TWI631218B - Fabricating method of maltitol - Google Patents

Abstract

The method for producing maltitol of the present invention comprises the following steps. Provide maltose. The maltose is hydrogenated by an electrode in a temperature range of 10 ° C to 80 ° C and a pressure range of 1 atm to 10 atm to produce a mixture including maltose and maltitol. The maltose in the mixture was separated from the maltitol by simulated moving bed chromatography.

Description

Method for producing maltitol

The present invention relates to a method for producing a sugar alcohol, and more particularly to a method for producing maltitol.

Diabetes derived from social progress has led to a rapid increase in the demand for low-glycemic index products, including stevioside extracted from natural sources, trehalose converted from maltose by enzymes, and various sugar alcohols obtained by hydrogenation after hydrolysis of starch ( Such as xylitol, sorbitol, and maltitol, etc., have gradually been accepted by the market.

However, the aforementioned sugars still encounter many difficulties in the promotion. For example, stevioside has the disadvantage of having a bitter taste or being too expensive to produce, and trehalose produced by metal catalyzed hydrogenation under high temperature and high pressure has a problem of sugar degradation. Therefore, there is an urgent need in the art to develop other manufacturing methods for low glycemic index products.

The present invention provides a method for producing maltitol to reduce manufacturing cost or improve operational safety.

The method for producing maltitol of the present invention comprises the following steps. Provide maltose. The maltose is hydrogenated by an electrode in a temperature range of 10 ° C to 80 ° C and a pressure range of 1 atm to 10 atm to produce a mixture including maltose and maltitol. The maltose in the mixture was separated from the maltitol by simulated moving bed chromatography.

In an embodiment of the invention, the electrode comprises a carbon electrode or a copper electrode.

In an embodiment of the invention, the electrode is coated with a catalyst layer.

In an embodiment of the invention, the catalyst layer is a nickel-based catalyst.

In an embodiment of the invention, the nickel-based catalyst is a nickel compound synthesized on the surface of the activated carbon support using NiSO ₄ or Ni(NO ₃ ) ₂ as a precursor.

In an embodiment of the invention, the nickel compound includes Ni, NiO, Ni(OH) ₂ or Ni(NO ₃ ) ₂ .

In an embodiment of the invention, the temperature range is from 15 ° C to 22 ° C.

In an embodiment of the invention, the simulated moving bed chromatography method comprises: (i) providing a simulated moving bed comprising at least three segments, which is composed of a moving phase and a stationary phase, and the three segments are sequentially a section, a second section and a third section respectively having a first relative flow velocity ratio m ₁ , a second relative flow velocity ratio m ₂ and a third relative flow velocity ratio m ₃ , the moving phase being the same in the simulated moving bed The direction flows through the three sections, the stationary phase simulates moving in the opposite direction with respect to the mobile phase; (ii) the mixture is injected between the second section and the third section of the simulated moving bed, and the maltose and maltitol in the mixture respectively have a first retention constant K _A and a second retention constant K _B , the second retention constant K _{B being} greater than the first retention constant K _A ; (iii) the first relative flow velocity ratio m _{1 of the} first segment is greater than the first retention constant K _A And (iv) the second relative flow rate ratio m ₂ and the third relative flow rate ratio m ₃ of the second and third sections are between the first retention constant K _A and the second retention constant K _B to separate Maltose and maltitol.

In an embodiment of the invention, the first section, the second section and the third section each comprise at least two columns, each of which is filled with a stationary phase having pores inside the particles.

In an embodiment of the invention, the first retention constant K _A is 0.03, the second retention constant K _B is 0.10, and the porosity inside the particles of the stationary phase is 0.2 to 0.8.

In an embodiment of the invention, the mobile phase comprises a flushing liquid, and the flushing liquid is deionized water.

Based on the above, the maltitol of the present invention is produced by hydrogenating maltose by an electrode at normal temperature and pressure to produce maltitol, and separating maltitol from maltose by simulated moving bed chromatography to purify maltitol. . Therefore, compared with the conventional high temperature and high pressure hydrogenation technology, the invention has the advantages of low energy consumption, low equipment demand, safe operation or high purification efficiency.

The above described features and advantages of the invention will be apparent from the following description.

The method for producing maltitol of the present invention comprises obtaining an electrochemical reaction at normal temperature and normal pressure, and the method for purifying maltitol comprises separating maltitol from maltose by simulated moving bed chromatography, thereby effectively improving separation efficiency and maltose. Alcohol purity. In detail, first, maltose is provided. Next, a maltose is hydrogenated by an electrode at a temperature ranging from 10 ° C to 80 ° C and a pressure of 1 atm to produce a mixture including maltose and maltitol. The maltose in the mixture was then separated from the maltitol by simulated moving bed chromatography. In one embodiment of the present invention, a nickel compound is attached to the surface of an activated carbon powder (ie, an activated carbon carrier) by a supercritical hydrothermal method to obtain a nickel-based catalyst, and a nickel-based catalyst is applied to a carbon electrode or a copper electrode. Above, the electrical hydrogenation is used to reduce the maltose to maltitol. The invention performs the synthesis of maltitol in a highly selective manner at a low temperature, and separates the unreacted maltose from the maltitol formed by the reaction by a simulated moving bed with an ion exchange resin to completely convert the maltose into a high Purity maltitol. In one embodiment, the above temperature range is from 15 °C to 22 °C. In one embodiment, the above temperature range is from 18 ° C to 20 ° C.

The following examples are given to illustrate the details or conditions of the preparation method and purification method of the present invention, and the following examples are mainly divided into two parts, the first part relates to the preparation method of maltitol, and the second part relates to maltitol and maltose. Separation. However, these examples are not intended to limit the scope of the invention. The drawings are schematic for the convenience of description and are not intended to limit the actual methods, conditions, or devices.

[ Example 1] Maltose hydrogenation

[ Electrode preparation ]

[Preparation of NiC/C electrode]

First, NiSO ₄ and Ni(NO ₃ ) _{2 were} used as precursors, respectively, and a nickel compound was synthesized on the surface of the activated carbon powder by supercritical hydrothermal method to form a nickel-based catalyst (referred to as NiC). Next, the mixture including NiC, polyethyleneimine and deionized water is stirred and mixed to form a mixed solution. Then, the above solution was uniformly dropped on the carbon sheet in a 100 μl manner and dried in the air, and then the above carbon sheet was baked at 50 ° C for 10 minutes. Repeat the above steps 5 times. Next, the carbon sheet was baked at 110 ° C for 60 minutes, and the carbon sheet was baked at 200 ° C for 120 minutes to complete the production of the NiC/C electrode.

1A and 1B are scanning electron microscope results of a nickel-based catalyst formed using NiSO ₄ and Ni(NO ₃ ) ₂ as precursors, respectively. 1A and 1B, a uniform nickel-based catalyst can be formed on the surface of the activated carbon powder regardless of whether NiSO ₄ or Ni(NO ₃ ) _{2 is} used as a precursor. 2A and 2B are XRD analysis results of a nickel-based catalyst synthesized by hydrothermal method using NiSO ₄ and Ni(NO ₃ ) ₂ as precursors, respectively. As shown in FIG. 2A, when NiSO _{4 is} used as a precursor, the obtained catalyst crystal grains are small, and the obtained nickel compound contains three kinds of Ni(OH) ₂ , Ni and NiO. Conversely, as shown in Fig. 2B, when Ni(NO ₃ ) _{2 is} used as a precursor, the obtained nickel compound is mainly nickel oxide, and its crystallinity is preferable and has large crystal grains.

[Preparation of Cu/C electrode]

1 g of the carbon glue was uniformly applied to the copper sheet, and calcined at 120 ° C for 1 hour using a calciner to complete the production of the Cu/C electrode.

[ Salt bridge preparation ]

[洋菜胶盐桥]

The agar extract was added to an aqueous Na ₂ SO ₄ solution and heated to dissolve in the acacia gum, which was then poured into a U-tube and allowed to solidify in an ice bath.

[Nafion film]

Nafion/NiSO ₄ film and Nafion/Ni(NO ₃ ) ₂ film were prepared by using a Nafion film of DuPontTM Nafion ^® series and reducing NiSO ₄ and Ni(NO ₃ ) ₂ on Nafion film.

[ Analysis of maltitol ]

The composition was analyzed by HPLC/RI (pump: 2130, Hitachi; RI: RID-20A, Shimadzu), wherein the column was YMC-Pack Polyamine II (YMC Co., Ltd., S-5 μm), and the column size was 4.6 × 250 mm, with acetonitrile (HPLC grade, Youhe Trading Co., Ltd.) and a deionized water ratio of 77.5:22.5 as the mobile phase, the flow rate is 0.5 mL / min, the column temperature is set to 30 ° C during analysis, used The injection loop volume is 20 μL. At the same time, maltose (food grade, New Sugar City Biochemical Technology Co., Ltd.) and 3, 7.5, 15, 22.5, 30 g / L of maltitol (food grade, New Sugar City Biochemical Technology Co., Ltd.) to establish a check line.

The HPLC/RI analysis of maltose and maltitol is shown in Figure 6, where the residence time of maltose and maltitol was 38.6 minutes and 34.9 minutes, respectively, to the extent of baseline separation. Further, if using an injection volume of 20 μL loop, the standard calibration curve of maltose _{(A maltose)} and maltitol standard calibration curve (A _maltitol) are as follows: In the formula (1), A is an absorbance value, and c is a solute concentration.

[ Hydrogenation reaction ]

In one embodiment, a carbon sheet was used as an anode, NiC/C was used as a cathode, and 0.1 M maltose (food grade, New Sugar City Biochemical Technology Co., Ltd.) and 0.1 M Na ₂ SO _{4 were} used as a reaction solution. At the same time, the anode and the cathode were connected by a rubber salt bridge, and different potentials were applied, and the product was taken once every hour, and the product was taken 4 times in total.

In one embodiment, a Cu/C electrode was used as the anode and cathode, and 0.1 M maltose and 0.1 M Na ₂ SO _{4 were} used as the reaction solution. At the same time, the Nafion film was sandwiched between the anode and the cathode, and different potentials were applied, and the product was taken once every hour for a total of 9 times.

Next, the maltose hydrogenation reaction test was carried out using the conventional salt bridge apparatus architecture. After applying different voltages, the samples were analyzed by HPLC for the content of maltose and maltitol, and the conversion was calculated, and the results are shown in FIG. It can be seen from Fig. 3 that after 4 hours of continuous reaction, the conversion rate is still low, mainly because the conductivity of the maltose solution is low, resulting in too high resistance in the reactor. Further, after the NiC/C electrode prepared using NiSO _{4 and} the NiC/C electrode prepared using Ni(NO ₃ ) ₂ were subjected to hydrogenation reaction of maltose, both conversion rates were less than 5%.

In this example, the Nafion film was used to replace the salt bridge, and the hydrogenation reaction of maltose was carried out by Cu/C electrode, and the sample was analyzed. As a result, the signal of maltitol was clearly found in the HPLC map, as shown in FIG. 4 . The content of maltose and maltitol in the sample can be calculated by the calibration curve, and the conversion of maltitol at different voltages of the two electrodes can be calculated, and the results are shown in FIG. 5. 5 shows that, when the reaction time was 6 hours, as compared to the precursor NiSO _4, if the Ni (NO _{3) 2} as precursor (i.e. mainly as NiO) catalyst was synthesized, then the generation of The catalyst has a better catalytic ability. In addition, the catalyst synthesized by Ni(NO ₃ ) ₂ can achieve a conversion of 22% after 4 hours of reaction. However, although the conversion rate increases as the applied voltage increases, when the voltage exceeds 1.4 V, the reaction gradually slows down, possibly because a high voltage causes by-products to be produced.

[ Example 2] Single column chromatography and trigonometry

In this example, a suitable ion exchange resin is first screened for separation of maltose and maltitol. The UBK555 was filled in a 1 x 25 cm column with a wet filling method, and water was used as a flushing solution (flow rate 3.0 mL/min) to provide maltose and maltitol as analytical samples (flow rate 3.0 mL/min). Then, a breakthrough curve of the concentration of the mobile phase in the section of maltose and maltitol relative to the residence time is obtained.

See the through graph of Figure 7, where C/C ₀ is the relative concentration and time is the residence time. In Fig. 7, since the residence time of NaCl is shorter than that of maltose and maltitol, NaCl can be regarded as a non-retention component for investigation of column parameters and isothermal adsorption behavior. Since maltitol has higher retention than maltose, it is easy to separate the two.

When the solute begins to be injected into the packed bed, its response at the packed bed outlet can be expressed as: (Formula 2) In equation (2), c is the concentration at the outlet of the column, c _o is the concentration of the feed, z is the axial coordinate of the column, t is the time after the feed enters the column, and ε _e is the interparticle pore Degree, D is the axial diffusion coefficient or axial dispersion coefficient of the solute, G is the isothermal adsorption constant, u = Q/A _c ε _e is the linear flow velocity of the mobile phase, where Q is the volume flow velocity of the mobile phase And A _c is the cross-sectional area of the empty pipe string. If NaCl is used as a non-retention component, the retention constants for maltose and maltitol are 0.03 and 0.10, respectively, the porosity between particles is 0.36, the porosity within the particles is 0.532, and the total porosity of the packed column is 0.7. In one embodiment, the porosity of the particles of the stationary phase is from 0.2 to 0.8.

[ Example 3] Separation of maltose from maltitol

[ Simulated use of moving beds ]

In the present embodiment, the simulated moving bed chromatography method comprises: (i) providing a simulated moving bed comprising at least three segments, which is composed of a mobile phase and a stationary phase, the three segments being sequentially the first segment a second section and a third section respectively having a first relative flow rate ratio m ₁ , a second relative flow rate ratio m _{2 ,} and a third relative flow rate ratio m ₃ , wherein the moving phase is in the same direction in the simulated moving bed Flowing through the three sections, the stationary phase simulates movement in a reverse direction relative to the moving phase; (ii) injecting a mixture between the second section of the simulated moving bed and the third section, The component A and the component B in the mixture respectively have a first retention constant K _A and a second retention constant K _B , and the second retention constant K _{B is} greater than the first retention constant K _A ; (iii) the first segment The first relative flow rate ratio m _{1 is} greater than the first retention constant K _A ; and (iv) the second relative flow rate ratio m _{2 of} the second segment and the third segment and the first ₃ interposed between the first and the retentate constant K _A constant K _B three second retention ratio relative flow rates m, to separate Component A and component B. In an embodiment, the first section, the second section, and the third section each comprise at least two tubular strings.

More specifically, a simulated moving bed chromatography (SMBC) including at least three sections is taken as an example of a stationary phase (Stationary phase, SP for short) and a mobile phase (Mobile phase). MP) The relative flow between the four segments to separate the material in the mixture. The stationary phase is filled in a plurality of columns of each section, the moving phase flows in the same direction in the column, and the feeding position of the mixture is changed by the inlet switching device to simulate the relative flow of the stationary phase and the moving phase direction. After the mixture enters the chromatography column (feed), the components A and B contained in the mixture are respectively retained by the stationary phase according to the Henry's constant H (or retention constant K) of each substance or separated by the mobile phase. Purification of component A and component B. Since the retention constant of the exclusion chromatography does not change with concentration, it is intended to be simulated by the triangle theory ("Optimization of a SMB based on an approximated Langmuir Model" AIChE J. 48, 2240-2246). Separation of component A and component B by bed chromatography requires that the relative volumetric flow rates of liquid and solid in each zone satisfy the following conditions: In the formula (3), K _A and K _B are the retention constants of the component A and the component B; m _j is the ratio of the relative flow velocity of the mobile phase volume to the relative flow velocity of the solid volume in the j segment, and m _j Defined as: In equation (3), Q _j is the flow velocity of the liquid in the j-th segment, t _sw is the column switching time, V _C is the empty column volume, ε is the total column porosity, and V _D is per The non-inductive volume of a column.

Figure 8 is a graph showing the operating conditions of simulated moving bed chromatography in accordance with the theory of separable solutes in the theory of triangles. As shown in FIG. 8, if m ₂ of the second section is the horizontal axis and m ₃ of the third section is the vertical axis, the operating conditions that can be completely separated are located within the triangle, that is, separable. The operating range is the triangle in this coordinate plot. At the apex of the triangle there is an optimum separation and separation efficiency. In addition to the condition that the relative flow rates of the second and third sections need to satisfy the conditions of being located within the triangle, the relative flow rates of the first and fourth sections must also satisfy the condition of equation (2).

Accordingly, this example uses a simulated moving bed equipped with UBK555 resin to separate maltose and maltitol. Figure 9 shows a schematic diagram of a three-section simulated moving bed chromatography column configuration, the column configuration is composed of 2 tubes / 3 tubes / 3 tubes of 8 tubes (C1 ~ C8). Specifically, the first section is formed by connecting two columns in series, and the second section and the third section are respectively formed by connecting three columns in series. The primary function of the second and third sections is to separate the maltose from the maltitol while the first section is being stripped. Each column has a diameter of 2.5 cm and a length of 25 cm.

Referring to Figure 9, maltose and maltitol (feed component A/B) are passed through the feed end between the second section and the third section (i.e., between the column C5 and the column C6) at 0.1. The flow rate of mL/min was injected into the simulated moving bed, while the deionized water was injected from the column C1 at a flow rate of 18 mL/min. At the same time, the extraction end (extract outlet end) between the first section and the second section (that is, between the column C2 and the column C3) is metered to extract a solution of 6.0 mL/min (ie, the extract ) and let the excess solution (ie, raffinate, 12.1 mL/min) flow out of the column C8 outlet (the raffinate end). In the simulated moving bed of the present embodiment, maltose and maltitol are used as feeds, and the extraction end mainly collects maltitol (ingredient B), and the raffinate mainly collects maltose (ingredient A).

When operating for a period of time using the above method, such as 5 minutes, all the outlets and inlets are switched to the next column. After continuing for a similar period of time, all the inlets and outlets are moved to the next column again. Thus, by continuously switching the column, the solid can be simulated to move in the left-hand direction of FIG. 9 to form a reverse flow with the liquid. Embodiments of the present invention tested different switching times to help identify operating conditions suitable for separating maltose and maltitol.

Table 1 shows the results of separation experiments obtained with different column switching times when the total feed concentration is 100.0 g/L (maltose and maltitol are each 50.0 g/L).

The purity in Table 1 is defined as follows: (Formula 5-1) In (Formula 5-2) (5-1) and formula (5-2), P _E is the purity of maltitol, C ^E _maltitol maltitol concentration extracted out terminated, C ^E _maltose extracted out end maltose concentration , P _R is the purity of maltose, C ^R _maltitol is the concentration of _maltitol at the raffinate end, and C ^R _maltose is the concentration of _maltose at the raffinate end.

The recovery rates in Table 1 are defined as follows: (Formula 6-1) (Formula 6-2) In the formulae (6-1) and (6-2), R _E is the recovery rate of maltitol, R _R is the recovery rate of maltose, Q ^E is the flow rate at the extraction end, and Q ^R is The flow rate at the end of the extraction.

Table 2  <TABLE border="1" borderColor="#000000" width="85%"><TBODY><tr><td> Switching time (minutes) </td><td> concentration (g/L) </td ><td> Purity (%) </td><td> Recovery (%) </td></tr><tr><td> Raffinate</td><td> Extract</td ></tr><tr><td> Maltose</td><td> Maltitol</td><td> Maltose</td><td> Maltitol</td><td> Raffinate </ Td><td> extractant</td><td> raffinate</td><td> extractant</td></tr><tr><td> 4.50 </td><td> 0.218 </td><td> 0.148 </td><td> 0.870 </td><td> 1.082 </td><td> 59.5 </td><td> 55.5 </td><td> 33.6 < /td><td> 78.4 </td></tr><tr><td> 4.75 </td><td> 0.277 </td><td> 0.109 </td><td> 0.271 </td> <td> 1.002 </td><td> 71.7 </td><td> 78.7 </td><td> 67.3 </td><td> 82.0 </td></tr><tr><td> 5.00 </td><td> 0.462 </td><td> 0.140 </td><td> 0 </td><td> 0.983 </td><td> 76.7 </td><td> 100.0 < /td><td> 100.0 </td><td> 77.6 </td></tr><tr><td> 6.00 </td><td> 0.637 </td><td> 0.160 </td> <td> 0 </td><td> 0.665 </td><td> 79.9 </td><td> 100.0 </td><td> 100.0 </td><td> 67.4 </td></ Tr></TBODY></TABLE>

It can be seen from Table 2 that when the switching time is 5 minutes, maltose and maltitol can be effectively separated, the purity of maltitol can reach 100%, and the recovery rate is also 77.6%. When the switching time is 6 minutes, although the purity and recovery rate are less than the experimental results of the switching time of 5 minutes, high-purity maltitol can also be obtained.

In summary, the method for producing maltitol of the present invention is carried out at normal temperature and pressure, so that the present invention has the advantages of low energy consumption, low equipment demand or safe operation compared to conventional high temperature and high pressure hydrogenation technology. In addition, compared to the traditional batch-type purification process, since the simulated moving bed chromatography is a continuous process, the separation of maltitol and unreacted maltose by simulated moving bed chromatography can greatly enhance the maltitol. Purification efficiency.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

no.

1A and 1B are scanning electron microscope results of a nickel-based catalyst prepared using NiSO ₄ and Ni(NO ₃ ) ₂ as precursors, respectively. 2A and 2B are XRD analysis results of a nickel-based catalyst prepared using NiSO ₄ and Ni(NO ₃ ) ₂ as precursors, respectively. Figure 3 shows the results of conversion of maltose hydrogenation using different NiC/C electrodes. Figure 4 shows the conversion results of the maltose hydrogenation reaction of NiC/C electrodes using different Nafion films. Figure 5 shows the conversion results of the maltose hydrogenation reaction using different Nafion films on the NiC/C electrode. Figure 6 is a HPLC/RI analysis of maltose and maltitol. Figure 7 is a cross-sectional graph of maltose, maltitol, and non-retained material. Figure 8 is a graph showing the operating conditions of simulated moving bed chromatography in accordance with the theory of separable solutes in the theory of triangles. Figure 9 is a schematic view showing the configuration of a three-section simulated moving bed chromatography column.

Claims (10)

A method for producing maltitol, comprising: providing maltose; and hydrolyzing a maltose to produce a mixture by using an electrode in a temperature range of 10 ° C to 80 ° C and a pressure ranging from 1 atm to 10 atm, the mixture comprising maltose and maltitol And separating the maltose in the mixture from the maltitol by simulated moving bed chromatography, wherein the simulated moving bed chromatography comprises: (i) providing a simulated moving bed comprising at least three segments, It consists of a mobile phase and a stationary phase, which are sequentially a first segment, a second segment and a third segment, respectively having a first relative flow rate ratio m ₁ and a second relative flow rate ratio m ₂ and a third relative flow rate ratio m ₃ , the moving phase flows through the three segments in the same direction in the simulated moving bed, and the stationary phase simulates moving in a reverse direction with respect to the moving phase; (ii) Causing the mixture between the second section of the simulated moving bed and the third section, the maltose and the maltitol in the mixture having a first retention constant K _A and a second retention constant K _B , the second retention constant K _{B being} greater than the first retention constant K _A ; (iii) the first relative flow velocity ratio m _{1 of} the first segment is greater than the first retention a constant K _A ; and (iv) the second relative flow velocity ratio m _{2 of} the second segment and the third segment and the third relative flow velocity ratio m _{3 are} between the first retention constant K _A between the _A and the second retention constant K _B to separate the maltose and the maltitol. The method for producing maltitol according to claim 1, wherein the electrode comprises a carbon electrode or a copper electrode. The method for producing maltitol according to claim 1, wherein the electrode is coated with a catalyst layer. The method for producing maltitol according to the third aspect of the invention, wherein the catalyst layer is a nickel-based catalyst. The method for producing maltitol according to the fourth aspect of the invention, wherein the nickel-based catalyst is a nickel compound synthesized on the surface of the activated carbon support by using NiSO ₄ or Ni(NO ₃ ) ₂ as a precursor. The method for producing maltitol according to claim 5, wherein the nickel compound comprises Ni, NiO, Ni(OH) ₂ or Ni(NO ₃ ) ₂ . The method for producing maltitol according to claim 1, wherein the temperature ranges from 15 ° C to 22 ° C. The method for producing maltitol according to claim 1, wherein the first section, the second section, and the third section each comprise at least two columns, each of the columns The stationary phase having pores inside the filler particles. The method for producing maltitol according to the first aspect of the invention, wherein the first retention constant K _A is 0.03, the second retention constant K _B is 0.10, and the porosity of the internal phase of the stationary phase Between 0.2 and 0.8. The method for producing maltitol according to claim 1, wherein the mobile phase comprises a flushing liquid, and the flushing liquid is deionized water.