a standard solution: the superior pure ammonium ferrous sulfate hexahydrate is adopted to prepare a series of standard solutions with ferrous concentration of 0.00, 0.025, 0.05, 0.10, 0.20, 0.50 and 1.00mg/L step by step.
Step two, transferring a standard solution: 20mL of each concentration of standard solution was injected into the glass developing tube 1 to which 4 drops of 1:1 hydrochloric acid had been added (to the position of 20mL of the glass developing tube at the scale 3).
Step three, color reaction: tearing the plastic sealing film 6 of the reagent notch in the cover of the color development tube by hand, pouring the solid mixed color developing agent in the reagent tank 5 into the glass color development tube 1 which is sampled, screwing the cover, oscillating forcefully, wherein the water sample can fully dissolve the residual solid mixed color developing agent in the reagent tank 5 in the oscillation process, so that the water sample in the glass color development tube 1 and the solid color developing agent are fully mixed and dissolved, and then waiting for 5 minutes.
Fourthly, field test: after the color reaction is carried out for 5 minutes, a user program is newly established in a portable spectrophotometer, a mode selects a single wavelength, the analysis wavelength is 515nm, the standard measurement or reading step is carried out after the setting is finished, a series of standard solution samples with the ferrous concentration of 0.00mg/L, 0.025, 0.05, 0.10, 0.20, 0.50 and 1.00mg/L are sequentially placed in a colorimetric hole for absorbance measurement, the concentration value of the standard solution needs to be input into the program when each standard solution sample is placed, the instrument automatically draws a calibration curve after the absorbance measurement is finished, the established field detection method for the ferrous concentration in water has the calibration curve data shown in the table 1, a linear equation is calculated, and finally the test program is stored. After the storage is finished, the on-site detection method of the concentration of the ferrous iron in the water established this time is automatically added into an instrument user program, and the method comprises a calibration curve, a linear equation calculated according to calibration curve data and an analysis wavelength.
TABLE 1 calibration curve data of the field detection method for ferrous concentration in water established by the invention
When the field test is completed on the same day, for example, at a long time interval (generally, more than three days, the calibration curve should be prepared again), and the field test method for the ferrous iron concentration in water is used again, the series of standard solutions is reconfigured, the calibration curve is updated (i.e., the operation is started again from the "standard measurement (or reading) step"), and the sample test can be continued after the calibration of the calibration curve is completed.
Fourthly, field test: after the calibration curve preparation is completed and the field detection method is stored in the instrument, the field test is carried out by the color reaction step.
First step, sampling: 20mL of a water sample to be tested was injected into a glass developing tube 1 to which 4 drops of 1:1 hydrochloric acid had been added.
And step two, color reaction: tearing a plastic sealing film 6 of a reagent notch in a cover of the color development tube by hand, pouring the solid mixed color development agent in the reagent tank 5 into the glass color development tube 1 which is sampled, screwing the cover, oscillating forcefully, fully dissolving the residual solid mixed color development agent in the reagent tank 5 by a water sample in the oscillation process, fully mixing the water sample in the glass color development tube 1 with the solid color development agent, dissolving, and waiting for 4-6 minutes.
And thirdly, after the color reaction of the water sample to be detected is carried out for 4-6 minutes, a newly established (or newly calibrated) in-water ferrous concentration field detection method is called out from a user program of the portable spectrophotometer, the instrument zero setting is carried out by taking a reagent blank (a 0.00mg/L standard solution sample) as a reference, then the glass color developing tube of the water sample to be detected which finishes the color reaction is placed in a color comparison hole of the portable spectrophotometer, and the ferrous concentration (the unit is mg/L) in the water sample to be detected is read. The field detection method for the ferrous iron concentration in water stored by the instrument comprises a calibration curve and a linear equation, so that the instrument can automatically calculate the ferrous iron concentration value in a water sample to be detected according to the measured absorbance during sample test and display the ferrous iron concentration value on a screen. The method is applied to test and research representative actual water samples (WSY 01-WSY 04) and simulated water samples (simulated water sample 1 and simulated water sample 2), the precision test result of the method is shown in table 2, and the sample standard adding recovery rate test result is shown in table 3.
Table 2 precision test results of the method of the present invention to determine ferrous iron concentration in a representative water sample (n ═ 7)
Note: ND-represents that the detection result is less than the detection limit.
TABLE 3 results of the recovery test of the samples in the process of the invention
The invention uses visual colorimetry instead of using a portable spectrophotometer. Namely: and (3) carrying out color development reaction on the series of standard solutions, then manufacturing the concentration of the standard solutions and the color depth of the developed solutions into a standard colorimetric tube, and subjectively finishing the on-site determination of the ferrous concentration in the water by adopting visual colorimetry. The defects are that the sensitivity and the accuracy are not enough, and the error of the ferrous concentration in the water sample is judged by visual colorimetry is larger.
If the solid mixed color developing agent is released in the reagent groove of the solid mixed color developing agent which is arranged in the cover of the color developing tube, the method is changed into a powder pillow bag mode to release the solid mixed color developing agent, namely, the prepared solid mixed color developing agent is filled into the powder pillow bag, the powder pillow bag is torn when the method is used, and the solid mixed color developing agent in the powder pillow bag is poured into the glass color developing tube. The defect that when the powder pillow package is torn open to release the solid mixed color developing agent, the solid mixed color developing agent is difficult to be completely poured into the glass color developing tube, and a part of the solid mixed color developing agent remains in the powder pillow package, so that the release of the solid mixed color developing agent is incomplete, and the color developing effect of a water sample to be detected and the accuracy of a detection result are influenced.
The color development tube for on-site determination of the ferrous concentration in water and the detection method have wide application range and can be applied to the following fields:
the water quality monitoring and evaluating field of surface water and underground water comprises the following steps: the invention can provide a large amount of rapid and accurate field detection and monitoring data for the field.
Secondly, the ecological environment restoration and treatment field: the invention can be effectively applied to field detection/monitoring in the field, and provides real-time monitoring data for ecological environment monitoring and restoration treatment processes in the field.
Pipeline water supply, drainage, circulating water and emergency monitoring field: enterprises in chemical industry, energy and mechanical manufacturing and the like have a large number of metal water supply and drainage pipelines, and need to frequently detect the concentration of ferrous iron in the water supply and drainage pipelines. In addition, the method can also be used for the environment related to iron element and the handling work of safe emergency, can rapidly monitor the ferrous concentration in the water environment on site, and provides real-time data support for environmental impact evaluation and iron ion migration and conversion behaviors.
The ferrous concentration test color development tube has low cost, can be produced in batches, is simple and convenient to operate, and is very suitable for popularization and application in the field of water quality and environment field monitoring. The method for detecting the ferrous concentration in water on site by adopting the color development tube has the advantages of high accuracy, good stability and strong timeliness.
Claims (10)
1. The color developing tube for on-site determination of ferrous iron concentration in water features that it includes glass color developing tube and color developing tube cover, and the cover has reagent tank with solid mixed color developing agent inside and tearable plastic sealing film in the mouth.
2. A color developing tube for on-site determination of ferrous iron concentration in water as claimed in claim 1, characterized in that the glass color developing tube is made of transparent hard glass material and has a circular, rectangular or square cross section, and the mouth of the glass color developing tube is a screw mouth.
3. A developing tube for on-site measurement of ferrous iron concentration in water as claimed in claim 2, characterized in that said glass developing tube has a diameter of 24mm, a wall thickness of 1.2mm and a height of 95 mm; the diameter of the spiral opening of the glass developing tube is smaller than that of the glass developing tube, and the height of the spiral opening of the glass developing tube is 9 mm; the glass color development tube is provided with 20mL of scale marks.
4. A developing tube for on-site measuring ferrous concentration in water as claimed in claim 1, characterized in that the developing tube cover is circular, made of plastic, and has an outer diameter consistent with the diameter of the glass developing tube and a height of 10 mm; a cylindrical solid mixed color developing agent reagent groove is arranged at the center inside the color developing tube cover and is made of plastics; the diameter of the reagent groove is 5mm, and the height of the reagent groove is 4 mm.
5. A color developing tube for on-site measurement of ferrous iron concentration in water according to claim 1, wherein the solid mixed developer is composed of: 0.012g of phenanthroline hydrochloride monohydrate, 0.075g of glycine and 0.005g of aminotriacetic acid.
6. A field detection method for ferrous concentration in water, which adopts the color development tube of any one of claims 1-5, and comprises the following steps:
(1) sampling: adding 4 drops of 1:1 hydrochloric acid into a glass color development tube, and then injecting a water sample into the glass color development tube to a position of a 20mL scale mark;
(2) and (3) color development reaction: tearing a plastic sealing film of a reagent notch in a cover of the color development tube, pouring the solid mixed color development agent in the reagent groove into the sampled glass color development tube, screwing the cover, oscillating repeatedly to fully and uniformly mix the solid mixed color development agent with a water sample, dissolving, and standing for 4-6 minutes to complete color development reaction;
(3) and (3) field test: and (4) carrying out on-site detection by adopting a portable spectrophotometer to obtain the concentration of the ferrous iron in the water sample.
7. The on-site detection method of ferrous iron concentration in water as claimed in claim 6, wherein when the water sample is turbid, the water sample is first filtered through a 0.45 μm filter membrane; the number of repeated oscillation is 3-5, and each oscillation time is 8-15 seconds.
8. The method for on-site detection of ferrous iron concentration in water as claimed in claim 6, wherein the method for on-site detection using a portable spectrophotometer comprises the steps of:
1) preparing a calibration curve, and establishing a detection method: firstly, preparing a series of ferrous standard solutions, referring to the step (1) and the step (2) in the claim 6, taking a standard solution sample, carrying out color development reaction, then testing by adopting a portable spectrophotometer to generate a calibration curve and a linear equation, storing a test program, and establishing a detection method;
2) on-site detection of a water sample: performing sampling and color reaction of the water sample according to the steps (1) and (2) of claim 6; and (3) carrying out field test on the water sample which finishes the color reaction after the blank reagent is used for zero adjustment by adopting a detection method stored in the portable spectrophotometer.
9. The method of claim 8, wherein the calibration curve is prepared and the in-situ test method is established, and the method comprises the following steps:
step one, preparing a standard solution: preparing series standard solutions with ferrous concentration of 0.00, 0.025, 0.05, 0.10, 0.20, 0.50 and 1.00mg/L by adopting ammonium ferrous sulfate hexahydrate;
step two, transferring a standard solution: adding 4 drops of 1:1 hydrochloric acid into a glass color development tube, and then respectively injecting 20mL of standard solutions with different concentrations;
step three, color reaction: tearing a plastic sealing film of a reagent notch in a cover of the color development tube, pouring the solid mixed color development agent in the reagent groove into the sampled glass color development tube, screwing the cover, oscillating repeatedly to fully and uniformly mix the solid mixed color development agent with a water sample, dissolving, and standing for 4-6 minutes to finish color development reaction;
fourthly, field test: a user program is newly established in a portable spectrophotometer, a single wavelength is selected in a mode, the analysis wavelength is 515nm, then a standard measurement or reading step is carried out, a blank sample of 0.00mg/L is taken as a reference solution to carry out instrument zeroing, then series standard solution samples of which the ferrous concentration is 0.00, 0.025, 0.05, 0.10, 0.20, 0.50 and 1.00mg/L are sequentially placed in a colorimetric hole to carry out absorbance measurement, the concentration value of the standard solution is firstly input into the program before each standard solution sample is placed, a calibration curve is automatically generated by the instrument after the absorbance measurement is finished, a linear equation is calculated, and finally a test program is stored, and the field detection method for the ferrous concentration in water is automatically added into the user program of the instrument.
10. The method for on-site detection of the ferrous iron concentration in water according to claim 8, wherein the on-site detection of the water sample comprises the following steps:
first step, sampling: adding 4 drops of 1:1 hydrochloric acid into a glass color development tube, and then injecting 20mL of water sample to be detected;
and step two, color reaction: tearing a plastic sealing film of a reagent notch in a cover of the color development tube, pouring the solid mixed color development agent in the reagent groove into the sampled glass color development tube, screwing the cover, oscillating repeatedly to fully and uniformly mix the solid mixed color development agent with a water sample, dissolving, and standing for 4-6 minutes;
step three, field detection: the established detection method is called out from a user program of the portable spectrophotometer, a blank sample is used as a reference to carry out instrument zero setting, then a glass color developing tube of a water sample to be detected which finishes color developing reaction is placed in a color comparison hole of the portable spectrophotometer, and the concentration of ferrous iron in the water sample to be detected is read.
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