RU36889U1 - LIQUID SAMPLE PREPARATION DEVICE FOR ISOTOPIC ANALYSIS OF HYDROGEN - Google Patents

Description

LIQUID SAMPLE DEVICE FOR ISOTOPIC ANALYSIS

The proposed device for sample preparation for isotopic analysis can be used in geochemistry, hydrology, medicine, ecology to determine the isotopic composition of hydrogen in natural aqueous materials.

A device for sample preparation of liquid samples for isotope analysis of hydrogen in pure water, serum, physiological fluids, volatile organic objects. The device includes a reactor with a heater, a vacuum pipe with valves for supplying hydrogen to the mass spectrometer, and an injection port for supplying a sample to the reactor, which consists of their seals. 1st in the upper part of the reactor and syringe. The reactor is a quartz tube with an inner diameter of 15 mm and a length of 220 mm, which contains about 50 g. chromium powder with a particle size of 0.3 mm

The sample is injected with a syringe into a reactor preheated to high vacuum and heated to 900-1400 0. The reaction between water and chromium proceeds within a few minutes, as a result of which the hydrogen formed through chromium enters the mass spectrometer inlet system for analysis according to the standard sample scheme, the total analysis time is 7 minutes. /1/

The disadvantage of this device is the creation of a very high temperature in the reactor, the toxicity of chromium powder, low reproducibility of the measurement results, high

hydrogen.

MKHGOINI / IO

the cost of the reactor and chromium powder, as well as the presence of a memory effect during the transition from analysis of one sample to another.

A device for determining isotopes of hydrogen and oxygen in water and water-containing minerals is known, using the method of decomposition of water using pyrolysis, consisting of a reduction reactor, a sample inlet unit and a system connecting the reactor to a mass spectrometer including a chromatophafic column

The reactor is a vertical ceramic tube with a diameter of 18 mm, made on the basis of aluminum oxide, the lower part of which is filled with silver wool to remove sulfur dioxide gases resulting from the destruction of the samples. Inside the tube there is a glassy carbon insert filled in the lower part by 1/3 of its length with coarse fragments of glassy carbon. The upper part of the tube is equipped with a sample and helium flow input unit. The sample inlet assembly consists of a rubber sealant (septa) with an inlet made for helium flow and a syringe for specimen injection.

Easily volatile analyzed samples are injected into the gas carrier - helium stream through a heated septum using a microsyringe. The sample volume is 0.1-0.15 microns. The sample volume can be increased by an order of magnitude when using dilution of the sample with helium. The decomposition temperature of the sample varies from 1320 ° C to, and the chromatographic system effectively decomposes H2 and CO. / 2 /

The disadvantage of this device is its complexity, significant analysis error (2-3 ° / oo), the need to introduce a chromatographic column into the system and the presence of a memory effect when moving from one analysis to another.

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The disadvantage of this device is its complexity in execution, the complexity of the process of decomposition of water, which is provided by this installation. For analysis, it is necessary to cool the cell with liquid nitrogen, a large electric current (up to 10A), a long analysis time, and the supply of a water-oxygen mixture to the mass spectrometer gives a large error in the isotope analysis. Moreover, the presence of a large amount of oxygen in the ion source leads to its rapid degradation and deterioration of the analysis results.

The objective of this technical solution is to simplify the preparation of samples for isotopic ayalysis, which allows to increase the speed and degree of decomposition of the sample.

The problem is solved in that in the sample preparation device for isotope analysis of hydrogen, containing a reactor with current leads, a sample inlet unit and a hydrogen supply line to the mass spectrometer, oxygen is used as a reactor, a solid electrolyte cell made in the form of a ceramic tube and equipped in the upper parts with a gasket made of heat-resistant sealant, in the cell there is an additional ceramic rod with two channels for sample injection and hydrogen removal, while the rod is fixed in a metal holding hardly with a Teflon liner, and is provided with an end face of the heat-resistant rubber gasket and a metal flange with two openings arranged in alignment channels of the ceramic rod. A heating furnace and an absorber for water are introduced into the device, placed on the hydrogen supply line to the mass spectrometer, one end of which is connected through a heat-resistant rubber gasket to the hydrogen removal channel of the ceramic rod.

It is advisable to carry out the reactor from oxygen chloride conductive ceramics based on zirconia stabilized with yttrium oxide.

in the proposed device used the method

catalytic decomposition of water on platinum, not leading to

significant fractionation of hydrogen isotopes, while

the oxygen formed as a result of the reaction is removed through

solid electrolytic cell into the atmosphere. Remaining clean

hydrogen is sent to an isotopic mass spectrometer.

In FIG. 1 shows a General view of the device.

The device consists of oxygen conducting

solid electrolyte ceramic cell 1 made of

oxygen conductive zirconia based ceramics,

stabilized by yttrium oxide in the form of a ceramic

test tubes. On the outside and inside of the tube

platinum electrodes are applied 2. From them to the contact

platforms 3 located in the unheated part of the ceramic

test tubes, conductive paths go 4. Heating furnace 5

provides a temperature of 800 ° C. The temperature inside the oven

measured using thermocouple 6. Inside the tube is placed

dual-channel aluminum oxide ceramic rod 7

for supplying sample 8 and removal of hydrogen 9 into line 10 of its supply to

mass spectrometer 11. The rod goes from the bottom of the tube and exits

outward at least 1/5 of its size. Outside

the rod is inserted into the Teflon insert 12, which

fixed in a steel holder. 13 (for fixing the rod in

holder uses 2 screws not shown).

Heat-resistant rubber gasket (septa) 14 is pressed against

two holes coaxial with the channels of the rod. The flange 15 is attracted to the steel holder 13 by bolts 16. A steel capillary 17 is inserted into the heat-resistant rubber gasket 14 coaxially to the hydrogen removal channel 9; it is a hydrogen removal line 10 connected through a valve 18 and a water absorber 19 with an isotopic mass spectrometer 11. The upper part of the ceramic tube equipped with a gasket 20 made of heat-resistant sealant, ensuring the tightness of the reactor during the decomposition of the sample.

The device operates as follows.

Through this capillary 17, the ceramic tube is evacuated by the fore-vacuum pump of the mass spectrometer 11 to a vacuum of 50 μbar. A sample of water with a volume of 1 μm is introduced into the channel 8 of the rod using a syringe 21 through a rubber gasket.

The cell is heated to a temperature of 800 ° C, at which catalytic decomposition of water occurs: 2Н2О 2Н2 + 02, its rapid evaporation occurs and steam fills the entire volume of the tube, while valve 18 is closed.

Oxygen in the form of an ion is transferred through ceramics located between the two electrodes from the cathode (negative electrode) to the anode (positive electrode). Thus, an electric current arises in the external circuit of the electrochemical cell. The voltage between the electrodes is 1.4V.

After complete catalytic decomposition of water on a platinum electrode 2 for 10-15 minutes and oxygen is vented through the wall of the ceramic tube 1 outward into the atmosphere, valve 18 opens and hydrogen, through the absorber 19, cooled by liquid nitrogen, enters the ion source of the mass spectrometer 11 for isotope analysis. The absorber 19 is necessary in order to prevent their entry into the mass spectrometer when the water vapor is not completely decomposed.

Since the current of oxygen ions passing through the electrolyte corresponds to the number of disintegrated water molecules per unit time, therefore, the flo, ad under this curve is equal to the total number of disintegrated molecules. Based on these data, the degree of decomposition of water during analysis can be calculated. To determine the isotopic composition of hydrogen in water, a calibration curve is constructed according to international water standards with a known isotopic composition of hydrogen. Samples of IAEA-OH-4 with isotopic composition, 4 ± 1.4%, GISP s, 5 ± 1.2%, SLAP s, 0% were used. The calibration graph is a straight line, 899bx-69.06, based on which the isotopic composition of hydrogen in water of unknown composition can be determined. The duration of the analysis is 10-15 minutes. To eliminate the memory effect during the transition from the analysis of one sample to the analysis of another, it is necessary to make a blank experiment with conducting the next water sample without taking measurements.

The error in measuring the isotopic composition of hydrogen is 0.5%.

The proposed device for sample preparation for isotopic analysis of hydrogen is much simpler than previously known in its manufacture, does not require significant preparatory work using liquid nitrogen, allows isotope analysis without the use of chemical reagents. The use of a solid electrolyte cell allows one to increase the rate of decomposition of a liquid sample by an order of magnitude. An additional advantage of this device is

providing the ability to monitor the process of decomposition of water and assess the degree of its decomposition.

The device is convenient in operation, while it is possible to replace its individual parts.

Sources taken into account when compiling the application materials:

1.J. Isotopes Enuiron, Heit Stud., 1996, v.32, s.263-273, New metod for fully automated isotope ratio determination from hydrogen at the natural abundance level. W.A. Brand, H. Avak.

2.J. Chemical Geology No. 178,2001, s.l97-210. A rapid method for determination of hydrogen and oxygen isotope ratios from water and hydroua mineral Z.D. Sharp, V. Atudorei.

3. J. Talanta, 1991, v. 38, No. 6, s.603-605, M.S. Lobal, F. Rashid, An elektrolitic device for preparation of hydrogen and oxigen from water for isotopic analysis.

Claims (2)

1. A device for preparing a liquid sample for isotopic analysis of hydrogen, comprising a reactor with current leads, a sample inlet unit and a hydrogen supply line to the mass spectrometer, characterized in that the oxygen-conducting solid-state cell made in the form of a ceramic tube and provided in the upper part is used as a reactor a gasket made of heat-resistant sealant, in the cell there is an additional ceramic rod with two channels for introducing the sample and removing hydrogen, while the rod is fixed in a metal holder with a teflon liner and is equipped with a heat-resistant rubber gasket on the front side and a metal flange with two holes aligned with the channels of the ceramic rod, while a heating furnace and an absorber for water are placed in the device located on the hydrogen supply line to the mass spectrometer, one end of which is connected through a heat-resistant rubber gasket with a hydrogen removal channel of the ceramic rod. 2. The device for preparing a liquid sample for isotopic analysis of hydrogen according to claim 1, characterized in that the reactor is made of oxygen-conducting ceramics based on zirconia stabilized with yttrium oxide.