RU2161790C2 - Multipurpose quartz dish for spectrophotometric measurements under pressure ( versions ) - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: there are proposed two versions of design of multifunctional quartz dish which combines functions of traditional spectrometric dishes for work under excessive pressure and makes it possible to separate two solutions of reagents, to mix them at any time determined by operator in addition. In agreement with first version all-quartz dish is made of rectangular optical part, quartz rod with 1.0 mm capillary, cylinder and cylindrical plug. According to second version split dish with microsection is separated from upper cylinder by location plug with 0.02 mm capillary. Capillary hole in dish of first type is diminished by inserted rod after filling with first solution. Solution in cylinder is separated from solution in dish and can be injected into volume of optical part of dish after rise of pressure only. EFFECT: design of proposed dish makes it feasible to conduct several subsequent injections with rise of pressure. 9 cl, 2 dwg

Description

 The invention relates to the field of physical organic chemistry, to the section of spectrophotometry of solutions under elevated pressure, and is used for scientific research. Such a cuvette makes it possible to carry out kinetic and equilibrium measurements at elevated pressures (up to 200 MPa, 2000 bar) and determine activation volumes and reaction volumes.

 In elevated pressure spectrophotometry, basically, two types of devices are used to study solutions isolated from pressure transmitting liquids: 1) a device using a mercury shutter and 2) a variable volume cuvette device. In the first type of device, a container with mercury is located above the test solution and mercury can penetrate into it through the capillary with increasing pressure. These designs with a mercury shutter are described in several works [N.S. Isaacs. Liquid Pase High Presuure Chemistry. John Wiley and Sons, Chichester, New York-Brisbabe, Toronto, 1981. Chapter 1 .; N. S. Isaacs, A. Laila // J. Phys. Organ. Chem., 1994, v. 7, p. 178-180], easy to operate, are currently used. The disadvantages of a cuvette with a mercury shutter include the possibility of blocking the light beam with mercury at the bottom of the cuvette, contamination of the transmission fluid with the test solution during depressurization.

 More convenient are the designs of quartz cuvettes of the second type, in which pressure transfer occurs due to a change in the volume of the cuvette itself. Cuvette Le Noble [W. J. Le Noble, R. Schlot // Rev. Sci. Instrum. 1976, v. 47, p. 770. (Russian translation - Instruments for scientific research, 1976, N 6, p. 125, see critical analysis of previously known cuvettes)]] is made from the outer and inner tubes of a quartz syringe. Quartz windows are welded to the ends of each of these parts. The free ends are inserted into each other and the test solution is poured through a special window with a syringe. After being released from air bubbles, parts of the cell are deployed along the axis of the cell half a turn. For these purposes, the cuvettes are very convenient, with the exception of the high probability of skewing of the composite tubes due to their horizontal arrangement, small approach and, as a result, breakdown of the cuvette under high pressure.

 In high pressure cuvettes for spectrophotometry described by Fleischmann, End and Strenks [F.K. Fleischmann, E.G. Konze, H. Kelm // Rev. Sci. Instrum. 1974, No. 11, p. 1427 (Russian translation - Instruments for Scientific Research, 1974, N 11, p. 128)] pressure transmission occurs when the Teflon rod is moved, which, when operated under pressure, gradually changes size due to its own compressibility and, as the authors themselves indicate, requires frequent replacements. In another embodiment, the design of the cell of the same authors [F.K. Fleischmann, E. G. Conze, H. Kelm // Rev. Sci. Instrum. 1974, No. 11, p. 1427 (Russian translation - Instruments for scientific research, 1974, N 11, p. 128)] the pressure is transferred to the cuvette by compressing a thin-walled Teflon tube with a solution screwed to the cuvette. In the latter case, the dimensions of the high-pressure apparatus increase sharply.

 The mixing of two solutions at elevated pressure using a striker is described for a fluoroplastic cuvette [G.P.Shakhovsky, B.S. Eljanov, N.I. Prokhorova // PTE, 1972, N 2, p. 164], which makes this cuvette unsuitable for the ultraviolet field of study and its use is no longer mentioned.

 Note that neither the earlier designs of the high pressure cuvette [W.J. le Noble.// J. Am. Chem. Soc. 1963, V. 85, N. 5, p. 1470 (see there different designs of the ditch); E. Gallei, S. Schadow // Rev. Sci. Instrum. 1974, N 12, p. 1504 (Russian translation - Instruments for scientific research, 1974, N 12, p. 8); E. Fishman, H. G. Drickamer. // Analytical Chemistry, 1956, v. 28. N 5, p. 804.6-8], nor the modern modifications described above [W.J. le Noble, R. Schlot // Rev. Sci. Instrum. 1976, v. 47, p. 770. (Russian translation - Instruments for scientific research, 1976, N 6, p. 125; FK Fleischmann, EGConze, H. Kelm // Rev. Sci. Instrum. 1974, N 11, p. 1427 (Russian translation - Instruments for scientific research, 1974, No. 11, p. 128)] cannot, in principle, perform one of the functions of our proposed cell. Purpose of the invention: Creation of a multifunctional quartz cell, the design of which allows you to combine both of the best known designs of spectrophotometric cells for operation high pressure and additionally, different from all known structures, allows you to isolate two astvora reagents and mix them at any time, as specified by the operator.

 This goal is achieved by the construction of two types of proposed cells.

 Type 1. An all-quartz cuvette for spectrophotometry at elevated pressure (Fig. 1) consists of a rectangular quartz optical part of the cuvette, with an internal cross section from 2x10 mm to 10x10 mm, with an optical path length of 2-10 mm (1), and a height of 20-50 mm to which a quartz rod (2) with an external diameter of 16 mm, a height of 10 mm and an internal capillary (3), with a diameter of 0.8-1.5 mm, and a height of 8 - 15 mm is welded. A quartz cylinder (4) with a diameter of 16 mm and a height of 10-30 mm with a polished inner surface is welded to the upper surface of the rod (2). A tightly fitted cylindrical plug-piston (5) with a height of 10-30 mm with a polished surface is inserted into the cylinder (4). In the hole of the capillary (3), a rod (6) can be inserted from a material stable (inert) to the reaction medium, for example, stainless steel with a diameter smaller than the diameter of the capillary by 0.01-0.03 mm. The upper part of the rod (4-6 mm) is bent at a right angle, which prevents it from falling into the cell.

 Type 2. A quartz cuvette for spectrophotometry at elevated pressure (Fig. 2) consists of a rectangular quartz optical part of the cuvette, with an internal cross section from 2x10 mm to 10x10 mm, with an optical path length of 2-10 mm (1), and a height of 20-50 mm to which a conical quartz thin section coupling is welded (2).

 The glass cylinder (5) is made of an external syringe barrel with a diameter of 16 mm and a height of 10-30 mm. The lower part of the cylinder (5) is made in the form of a conical landing thin section core (3), with an internal capillary (4), with a diameter of 0.2-0.3 mm, and a height of 8 - 15 mm. A cylindrical plug-piston (6) with a height of 10-30 mm, made of a glass piston of the same syringe, is inserted into the cylinder (5).

 The proposed universal (multifunctional) cuvette (type 1 and type 2) can perform three functions: two main functions of high-pressure quartz cuvettes described above and, unlike all known cuvettes, the third function allows mixing of isolated reagent solutions at a time determined by the operator .

 First function. (Type 1, Fig. 1). Work with a reagent solution at elevated pressure due to a change in the volume of the cell. This function is also performed by the design of the cuvette Le Noble and Fleischmann described above. When working with a type 1 cuvette (Fig. 1), the reagent solution is injected through a capillary hole (3) into the cuvette (1) and then into the cylinder (4) using a syringe, the piston plug (5) is inserted to the middle of the cylinder volume (4) . Then, the cell filled in this way is lowered into the cell holder located in the cavity of the high-pressure steel block. Pour the pressure transfer fluid (in our case, n-hexane) and tighten the lid of the high pressure unit. The high-pressure unit is inserted into the cuvette compartment of the spectrophotometer and closed with a special cover to prevent uncontrolled lighting from entering the spectrophotometer.

 After the solution has been thermostated, the pressure is increased by a special compressor connected to a separation cylinder, in which the liquid (oil) compressed by the compressor and the pressure-transmitting liquid (in our case, n-hexane) are separated by a floating piston. n-Hexane, which flows under high pressure into the cavity of the high-pressure cell, moves the piston plug (5) in the cell into the cylinder (4), creating the same pressure in the measuring cell (1). The vertical arrangement of the cylinder (4) and the plug-piston (5) eliminates the possibility of skew, and the use of a quartz plug-piston (5) instead of the Teflon plug eliminates its volumetric deformation.

 When working with a type 2 cuvette (Fig. 2), the reagent solution is injected through the throat (2) into the cuvette (1), tightly closed with the core plug (3) of the cylinder (5) and the same reagent solution is poured into the cylinder (5), insert the plug-piston (6) to the middle of the cylinder volume (5). Further operations are carried out in the manner described above for the cell type 1.

 The second function. (Type 1, Fig. 1). The reagent solution is poured with a syringe into the cell compartment (1) and the capillary (3). A rod (6) is inserted into the hole of the capillary (3). Mercury is poured into the cylinder (4) and the cuvette assembly is placed in the cuvette holder of the high pressure cell.

 Type 2 (Fig. 2). The reagent solution is poured into the cuvette compartment (1), the core plug (3) of the cylinder (5) is tightly inserted. Mercury is poured into the cylinder (5) and the cuvette assembly is placed in the cuvette holder. Further operations coincide with the description of the first function of the cell. At elevated pressure, mercury passes through the free section in the capillary hole, creating a pressure in the test solution inside the quartz cell (1), equal to the pressure in the system.

 The third function. This function fundamentally distinguishes the proposed design from all known ones.

Type 1 (Fig. 1). A solution of one reagent is poured into the cell compartment (1). A rod (6) is inserted into the capillary (3). Next, a solution of the second reagent is poured into the volume of the cylinder (4), which does not mix with the solution of the first reagent due to the very low diffusion rate through the residual cross section between the capillary (3) and the rod (6). The cylinder (4) is closed with a plug-piston (5). The cuvette assembly is placed in its nest in the high pressure cell. During the filling of the cuvette, the assembly of the high-pressure unit, its placement in the cuvette compartment of the spectrophotometer, and thermostating of the unit, the reaction does not proceed. The reaction can be started at a time convenient for the operator by raising the pressure in the system, which leads to immersion of the piston plug (5) and to the injection of a solution of the second reagent from the cylinder (4) into the solution of the first reagent in the cuvette compartment (1) due to pressure equalization in system. Since the volume of the solution in the cell (1) is about 3 cubic cm and the compressibility factor of most organic solvents at 298 K is (8-16) · 10 ^-5 atm ^-1 , already at 100 atm the volume of solution injection of the second reagent into the quartz cell with the solution of the first reagent is 0.024 - 0.048 cm ³ , and at 500 atm ≈ 0.1 - 0.2 cm ³ . These volume changes in the cell occur only due to the displacement of the second reagent solution from the cylinder (4) into the volume of the first solution in the cell (1). In this way, one can easily calculate the initial concentrations of solutions of the first and second reagents in order to create conditions for the reaction to occur in the all-first-order mode after compression, when only the concentration of the solution of the first reagent in the cell (1) located in a large excess (≥ 10) compared with the concentration of the second reagent obtained in the volume (1) after compression. After accumulating data for calculating the rate constant at the initially selected pressure, it is possible to additionally increase the pressure by pumping an additional part of the reagent from the volume (4) into the volume of the cell (1) and obtain additional kinetic data for the same system at a different pressure.

 Type 2 (Fig. 2). A solution of one reagent is poured into the cell compartment (1). Insert the core plug (3) of the cylinder (5) into the neck (2) of the cuvette (1). Next, a solution of the second reagent is poured into the volume of the cylinder (5), which does not mix with the solution of the first reagent due to the very low diffusion rate through the capillary (4). The cylinder (5) is closed with a plug-piston (6). Further operations are carried out similarly as described for type 1.

 Components of the proposed quartz cell are available for manufacture. An all-welded rectangular quartz cuvette (1) (type 1, Fig. 1) is manufactured in series. The capillary (3) in the quartz column (2) can be made in different ways, for example by drilling. Cylinder (4) and plug-piston (5) are manufactured in accordance with the requirements for glass syringes. Another variant of this cuvette (type 2, Fig. 2) facilitates the cleaning of the cuvette and eliminates the need for a rod (6, Fig. 1) to reduce the cross section of the capillary. We made and tested such cuvettes in all three modes described above.

 Distinctive features.

 A type. 1. An all-quartz cuvette for spectrophotometric measurements at elevated pressure differs from all known spectrophotometric cuvettes in that it realizes the possibility of isolating two reagent solutions from each other in the volume of the optical part of the cuvette and in the cylinder volume due to the small free area of the capillary with an inserted rod, allowing mix solutions only during pressure increase in the system, when a solution is injected from a cylinder into a solution in the optical part.

 Type 2. This version of the cuvette differs from the previous one (type 1) in that the optical part of the cuvette is not welded to the upper part, but is connected to it by carefully fitted sections. This collapsible model allows you to reduce the diameter of the capillary in the cylinder plug and work without a liner. This makes it easy to fill and rinse the cuvette.

 Both types of design of the cuvette allow several consecutive kinetic measurements to be made with the same initial solution with a sequential increase in pressure in the system without disassembling the setup.

Claims (9)

 1. A universal quartz cuvette for spectrophotometric measurements under pressure, containing a rectangular cuvette, a cylindrical quartz rod welded to it with a capillary hole, into which a smaller diameter rod is inserted, and a cylinder with a piston plug is welded to the rod.  2. The cuvette according to claim 1, characterized in that the capillary in the quartz rod has a diameter of 0.8 - 1.5 mm and a length of at least 8 mm.  3. The cuvette according to claim 1, characterized in that the rod inserted into the capillary is made of inert metal, for example, stainless steel with a diameter of 0.01 - 0.03 mm less than the diameter of the capillary hole.  4. The cuvette according to claim 1, characterized in that the rectangular optical part of the cuvette has a length of 2-10 mm, a width of 10 mm, a height of 20-50 mm.  5. The cuvette according to claim 1, characterized in that the cylinder has an external diameter of 15 to 20 mm, a height of 10 to 30 mm.  6. A universal quartz cuvette for spectrophotometric measurements under pressure, containing a rectangular cuvette, a sleeve welded to it, into which a core with a capillary hole is inserted, a cylinder with a piston welded to the core.  7. The cuvette according to claim 6, characterized in that the capillary in the core has a diameter of 0.2 - 0.3 mm  8. The cuvette according to claim 6, characterized in that the rectangular optical part of the cuvette has a length of 2-10 mm, a width of 10 mm, a height of 20-50 mm.  9. The cuvette according to claim 6, characterized in that the cylinder has an external diameter of 15 to 20 mm, a height of 10 to 30 mm.

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