RU2585369C1 - Method of determining content of cadmium, lead, arsenic, chromium, nickel, copper, zinc, manganese, vanadium, strontium, selenium, thallium in blood by mass spectrometry with inductively coupled plasma - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to analytical chemistry and can be used in sanitary-hygienic, ecological, medical and research organisations, operating in area of occupational pathology and human ecology. Summary: blood is sampled and prepared by adding to sample concentrated nitric acid, heating mixture and its dilution with deionised water with subsequent introduction of prepared sample into sampling device of mass-spectrometer with inductively coupled plasma, performance of measurements and determination of content of specific metal using calibration curve. Prior to adding to blood sample with concentrated nitric acid with density of 1.415 g/cm³ in sample is introduced complex internal standard solution of terbium, indium and germanium in deionised water with weight concentration of each of said element 100 mcg/dm³ in volume ratio of above complex solution to blood sample as 1:1 or 1:2 and in volume ratio of blood sample to concentrated nitric acid as 1:2. Mixture of sample with the above complex internal standard solution and with concentrated nitric acid is heated in water bath at a temperature of 65-70 °C to homogenisation. Further dilution of obtained mixture with deionised water is performed by introducing latter in volume of sum with volume of mixture of 100 vol parts and before prepared sample into sampler of mass spectrometer is centrifuged for 10 minutes at 2,700-3,000 rpm. At that, performance of measurements in prepared sample content of specific metal in mass spectrometer is carried out using reactive/collisional cell at passage through it of helium at a rate of 4.5-5.0 cm³/min. With specified measurement of content of lead and thallium in internal standard used is terbium, when determining cadmium are indium or terbium, and determination of other metals is germanium.

EFFECT: high sensitivity and accuracy of analysis while simultaneously reducing amount of blood sample required for analysis.

1 cl, 4 dwg, 11 tbl

Description

The invention relates to the field of analytical chemistry and can be used in sanitary-hygienic, environmental, medical and scientific organizations operating in the field of occupational pathology and human ecology when measuring mass concentrations of vanadium, chromium, manganese, nickel, copper, zinc, selenium, strontium, thallium, lead, cadmium and arsenic in the blood.

The relevance of the determination of heavy metals and trace elements in biological media grows with the deterioration of the environmental situation associated with the work of industrial enterprises, as well as the supply of harmful and dangerous chemical compounds from the exhaust gases of vehicles. One of the mechanisms of the toxic effect of metals is their ability to integrate into biologically active molecules and enzymes, displacing the vital elements on a competitive basis, the microelement composition in various organs and tissues changes, causing biochemical changes in the body, and the development of pathogenesis and the course of chronic diseases are aggravated.

In this regard, it is necessary to develop and improve methodological support for determining the quantitative content of cadmium, lead, arsenic, chromium, nickel, copper, zinc, manganese, vanadium, strontium, selenium, thallium in whole blood in a wide range of concentrations, including at the level of reference concentrations using a highly sensitive method of mass spectrometry with inductively coupled argon plasma.

The following methods are known from the prior art for determining metals in the blood, namely:

- Guidelines MUK 4.1.1897-04 "Atomic absorption measurement of mass concentrations of lead, cadmium, zinc and nickel in the blood", are intended to determine the mass concentration of lead, cadmium, nickel and zinc in the blood by atomic absorption analysis in a graphite furnace. This method is based on the atomization of the elements being determined by heating the sample to a high temperature in a graphite furnace or by spraying in a flame and measuring the absorption value of the characteristic radiation. Moreover, the detection limits of lead are 10 μg / dm ³ , cadmium - 0.4 μg / dm ³ , nickel - 20 μg / dm ³ , zinc - 1000 μg / dm ³ (method 1);

- Guidelines MUK 4.1.2103-06 “Determination of the mass concentration of vanadium in blood samples by atomic absorption spectrometry with electrothermal atomization”, designed to determine the mass concentration of vanadium in blood samples by atomic absorption analysis in a graphite furnace, provide the determination of vanadium in the range concentrations of 1.50-15.00 μg / dm ³ (method 2);

- Guidelines MUK 4.1.1899-04 "Atomic absorption measurement of mass concentrations of selenium in red blood cells and blood plasma" are intended to determine the mass concentration of selenium in red blood cells and blood plasma by atomic absorption analysis. The method is based on the production of volatile selenium hydride, its thermal decomposition, and subsequent measurement of the resonance absorption of the selenium line on an atomic absorption spectrometer with a hydride attachment in a concentration range of 0.001-0.02 μg / dm ³ (method 3).

The disadvantages of these known methods are the duration of the analysis (methods 1, 2, 3); insufficient sensitivity (method 1, 2); the complexity of sample preparation (method 3).

Also known is a method for determining the content of heavy metals in whole blood (RF Patent No. 2184973), according to which the test blood sample is treated with acid, its subsequent ashing is carried out, the resulting ash is treated with concentrated mineral acid, evaporation to the state of wet salts, the introduction of a background solution and determination of metal content using the instrumental method, while 0.5-5.0% aqueous nitric acid solution is used as the acid for processing the test sample and as the background solution at a volume ratio of sample: acid as 1: 1, while before ashing the sample is dried in two stages at a temperature of 110 ° C and 250 ° C, ashing is carried out at a temperature of 430 ° C, concentrated ash is used as a concentrated mineral acid for processing nitric acid, and atomic absorption spectrophotometry is used as an instrumental method. The disadvantage of this known method is that:

- in the process of ashing of the sample, the loss of easily volatile compounds of arsenic, selenium occurs, which reduces the accuracy of determination;

- the measurement of each ingredient is carried out sequentially, which significantly increases the analysis time in comparison with the measurement of several elements simultaneously;

- the method of atomic absorption spectrophotometry specified in the patent does not allow determination of arsenic, vanadium, strontium, selenium, thallium;

- the sensitivity of the method does not allow to determine the concentration of Nickel, chromium, manganese, lead at the level of reference values.

Closest to the proposed method is the method described in the Guidelines MUK 4.1.1483-03 "Determination of the content of chemical elements in diagnosed biosubstrates, preparations and biologically active additives by mass spectrometry with inductively coupled argon plasma". The known method described in these MUKs is designed to determine chemical elements, including vanadium, chromium, manganese, nickel, copper, zinc, selenium, strontium, thallium, lead, cadmium and arsenic in the blood by ICP-MS. According to the known method, a blood sample is taken from the ulnar vein (venous, in a hospital) or from the fingers (capillary). The volume of blood taken should be at least 1 ml. Next, it is sampled by adding 0.3-1.0 ml of concentrated nitric acid to it and then placing the mixture in a fuser heated to 115 ° C. The mixture is kept in the thermal block for 0.5-1.0 hours until the sample is homogenized. Next, the sample is transferred into a measuring tube, diluted with deionized water. Next, the prepared sample is introduced into the sampling device of the mass spectrometer with inductively coupled plasma, measurements are taken and the specific metal content is determined using the previously constructed calibration graph.

However, this known method is not sufficiently accurate, sensitive and selective, because It does not describe the specific conditions for the use of an octopole reaction / collision cell, the use of comparison elements (internal standard) for the effective elimination of polyatomic and isobaric overlays, traffic noise, possible errors in sample preparation and taking into account the sensitivity drift of the mass spectrometer.

In addition, this method does not allow determining the content of some metals at the reference level, for example, chromium - 0.7 μg / dm ³ , vanadium - 0.1 μg / dm ³ , and at the same time requires a large volume sample of whole blood for analysis.

In addition, the known method does not meet the modern requirements of metrological certification, provides only general recommendations, and not the exact modes of analysis for various biosubstrates.

The technical result achieved by the proposed method is to increase the sensitivity and accuracy of determining the metal content in the blood at a level of from 0.05 μg / dm ³ while reducing the volume of blood sample required for analysis.

Additionally, the accuracy is also enhanced by the fact that sample preparation takes place in one test tube, which reduces the risk of contamination or loss of analyte.

The certification of metrological characteristics for concentrations in the ranges characteristic / possible for whole blood was carried out.

The specified technical result is achieved by the proposed method for determining the content of cadmium, lead, arsenic, chromium, nickel, copper, zinc, manganese, vanadium, strontium, selenium, thallium in the blood by mass spectrometry with inductively coupled plasma, including blood sampling, sample preparation by adding concentrated nitric acid to the sample, heating the mixture and diluting it with deionized water; introducing the prepared sample into the sampling device of an inductively coupled plasma mass spectrometer, taking measurements and determining the content of a specific metal using a calibration graph, it is new that before adding concentrated nitric acid with a density of 1.415 g / cm ³ to the sample, it is introduced into the sample complex solution of internal standard terbium, indium and germanium in deionized water with a mass concentration of each of said element 100 g / dm ³ at a volume ratio ukazannog a complex solution to a blood sample as 1: 1 or 1: 2, respectively, and when the volume ratio of a blood sample to concentrated nitric acid is 1: 2, respectively, the mixture of the sample with the specified complex solution of the internal standard and with concentrated nitric acid is heated in a water bath at a temperature 65-70 ° C until homogenization, and subsequent dilution of the resulting mixture with deionized water is carried out by introducing the latter in a volume amounting to a total of 100 vol. h, and before introducing the prepared sample into the sampling device of the mass spectrometer, it is centrifuged for 10 minutes at a speed of 2700-3000 rpm, moreover, the measurements in the prepared sample of the specific metal content in the mass spectrometer are carried out using a reaction / collision cell at passing helium through it as a gas-reactant at a rate of 4.5-5.0 cm ³ / min and measuring at said lead and thallium is used as an internal standard terbium, when determining cad Ia - indium or terbium, and the determination of other metals - germanium.

When a mixture of a sample with a complex solution of an internal standard and with concentrated nitric acid is heated in a water bath, the homogenization time is 45-60 minutes.

The specified technical result is achieved due to the following.

The proposed method differs from the prototype in terms of sample preparation, the choice of an internal standard for each element to be determined, as well as the use of a reaction / collision cell with helium in a mass spectrometer to eliminate polyatomic overlays.

Due to the fact that before adding concentrated nitric acid with a density of 1.415 g / cm ³ to the blood sample, a complex solution of the internal standard of terbium, indium and germanium in deionized water with a mass concentration of each indicated element of 100 μg / dm ³ is introduced, increasing the accuracy and accuracy of the analysis, taking into account possible errors associated with the process of preparing samples in a known manner.

Due to the fact that the heating of the sample mixture with the specified complex solution of the internal standard and with concentrated nitric acid is carried out in a water bath at a temperature of 65-70 ° C until homogenization, the analyte is extracted from the blood (opening of the sample), there is no loss of volatile compounds, because . sample processing temperature is quite low. Heating to this temperature does not require special sophisticated equipment.

Performing centrifugation of the prepared sample into the sampling device of the mass spectrometer for 10 minutes at a speed of 2700-3000 rpm allows separating the undissolved carbon residue of the sample to prevent clogging of the microaerosol atomizer of the mass spectrometer.

The use of a reaction / collision cell when passing helium through it as a reactant gas at a speed of 4.5-5.0 cm ³ / min ensures the separation of analyte ions and interfering polyatomic ions while maintaining the high sensitivity of the method.

And due to the fact that the complex solution of the internal standard contains terbium, indium and germanium, it provides both an increase in the sensitivity of the method and an increase in the accuracy of determination, since Studies have shown that it is precisely if terbium is used as the internal standard when measuring the lead and thallium content, indium or terbium is used as the cadmium determination, and germanium is used as the other metals, then the found values of these chemical elements in a real blood sample will almost completely coincide with certified average values in certified SERONORM blood samples.

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:

- multi-element calibration standard with a concentration of 10 mg / l of silver, aluminum, arsenic, barium, beryllium, calcium, cadmium, cobalt, chromium, cesium, copper, iron, gallium, magnesium, manganese, sodium, nickel, lead, rubidium, selenium, strontium, thallium, uranium, vanadium, zinc in 5% nitric acid (Multi-element Calibration Standart 2A, USA);

- nitric acid density of 1.415 g / cm ³ highly pure GOST 701-89;

- deionized water, GOST R 52501;

- a complex solution of an internal standard with the content of comparing elements of bismuth, germanium, indium, lithium ⁶ , scandium, terbium, yttrium 10 mg / dm ³ ;

- a sensitivity adjustment solution for a mass spectrometer containing lithium, magnesium, yttrium, cerium, thallium, cobalt 1 μg / dm ³ or 10 μg / dm ³ ;

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

- gaseous helium of high purity (99.995%), TU 0271-135-31323949;

- Inductively coupled plasma mass spectrometer with an Agilent 7500 _cx octopole reaction / collision cell with the following characteristics:

mass scanning range, amu: 2-260;

detection limits: beryllium ≤1.5 ng / dm ³ , indium ≤0.5 ng / dm ³ , bismuth ≤0.5 ng / dm ³ ;

sensitivity (imp./s per 1 mg / dm ³ ): lithium (7) ≥30 · 10 ⁶ , strontium (88) ≥80 · 10 ⁶ , thallium (205) ≥40 · 10 ⁶ ;

short-term stability, standard deviation: ≤3%;

long-term stability, standard deviation: ≤4%;

doubly charged ions (cerium ²⁺ / cerium ⁺ ): ≤3%;

oxide ions (cerium II / cerium oxide): ≤1.5%;

background level at mass 9: <5 pulses / s;

detector speed: ≥100 μs per 1 ion;

MicroMist microaerosol spray;

peristaltic pump for sample supply;

spray chamber with electronic Peltier cooling;

injector diameter 2.5 mm.

- certified blood samples SERONORM (Norway).

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

- air temperature (20 ± 5) ° C;

- atmospheric pressure 630-800 mm RT. st .;

- humidity from 30 to 80%.

Performing measurements on a mass spectrometer is carried out in laboratory rooms equipped in accordance with the requirements of the instrument manual. The temperature gradient should not exceed 2 ° C / hour according to the “Instructions and Guidelines for the setup and operation of an inductively coupled plasma mass spectrometer”.

Solution preparation

1. The main multi-element standard sample with a concentration of mass concentrations of the analyzed elements of 10 mg / DM ³ .

2. Solution No. 1 with mass concentrations of ions of the analyzed elements of 100 μg / DM ³ .

Prepared from a solution of the basic multi-element standard sample with mass concentrations of the analyzed elements of 10 mg / DM ³ .

Volumetric flask with 50 cm ³ of making a pipette or an automatic dispenser of 0.5 cm ³ of solution the main multi-element standard sample with mass analyzed elements concentrations of 10 mg / dm ³ and the volume in the flask to the mark with 1% solution of nitric acid. Store 3-5 days in polypropylene tubes.

3. Solution No. 2 with mass concentrations of the analyzed elements of 50 μg / DM ³ .

Prepared from a solution of the basic multi-element standard sample with mass concentrations of the analyzed elements of 10 mg / DM ³ .

Volumetric flask of 100 cm ³ is made pipette or dispenser 0.5 cm ³ of solution the main multi-element standard sample with mass analyzed elements concentrations of 10 mg / dm ³ and the volume in the flask to the mark with 1% solution of nitric acid. Store 3-5 days in polypropylene tubes.

4. Solution No. 3 with mass concentrations of the analyzed elements of 10 μg / DM ³ .

Prepared from solution No. 1 with mass concentrations of the analyzed elements of 100 μg / DM ³ .

In a volumetric flask with a capacity of 50 cm, add a dispenser or pipette 5 cm ^{3 of} solution No. 1 and bring the volume in the flask to the mark with a 1% solution of nitric acid. Store 3-5 days in polypropylene tubes.

5. A complex solution of an internal standard with mass concentrations of each element of comparison (germanium, indium, terbium and there may be others) 100 μg / dm ³ .

Prepared from the main complex solution with mass concentrations of the elements of comparison of 10 mg / DM ³ .

In a volumetric flask with a capacity of 50 cm ³ make a dispenser or pipette 0.5 cm ^{3 of the} main complex solution with mass concentrations of each element of comparison of 10 mg / DM ³ and bring the volume in the flask to the mark with a 1% nitric acid solution. The solution is stored in a polypropylene tube for 2-3 days.

6. An integrated internal standard solution with mass concentrations of each reference element (germanium, indium, terbium) 1 g / ^dm3.

0.5 cm ^{3 of a} complex solution of an internal standard with mass concentrations of reference elements of 100 μg / dm ^{3 is} pipetted or pipetted into a volumetric flask with a capacity of 50 cm ³ and the volume is adjusted with a 1% nitric acid solution to the mark. Pour into a polypropylene tube. Use freshly prepared.

7. A solution of nitric acid 1%.

Measured with a dispenser or pipette 4.7 cm ^{3 of} concentrated nitric acid with a density of 1.415 g / cm ³ are mixed with 493 cm ^{3 of} deionized water, measured by a cylinder. Store in a plastic container.

8. A tuning solution with mass concentrations of lithium, magnesium, yttrium, cerium, thallium, cobalt 1 μg / DM ³ . Apply without additional preparation procedures.

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

The calibration characteristic is set daily on the prepared calibration solutions. A working series consisting of 5-6 solutions is prepared immediately before use by diluting the working solutions of the elements to be determined and a complex solution containing comparison elements (internal standard) of terbium, indium, germanium (table 1).

Determination of the calibration dependence, processing and storage of calibration results are performed by the mass spectrometer software.

The proposed method is as follows.

- Blood samples are taken in chemically clean tubes with the addition of an anticoagulant (heparin) or in vacuum tubes with an anticoagulant added.

- Then, blood samples are prepared by the method of acid dissolution as the most optimal during routine clinical analysis. For this, a blood sample with a volume of 0.1 cm (or 0.2 cm ³ ) is dispensed into a tapered graduated polypropylene tube with a capacity of 15 cm ³ , 0.1 cm ^{3 of a} complex solution of the internal standard of terbium, indium, germanium with a mass concentration of each the comparison element is 100 μg / dm ³ and 0.2 cm ³ (or 0.4 cm ³ ) of concentrated nitric acid with a density of 1.415 g / cm ^{3 is} added. The tube is closed with a lid, shaken and heated in a water bath at a temperature of (65-70) ° C until homogenization, mainly 45-60 minutes. Then it is brought to 10 cm ^{3 with} deionized water, centrifuged for 10 minutes at a speed of 2700-3000 rpm. At this stage, the sample preparation is completed.

- A sample prepared for analysis is transferred to a test tube of an automatic sampler of a mass spectrometer and for measuring mass concentrations of chemical elements: cadmium, lead, arsenic, chromium, nickel, copper, zinc, manganese, vanadium, strontium, selenium, thallium. Moreover, the measurements in the prepared sample of the content of a particular metal in the mass spectrometer are carried out using a reaction / collision cell while passing helium through it as a reactant gas at a speed of 4.5-5.0 cm ³ / min.

When implementing the proposed method, two parallel blood samples are prepared, while a blank sample is prepared. You can also prepare a control (verification) sample. As the specified control sample can serve blood samples with a known concentration (for example, certified blood samples SERONORM (Norway)) or samples with the addition of a known amount of the determined element.

At least two blank samples are prepared for each series of measurements, repeating the procedure for preparing samples containing all components except the test sample. In this case, utensils from the same batch that is used for analysis are used, and reagents are added as in the analyzed samples.

The mass concentration of the internal standard in the complex solution should be the same in calibration solutions, in the analyzed and in blank samples.

When measuring lead and thallium, it is recommended to use terbium as an internal standard, when determining cadmium - indium or terbium, and when determining the remaining elements - germanium.

When measuring sample solutions with a mass concentration above 25 μg / dm ³ for thallium and lead and 50 μg / dm ³ for other elements, it is preferable to additionally dilute the sample with deionized water, taking into account this dilution when calculating the results (coefficient K).

The concentration of chemical elements in a blood sample is determined using a calibration graph.

The result of the determination is presented as the average of the measurements of two parallel samples.

The mass concentration of the determined element in the blood is calculated by the formula:

где

Where

C is the mass concentration of the determined element in the blood, mcg / dm ³ ;

- среднее значение (определено по градуировочному графику) массовой концентрации элемента в растворе пробы крови, мкг/дм³;

- the average value (determined by the calibration graph) of the mass concentration of the element in the blood sample solution, mcg / dm ³ ;

- среднее значение (определено по градуировочному графику) массовой концентрации элемента в растворе холостой пробы, мкг/дм³;

- the average value (determined by the calibration graph) of the mass concentration of the element in the solution of blank sample, µg / DM ³ ;

K is the dilution coefficient;

V ₁ - sample volume obtained as a result of sample preparation, dm ³ ;

V ₀ - the volume of a blood sample taken for analysis, dm ³ .

The results obtained, on the example of measurements of thallium and vanadium in the blood (working sample) of the proposed method, are shown in tables 2 and 3 (indicators of repeatability and reproducibility of the results are calculated from these values). At the same time, according to the results of the determinations (X _n ) for these metals given in Tables 2 and 3, respectively, one can judge the sensitivity of the method (values obtained near the lower end of the range).

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

To do this, an analysis of blood samples is carried out with the addition of a certain amount of the analyzed component (the additive is 50-150% of the found metal concentration in the working sample), in this example thallium and vanadium, to determine the correctness and accuracy of the proposed method (relative error). The obtained measurement results of thallium and vanadium in the prepared sample with its addition to the blood sample are shown in tables 4 and 5, respectively. In this example, the amount of thallium supplementation in the blood sample was 0.05 μg / dm ³ , and the addition of vanadium was 0.5 μg / dm ³ . The average detected value of the added thallium additive was 0.057 μg / dm ³ , and the addition of vanadium was 0.49 μg / dm ³ .

The data shown in tables 4 and 5 show that the proposed method is characterized by high accuracy and accuracy of analysis.

Also, during laboratory tests of the proposed method, the following characteristics were established: the measurement range of 12 elements in the blood, the values of accuracy, correctness, repeatability and intralaboratory precision. The data obtained are shown in table 6.

The data shown in table 6, the data show that the proposed method allows with high accuracy to determine 12 chemical elements in the blood in a concentration range of 0.05-15000 μg / DM ³ . The sensitivity of the proposed method allows to detect low concentrations, including at the level of reference values, as well as high concentrations associated with intoxication of the body with chemical elements of these metals.

During laboratory tests, the results of analysis of real blood samples were also monitored by comparison with standard blood samples SERONORM® L1, L2, L3 (Norway).

The results of determining 12 elements in standard blood samples of SERONORM level L1 and L2 (the number of parallel experiments n = 5) are shown in Fig. 1. and Fig. 2. In Fig. Figure 1 shows the results of the determination of cadmium, lead, arsenic, chromium, nickel, copper, zinc, manganese, vanadium, strontium, selenium, thallium in% relative to the certified values in blood samples of SERONORM level L1, in Fig. 2 - results of determination of cadmium, lead, arsenic, chromium, nickel, copper, zinc, manganese, vanadium, strontium, selenium, thallium in% relative to the certified values in blood samples SERONORM level L2.

From those presented in Fig. 1 and 2 of the diagrams it can be seen that the content of 12 chemical elements in the certified SERONORM blood samples of levels L1 and L2 corresponds to the range of their concentrations in real blood samples established by the claimed method, which proves the accuracy of the proposed method.

In the course of laboratory tests, the effect of using the standard mode and the use of the reaction / collision cell when passing helium through it as a reactant gas at a rate of 4.5-5.0 cm ³ / min on the result of the analysis of certified blood samples using the example of determining vanadium was established (table 7) and the effect of various comparison elements (terbium, indium, germanium) of a complex solution of an internal standard on the result of the analysis of certified blood samples using the example of determination of vanadium, cadmium, lead (table 8).

The data shown in Table 7 show that the error in determining the metal content (for example, vanadium for various concentrations) in a certified sample using a reaction / collision cell and an internal standard (Ge reference element) is significantly lower than when operating in standard mode.

The data shown in table 8 show the value of the selected internal standard (element of comparison) on the result of the analysis of a certified blood sample. The table shows that, for example, when measuring cadmium it is more efficient (reducing the values of the analysis error) to use indium or terbium, when measuring lead (especially for low concentrations) - terbium compared to germanium, and for vanadium - germanium compared to indium and terbium.

Table 9 shows the conditions for the implementation of the proposed method in a reaction mode using helium as a reactant gas using a reaction / collision cell. In this case, before analysis, it is necessary that the reactant gas fill all the supply paths and the reaction cell, set the helium flow rate to 10 ml / min and leave the device for 30 minutes to stabilize, after which the analytical signal can be measured.

, ионам хрома Cr⁵²-⁴⁰Ar¹²C⁺ и ³⁶Ar¹⁶O⁺. Такие помехи и устраняются предлагаемым способом с помощью реакционно-столкновительной обработки экстрагируемой плазмы. Для этого устанавливали оптимальную скорость потока газа - гелия, заполняющего реакционно/столкновительную ячейку. Полученные данные приведены на Рис. 1, 2, 3 и 4. На указанных рисунках представлено графическое изображение зависимости интенсивности аналитических сигналов определяемых ионов, а также мешающих их определению полиатомных ионов от скорости потока гелия: Рис. 3 - определение ионов ванадия; Рис. 4 - определение ионов мышьяка.The inductively coupled plasma mass spectrometry method ICP-MS is highly selective, but interference analysis (polyatomic overlays) may occur when analyzing bioobjects of complex composition. The natural content of chloride ions in the composition of biosubstrates determines the interference superposition of chloride ions ClO ⁺ when determining vanadium ions V ⁵¹ , ArCl ⁺ ions when determining arsenic As ⁷⁵ . Plasma-forming gases can also cause polyatomic interference: the detection of doubly charged argon ions interferes with the determination of Se ⁸⁰ selenium ions

, chromium ions Cr ⁵² - ⁴⁰ Ar ¹² C ⁺ and ³⁶ Ar ¹⁶ O ⁺ . Such interference is eliminated by the proposed method using reaction-collision processing of the extracted plasma. For this, the optimal gas flow rate was determined - helium filling the reaction / collision cell. The data obtained are shown in Fig. 1, 2, 3, and 4. The figures show a graphical representation of the dependence of the intensity of the analytical signals of the ions being determined, as well as the interfering determination of the polyatomic ions on the helium flow rate: Fig. 3 - determination of vanadium ions; Fig. 4 - determination of arsenic ions.

, ⁴⁰Ar¹²C⁺ и ³⁶Ar¹⁶O⁺.The analysis of the given graphic image in Fig. 3 and Fig. 4 shows that at a flow rate of the reactant gas - helium, 2-3 cm ³ / min separation does not occur. Optimal inhibition interfering effect without loss of sensitivity in the determination of metals by the proposed method takes place at a helium flow rate of 4.5-5.0 cm ³ / min. It should be noted that such an addition of helium to a plasma-forming gas minimizes the intensity of polyatomic ions from the group

, ⁴⁰ Ar ¹² C ⁺ and ³⁶ Ar ¹⁶ O ⁺ .

Table 10 shows the recommended elements of internal comparison for each measured element, the measurement ranges and the mass of isotopes used in the measurement.

Table 11 shows the difference in the determination of vanadium by the proposed method and the prototype method.

Thus, the claimed method is characterized by the following advantages over the known:

- higher accuracy and sensitivity;

- the use of a reaction cell to effectively eliminate polyatomic and isobaric overlays;

- application of the “internal standard” method to reduce transport interference, sample preparation errors, sensitivity drift of the mass spectrometer;

- a simpler method of sample preparation, passing in almost one test tube, which reduces the risk of contamination of the sample from dishes and possible losses if it is necessary to transfer the sample, which also affects the accuracy of determination;

- metrological certification was carried out for concentrations in the ranges characteristic / possible for whole blood.

Claims (2)

1. The method of determining the content of cadmium, lead, arsenic, chromium, nickel, copper, zinc, manganese, vanadium, strontium, selenium, thallium in the blood by inductively coupled plasma mass spectrometry, including sampling a blood, conducting sample preparation by adding to the sample concentrated nitric acid, heating the mixture and diluting it with deionized water, introducing the prepared sample into the sampling device of an inductively coupled plasma mass spectrometer, taking measurements and determining the content of a specific metal with using a calibration graph, characterized in that before adding concentrated nitric acid with a density of 1.415 g / cm ³ to the blood sample, a complex solution of the internal standard of terbium, indium and germanium in deionized water is introduced into the sample with a mass concentration of each indicated element of 100 μg / dm ³ at volume the ratio of the specified complex solution to the blood sample as 1: 1 or 1: 2, respectively, and when the volume ratio of the blood sample to concentrated nitric acid as 1: 2, respectively, heating the sample mixture with The complex solution of the internal standard and with concentrated nitric acid is produced in a water bath at a temperature of 65-70 ° C until homogenization, and the subsequent dilution of the resulting mixture with deionized water is carried out by introducing the latter in a volume of 100 vol. o'clock, and before introducing the prepared sample into the sampling device of the mass spectrometer, it is centrifuged for 10 minutes at a speed of 2700-3000 rpm, and the measurements in the prepared sample of the content of a specific metal in the mass spectrometer are carried out using a reaction / collision cell when helium is passed through it as a reactant gas at a rate of 4.5-5.0 cm ³ / min and with the indicated measurement of lead and thallium content, terbium is used as the internal standard, when determining cad Miya - indium or terbium, and in the determination of the remaining metals - germanium. 2. The method according to p. 1, characterized in that when the sample mixture is heated in a water bath with a complex solution of an internal standard and with concentrated nitric acid, the homogenization time is 45-60 minutes.

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