DD268877A1 - METHOD AND ARRANGEMENT FOR ELECTROPHORESIS WITHOUT SEKUNDAERE ELECTRODE REACTIONS - Google Patents

Abstract

The invention relates to a method for producing a directed movement of charge carriers in solutions or emulsions and is particularly suitable for the electrophoretic separation of amino acids. It is characterized by the fact that no electrode reactions take place, there is no galvanic current flow through the solution, the expenditure on equipment is reduced and the process management becomes uncritical. It is characterized in that a sequential electrode arrangement is interconnected to form a multi-phase system and a migration of potential wells in the electrode gap is generated by multi-phase activation, in which the charge carriers to be transported are enriched.

Description

For this 3 pages drawings

Field of application of the invention

The invention relates to a method and arrangements for producing a directed movement of electrically charged particles in solutions and emulsions and is particularly suitable for the electrophoretic separation of amino acids in aqueous solution.

Characteristic of the known technical solutions Aufm currently known technical solutions of electrodialysis and electrophoresis is common that in the electrolyte

forms a stationary electrical flow field. The charge carriers to be separated are only insignificantly involved in the current flow, which is mainly formed by the movement of the ions of the auxiliary electrolyte. The inevitable

Electrode reactions at the cathode and anode cause i.a. a strong gas evolution and shift in pH levels in the Elckttodenräumen and in the individual separation chambers. The anodic dissolution of metals forces the use of precious metals such as gold, platinum or iridium, of special Metals such as titanium with platinum / iridium coating or other inert electrodes such as graphite and carbon as Anodenmatria!. The current heat leads to an increase in the temperature of the electrolyte. Bd the separation of amino acids in the electric field, it depends very much on the compliance of the process parameters, which because

the secondary electrode reactions can be secured only with high equipment cost.

Methods are known which comprise a whole system of a plurality of ion exchange membranes separated from each other by ion exchange membranes Use chambers. By the electric current from the electrode chambers in the separation and Penetration chambers transported ions of the supporting electrolyte cause strong changes in pH caused by use

must be prevented by buffer solutions. Such a system is only capable of functioning for a limited time without constant replacement of the aqueous humor. The foreign ions of the buffer solution and the electrolyte must be retrofitted from the

Amino acid solution are removed chemically. In other methods, the electrolyte contained in the electrode chambers of the separation and Penetration chambers blocked by anion or cation exchange membranes. This will make it possible

on the one hand to use a different ionic conducting electrolyte and umzupur.ipen the electrode chambers separately for neutralization or in the Anodeumument standing cations and cathode space anions (1), so as to extend the duration of the experiment and on the other hand as Katolvt use a much higher concentration of the electrolyte than that of

Hilfseiektrolyten (H). However, catholyte and anolyte must be supplemented after a certain period of experimentation. In another method of electrodialysis, a cell battery is used from a plurality of narrow chambers, the

are alternately separated by cation and anion exchange membranes and between a

Electrode pair are located. To maintain the pH, electrical conditions are created Concentration polarization phenomena at the membranes result and therefore build up pH batteries. Additions of alkalis and acids to the food cells (6) and buffer solutions are also necessary to maintain the conditions

required.

For the elimination of sources of interference in electrochemical processes, especially the prevention of pH changes,

recommends the procedure according to (5); the cathode compartment through a cation exchange membrane and the anode compartment by a

To demarcate anion exchange membrane, whereby the buffer solutions of Trennkammem replaced by pure water and the Field strength without cooling can be significantly increased.

These and the methods mentioned in the other sources for the treatment and purification of amino acid solutions by electrodialysis are subject to analogous conditions and require similar apparatus systems. Consequently, they all have the following disadvantages:

You need for the power supply dimensio-stable electrodes, a conducting electrolyte with possibly own circuit; oxygen or hydrogen are produced at the electrodes, which must be dissipated separately; Cations form in the anolyte and anions in the catholyte which gradually neutralize the electrolyte, which therefore have to be renewed after a certain experimental period; Within the cell battery, pH shifts occur due to ion migration, which must be corrected by buffer solutions or other ionic additives during the process.

There is also known a method (12) in which ions are moved by means of a sequential electrode arrangement by means of periodic electrical pulses, which, however, differs in essential points from the method according to the invention.

In (12), as the electrode material, platinum or copper coated with gold, nickel, tin, rhodium, palladium or other corrosion-resistant metal is used. Since there is a galvanic connection between the electrodes and the solution, it is only possible to work with low voltages (1.5 volts), since otherwise the secondary electrode reactions would take precedence.

The transport of the ions is thus also accomplished in the said method (12) by a flow field between the electrodes, wherein by selecting a suitable pulse frequency for driving dor sequential electrode arrangements secondary electrode reactions are pushed back, but not completely interrupted, whereby gas evolution occurs at the electrodes. The directed movement of the ions occurs by their constant transfer and attachment to the electrodes.

In contrast, the method according to the invention is characterized by the following advantages:

Since the strip electrodes used are insulated with a PE film over the solution containing the ions, there is no electrical flow field in the solution. There is no anode or cathode in the sense of electrolysis. The electric field formed between the strip electrodes drives the ions forward with a force whose magnitude is proportional to the amplitude of the voltage, the insulated electrodes allowing very high voltages.

Secondary electrode reactions and gas evolution do not take place because no galvanic current flows. The forward movement of the ions takes place through controlled potential wells without accumulation on electrode surfaces.

Sources of information on the characteristics of the known technical solutions [1] Fioschin.M.Ya. in: Progress in the Electrochemistry of Organic Compounds Ed .: A.N. Frumkirt and A.B. Ershler

London / New York: Plenary Press 1971, No. 1 "Demineralization and Separation of Amino Acids" [2 | YujiroHara

"The Separation of Amino Acids with an Ion-exchange Membrane"

Bulletin of the Chemical Society of Japan B.36, 1963, 1373-1376

[3] Fritz Beck "Electro-organic Chemistry" Akademie-Verlag, 1974, Electrodialysis of Amino Acids [4] Milan Bier, Electrophoresis Theory, Metkods, and Applications Academic Press Inc. Publishers, 1959, p

patents

[5] GDR 135353 Bergakademie Freiberg "Apparatus and method for carrying out electrophoretic processes" [6] BRD 02907450

"Process for separation of an aqueous solution of a gum by electrodialysis" I7] USPO 3,231,485

"Process for the purification of amino acids" [81 USPO 3,330,749

Process for treating Amino Acid Solution 19] USPO 3,459,650

Process for the purification of amino acids [10] USPO 3,398,078

Recovery of glutamic acid Values ley electroradialysis ΙΠ] USPO 3,051,640

Amino acid separation process [12] USP 3,846,274

Object of the invention

The aim of the invention is to drive a Vei and provide associated electrode arrangements, which are characterized by the following advantages:

- Process without stationary electrical flow

- no electrode reactions

- therefore no shift in pH

- no gas evolution even at high separation rates

- no precious metal or rare metal coated with precious metal such as ζ. Β. Titanium required

- Power consumption minimal

- uncritical process control

- no conductive or auxiliary electrolyte required - no buffer solutions required

Explanation of the essence of the invention

In contrast to known methods in which the cathode and anode are used and the current driving field strength at each point of the field is adjusted according to the Ruumladunggsdichte and the conductivity of the electrolyte, according to the invention by a system of isolated electrodes in each point of the field temporally and locally periodically changing potential distribution forced. The Fe'istärke causing charge transport is also periodic in place and time. A point of the same field strength moves at a uniform speed you rc ι the solution located in the electrode system. The forming potential wells and mountains migrate in the same way and serve as a kind of transport container for the charged particles that accumulate in them. If the rate of migration of the potential distribution is in the order of magnitude of the mobility of the charge carriers, then the particles which break out are forced back into the trough by the electric field strength growing toward the edge of the potential well. Since all charged particles aim for the lowest energy state, the charge carriers to be transported remain stuck in the potential wells.

According to the invention, electrically insulated electrodes which are permeable to the particles to be transported are arranged one after the other in the transport direction and connected so that each more than second electrode leads to the same potential. If a corresponding multiphase symmetrical voltage system is applied to the electrode chains thus formed, then the traveling potential field is formed in the interelectrode space. The rate of migration of the field depends on the period of the signals. Sinusoidal electrode voltages cause a continuous migration of the potential wells. The necessary low-frequency sinusoidal oscillations can be suitably approximated by stair curves.

embodiment

The invention will be explained in more detail using an exemplary embodiment. Figure 1 shows the basic structure of the electrophoresis depot for the separation of amino acids in the electrostatic field.

The electrode system TES was realized on double laminated printed circuit board material in such a way that on both sides of each printed circuit board a strip structure was created, which, as shown in picture 1, is connected to the three-phase system. Several printed circuit boards are arranged at a distance parallel to each other, which corresponds approximately to the strip width (Figure 2). The ratio of the strip width to the plate spacing significantly influences the field profile and is a size to be optimized for the specific application.

These parallel strip electrode support plates have the advantage that turbulence in the plane perpendicular to the transport direction is suppressed and thereby the remixing tendency is reduced. This strip electrode system TES is located in the transport space TR. In TR, the pH can be adjusted in a known manner and remains constant during the separation process, because the strip electrode are electrically isolated by occupying with a Pt-FoMe against the solution and secondary electrode reactions can not occur.

Figures 3 and 4 serve to illustrate the field migration in the electrode gap TR. A step-shaped approximation of a symmetrical sinusoidal three-phase system with 7 discrete voltage steps was used, which requires discretization of the phase angle in 30 ° steps. A period is thus subdivided into 12 switching steps, which are processed with the same switching frequency. The image of the potential distribution is given with the proviso that

- the potential run inside TR

- To be removed on the center line between two strip plates and the approximation that

- the potential in the central area be constant and

- The potential profile in the gap region between the strips should be linear.

In this way, a clear representation of the field migration is obtained and it is recognized that after a period of the electrode voltages, the potential distribution has advanced further by exactly 3 strip electrodes. The drift velocity of the particles and the rate of migration of the field should be roughly the same, otherwise either particles can be "lost", ie they can overcome the potential peak with the help of their diffusion forces, or static states can be achieved that do not contribute to the separation of the amino acids.

In the horizontal direction, imposed by the potential distribution, there is a periodic distribution of positive and negative charge carriers or especially of acidic and basic amino acids. Likewise, the potential distribution of the amino acid distribution has a period of three stripe electrodes. To enable the formation of potential wells, the solution should have the lowest possible conductivity. If the pH is adjusted by addition of acids or bases, this significantly increases the conductivity of the solution, which would counteract the actual transport mechanism. Only the charge carriers should contribute to the conductivity, the transport of which through the electric field is desired, because through the again and again excited charge balance, which is caused by the field shift, it comes to the movement of the charge carriers. Unaffected by the transport mechanism are all neutral particles, including the amino acids, which are in the isoelectric point.

With the principle realized by the present arrangement, therefore, it is possible to change the concentration of those amino acids in the solution whose isoelectric point is smaller or larger than the pH set in the solution. The results of Examples 1 to 3 were ei aims with the following simple experimental arrangement:

Inner dimensions of the glass tub 180mm long, 120mm high, 20mm wide

electrodes

Number of stripes per page 32

Slat width 5 mm

Strip spacing 1 mm

3 double-sided strip electrode carrier plates

Plate spacing 5 mm

Immersion depth 60 mm

System not cascaded; thereby stationary remixing disorder

example 1

An aqueous solution containing 4 mg of glutamic acid per ml and 4 mg of glycine per ml and having a pH of 3.6, was filled in the transport space and subjected to the transport mechanism according to the invention. The amplitude of the three-phase voltage was 200 volts, the period was 1 minute and the test duration 1 hour.

After the experiment, glycine accumulation at the end of the electrode system was 8.88 mg / ml = 220%, whereas the glutamic acid, whose isoelectric point is at pH 3.2, was accordingly only transported insignificantly and only at 5, 76mg / ml = 144% enriched.

Example 2

An aqueous solution containing 9 mg of glutamic acid per ml and 7.5 mg of glycerol per ml and adjusted to the isoelectric point of glycine, pH 6.2, with sodium hydroxide solution was charged into the transport space and subjected to the transport mechanism according to the invention as in Example 1.

After the experiment in the SRg at the end of the electrode system ^ an accumulation of glutamic acid to 11.08 mg / ml = 123% occurred while the glycine was not transported.

Example 3

An aqueous solution of a mixture of 16 amino acids with a total of 7.7 mg / ml, which had a pH of 8.3, was filled into the transport space and subjected to the transport mechanism according to the invention. The amplitude of the three-phase voltage was 220 volts, the period was 1 minute and the test duration was 1 hour.

After the experiment, an accumulation of the total amount of amino acid at the end of the electrode system was

14,97mg / ml = 194%.

The following table provides information on the migration of the individual amino acids.

In the TR turned concentration out for Anrei sat in SRg at the end TR added insurance ace solution the stripe immigrated on% electrodes after AS the attempt mg / ml rng / ml mg / ml lysine 0.558 1,192 0.634 214 histidine 0.05 0.09 0.04 180 arginine traces 0,075 0,075 - asparagine traces 0.037 0.037 - threonine 0,478 1,481 1,003 310 serine 0.636 1,226 0.59 193 glutamic acid traces traces - - proline 1,649 3,565 1,916 216 glycine 0.303 0,565 0.252 183 alanine 0.586 1,112 0.526 190 valine 0.457 0.677 0.22 148 methionine 0,360 0/90 0.13 136 I-leucine 0,798 1.345 0.547 169 leucine 1,283 2,457 1,174 192 tyrosine 0,107 0.138 0.031 129 phenylalanine 0.452 0.531 0.079 117 AS 7,717 14.971 7,254 194

If the described process is cascaded, a backmixing is excluded, and it is z. For example, it is possible to gradually reduce from an amino acid mixture in each case the concentrations of that amino acid whose isoelectric point is furthest from the adjusted pH. Due to the concentration gradient and the resulting diffusion forces, the neutral amino acids in SRg will be in equilibrium.

Technically conceivable would be a continuous operation of a cascaded apparatus. In the TR of the first apparatus, a mixture of amino acids is continuously supplied, the concentration of which is gradually changed and present in the SRg of the last cascade stage in the desired purity and concentration. The amplitude of the three-phase voltage, the period duration and the test duration are process parameters to be optimized.

Claims (2)

1. A method for generating a directed movement of charge carriers in solutions or emulsions by electrical means, characterized in that with the aid of an insulated electrode system, an electric field is generated, which changes locally and in time such that the forming potential wells in the electrode gap, in which the electrically charged particles accumulate, move directionally and without the aid of an electric flow field, the charge transport in one direction, eliminating all secondary electrode reactions, the separation process proceeds with the lowest performance and the Prozdßparameter are more stable. 2. electrode assembly for carrying out the method according to item!, Characterized in that for the particles to be separated from the solution isolated electrodes are arranged in the separation direction successively, this arrangement by secured insulated wire mesh or in the separation direction parallel support plates with insulated strip electrodes can be realized and this electrode system is interconnected by connecting each more than the second electrode with each other to a multi-phase system, which is controlled with a multi-phase voltage system.