Method for removing carbon dioxide

Abstract

The invention discloses a method for removing carbon dioxide, which is matched with an ion chromatography system and comprises the following steps: loading a sample into the ion chromatography system; combining the sample with the liquid mobile phase to form a to-be-detected substance, wherein the to-be-detected substance comprises target anions and cations; separating target anions in the object to be detected into a plurality of groups; replacing cations in the to-be-detected substance with hydrogen ions; a vacuum environment is formed; inputting an object to be detected to a vacuum environment; and removing carbon dioxide molecules, carbonic acid molecules, bicarbonate ions or carbonate ions in the object to be detected, so that the concentration of the carbonate ions and the bicarbonate ions is less than or equal to 1 / billion.

Description

Technical Field

[0001] The present invention relates to a method for removing carbon dioxide used in a chromatography system. Background Art

[0002] Ion chromatography is an analytical technique for separating and detecting different ions in aqueous solutions. The main steps are: introducing the sample into a chromatography system; separating the target ions through the mobile phase and the chromatography system; passing through an ion suppressor; and detecting and analyzing the target ions using a conductivity detector.

[0003] Ion chromatography technology is categorized into cation chromatography and anion chromatography systems based on the charge of the target ions after dissociation. Anion chromatography systems typically use an alkaline solution as the mobile phase. The anions in the alkaline mobile phase are used for target anion chromatography to separate the target anions in the sample. A cation suppressor is then used to replace all cations in the mobile phase with hydrogen ions through cation exchange. Finally, the separated and suppressed sample is introduced into a conductivity detector to measure the conductivity of the charged target anions in the mobile phase background, thereby achieving qualitative and quantitative identification of the target anions.

[0004] Carbonic acid in the alkaline mobile phase usually comes from the mobile phase containing carbonates or carbon dioxide gas in the environment dissolved in the alkaline mobile phase, resulting in an increase in the background conductivity value of the analysis, which is not conducive to the conductivity detection of the sample.

[0005] The carbonic acid in the sample solution usually comes from carbon dioxide gas in the environment dissolved in the sample solution or the sample solution itself contains carbon dioxide.

[0006] Carbon dioxide reacts with water to form carbonic acid, which dissociates into carbonate and bicarbonate ions in solution. In anion chromatography systems, these carbonate and bicarbonate ions interfere with the conductivity and accuracy of target anions. Therefore, removing carbon dioxide, carbonate, bicarbonate, and carbonate molecules is a pressing issue. Summary of the Invention

[0007] The present invention provides a method for removing carbon dioxide. When used in conjunction with an ion chromatography system, the method can remove carbon dioxide molecules, carbonate molecules, bicarbonate ions, and carbonate ions from an alkaline mobile phase and a sample solution, thereby increasing the detection sensitivity of the ion chromatography system to a target ion concentration of one part per billion.

[0008] The present invention provides a method for removing carbon dioxide, which is used in conjunction with an ion chromatography system. The method includes loading a sample into the ion chromatography system; combining the sample with a liquid mobile phase to form an analyte, wherein the analyte includes target anions and cations; separating the target anions in the analyte into multiple groups; replacing the cations in the analyte with hydrogen ions; creating a vacuum environment; introducing the analyte into the vacuum environment; and removing carbon dioxide molecules, carbonate molecules, bicarbonate ions, or carbonate ions from the analyte, so that the concentration of the carbonate ions and bicarbonate ions is less than or equal to one part per billion.

[0009] In some embodiments, the removal method further includes creating a vacuum environment with a vacuum level of 50 mmHg.

[0010] In some embodiments, the removal method further includes controlling the vacuum flow rate to be less than or equal to 10 standard cubic centimeters per minute under a vacuum environment of 50 mmHg.

[0011] In some embodiments, the removal method further includes controlling the intake air flow rate to be less than or equal to 10 standard cubic centimeters per minute.

[0012] In some embodiments, the removal method further includes filtering the carbon dioxide gas flowing in due to the intake air flow rate.

[0013] In some embodiments, the removal method further includes removing carbon dioxide gas from the analyte through a gas permeable membrane.

[0014] In some embodiments, the removal method further includes preventing the sample from flowing into the vacuum pump by a buffer device when the gas permeable membrane is damaged.

[0015] In some embodiments, the removal method further includes a buffer device capable of reducing the instantaneous pressure difference when the pressure changes instantaneously to protect the gas from penetrating the membrane.

[0016] In some embodiments, the removal method further includes measuring a vacuum level of the vacuum environment.

[0017] In some embodiments, the removal method further includes adjusting the pumping flow rate according to a result of measuring the vacuum level of the vacuum environment.

[0018] In some embodiments, the removal method further includes adjusting the intake air flow rate according to a result of measuring the vacuum level of the vacuum environment.

[0019] In some embodiments, the removal method further includes controlling the opening and closing of the vacuum pump via a relay.

[0020] In summary, conventional anion chromatography techniques do not remove carbon dioxide, and therefore can only detect solutions with target ion concentrations above 1 part per billion. In semiconductor fabs, solutions extracted from contaminated ambient air may have concentrations below 1 part per billion, severely impacting semiconductor manufacturing processes. Furthermore, since carbon dioxide itself is present in the sample as an environmental contributor, conventional anion chromatography techniques cannot analyze which anions contaminate the solution. The carbon dioxide removal method of the present invention can release carbon dioxide molecules, carbonic acid molecules, bicarbonate ions, and carbonate ions from the sample by creating a vacuum environment and introducing the sample into the vacuum environment. Carbon dioxide gas can be removed from the sample via a gas-permeable membrane. A vacuum of 50 mmHg can be achieved by controlling the intake and exhaust flow rates to 10 standard cubic centimeters per minute or less. This creates a stable vacuum zone, reduces vibration, and provides a steady airflow to circulate carbon dioxide gas within the vacuum zone, helping to remove the carbon dioxide. By filtering the carbon dioxide gas introduced by the intake flow rate, the flow of carbon dioxide into the vacuum environment can be reduced, allowing the carbon dioxide concentration within the vacuum zone to be stably controlled. The vacuum degree of the vacuum environment can be measured, and the exhaust flow rate can be adjusted according to the result of measuring the vacuum degree of the vacuum environment to stably form a vacuum area. When the gas permeable membrane is damaged, the buffer device prevents the flow to be measured from flowing into the vacuum pump, thereby avoiding damage to the vacuum pump. When there is an instantaneous pressure change, the buffer device can reduce the instantaneous pressure difference and protect the gas permeable membrane. The opening and closing of the vacuum pump can be controlled by a relay to improve the convenience of operation. The method of the present invention can make the concentration of carbonate ions and bicarbonate ions less than or equal to one billionth, and when the concentration of any target anion is greater than one billionth, it can be detected by the ion chromatography system. It can be applied to semiconductor factories, chemical factories, equipment factories and environmental pollution fields to provide precise chemical analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The details of one or more embodiments of the subject matter described in this specification are set forth in the following drawings and description. Other features, aspects, and advantages of the subject matter of this specification will be apparent from the description, drawings, and claims, including:

[0022] Figure 1 is a block diagram of an embodiment of a removal method of the present invention;

[0023] Figure 2 is a schematic diagram of an ion chromatography system according to an embodiment of the present invention;

[0024] Figure 3 is a schematic diagram of an embodiment of a gas permeable membrane of the present invention;

[0025] Figure 4is a schematic diagram of an embodiment of the conductivity detection result of the present invention;

[0026] Wherein, the reference numerals:

[0027] S01-S07: removal method steps;

[0028] 1: ion chromatography system;

[0029] 11: sample;

[0030] 12: liquid mobile phase;

[0031] 13: object to be tested;

[0032] 131: target anion;

[0033] 132: cation;

[0034] 1311: carbonate ion;

[0035] 1312: bicarbonate ion;

[0036] 1313: Carbonic acid molecule;

[0037] 1314: Carbon dioxide molecule;

[0038] 14: gas permeable membrane;

[0039] 2: Vacuum environment;

[0040] 21: suction flow rate;

[0041] 22: intake air flow rate;

[0042] 3: Buffer device. DETAILED DESCRIPTION

[0043] Figure 1 For a block diagram of an embodiment of the removal method of the present invention, please refer to Figure 1 As shown,

[0044] Step S01 is loading a sample into the ion chromatography system. Step S02 is combining the sample with a liquid mobile phase to form an analyte, which includes target anions and cations. Step S03 is separating the target anions in the analyte into multiple groups. Step S04 is replacing the cations in the analyte with hydrogen ions. Step S05 is creating a vacuum environment. Step S06 is inputting the analyte into the vacuum environment. Step S07 is removing carbon dioxide molecules, carbonate molecules, bicarbonate ions, or carbonate ions from the analyte, reducing the concentration of carbonate ions and bicarbonate ions to less than or equal to one part per billion.

[0045] Figure 2 This is a schematic diagram of an embodiment of the ion chromatography system 1 of the present invention. Figure 1 and Figure 2 As shown, in step S01, the sample 11 is loaded into the ion chromatography system 1. In some embodiments, the sample 11 can be, for example, an aqueous solution or extract taken from a semiconductor factory, a chemical plant, an equipment factory, an artificial sewage ditch, and a natural environment, but this is not limiting. The sample 11 can contain ions, such as carbonate ions 1311, bicarbonate ions 1312, fluoride ions, chloride ions, nitrite ions, bromide ions, nitrate ions, hydrogen phosphate ions, sulfate ions, hydrogen ions, and ammonium ions, or other corresponding ions to be detected, which are not intended to limit the present invention. The ion chromatography system 1 is a device that utilizes ion chromatography, that is, a type of liquid chromatography, to perform qualitative and quantitative analysis of the ion components in the solution. In some embodiments, the sample 11 can be placed, injected, or sucked into the ion chromatography system 1 to load the sample 11 into the ion chromatography system 1.

[0046] Figure 3 This is a schematic diagram of an embodiment of the gas permeable membrane 14 of the present invention. Figure 1 、 Figure 2 and Figure 3 Shown, in step S02, combine sample 11 and liquid mobile phase 12 to become test substance 13, test substance 13 comprises target negative ion 131 and cation 132.In certain embodiments, because sample 11 is aqueous solution, mobile phase also selects aqueous solution, mainly uses diluted acid, alkali, salt solution, but its non-restrictive.Sometimes also can add trace organic matter that can be miscible with water in aqueous solution, for example acetone is as mobile phase.Alkaline solution for example can be potassium hydroxide solution, sodium hydroxide solution or sodium bicarbonate solution, but its non-restrictive.After sample 11 is mixed with liquid mobile phase 12, can regulate the ion dissociation state of sample 11, form the test substance 13 that is suitable for carrying out ion chromatography. The analyte 13, formed by mixing the sample 11 with the liquid mobile phase 12, includes target anions 131 and cations 132. Target anions 131 include, for example, fluoride, chloride, nitrite, bromide, nitrate, hydrogen phosphate, and sulfate; cations 132 include, for example, hydrogen, potassium, sodium, and ammonium. However, the analyte 13 may contain anions other than the target anions 131, such as carbonate ions 1311 and bicarbonate ions 1312, which can contribute to noise in the detection of the target anions 131.

[0047] In step S03, the target anions 131 in the analyte 13 are separated into a plurality of groups. In certain embodiments, because different target anions 131 in the analyte 13 experience different forces in the ion chromatography system 1, after a period of chromatography on the analyte 13, the retention capacities of the different target anions 131 are different, thereby separating the target anions 131 into a plurality of groups. For example, a group of fluoride ions, a group of chloride ions, a group of nitrite ions, a group of bromide ions, a group of nitrate ions, a group of hydrogen phosphate ions, and a group of sulfate ions may be separated, but this is not limiting.

[0048] In step S04, hydrogen ions are used to replace cations 132 in the sample 13. In some embodiments, the cations 132 in the sample 13 are replaced with hydrogen ions, such as potassium ions, sodium ions, and ammonium ions, but are not limited thereto, thereby reducing the interference of the cations 132 on the conductivity detection of the target anion 131.

[0049] In step S05, a vacuum environment 2 is formed. In some embodiments, for example, a rough vacuum of 760 mmHg to 25 mmHg, a medium vacuum of 25 mmHg to 10 mmHg, and a vacuum of 100 mmHg to 250 mmHg can be formed. -3 mmHg, high vacuum 10 -3 mmHg~10 -9 mmHg or ultra-high vacuum 10 -9 mmHg~10 -12 In some embodiments, a vacuum environment 2 with a vacuum degree of approximately 50 mmHg is formed. The vacuum degree refers to the air pressure value of the vacuum environment 2. In some embodiments, in a vacuum environment 2 with a vacuum degree of approximately 50 mmHg, the exhaust flow rate 21 can be controlled to be less than or equal to approximately 10 standard cubic centimeters per minute. The exhaust flow rate 21, for example, is the volume of gas exhausted from the vacuum pump or the volume of gas exhausted from the vacuum environment 2 per unit time. In some embodiments, in a vacuum environment 2 with a vacuum degree of 50 mmHg, the intake flow rate 22 can be controlled to be less than or equal to approximately 10 standard cubic centimeters per minute. When the exhaust flow rate 21 is less than or equal to approximately 10 standard cubic centimeters per minute, a flowable vacuum environment 2 with a vacuum degree of approximately 50 mmHg is formed. The intake flow rate 22, for example, is the volume of gas entering the vacuum environment 2 per unit time. In some embodiments, the carbon dioxide gas flowing in due to the intake flow rate 22 is filtered to reduce the flow of carbon dioxide gas into the vacuum environment 2.

[0050] In some embodiments, the vacuum level of the vacuum environment 2 can be measured, and the exhaust flow rate 21 can be adjusted based on the result of the vacuum level measurement of the vacuum environment 2. For example, when the vacuum level is greater than 50 mmHg, the exhaust flow rate 21 can be reduced, and when the vacuum level is less than 50 mmHg, the exhaust flow rate 21 can be increased. In some embodiments, the intake flow rate 22 can be adjusted based on the result of the vacuum level measurement of the vacuum environment 2. For example, when the vacuum level is greater than 50 mmHg, the intake flow rate 22 can be increased, and when the vacuum level is less than 50 mmHg, the intake flow rate 22 can be reduced.

[0051] In step S06, the sample 13 is introduced into the vacuum environment 2. In step S07, carbon dioxide molecules 1314, carbonate molecules 1313, bicarbonate ions 1312, or carbonate ions 1311 are removed from the sample 13, reducing the concentration of carbonate ions 1311 and bicarbonate ions 1312 to less than or equal to about 1 part per billion. According to the principle of chemical equilibrium, reducing the partial pressure of carbon dioxide gas can release carbon dioxide molecules 1314, carbonate molecules 1313, bicarbonate ions 1312, or carbonate ions 1311 in the solution, as can be represented by reaction equations 1 to 4, for example:

[0052] Reaction 1:

[0053] Reaction 2:

[0054] Reaction 3:

[0055] Reaction 4:

[0056] In certain embodiments, after the analyte 13 is introduced into the vacuum environment 2 , the partial pressure of carbon dioxide gas in the vacuum environment 2 is lower than that at atmospheric pressure. According to the Le Chatelier principle of chemical dynamic equilibrium, reactions 1 to 4 proceed to the left, releasing carbon dioxide molecules 1314 , carbonate molecules 1313 , bicarbonate ions 1312 , or carbonate ions 1311 in the analyte 13 , generating carbon dioxide gas. Since the vacuum environment 2 remains in a vacuum, the released carbon dioxide gas is expelled, thereby reducing the concentration of carbon dioxide molecules 1314 , carbonate molecules 1313 , bicarbonate ions 1312 , or carbonate ions 1311 in the analyte 13 .

[0057] In the conductivity detection of the anion chromatography system 1, carbonate ions 1311 and bicarbonate ions 1312 are anions, but they are not the target anions 131. This causes background noise, which is detrimental to the conductivity detection of the sample 11. Therefore, by removing carbon dioxide molecules 1314, carbonate molecules 1313, bicarbonate ions 1312, or carbonate ions 1311 from the analyte 13, the concentrations of carbonate ions 1311 and bicarbonate ions 1312 can be reduced to approximately 1 part per billion or less. This allows the ion chromatography system 1 to detect any target anion 131 when the concentration is greater than approximately 1 part per billion. Concentration refers to weight concentration. In other words, when the concentration of the target ion is greater than approximately 1 part per billion, its conductivity is still greater than the background noise generated by carbonate ions 1311 or bicarbonate ions 1312 during detection by the ion chromatography system 1, allowing the target ion to be detected.

[0058] In certain embodiments, carbon dioxide gas is removed from the analyte 13 via a gas-permeable membrane 14. The gas-permeable membrane 14 is a non-specific membrane that separates molecules of different sizes based on their size. It allows smaller, monomeric gas molecules in a solution to pass through while preventing all larger molecules from passing through. In certain instances, the gas-permeable membrane 14 allows smaller, monomeric gas carbon dioxide molecules 1314 in the analyte 13 to pass through while preventing larger, liquid molecules from passing through. In certain embodiments, the analyte 13 is located on the inside of the gas-permeable membrane 14, while the 50 mmHg vacuum environment 2 is located on the outside. This allows the carbon dioxide molecules 1314 in the analyte 13 to be expelled from the gas-permeable membrane 14 through the pressure differential.

[0059] In some embodiments, if the gas permeable membrane 14 is damaged, the buffer device can prevent the test object 13 from flowing into the vacuum pump. If careless operation or force majeure occurs during the formation of the vacuum environment 2, the buffer device can prevent the test object 13 from flowing into the vacuum pump and damaging the vacuum pump.

[0060] In some embodiments, a relay may be electrically connected to the vacuum pump to control the opening and closing of the vacuum pump.

[0061] Figure 4 This is a schematic diagram of an embodiment of the conductivity detection result of the present invention, please refer to Figure 4As shown, after a period of chromatography, different target anions 131 have different retention capacities, resulting in the target anions 131 being separated into multiple groups. For example, a group of fluoride ions, a group of chloride ions, a group of nitrite ions, a group of bromide ions, a group of nitrate ions, a group of hydrogen phosphate ions, a group of sulfate ions, or other anion groups, which are not intended to limit the present invention. Therefore, conductivity peaks above background noise can be measured at different times, and the anions corresponding to the conductivity peaks at specific times can be determined by looking up a table or using a standard.

[0062] As mentioned above, conventional anion chromatography techniques do not remove carbon dioxide and can therefore only detect solutions with target ion concentrations above 1 part per billion. However, in semiconductor fabs, solutions extracted from contaminated ambient air may have concentrations below 1 part per billion, severely impacting semiconductor manufacturing processes. Furthermore, because carbon dioxide itself is present in the sample as an environmental contributor, conventional anion chromatography techniques cannot analyze which anions are contaminating the solution. The carbon dioxide removal method of the present invention can release carbon dioxide molecules, carbonic acid molecules, bicarbonate ions, and carbonate ions from the sample by creating a vacuum environment and introducing the sample into the vacuum environment. Carbon dioxide gas can be removed from the sample via a gas-permeable membrane. A vacuum of approximately 50 mmHg can be achieved by controlling the intake and exhaust flow rates to be less than or equal to approximately 10 standard cubic centimeters per minute. This creates a stable vacuum region, reduces vibration, and provides a steady flow of carbon dioxide gas within the vacuum region, helping to remove the carbon dioxide. Carbon dioxide gas introduced by the intake flow rate can be filtered to reduce the amount of carbon dioxide flowing into the vacuum environment and stably control the carbon dioxide concentration within the vacuum region. The vacuum degree of the vacuum environment can be measured, and the exhaust flow rate can be adjusted according to the result of measuring the vacuum degree of the vacuum environment to stably form a vacuum area. When the gas permeable membrane is damaged, the buffer device prevents the flow to be measured from flowing into the vacuum pump, thereby avoiding damage to the vacuum pump. When there is an instantaneous pressure change, the buffer device can reduce the instantaneous pressure difference and protect the gas permeable membrane. The opening and closing of the vacuum pump can be controlled by a relay to improve the convenience of operation. The method of the present invention can make the concentration of carbonate ions and bicarbonate ions less than or equal to about one billionth, and when the concentration of any target anion is greater than about one billionth, it can be detected by an ion chromatography system. It can be applied to semiconductor factories, chemical factories, equipment factories and environmental pollution fields to provide precise chemical analysis.

[0063] As used herein and not otherwise defined, the terms "substantially" and "about" are used to describe and describe small variations. When applied to an event or circumstance, the terms may include the exact moment the event or circumstance occurred, as well as the point at which the event or circumstance occurred to a close approximation. For example, when applied to a numerical value, the terms may include a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%.

[0064] The above summarizes several embodiments so that those with ordinary knowledge in the technical field to which the present invention belongs can better understand the concepts of the embodiments of the present invention. Those with ordinary knowledge in the technical field to which the present invention belongs should understand that the embodiments of the present invention can be used as a basis to design or modify other processes and structures to achieve the same purposes and / or achieve the same benefits as the embodiments introduced herein. Those with ordinary knowledge in the technical field to which the present invention belongs should also understand that these equivalent structures do not depart from the spirit and scope of the present invention, and various changes, substitutions and other options can be made here without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be defined as the scope of the patent application.

Claims

1. A method for removing carbon dioxide, in conjunction with an ion chromatography system, characterized in that: The removal method includes: loading a sample into the ion chromatography system; Combining the sample with a liquid mobile phase to form an analyte, wherein the analyte includes a plurality of target anions and a plurality of cations; Separating the target anions in the analyte into multiple groups; replacing the cations in the analyte with hydrogen ions; forming a vacuum environment; Inputting the object to be tested into the vacuum environment; and A plurality of carbon dioxide molecules, a plurality of carbonic acid molecules, a plurality of bicarbonate ions or a plurality of carbonate ions in the analyte are removed so that the concentration of the carbonate ions and the bicarbonate ions is less than or equal to one part per billion.

2. The removal method according to claim 1, characterized in that: The forming of the vacuum environment further includes: A vacuum environment with a vacuum degree of 50 mmHg is formed.

3. The removal method according to claim 2, characterized in that: The step of forming the vacuum environment with a vacuum degree of 50 mmHg further includes: Under the vacuum environment with a vacuum degree of 50 mmHg, the exhaust flow rate is controlled to be less than or equal to 10 standard cubic centimeters per minute.

4. The removal method according to claim 3, characterized in that: The step of controlling the pumping flow rate to be less than or equal to 10 standard cubic centimeters per minute under the vacuum environment with a vacuum degree of 50 mmHg further includes: Control the intake air flow rate to be less than or equal to 10 standard cubic centimeters per minute.

5. The removal method according to claim 4, characterized in that: The controlling the intake air flow rate to be less than or equal to 10 standard cubic centimeters per minute further includes: The carbon dioxide gas flowing in due to the intake flow rate is filtered.

6. The removal method according to claim 1, characterized in that: The removing of a plurality of carbon dioxide molecules, a plurality of carbonic acid molecules, a plurality of bicarbonate ions or a plurality of carbonate ions from the analyte so that the concentration of the carbonate ions and the bicarbonate ions is less than or equal to one part per billion further includes: The carbon dioxide gas in the sample is removed through a gas permeable membrane.

7. The removal method according to claim 6, characterized in that: The removing of carbon dioxide gas from the analyte through the gas permeable membrane further includes: When the gas permeable membrane is damaged, the buffer device prevents the sample from flowing into a vacuum pump.

8. The removal method according to claim 2, characterized in that: The step of forming the vacuum environment with a vacuum degree of 50 mmHg further includes: The vacuum degree of the vacuum environment is measured.

9. The removal method according to claim 8, characterized in that: Measuring the vacuum degree of the vacuum environment further includes: An exhaust flow rate is adjusted according to a result of measuring the vacuum degree of the vacuum environment.

10. The removal method according to claim 9, characterized in that: The adjusting the pumping flow rate according to the result of measuring the vacuum degree of the vacuum environment further includes: An intake air flow rate is adjusted according to a result of measuring the vacuum degree of the vacuum environment.

11. The removal method according to claim 1, characterized in that: Also includes: A vacuum pump is turned on and off by a relay.

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