RU2466096C1 - Method of determining concentration of vanadium in atmospheric air by inductively coupled plasma mass spectrometry (versions) - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of determining concentration of vanadium in atmospheric air by inductively coupled plasma mass spectrometry (versions). One of the versions is characterised by that atmospheric air samples are collected by drawing the analysed air through an analytical aerosol filter at a rate of 50 l/min for 20 minutes and air temperature and atmospheric pressure at the sampling time are recorded. After sampling, the filter is decomposed by microwave sample preparation, where the filter is placed into a fluoroplastic cup and an internal standard solution of erbium or terbium in deionised water with concentration of 1 mg/dm³ and concentrated nitric acid are successively added. The sample is then mineralised according to the program to the microwave sample preparation system. The obtained mineralised product is transferred to a polypropylene test tube. The fluoroplastic cup is washed from the sample 2-3 times by adding 1 ml of deionised water each time, shaking and transferring each wash-off into said test tube. The volume of the sample is then increased to 10 ml by adding deionised water. The contents are stirred and the obtained sample is diluted with deionised water in volume ratio 1:9 respectively. The sample is placed into the test tube of the sampling device of an inductively coupled plasma mass spectrometer and measurements are taken. Concentration of vanadium in air is determined using a calibrated curve by bringing volume air collected for analysis to normal conditions.

EFFECT: use of the present invention increases sensitivity and selectivity while providing a wider range of detecting vanadium from 0,000005 mg/m³ to 0,02 mg/m³.

6 cl, 6 tbl

Description

The invention relates to the field of analytical chemistry and may find application in the field of ecology and environmental protection in the control of atmospheric pollution to determine one-time and daily average concentrations of vanadium in atmospheric air.

As a result of increasing anthropogenic impact, atmospheric air pollution with heavy metals, including vanadium, is observed. Vanadium is a highly toxic element, belongs to the first hazard class. The physiological role of vanadium is not well understood. It is believed that vanadium is involved in the regulation of carbohydrate metabolism and cardiovascular activity, enhances the absorption of oxygen by liver tissues and catalyzes oxidation by enzymes. Vanadium intoxication in humans is almost always associated with anthropogenic factor.

To expand analytical capabilities, to establish a real concentration of vanadium in the air when assessing public health risks, it is necessary to determine the content of vanadium in the air at the level of the reference concentration. In this regard, the development of a sensitive and selective method using modern physical and chemical methods of analysis is relevant.

Known methods for the determination of vanadium in atmospheric air, namely:

- Method M-MVI-151-2005, designed to determine a number of metals, including vanadium, in atmospheric air by the X-ray fluorescence method;

- Methodology 5.2.5.1 in RD 52.04 186-89 “Guidelines for the Control of Atmospheric Pollution”, designed to determine vanadium in atmospheric air in the range of 0.001-0.01 mg / m ^{3 by the} photometric method. The method is based on trapping vanadium on AFA-KhP-18 filters and photometric determination of its mass by the complexed compound colored in violet, which is formed during the interaction of vanadium with salicylic hydroxamic acid.

The disadvantages of these known methods is the lack of sensitivity and selectivity.

The technical problem solved by the proposed variants of the method is to enable the determination of vanadium in atmospheric air at the level of reference concentration. A single technical result is an increase in the sensitivity and selectivity of the method while providing an extension of the vanadium detection range from 0.000005 mg / m ³ to 0.02 mg / m ³ , while reducing the volume of air drawn through the filter to 1 m ³ and simplifying the sample preparation operation in way.

The specified technical result is achieved by the proposed method for determining the concentration of vanadium in atmospheric air by inductively coupled plasma mass spectrometry, according to which, according to the first embodiment, atmospheric air is sampled by pulling the test air through an analytical aerosol filter at a speed of 50 l / min for 20 minutes and record the air temperature and atmospheric pressure at the time of sampling, after sampling the filter is subjected to decomposition by microwave sample preparation in which the filter is placed in a fluoroplastic glass and a solution of the internal standard of erbium or terbium in deionized water with a concentration of 1 mg / dm ³ and concentrated nitric acid is successively added to it, the sample is mineralized according to the program to the microwave sample preparation system, the resulting mineralizate is transferred to polypropylene test tube, flush the fluoroplastic beaker from the sample 2-3 times by introducing 1 ml of deionized water, shaking and transferring each wash to the specified test tube, bring about the sample is taken up with deionized water up to 10 ml, the contents are mixed, then the sample obtained is diluted with deionized water in a volume ratio of 1: 9, respectively, placed in a test tube of the sampling device of the mass spectrometer with inductively coupled argon plasma and measured, and the concentration of vanadium in the air is determined using a calibration graph taking into account the reduction of the air volume selected for analysis to normal conditions; and according to the second variant, atmospheric air is sampled by drawing the test air through an analytical aerosol filter at a speed of 50 l / min for 20 minutes and the air temperature and atmospheric pressure are recorded at the time of sampling; after sampling, the filter is decomposed by sample preparation in a muffle furnace in which the filter is placed in a quartz glass and a solution of the internal standard of erbium or terbium in deionized water with a concentration of 1 mg / dm ³ is added, the glass is placed in a muffle furnace and incubated sequentially at a temperature of 100 ° C for 40-60 minutes, at a temperature of 250 ° C for 40-60 minutes, then ashing is carried out at a temperature of 450-500 ° C for 3.5 hours, the resulting ash is moistened with concentrated nitric acid, heated on sand the bath and evaporate to the state of wet salts, after cooling, dissolve in a 1% aqueous solution of nitric acid to obtain a mineralizate, transfer the obtained mineralizate to a measuring tube, wash the quartz glass from the sample 2-3 times by introducing 1 ml of 1% aqueous solution and nitric acid, transferring the washings to the test tube with the sample, the resulting volume is adjusted to 10 ml with a 1% aqueous solution of nitric acid, then the resulting sample is diluted with a 1% aqueous solution of nitric acid in a volume ratio of 1: 9, respectively, placed in a test tube of a sampling device of a mass spectrometer with inductively coupled argon plasma and measure, and the concentration of vanadium is determined using a calibration graph taking into account the reduction of the volume of air selected for analysis to normal conditions fishing.

In both cases, AFA-HA filters are used as an analytical aerosol filter.

The specified technical result is achieved due to the following. The basis of the proposed method is the use of argon inductively coupled plasma as a source of ions and a mass spectrometer for their separation and detection.

The possibility of determining vanadium in atmospheric air at the reference concentration level was made possible due to the fact that a highly sensitive and selective MS-ICP method was used, analysis conditions were selected on a mass spectrometer, methods and conditions for sample preparation, the value of blank experiment was reduced due to sample preparation with the introduction of internal standard, selection of conditions for the use of high-purity reagents and materials.

Simplification of sample preparation for both options is achieved due to the fact that the steps that are typical for known methods are excluded:

- pre-synthesis of salicylic hydroxamic acid,

- preparation of a basic (initial) solution for calibration of dry ammonium metavanadate, requiring, in turn, preliminary recrystallization, washing with ethanol and drying,

- sample preparation of additional filters with the application of a working calibration solution to build a calibration graph,

- heating in a water bath,

- filtering,

- in addition, the use of glacial acetic acid (is a precursor) and the need to observe and control the exact time between the end of the sample preparation and the analysis on the device are excluded.

Thus, the claimed technical result is achieved due to the totality of certain operations, their sequence and modes in the claimed method, as well as due to the totality of reagents used in sample preparation.

The proposed method was tested in laboratory conditions. The following substances and equipment were used for its implementation:

- state standard sample of the solution: vanadium ions GSO - 7266-96;

- the main solution of the internal standard of erbium (Er) or terbium (Tb) concentration of 1 mg / DM ³ ;

- nitric acid, special part, GOST 11125-84;

- distilled water, TU 6-09-2502-77;

- deionized water;

- liquid argon of high purity (99.998%), TU-2114-005-00204760-99.

- nitric acid (HNO ₃ ), 1% concentration;

- a solution of the internal standard Er or Tb with a mass concentration of 1 μg / DM ³ in deionized water.

- Inductively coupled plasma mass spectrometer Agilent 7500 _cx octopole cell.

When carrying out the processes of preparing solutions and preparing samples for analysis, the following conditions are met:

- air temperature 18-25 ° C;

- atmospheric pressure 630-800 mm Hg;

- humidity not more than 80% at a temperature of 25 ° C.

Solution preparation

1. A solution of nitric acid 1%.

8 cm ^{3 of} concentrated nitric acid with a density of 1.415 g / cm ³ are mixed with 512 cm ^{3 of} deionized water. Store in a plastic container.

2. An intermediate solution of an internal standard with an erbium (or terbium) content of 100 μg / dm ³ .

Prepared from a basic solution with a content of 1 mg / DM ³ . In a volumetric flask with a capacity of 50 cm ³ make 5 cm ^{3 of the} basic solution with a content of 1 mg / DM ³ and bring the volume in the flask to the mark with a 1% solution of nitric acid. The solution is stored in a polypropylene tube for 2-3 days.

3. A solution of the internal standard with a mass concentration of 1 μg / DM ³ in deionized water.

0.5 cm ^{3 of} an intermediate solution of an internal standard with a content of, for example, erbium (or terbium) 100 μg / dm ^{3 is} introduced into a volumetric flask with a capacity of 50 cm ³ and the volume is adjusted to the mark with deionized water. Pour into a polypropylene tube.

4. The basic standard solution with a vanadium content of 100 mg / DM ³ .

The solution is prepared from GSO with a mass concentration of metal ions of 1 g / DM ³ . In a volumetric flask with a capacity of 50 cm ³ contribute 5 cm ³ GSO composition of the solution of metal ions and bring the volume in the flask to the mark with a 1% solution of nitric acid.

5. An intermediate solution of a standard sample with a mass concentration of vanadium 10 mg / DM ³ .

Prepared from a stock solution of a standard sample with a mass concentration of vanadium 100 mg / DM ³ . In a volumetric flask with a capacity of 100 cm ³ contribute 10 cm ^{3 of the} basic standard solution and bring the volume in the flask to the mark with a 1% solution of nitric acid. The solution is stored in a plastic container for 3 months.

6. Auxiliary solution No. 1 with a mass concentration of vanadium of 100 μg / DM ³ .

Prepared from an intermediate solution of a standard sample with a mass concentration of vanadium 10 mg / DM ³ .

In a volumetric flask with a capacity of 50 cm ³ make 0.5 cm ^{3 of} an intermediate solution of a standard sample and bring the volume in the flask to the mark with a 1% solution of nitric acid.

7. Auxiliary solution No. 2 with a mass concentration of vanadium 50 μg / DM ³ .

Prepared from an intermediate solution of a standard sample with a mass concentration of vanadium 10 mg / DM ³ .

In a volumetric flask with a capacity of 100 cm ³ make 0.5 cm ^{3 of} an intermediate solution of a standard sample and bring the volume in the flask to the mark with a 1% solution of nitric acid.

8. Auxiliary solution No. 3 with a mass concentration of vanadium 10 μg / DM ³ .

Prepared from auxiliary solution No. 1 with a mass concentration of vanadium of 100 μg / DM ³ .

In a volumetric flask with a capacity of 50 cm ³ make 5 cm ³ auxiliary solution No. 1 and bring the volume in the flask to the mark with a 1% solution of nitric acid.

The construction of the calibration schedule is performed using the solutions shown in table 1.

The calibration schedule is set on the above calibration solutions. Determination of the calibration dependence, processing and storage of calibration results are performed by the mass spectrometer software.

The proposed method is as follows:

- for both options, at first they take a sample of atmospheric air in a volume of 1 m ³ by pulling the test air through an analytical aerosol filter, for example, AFA-XA grade at a speed of 50 l / min for 20 minutes;

- at the same time, air temperature and atmospheric pressure are recorded at the time of sampling, taking into account that in the future, when establishing the concentration of vanadium, the volume of air taken for analysis is brought to normal conditions;

- after selection, the filter is folded four times the exposed surface inside, placed in a bag of tracing paper and a plastic bag;

- after sampling, the specified filter is subjected, according to the first embodiment, to decomposition by microwave sample preparation, in which:

- the exposed filter is placed in a fluoroplastic glass,

- add 0.1 ml of a solution of erbium (or terbium) in deionized water with a mass concentration of 1 mg / DM ³ and add 5 ml of concentrated nitric acid with a density of 1.415 g / cm ³ ,

- the sample is mineralized according to the program for the microwave sample preparation system (the MC-6 furnace manufactured by Volta Association, St. Petersburg, to which a number of Methods, in particular the Filter Mineralization Method) was applied, was used as the microwave system;

- then the mineralized sample is transferred to a 15 ml polypropylene volumetric tube, then the remainder of the sample is washed 2-3 times by adding 1 ml of deionized water to a glass, shake and transfer each wash to a mineralized tube, bring the sample volume to 10 ml with deionized water ,

- close the tube with a laboratory sealing film, mix the sample. This completes the microwave sample preparation cycle.

In the second embodiment, sample preparation is performed in a muffle furnace, in which:

- exposed filters are placed in quartz glasses, add 0.1 ml of an internal standard with a mass concentration of Er (or Tb) of 1 mg / dm ³ . Cups are installed in a muffle furnace. It is kept at a temperature of 100 ° C for 40-60 minutes, then at a temperature of 250 ° C for 40-60 minutes, it is ashed at a temperature of 450-500 ° C for 3.5 hours. The resulting ash is moistened with 0.3 ml of concentrated HNO _{3 with a} density of 1.415 g / cm ³ , heated in a sand bath, evaporated to the state of wet salts. After cooling, dissolve in 5 ml of a 1% aqueous solution of HNO ₃ , transfer to a measured polypropylene tube with a capacity of 15 ml, rinse a quartz glass 2-3 ml of 1 ml of a 1% aqueous solution of HNO ₃ , transferring each wash to a test tube, the volume is adjusted to 10 ml of 1% HNO ₃ , close the tube with a laboratory sealing film, mix the sample. This completes the sample preparation cycle in the muffle furnace.

Simultaneously with the analyzed samples, 2-3 blank samples are prepared, consisting of unexposed filters from the same batch as the exposed filters.

Samples after dissolution are prepared for measurement by diluting them. To do this, 0.5 ml of sample and 4.5 ml of deionized water (for samples with sample preparation in the microwave system) or 4.5 ml of 1% are added to a test tube of an automatic sampler of a mass spectrometer (or another tube from which a sample is sprayed during measurement) solution of nitric acid (HNO ₃ ) (for samples from a muffle furnace). Close the tube with a sealing film, mix. They are sent for measurement on an Agilent 7500 _cx mass spectrometer under the following conditions:

Parameter Value High Frequency Power (W) 1500 Distance from burner to bleed cone (mm) 7.2 Horizontal burner offset (mm) 0.4 Burner vertical offset (mm) one Carrier gas flow rate (dm ³ / min) 0.9 Charge gas flow rate (dm ³ / min) 0.25 Spray Pump (rpm) 0.1 Spray chamber temperature (° C) 2 Extraction lens 1 (B) 4,5 Extraction lens 2 (B) - one hundred Displacement Omega Lens for 7500 _CX (V) - 16 Omega lens (separates ions) for 7500 _cx (B) 3.8 Reaction cell inlet lens (B) - twenty Quadrupole Focusing Lens (B) 5 Reaction cell outlet lens - twenty High-frequency voltage on the octopole (V) 160 Octopol bias voltage (V) - 6 Quadrupole bias voltage (V) - 3 Integration period at a concentration of up to 50 μg / dm ³ (s) 0.10 The integration period at a concentration of from 50 to 100 μg / DM ³ (sec) 0.010 Sample feed rate (cm ³ / min) 0.4

In solutions of single and test samples, in calibration solutions should be the same concentration of the internal standard (1 μg / DM ³ ).

The concentration of vanadium is determined using a calibration curve taking into account the reduction of the volume of air selected for analysis to normal conditions.

The result of determining vanadium in atmospheric air is presented as the average of several parallel measurements of the analyzed solution.

The mass concentration of vanadium in atmospheric air (mg / m ³ ) is calculated by the formula:

where X is the mass concentration of vanadium in atmospheric air, mg / m ³ (μg / dm ³ );

a - mass concentration of vanadium in the solution of the prepared sample, determined according to the calibration graph, µg / DM ³ ;

õï - mass concentration of vanadium in a blank sample solution, determined according to the calibration schedule, µg / dm ³ ;

V ₁ - the volume of the sample solution, taking into account dilution, dm ³ ;

V ₀ - the volume of air selected for analysis and reduced to normal conditions, dm ³ .

V ₀ calculated by the formula:

where V is the volume of stretched air, dm ³ ;

P - atmospheric pressure when sampling air, mm Hg;

t is the air temperature at the time of selection, ° C.

The obtained measurement results of vanadium by the proposed method are shown in table 2 (according to these determination results, indicators of repeatability and reproducibility of the results are calculated). At the same time, according to the results of the determinations (X _n ) given in this table 2, one can judge the sensitivity of the method.

Table 3 shows the influence of the internal standard on the determination of vanadium by the proposed method, it is especially important to introduce an internal standard to more accurately determine low concentrations of vanadium (0.05; 0.1 μg / dm ³ ).

To determine the relative error of the method used the method of "entered - found."

The samples are analyzed with the addition of a certain amount of the analyzed component of vanadium (the additive is 50-150% of the concentration in the working sample), in this case, vanadium, to determine the correctness and accuracy of the analysis (relative error). The obtained measurement results of vanadium in the prepared sample with its additive are shown in Table 4. In this example, the value of the vanadium additive is C = 0.1 μg / dm ³ , the average detected value of the added additive was 0.095 ± 0.009 μg / dm ³ .

During laboratory tests of the proposed method, the following data were established: the range of measurements of vanadium in atmospheric air, the values of accuracy, repeatability, intralaboratory precision, reproducibility of the proposed method. The data are shown in table 5.

The data presented in table 5 show that the proposed method allows with a high degree of accuracy and reliability to determine vanadium in the air in the concentration range of 0.000005-0.02 mg / m ³ . The sensitivity of the method allows to detect low concentrations of vanadium in atmospheric air, including at the level of reference values (0.00007 mg / m ³ ). For example, based on the results of the determinations (table 2), after calculations (using the calibration graph and formulas), taking into account the values of blank experience and the conditions specified in the proposed method (1 m ³ , selected air, dilution of the mineralizate 100 times), the content vanadium in atmospheric air will be 0.000006 mg / m ³ , which is even lower than the reference concentration.

In addition, the proposed method provides high measurement accuracy of 21% and is characterized by high selectivity (table 6).

Table 1 Preparation of solutions for constructing a calibration graph for determining the concentration of vanadium by the proposed method Solution number one 2 3 four 5 6 7 The volume of the intermediate solution of erbium (terbium) (100 μg / DM ³ ), cm ³ 0.05 0.05 0.05 0.05 0.05 0.05 0.05 The volume of the solution is 1% HNO ₃ , cm ³ 4,5 4.45 4.9 4.45 4.45 4.45 2.45 The volume of solution No. 1 (100 μg / dm ³ ), cm ³ - - - - - 0.5 2.5 The volume of solution No. 2 (50 μg / dm ³ ), cm ³ - - 0.05 - 0.5 - ^- The volume of solution No. 3 (10 μg / dm ³ ), cm ³ - 0.5 - 0.5 - - - Mass concentration of vanadium in calibration solutions, μg / dm ³ 0 0.1 0.5 1,0 5,0 10.0 50,0

table 2 The results of the analysis of solutions of prepared samples, μg / DM ³ L, result number
ℓ = 1, L N, number of parallel definitions
n = 1, N X _n , result of parallel determination

, среднее арифметическое параллельных определений
N=2

, arithmetic mean of parallel definitions
N = 2

, values of sample variances one one 0.0840 0.0842 8 · 10 ^-8 2 0.0844 2 one 0.0878 0.0901 1,05810 ^-5 2 0.0924 3 one 0,0787 0,07845 1.25 · 10 ^-7 2 0,0782 four one 0.0828 0.0813 4,5 · 10 ^-6 2 0,0798 5 one 0,0765 0,0735 1.8 · 10 ^-5 2 0,0705

Table 3 Solutions of standard samples of vanadium, measured with an internal standard and without an internal standard try With ext. (Er) Without ext.standard 0.05 mcg / dm ³ 0.045; 0,055 0,034 0.1 mcg / dm ³ 0.084; 0.110; 0,101 0,079 0.5 mcg / dm ³ 0.430; 0.503 0.45 1.0 mcg / dm ³ 0.83; 0.94; 1.02; 1,07 0.88; 0.94 5.0 mcg / dm ³ 5.05; 5.5 4.55; 4.71 10.0 mcg / dm ³ 9.8 9.6

Claims (4)

1. A method for determining the concentration of vanadium in atmospheric air by inductively coupled plasma mass spectrometry, characterized in that atmospheric air is sampled by drawing test air through an aerosol analyzer at a speed of 50 l / min for 20 minutes and fixing the air temperature and atmospheric pressure at the time of sampling, after sampling, the filter is decomposed by microwave sample preparation, in which the filter is placed in a fluoroplastic glass, and then a solution of the internal standard of erbium or terbium in deionized water with a concentration of 1 mg / dm ³ and concentrated nitric acid are added to it, the sample is mineralized according to the program to the microwave sample preparation system, the obtained mineralized substance is transferred to a polypropylene tube, the fluoroplastic glass is washed out from under the sample 2-3 times by introducing 1 ml of deionized water, shaking and transferring each wash to the indicated tube, bring the sample volume to 10 ml with deionized water, mix the contents, then the sample obtained is diluted with deionized water in a volume ratio of 1: 9, respectively, placed in a test tube of a sampling device of a mass spectrometer with inductively coupled argon plasma, and the measurement is carried out, and the concentration of vanadium in air is determined using a calibration curve taking into account the reduction in the volume of air taken for analysis, to normal conditions. 2. The method according to claim 1, characterized in that AFA-XA filters are used as an analytical aerosol filter. 3. A method for determining the concentration of vanadium in atmospheric air by inductively coupled plasma mass spectrometry, characterized in that atmospheric air is sampled by drawing test air through an analytical aerosol filter at a rate of 50 l / min for 20 minutes and fixing the air temperature and atmospheric pressure at the time of sampling, after sampling, the filter is decomposed by the method of sample preparation in a muffle furnace, in which the filter is placed in a quartz glass and added creates internal standard terbium or erbium in deionized water at a concentration of 1 mg / dm ^{3, the} cup was placed in a muffle furnace and heated successively at 100 ° C 40-60 minutes at a temperature of 250 ° C 40-60 min, then digestion is conducted at a temperature 450-500 ° C for 3.5 hours, the resulting ash is moistened with concentrated nitric acid, heated in a sand bath and evaporated to the state of wet salts, after cooling it is dissolved in a 1% aqueous solution of nitric acid to obtain a mineralizate, and the resulting mineralate is transferred to A black test tube, quartz glass washes out from the sample 2-3 times by introducing 1 ml of a 1% aqueous solution of nitric acid, transferring the washings to a test tube with a sample, the resulting volume was adjusted to 10 ml with a 1% aqueous solution of nitric acid then the sample is diluted with a 1% aqueous solution of nitric acid in a volume ratio of 1: 9, respectively, placed in a test tube of a sampling device of a mass spectrometer with inductively coupled argon plasma, and the measurement is carried out, and the concentration of vanadium is determined using the calibration curve with the actuating volume of air sampled for analysis to normal conditions. 4. The method according to claim 1, characterized in that AFA-XA filters are used as an analytical aerosol filter.