RU2715478C1 - Method of determining concentration of lead (ii) in aqueous samples - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to measurement equipment and a method of determining concentration of lead (II) in aqueous samples. Method involves preparation of a polymer sensor film placed on the carrier, contact thereof with the test sample and determination of lead concentration by comparing optical density with a calibration scale at a wavelength of light of 580 nm. Sensor film used is a photopolymerized material in monomers of trimethylol propane ethoxylate (1 EO/OH) methyl ether diacrylate, 2-carboxyethylacrylate and polyethylene glycol polymer, with introduced zinc oxide nanoparticles with size of 5–10 nm, on the surface of which xylene orange dye is immobilized, as well as gold nanoparticles and polymerization initiator 2,2-dimethoxy-2-phenylacetophenone.

EFFECT: technical result consists in improvement of sensor film sensitivity and exclusion of human factor influence during measurements.

3 cl, 1 dwg

Description

The invention relates to the field of special nanocomposite materials, in particular to materials intended for use as a sensitive element of a spectrophotometric sensor for the concentration of lead (II) ions in aqueous solutions.

A known visual method for determining lead (II) ions in solution (patent RU No. 2441232, IPC G01N 31/22, IPC G01N 21/78, priority date 02.08.2010, published 01.27.2012). The method is based on the reaction of lead (II) ions with 1-phenyl-3-isopropyl-5- (benzylbenzimidazol-2-yl) formazan. The determination is carried out by sorption of lead (II) ions from the analyzed solution on a tissue calico carrier, followed by separation of the liquid phase and the photometric reaction. To assess the content of lead (II) visually compare the color intensity of the tissue carrier with a simulated color scale. However, the known method does not have expressivity due to complex sample preparation, the need to standardize the preparation of coarse calico discs, does not have a sufficiently wide range of determined concentrations of lead (II) for determining lead in real objects, is not applicable for the analysis of colored objects.

A known sorption spectrophotometric method for determining lead (II) (patent RU No. 2529660, IPC G01N 21/77, priority date 03/03/2013, published 03/12/2013). The concentration of metal from the sample is carried out at a fixed pH value, for which acetate buffer with a pH of 3.5-4.5 is added to the analyzed solution, the indicator film is immersed for 30-60 minutes, after its extraction, the optical density is measured on a spectrophotometer with a length Waves 610 nm. The concentration of lead (II) is determined by the standard addition method or by the calibration curve method. As an indicator film, a transparent polymer substrate is used, on which a gelatin layer with a thickness of up to 20 μm is deposited, immobilized with an aqueous solution of bromopyrogallol red. However, this method requires a long (at least 20 min) analysis time, it is impossible to use in stained samples, it has a short sensor lifetime due to degradation of the gelatin matrix, it does not allow determination of lead (II) at or below the MPC in aqueous and biological objects , as well as with its significant excess of MPC, due to the narrow range of measured concentrations.

A known method for the determination of lead (II) in aqueous and biological samples (patent RU No. 2682162, IPC G01N 31/22, G01N 33/20, G01N 33/50, G01N 21/78, priority date 16.08.2018, published 03.15.2019) closest to the claimed invention to solve the technical problem and adopted as a prototype. The method involves the preparation of a polymer sensor film, which is placed in the test sample and the color of the polymer sensor film determines the presence of lead (II) in it, the amount of which is determined by a calibrated color scale previously obtained from at least 5 test samples with known concentrations of lead (Ii) The polymer sensor film is placed in a test sample of an analyzed solution of known volume from 0.5 ml to 10 ml together with a mixture of magnesium acetate and acetic acid, taken in a ratio of 2.50⋅10 ^-3 mol / l: 1.25⋅10 ^-4 mol / l of the analyzed solution, and incubated for 2-18 minutes. A plasticized bis (ethylhexyl) ester of sebacic acid (DOS) poly (vinyl chloride) (PVC) film 2–7 μm thick containing a neutral chromoionophore indicator 9-dimethylamino-5- [4- (15-butyl-1) is taken as a polymer sensor film , 13-dioxo-2,14-yoxanonadecyl) phenylimino] benzo [a] phenoxazine (ETH5418), ionophore 4-tert-butyl-calix [4] arene-tetrakis (N, N-dimethylthioacetamide) (lead ionophore IV) and sodium tetrakis- [3.5-bis (trifluoromethyl) phenyl] borate (NaTFPB) ionic additive in the ratio: 16.7 mg PVC, 33.3 μl DOS, 10 mmol / kg DOS ETN5418, 11 mmol / kg DOS NaTFPB, 60 mmol / kg dos l ead ionophore IV placed on the carrier. The disadvantage of the prototype is that the determination of the presence of lead (II) in the test sample is carried out by a visual test method by comparing the color of the polymer sensor film with a calibrated color scale, which is the reason for the low accuracy of determining the concentration.

The task to which the proposed method is aimed is to increase the accuracy of determining the concentration of lead (II) in aqueous samples.

The problem is solved by achieving a technical result, which consists in increasing the sensitivity of the sensor film and eliminating the influence of the human factor.

The technical result is achieved by the fact that the method for determining the concentration of lead (II) in aqueous samples involves the preparation of a polymer sensor film placed on a carrier, the contact of which with the test sample is maintained for about 10 minutes, and the concentration of lead in it is determined by changing the optical density of the polymer sensor film (II ), the value of which is determined by comparison with a previously obtained calibration scale, and the concentration of lead (II) is determined by comparing the optical density of the polymer sensor plate nanocrystals with a calibration scale at a wavelength of light of 580 nm, as a polymer sensor film take photopolymerized under the influence of ultraviolet radiation with a wavelength of 340-370 nm material consisting of trimethylol propane ethoxylate monomers methyl ether diacrylate, 2-carboxyethyl acrylate and polyethylene glycol polymer (PEG), with introduced zinc oxide nanoparticles 5-10 nm in size, on the surface of which xylene orange dye is immobilized, as well as gold nanoparticles and 2,2-dimethoxy-2-phenylacentophenone polymerization initiator, at it xylenol orange indicator dye immobilized on the surface of zinc oxide nanoparticles with adsorbed gold nanoparticles. The contact of the polymer sensor film placed on the carrier with the test sample is provided by immersion in an aqueous sample or by supplying an aqueous sample to the channels formed in the polymer sensor film.

The developed composite transparent material with gold and zinc oxide nanoparticles, as well as an indicator dye introduced into a hydrophilic photopolymer matrix, suitable for use as a sensitive element for the quantitative determination of lead (II) in water, does not require manual analysis and contains a hydrophilic nanocomposite film all the necessary components. Immersion of it in water, brings the sensitive element into working condition without the participation of the operator.

The essence of the invention lies in the fact that to achieve a technical result, a sensitive element is proposed consisting of a hydrophilic photopolymerizable nanocomposite having a swelling coefficient of up to 3.0 and deposited on a glass or polymer substrate in the form of a thin layer, 300 μm thick, or in the form of a system of channels for the transmission of water to be measured. The photopolymerizable material consists of a mixture of monomers and polymer Trimethylolpropane ethoxylate (1 ЕО / ОН) methyl ether diacrylate (TMP), methyl ether diacrylate (TMP), 2-Carboxyethyl acrylate (Car) and polyethylene glycol (PEG), composition Car - TMP - PEG with the introduced ZnO nanoparticles on the surface of which the xylene orange dye is immobilized, as well as AuNP gold nanoparticles, which increase the sensitivity due to plasmon resonance. When the sensor is immersed in the water to be measured, the polymer, hydrophilic matrix, which contains Car carboxylic acid, partially neutralized with PEG polymer, acts as a buffer that maintains a fixed pH = 4.54, and the dye immobilized on nanoparticles and not washed out from them is a sensor. The optical density is measured at a wavelength of 580 nm. The concentration of heavy metal is determined by the method of the calibration graph entered in the memory of the photometer.

In FIG. The absorption spectrum of the sensor element in the presence of lead (II) is shown, characterized by two absorption maxima, while the maximum at a wavelength of 580 nm corresponds to samples with lead (II). Absorption spectrum of the nanocomposite after exposure for 10 min.

in an aqueous solution containing lead (II) ions:

1 - the initial spectrum of the composite film in distilled water,

2 - the content of Pb in solution is 0.002%,

3 - the content of Pb in solution is 0.006%.

Sensor Sensitivity Parameters:

The sensitivity to lead Pb2 + is 1 mg / L (1 mg lead per 1 liter of water sample). The dynamic range of the measured pb2 + lead concentration is 30 times.

The proposed technical solution is illustrated by examples.

Example 1

The initial components of the sensitive element and their ratio:

Trimethylolpropane ethoxylate (1 EO / OH) methyl ether diacrylate (Aldrich No. 415871), TMP-6.98%;

Poly (ethylene glycol) (Aldrich No. 94646), PEG - 29.92%;

Carboxyethyl acrylate (Aldrich No. 552348) Car - 56.85%;

ZnO nanoparticles, 6 nm - 5.99%;

2,2-Dimethoxy-2-phenylacetophenone (Aldrich 19,611-8), initiator 0.2%;

Gold nanoparticles, diameter 10 nm - 0.05%.

To obtain a polymer matrix, PEG granules are dissolved (with vigorous stirring with ultrasound) in the Car + TMP monomer composition, ZnO nanoparticles are calcined in air at 400 C for 20 minutes to activate the surface. Hot nanoparticles are poured into the xylene orange dye aqueous solution and mixed vigorously, after which the solution is poured into isopropyl alcohol with vigorous stirring. After the deposition of nanoparticles with a dye adsorbed on their surface, centrifugation is performed to separate the nanoparticles from the mother liquor. Without drying, the obtained nanoparticles are introduced into a pre-prepared monomer-polymer composition. Gold nanoparticles are introduced into the resulting composition and then dispersed by ultrasound with a power density of 70 W / kV cm to achieve transparency of the colloidal solution, after which a polymerization initiator is introduced in liquid form. To obtain a film, a drop of the solution is applied to a glass substrate, covered with a mylar film and the composition is polymerized by ultraviolet radiation with a wavelength in the range of 340-370 nm. After polymerization, the lavsan film is removed and the sensitive element (polymer film about 300 microns thick on a glass substrate) is ready for use. To carry out the analysis, it is necessary to place the sensitive element in the studied water sample for 10 min, and then to measure the absorption spectrum in the visible region. The amplitude of the absorption maximum at a wavelength of 580 nm is proportional to the concentration of lead (II) ions in the sample.

Example 2

The initial composition is prepared analogously to example 1. For polymerization, the liquid composition is applied to a substrate and covered with a photomask through which the composition is polymerized by ultraviolet radiation with a wavelength in the range of 340-370 nm. The photomask is a system of channels with a thickness of 500 microns. After exposure, the template is removed, and washing is carried out in isopropyl alcohol to form a given channel structure. The resulting system is covered with a glass substrate. To carry out the measurement, the test fluid is passed through the channels, since the composition is transparent to water, on the one hand, and the introduced dye is able to form a complex with lead (II) ions, the corresponding ions accumulate. By measuring the absorption spectrum of the element, the concentration of lead (II) in the test sample can be determined from the amplitude of the maximum at a wavelength of 580 nm.

Claims (3)

1. A method for determining the concentration of lead (II) in aqueous samples, comprising preparing a polymer sensor film placed on a carrier, the contact of which with the test sample is maintained for about 10 minutes, and the concentration of lead (II) in it is determined by changing the optical density of the polymer sensor film, the value of which determined by comparison with a pre-obtained calibration scale, characterized in that the concentration of lead (II) is determined by comparing the optical density of the polymer sensor film with a calibration scale At a wavelength of light of 580 nm, a material consisting of trimethylolpropane ethoxylate monomers (1 ЕО / ОН) methyl ether diacrylate, 2-carboxyethyl acrylate and polyethylene glycol polymer is taken as a polymer sensor film under ultraviolet radiation with a wavelength of 340-370 nm. introduced nanoparticles of zinc oxide with a size of 5-10 nm, on the surface of which xylene orange dye is immobilized, as well as gold nanoparticles and a polymerization initiator 2,2-dimethoxy-2-phenylacentophenone. 2. A method for determining the concentration of lead (II) in aqueous samples according to claim 1, characterized in that the contact of the polymer sensor film placed on the carrier with the test sample is immersed in an aqueous sample. 3. The method for determining the concentration of lead (II) in aqueous samples according to claim 1, characterized in that the contact of the polymer sensor film placed on the carrier with the test sample is provided by supplying an aqueous sample to the channels formed in the polymer sensor film.

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