Conductivity detector and ion chromatography system including the same

A conductivity detector includes a flow channel, an electrode arrangement, and a detector. The flow channel has a tube shape with a channel diameter through which a solution including ion components flows. The electrode arrangement is on the flow channel and includes at least an anode and at least a cathode. The anode and cathode are spaced apart by an electrode gap less than or equal to the channel diameter. The detector is connected to the electrode arrangement to detect electrical conductivity of the ion components.

CROSS-REFERENCE TO RELATED APPLICATION

Korean Patent Application No. 10-2015-0145888, filed on Oct. 20, 2015, and entitled, “Conductivity Detector and Ion Chromatography System Including the Same,” is incorporated by reference herein in its entirety.

BACKGROUND

One or more embodiments described herein relate to a conductivity detector and an ion chromatography system including a conductivity detector.

2. Description of the Related Art

Ultra pure water (UPW) has been used in various manufacturing processes for semiconductor devices. When using UPW, the ion concentration of impurities has been a focus and thus is often subject to careful monitoring, especially during the fabrication of highly integrated semiconductor devices of small size.

One approach for UPW monitoring involves performing a component analysis using ion chromatography. Ion chromatography may be performed by separating ionic components in the UPW in a separation column. The electrical conductivity of each ionic component is then detected by a conductivity detector. Qualitative and quantitative analyses are then performed based on the detected electrical conductivity for each ionic component.

A conductivity detector may detect ion components from UPW in a maximal concentration degree of parts per billion (ppb). Thus, detection of ion components from UPW, having a concentration below a certain degree of ppb or in a degree of parts per trillion (ppt), may not be accurate. When the concentration of UPW is excessively small (e.g., below a certain level of ppb), a larger UPW sample may be provided to the conductivity detector in an attempt to increase detection accuracy. However, providing a larger UPW sample increases the time and cost of performing conductivity detection.

SUMMARY

In accordance with one or more embodiments, a conductivity detector includes a flow channel having a tube shape with a channel diameter through which a solution including ion components flows; an electrode arrangement on the flow channel, the electrode arrangement including at least an anode and at least a cathode spaced apart by an electrode gap less than or equal to the channel diameter; and a detector connected to the electrode arrangement to detect electrical conductivity of the ion components.

The flow channel may include an inlet enclosed by the anode and into which the solution flows; an outlet enclosed by the cathode and out of which the solution flows; and a flow cell between the inlet and the outlet and across which the solution passes to provide an ion flow from the inlet to the outlet. The electrode gap may be substantially 0.3 to 1.0 times the channel diameter. The inlet, the outlet, and the flow cell may have substantially a same diameter, such that the flow channel has a uniform channel diameter along a flow path of the ion flow.

The detector may amplify the electrical conductivity by an amplification constant based on the following equation:

k=(DDref)2ddref=γD2γd
where k denotes the amplification constant, D denotes the channel diameter of the flow channel, Drefdenotes a reference diameter of the flow channel, d denotes the electrical distance, γddenotes a reduction ratio of the electrode gap and γDdenotes an increase ratio of the channel diameter.

Each of the inlet and the outlet may have a first diameter, and the flow cell may have a second diameter greater than the first diameter such that the flow cell has a volume greater than those of the inlet and the outlet. The electrode gap may be substantially in a range of 0.3 mm to 0.8 mm, and the channel diameter may be substantially in a range of 0.5 mm to 0.8 mm.

The conductivity detector may include an insulator between the anode and the cathode, wherein the insulator has a tube shape enclosing the flow channel. The conductivity detector may include a supplementary electrode to reduce polarization at the electrode. The supplementary electrode may include a first electrode on the flow channel and spaced from the anode, and a second electrode on the flow channel and spaced from the cathode.

The ion components in the solution may include one of positive ions or negative ions, and the solution may include an aqueous solution in which traces of the ion components are dissolved. The positive ion may include one of a lithium ion (Li+), a sodium ion (Na+), a potassium ion (K+), or an ammonium ion (NH4+), and the negative ion may include one of a fluorine ion (F−), a chlorine ion (Cl−), a bromide ion (Br−), a nitrite ion (NO2−), a nitrate ion (NO3−), a phosphate ion (PO43−), a sulfate ion (SO42−), a carboxyl group (COOH−), or an organic acid.

In accordance with one or more other embodiments, an ion chromatography system includes a sample supplier to supply a sample solution into a flow of an eluent that is a moving phase of an ion chromatography, to thereby generate a multi-component solution in which a plurality of ion components of a type is dissolved; a separation column to sequentially separate the ion components from the multi-component solution to generate a single component solution having a single type of the ion components and to sequentially discharge a plurality of the single component solutions in a time order; and a conductivity detector to detect a concentration of the ion components in the single component solution based on an electrical conductivity of the ion components.

The conductivity detector includes a flow channel having a tube shape with a channel diameter through which the single component solution flows, an electrode arrangement on the flow channel and including at least an anode and at least a cathode spaced apart by an electrode gap less than or equal to the channel diameter, and a detector connected to the electrode arrangement to detect the electrical conductivity of the ion components in the single component solution.

The ion chromatography system may include an eluent supplier having an eluent reservoir to store the eluent, and a delivery pump to deliver the eluent from the eluent reservoir through the separation column and the conductivity detector.

The sample supplier may include a sample dispenser to provide a fixed analysis quantity of the sample solution to a sample loop at a constant speed, and an auto injector to automatically inject the sample solution of the sample loop to an eluent flow path.

The separation column may include an ion exchange resin that is a stationary phase of the ion chromatography, the ion components in the multi-component solution sequentially separated according to a bonding strength between each of the ion components and a resin of the ion exchange resin.

The flow channel may include an inlet enclosed by the anode and connected to the separation column into which the single component solution flows in, an outlet enclosed by the cathode and out through which the single component solution flows, and a flow cell between the inlet and the outlet and across which the single component solution passes to provide an ion flow from the inlet to the outlet. The inlet, the outlet, and the flow cell may have substantially a same diameter, such that the flow channel has a uniform channel diameter along the ion flow. Each of the inlet and the outlet may have a first diameter, and the flow cell may have a second diameter greater than the first diameter such that the flow cell has a volume greater than the inlet and the outlet.

The ion chromatography system may include a suppressor between the separation column and the conductivity detector to remove noise ions having a polarity opposite to the ion components of the single component solution, the suppressor to remove noise from a signal of the electrical conductivity of the ion components in the single component solution.

In accordance with one or more other embodiments, a detector includes a channel; a first electrode on the channel; and a second electrode on the channel, wherein the channel is to carry a solution including ion components, wherein a gap between the first and second electrodes is less than or equal to a cross-sectional size of the channel, and wherein the first and second electrodes are to produce a detection signal indicative of a conductivity of the ion components, a detection accuracy of the detector based on the gap between the first and second electrodes and the cross-sectional size of the channel. Changing at least one of the gap or the cross-sectional size may change the electrical conductivity of the ion components. The cross-sectional size of the channel may be substantially uniform from an inlet to an outlet of the channel. The cross-section size may be a diameter of the channel. The gap between the first and second electrodes may be less than the cross-sectional size of the channel.

DETAILED DESCRIPTION

It will be understood that when an element is referred to as being “on,” “connected to,” “electrically connected to,” or “coupled to” to another component, it may be directly on, connected to, electrically connected to, or coupled to the other component or intervening components may be present. In contrast, when a component is referred to as being “directly on,” “directly connected to,” “directly electrically connected to,” or “directly coupled to” another component, there are no intervening components present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

FIG. 1illustrates an embodiment of a conductivity detector500, which, for example, may detect a small amount of ion components in a solution. Referring toFIG. 1, conductivity detector500may include a flow channel100, an electrode arrangement200, and a detecting unit400. The flow channel100has a tube shape with a channel diameter D for carrying a solution S with ion components I. The electrode arrangement200is on an outer surface of the flow channel100and has at least an anode210and at least a cathode220spaced apart by an electrode gap d that is less than the channel diameter D. The detecting unit400is connected to the electrode arrangement200for detects electrical conductivity of the ion components I.

The flow channel100may provide a flow path for the solution S having ion components I, and the ion components I passing through the flow path may be detected as an electrical signal proportional to the concentration of the ion components I in the solution S. Thus, the electrical conductivity and the concentration of ion components I may be determined based on electrical signal. Various materials may be used to form the flow channel100as long as the flow channel100have sufficient conductivity for detecting the electrical signal and sufficient etching resistivity with respect to the solution including the ion components I.

The flow channel100may include an inlet110enclosed by the anode210and into which the solution S flows, an outlet130enclosed by the cathode220through which the solution S flows, and a flow cell120between the inlet110and the outlet130and across which the solution S passes and thereby providing ion flow from the inlet110to the outlet130.

The solution may include an aqueous solution, in which a small quantity or traces of the ion components I may be dissolved in ultra pure water (UPW) at a concentration below a degree of parts per billion (ppb) or in the degree of parts per trillion (ppt). For example, the ion components in the solution S may include one of positive ions or negative ions. Examples of positive ions include lithium ion (Li+), a natrium ion (Na+), a potassium ion (K+), an ammonium ion (NH4+), and combinations thereof. Examples of negative ions include fluorine ion (F−), a chlorine ion (Cl−), a bromide ion (Br−), a nitrite ion (NO2−), a nitrate ion (NO3−), a phosphate ion (PO43−), a sulfate ion (SO42−), a carboxyl group (COOH), an organic acid, and combinations thereof.

In the present example embodiment, the flow channel100may be an open system in which the solution S may flow through the flow cell120substantially in a steady state steady flow (SSSF).

For example, the inlet110may be connected to a separation column in which a plurality of ion components of a certain type may be individually and sequentially separated. Thus, a solution having a single type of ion components may flow into the flow cell120through the inlet110. The solution may flow out from the flow cell120through the outlet130and into, for example, a waste tank, another separation column, or another analysis apparatus. When the solution has multiple types of ion components, the solution may flow again into the flow cell120through the inlet110in a predetermined time interval to separate another type of ion components. In one example embodiment, the inlet110, the flow cell120, and the outlet130may have the same diameter, so the flow channel100may have a uniform channel diameter D along a flow path of the solution.

The electrode arrangement200may be arranged on an outer surface of the flow channel100. The anode210and the cathode220of the electrode arrangement200may be spaced apart by an electrode gap d less than the channel diameter D. The electrode arrangement200may have, for example, a ring shape enclosing the tube shaped flow channel100. Thus, the flow channel100may penetrate through the ring-shaped electrode arrangement200.

In one example embodiment, the outer surface of the inlet110may be enclosed by the anode210and the outer surface of the outlet130may be enclosed by the cathode220. As a result, the flow cell120may be interposed between the anode210and the cathode220. The flow cell120may have, for example, a disk shape with a channel diameter D greater than the electrode gap d. The width of the flow cell120may correspond, for example, to the electrode gap d.

The flow cell120may be enclosed by an insulator300between the anode210and the cathode220. Thus, the anode210and the cathode220may be electrically separated from each other and the flow cell120may be protected from surroundings.

The insulator may include, for example, one of polyether ether ketone (PEEK) and polytetra fluoro ethylene (PTFE). The electrode may include, for example, one of stainless steel and platinum (Pt).

Since the anode210and the cathode220are separated by the insulator300and are arranged at respective ends of the flow cell120, the flow of ion components I through the flow cell120may be detected as an electrical current. The detecting unit400may be connected to the anode210and the cathode220to detect an electrical voltage between the inlet110and the outlet130. Thereafter, the detecting unit400may analyze the electrical signal to determine the electrical conductivity and concentration of the ion components I in the solution S.

In an example embodiment, the detecting unit400may include a power source410for applying electrical power to the electrode arrangement200and a measuring instrument420for detecting a voltage and current intensity between the anode210and the cathode220.

The measuring instrument420may include, for example, a nano voltmeter and/or a nano ampere meter having a wheatstone bridge or an amplifying circuit. The measuring instrument420may include, for example, a temperature compensation circuit for converting the detected electrical conductivity of the ion components I to a standard conductivity at a temperature of about 25° C. The measuring instrument420may have a configuration based on the structure of the electrode arrangement200and the flow channel100.

When electrical power is applied to the electrode arrangement200, the electrical conductivity of ion components I may be detected by the detecting unit400according to the Equation 1.

(1)C=LKc(1)
where C denotes electrical conductivity, L denotes a specific conductivity of the ion component, and Kcdenotes a cell constant of the conductivity detector500.

Since the solution S flows through the flow cell120enclosed by the electrode arrangement200, the anode210, the flow cell120, and the cathode220may function as a single electrode of a virtual electrical circuit connected to the detecting unit400. Thus, ion components I may penetrate through a cross-sectional area of the flow channel100and may travel the distance between the anode210and the cathode220. For example, the ion components I in the solution S may move along the flow cell120a distance corresponding to the electrode gap d.

Therefore, the cell constant Kcmay be expressed by Equation 2.

Kc=lA=4⁢⁢dπ⁢⁢D2(2)
where A denotes the cross-sectional area through which the solution S flows and thus the ion components I flow and l denotes the gap between the anode and cathode.

The electrical conductivity of the ion components I may be obtained according to Equation 3, which is based on Equations 1 and 2.

Thus, the electrical conductivity C of ion components I in the solution S may be proportional to a form factor of the conductivity detector500determined by the channel diameter D of the flow channel100and the electrode gap d between the anode210and the cathode220. The electrical conductivity C of the ion components I may therefore be amplified just by varying the form factor of the conductivity detector500, and the form factor of the conductivity detector500may be varied just by changing the channel diameter D and the electrode gap d.

A conductivity ratio k of the electrical conductivity C, detected in accordance with the present example embodiment of the conductivity detector500with respect to that of a reference electrical conductivity Crefdetected by another type of conductivity detector, may be expressed by Equation 4.

When the conductivity ratio k is over 1, the electrical conductivity C may be amplified more than the reference electrical conductivity Cref. The other conductivity detector may include a reference flow channel having a reference channel diameter Dref, and the anode and the cathode may be spaced apart on the reference flow channel by a reference gap dref. Therefore, the conductivity ratio k in Equation 4 may indicate an amplification constant that determines the magnitude of a signal amplification of the electrical conductivity due to modification of the shape or form of the conductivity detector500. For that reason, the conductivity ratio k may also be referred to as the amplification constant for convenience.

Thus, the amplification constant k may be proportional to a reduction ratio γdof an electrode gap and an increase ratio γDof the channel diameter in the conductivity detector500, as indicated in Equation 5.

Therefore, a decrease in the electrode gap d and an increase in the channel diameter D may lead to an increase of the amplification constant k. Thus, since the amplification constant k is inversely proportional to the reduction ratio γdof the electrode gap d and proportional to a square of the increase ratio γDof the channel diameter D, electrical conductivity may be sufficiently detected just by a proper combination of the reduction ratio γdand the increase ratio γD, no matter how small the amount of ion components may be in the solution S. Accordingly, the impurity ions in ultra pure water (UPW) may be sufficiently detected by the conductivity detector500, even though the concentration of the impurity ions may be under a degree of ppb or ppt.

Changing the channel diameter D may require the flow channel100to be exchanged for another flow channel and may also require relatively high maintenance costs of the conductivity detector500. However, changing the electrode gap d may just require a modification in the location of the anode210and/or the cathode220on the flow channel100and thus involves relatively low maintenance costs of the conductivity detector500.

For these reasons, the amplification constant k may be controlled just by varying the electrode gap d, which may be accomplished without changing the channel diameter D of the flow channel100in accordance with the present example embodiment. For example, when the electrode gap d is reduced to about 80% of the reference gap dref, and thus the reduction ratio γdof an electrode gap may be about 20%, the electrical conductivity C may be amplified to about 1.25 times the reference electrical conductivity Cref. Thus, the amplification constant k may be controlled to be 1.25 just by varying the reduction ratio γdas much as about 0.2. However, the amplification constant k may be more accurately controlled by varying the increase ratio γDof the channel diameter D together with the reduction ratio γd.

In one example embodiment, the electrode gap d may be controlled to be less than the channel diameter D of the flow channel100, so that the conductivity detector500may have a disk shape. While other types of conductivity detectors are shaped into a cylinder, with the reference electrode gap larger than the reference channel diameter, the electrode gap d may be controlled to be less than or maximally equal to the channel diameter D in the conductivity detector500, thereby sufficiently amplifying the electrical conductivity C.

For example, the electrode gap d may be about 0.3 times to about 1.0 times the channel diameter D, and more particularly about 0.4 times to about 0.6 times the channel diameter D. In the present example embodiment, the channel diameter D may be in a range of about 0.5 mm to about 0.8 mm and the electrode gap d may be in a range of about 0.3 mm to about 0.8 mm. When the flow channel100has a channel diameter D of about 0.5 mm, the electrode gap d may be controlled to about 0.3 mm to about 0.5 mm. Thus, the conductivity detector500may have a disk shape. In addition, when the flow channel100is substituted with a new flow channel having the channel diameter D of about 0.8 mm, the electrode gap d may also be controlled to about 0.3 mm to about 0.8 mm, to thereby provide a disk-shaped conductivity detector500in spite of exchange of the flow channel100.

While the present example embodiment discloses that the channel diameter D may be varied in a range of about 0.5 mm to about 0.8 mm and the electrode gap d may be varied in a range of about 0.3 mm to about 0.8 mm, any other variation ranges of the channel diameter D and the electrode gap d may be allowable as long as the channel diameter D and the electrode gap d sufficiently satisfy Equation 5 with respect to the expected amplification constant in view of configuration and operation requirements of the conductivity detector500.

Therefore, the electrical conductivity of the ion components I in the solution S may be accurately detected without any amount increase of the solution S by the conductivity detector500, irrespective of how small the concentration of ion components I is in the solution S. Thus, the impurity ions in ultra pure water (UPW) having a concentration may under ppb or ppb may be sufficiently detected by the conductivity detector500just by varying the locations of the anode210and the cathode220, without increasing the amount of UPW to be supplied.

FIG. 2illustrates another embodiment of a conductivity detector501which has substantially the same structure as the conductivity detector500inFIG. 1, except for a supplementary electrode on the flow channel.

Referring toFIG. 2, the conductivity detector501includes a supplementary electrode290for reducing or minimizing a polarization at the electrode arrangement200. For example, the supplementary electrode290may include a first electrode230on the outer surface of the flow channel100and spaced apart from the anode210and a second electrode240on the outer surface of the flow channel100and spaced apart from the cathode220. An additional insulator310may be between the first electrode230and the anode210and between the second electrode240and the cathode220. Thus, the first electrode230and the anode210may be electrically separated from each other, and the second electrode240and the cathode220may be electrically separated from each other by the additional insulator310.

The supplementary electrode290may have a ring shape enclosing the flow channel100. The flow channel100may also penetrate through the ring-shaped supplementary electrode290. In the present example embodiment, the electrode arrangement200, the insulator300, the supplementary electrode290, and the additional insulator310may be configured into a single ring structure through which the flow channel100may penetrate.

When electrical power is applied to the electrode arrangement200, polarizations and oxidation-reduction reactions may be carried out at a boundary surface between the solution S and the electrode arrangement200. As a result, a plurality of bubbles may be generated on the surface of the electrode arrangement200. The bubbles on the electrode arrangement200may restrict current flow between the flow channel100and the electrode arrangement200, thereby reducing the detecting efficiency of the detecting unit400.

In the conductivity detector501, electrical power may be applied to the first and the second electrodes230and240in place of the anode210and the cathode220, and the detecting unit400may still detect the electrical voltage and/or the electrical current between the anode210and the cathode220. Thus, no bubbles may be formed between the electrode arrangement200and the solution S, and electrical conductivity may be accurately detected without any detection interrupts from the polarization. Thus, a small quantity of ion components I in the solution S (such as impurity ions in the UPW) may be accurately detected with sufficiently high accuracy.

FIG. 3illustrates another embodiment of a conductivity detector502which has the same structure as the conductivity detector500inFIG. 1, except that the size of the flow cell120is different from those of the inlet110and the outlet130.

Referring toFIG. 3, the conductivity detector502includes a modified flow channel100ain which the flow cell120has a volume larger than those of the inlet110and the outlet130. For example, the inlet110and the outlet130may have a tube shape with a first channel diameter D1. The flow cell120may have a tube shape connected to the inlet110and the outlet130and a second channel diameter D2greater than the first channel diameter D1.

The flow speed may decrease in the flow cell120when the solution S flows into the flow cell120and may increase when the solution S flows out from the flow cell120through the outlet130. Thus, the number of ion components I in the flow cell120may increase when the solution S penetrates through the conductivity detector502. Since the anode210, the flow cell120, and the cathode220may be provided as a single electrode and the flow speed of the solution S may decrease in the flow cell120due to volume expansion, the average number of ion components I in the solution S may increase compared with the flow channel100of the conductivity detector500inFIG. 1when the ion components I are uniformly solved in the solution S.

Thus, the detection limit of the detecting unit400may be improved in accordance with an increase in the number of ion components I in the flow cell120. The number of ion components I in the flow cell120may be determined by the volume expansion of the flow cell120, and the volume expansion of the flow cell120may be varied based on the diameter ratio of the first and the second channel diameters D1and D2. Accordingly, the detection limit may be easily improved in the conductivity detector502just by controlling the diameter ratio of the first and the second channel diameters D1and D2.

In the present example embodiment, the first channel diameter D1may be in a range of about 50% to 70% of the second channel diameter D2.

While ion components are dissolved in the aqueous solution (such as impurity ions in UPW) in the present embodiment, other solvents may also be used for detecting the electrical conductivity of traces of ion components in the solvent in view of electrical characteristics between the ion components and the solvent.

According to the example embodiments of the conductivity detector, the conductivity detector may be modified into a disk shape, in which the electrical gap between the anode and the cathode may be less than the channel diameter of the flow channel. As a result, the detection limit may be improved without design changes or instrumental modification thereof. For example, electrical conductivity may be sufficiently detected with high accuracy just by changing the form factor of the conductivity detector, irrespective of how small the amount of ion components I may be in the solution S. Accordingly, the impurity ions in ultra pure water (UPW) may be sufficiently detected by the conductivity detector500, even though the concentration of the impurity ions may be under a degree of ppb or ppt.

FIG. 4illustrates an embodiment of an ion chromatography system1000, which may include an eluent supplier1100, a sample supplier1200, a separation column1300, and a conductivity detector1400. The eluent supplier1100supplies an eluent E that may be a moving phase of an ion chromatography. The sample supplier1200supplies a sample solution into a flow of the eluent E, thereby generating a multi-component solution in which a plurality type of ion components may be dissolved. The separation column1300sequentially separates the ion components from the mixed solution to thereby generate a single component solution having a single type of ion components and sequentially discharges a plurality of the single component solutions in a time order. The conductivity detector1400detects a concentration of the ion components in the single component solution based on an electrical conductivity of the ion components.

For example, the eluent supplier may include an eluent reservoir1110storing the eluent E, a delivery pump1120delivering the eluent E via the separation column1300and the conductivity detector1400from the eluent reservoir1110, and a degassing member1130for reducing or minimizing damping characteristics of the eluent E in the separation column1300.

The eluent E may function as a moving phase of an ion chromatography, so that a plurality of ion components may be solved into the eluent E from the sample solution. Thus, the eluent E and the sample solution may be mixed into the multi-component solution in which a plurality of ion components of a certain type may be dissolved in the ion chromatography system1000. The eluent E may have low viscosity for good fluidity in the ion chromatography system1000and high dissolubility to the solutes of the sample solution. For example, the eluent E may have high chemical stability with respect to a base material of the separation column that may function as a stationary phase of the ion chromatography.

One or more additives may be supplied to the UPW for increasing the dissolubility and miscibility with respect to an analysis specimen. In addition, a buffer solution may be added to the UPW for separating ionic components from the analysis specimen.

The delivery pump1120may generate a pressure for delivering the eluent E from the eluent reservoir1110through the separation column1300and the conductivity detector1400, so that the eluent E may sufficiently reach the conductivity detector1400from the eluent reservoir1110. The eluent E may move, for example, at a constant speed in the ion chromatography system1000by the deliver pressure.

The degassing member1130may include a membrane tube1132arranged in a vacuum chamber1131and connected to the delivery pump1120. The eluent E including gas components may flow into the membrane tube1132in the vacuum chamber1131. The gas components may be removed from the eluent E into the vacuum chamber1131by the vacuum pressure. Thus, gases components in the eluent E may be reduced or minimized by the degassing member1130, thereby reducing or minimizing the damping characteristics of the eluent E in the separation column1300.

While the present example embodiment discloses that the degassing member1130is arranged between the delivery pump1120and the sample supplier1200, the degassing member1130may be between the eluent reservoir1110and the delivery pump1120in at least one example embodiment.

The sample supplier1200may include a sample loop1210holding a sample solution, a sample dispenser1220providing a fixed quantity of the sample solution to the sample loop1210at a constant speed, and an auto injector1230automatically injecting the sample solution of the sample loop1210to a flow path of the eluent E. For example, the sample dispenser1220may include a peristaltic pump, and the auto injector1230may include a plurality of holding ports1231and a multiport valve system in which the sample solution in the sample loop1210may be supplied to the eluent E just by changing the holding port1231.

In the present example embodiment, the sample solution may include an ultra pure water (UPW) having an electrical resistance more than about 18MΩ. For example, when the sample solution includes UPW in which a plurality of impurity ions are dissolved and water or an aqueous solution is used for the moving phase of the ion chromatography system1000, no eluent supplier may be provided with the ion chromatography system1000. In such a case, the UPW may be supplied to the ion chromatography system1000for detecting the concentration of the impurity ions in the UPW by the sample supplier1200with comparatively fewer elements.

For example, when the sample solution including one or more solvents for semiconductor manufacturing processes such as UPW is supplied to a sample reservoir for detecting the impurity ions therein, the sample dispenser1220may extract a fixed analysis quantity of the sample solution from the sample reservoir and may provide the fixed analysis quantity into the sample loop1210. Then, the extracted sample solution may be supplied to the holding port1231of the auto injector1230from the sample loop1210, and the auto injector1230may linearly move or rotate by a predetermined unit in such a way that the holding port1231in which an analysis quantity of the sample solution may be hold may be aligned with the flow path of the eluent E. Thereafter, the port valve of the holding port1231may be open and the sample solution may be mixed with the eluent E.

Thus, the sample solution and the eluent E may be mixed into the multi-component solution in which a plurality of ion components of a certain type may be dissolved. For example, various ion components in the sample solution may be mixed with the eluent E, and the multi-component mixed solution may be supplied to the separation column1300.

A plurality of the holding ports1231having different holding volumes may be provided with the auto injector1230, and the analysis quantity of the sample solution may be varied in view of the concentration degree of the ion components in the sample solution. In the present example embodiment, 10 holding ports1231may be provided with the auto injector1230.

After mixing of the sample solution with the eluent E has been completed, the multi-component mixed solution may be supplied to the separation column1300. The ion components may be sequentially separated, one by one, in accordance with an ionic bond of each ion component and the stationary phase materials in the separation column1300. For example, the separation column1300may include an ion exchange resin1310arranged in a tube-shaped housing as the stationary phase of the ion chromatography, and a temperature controller1320for controlling the temperature of the solution in the separation column1300to be uniform.

The ion exchange resin1310may be fixed into the housing and may be physically and chemically stable to the eluent E passing through the separation column1300. Thus, the ion exchange resin1310may function as the stationary phase of the ion chromatography, while the eluent E may function as the moving phase of the ion chromatography.

When the multi-component solution reaches the ion exchange resin1310in an equilibrium state with ions of the eluent E, the chemical equilibrium state in the ion exchange resin1310may be broken and the ion components in the multi-component solution may bond to the resin of the ion exchange resin1310.

Since the eluent E may be continuously supplied to the separation column1300by the delivery pump1120, bonding of the ion components and resin of the ion exchange resin1310may be sequentially broken in accordance with the bonding strength of each ion component to the stationary phase resin. Thus, the stronger the bonding strength of the ion component is, the longer the ion component stays in the separation column1300. Thus, a retention time (or a stay time) of each ion component in the separation column1300may vary according to the bonding strength, and each ion component may be individually discharged from the separation column1300as the retention time may pass.

The separated ion components from the stationary phase resin of the ion exchange resin1310may still be dissolved in the eluent E and discharged from the separation column1300. Thus, the multi-component solution may be changed into a single component solution, in which a single type ion components are dissolved, when discharging the separation column1300. Thus, the single component solution may be sequentially discharged from the separation column1300in a time order according to the bonding strength of each ion component therein.

For example, the temperature controller1320may control an inner temperature of the separation column1300under a uniform temperature, so that the multi-component solution, the eluent E, and the single component solution flows through the separation column1300under the uniform temperature.

The conductivity detector1400may detect the electrical conductivity of the ion components in the single component solution, thereby obtaining the concentration of the ion components of the sample solution. The conductivity detector1400may have the same structure as any one of the conductivity detectors500to502inFIGS. 1 to 3.

For example, the conductivity detector1400may include a flow channel100having a tube shape and a channel diameter D through which the single component solution may flow, an electrode arrangement200on an outer surface of the flow channel100and having at least an anode210and at least a cathode220spaced apart by the electrode gap d less than the channel diameter D, and a detecting unit400connected to the electrode arrangement200for detecting electrical conductivity of the ion components in the single component solution.

The flow channel may include an inlet110enclosed by the anode210and connected to the separation column1300, and into which the single component solution may flow in, an outlet130enclosed by the cathode220and through which the single component solution may flow out, and a flow cell120between the inlet110and the outlet130and across which the single component solution may pass, thereby providing ion flow from the inlet110to the outlet130.

The inlet110, the outlet130, and the flow cell120may have the same diameter, so the flow channel100may have a uniform channel diameter D along the ion flow. The conductivity detector1400may have a disk shape in such a configuration that the electrode gap d between the anode210and the cathode220is less than the channel diameter D. Therefore, the cell constant Kc of the conductivity detector1400may be reduced just by varying the electrode gap and the channel diameter. Thus, the detected signal may be amplified by the amplification constant in the conductivity detector1400. As a result, the conductivity detector1400may accurately detect the electrical conductivity of ion components, and the concentration of the ion components in the single component solution may be obtained from the detected conductivity. For example, impurity ions in UPW may be sufficiently detected by the conductivity detector1400, even though the concentration of impurity ions may be under a degree of ppb or ppt due to a small cell constant Kc of the conductivity detector1400.

As shown inFIG. 3, the inlet110and the outlet130may have a first diameter D1and the flow cell120may have a second diameter D2lager than the first diameter D1. Thus, the flow cell120may have a volume greater than those of the inlet110and the outlet130. Thus, the number of ion components in the flow cell120may increase when the single component solution flows through the flow cell120, thereby increasing the detection accuracy of the conductivity detector1400.

In addition, the conductivity detector1400may include a supplementary electrode290for reducing or minimizing a polarization at the electrode arrangement200. As shown inFIG. 2, the supplementary electrode290may include a first electrode230and a second electrode240. The first electrode230is arranged on the outer surface of the flow channel100and spaced apart from the anode210. The second electrode240is arranged on the outer surface of the flow channel100and spaced apart from the cathode220. Thus, bubbles that otherwise might be caused by polarization of the single component solution do not occur between the electrode arrangement200and the single component solution.

For example, electrical power410may be applied to the supplementary electrode290, not to the electrode arrangement200. In this case, bubbles caused by polarization of the solution may be generated between the single component solution and the first and the second electrodes230and240, and no bubbles may be generated at the anode210and the cathode220. Therefore, electrical conductivity may be accurately detected without any detection interrupts. For example, a small quantity of ion components (such as impurity ions in UPW) may be accurately detected with sufficiently high accuracy.

The electrical conductivity or concentration of ion components may be categorized by each ion component and may be visually displayed on a display device by a system controller1600.

In the present example embodiment, ion components may include positive ions or negative ions dissolved in UPW as impurity ions. Thus, the multi-component solution and the single component solution may include an aqueous solution in which the ion components may be dissolved. Examples of the positive ions include one of a lithium ion (Li+), a sodium ion (Na+), a potassium ion (K+), an ammonium ion (NH4+) and combinations thereof. Examples of negative ions may include one of a fluorine ion (F−), a chlorine ion (Cl−), a bromide ion (Br−), a nitrite ion (NO2−), a nitrate ion (NO3−), a phosphate ion (PO43−), a sulfate ion (SO42−), a carboxyl group (COOH−), an organic acid and combinations thereof.

The ion chromatography system1000may further include a suppressor1500between the separation column1300and the conductivity detector1400for removing noise ions having a polarity opposite to the ion component of the single component solution. As a result, noise signals may be removed from a signal corresponding to the electrical conductivity of the ion components in the single component solution.

When the ion components of the single component solution include positive ions and the suppressor1500substitutes the noise ions having negative polarity with hydroxyl ions (OH−), noise signals may be removed from the signal corresponding to the electrical conductivity of the positive ion components in the single component solution. In contrast, when ion components of the single component solution include negative ions and the suppressor substitutes the noise ions having positive polarity with hydrogen ions (H+), noise signals may be removed from the signal corresponding to the electrical conductivity of the negative ion components in the single component solution.

In accordance with one or more of the aforementioned embodiments, a conductivity detector has a disk shape and an electrical gap between an anode and a cathode of the detector may be less than the channel diameter of the flow channel. As a result, the cell constant Kc may be reduced and detection accuracy of the conductivity detector may be increased without design changes or instrumental modification thereof. Thus, electrical conductivity may be sufficiently detected with high accuracy just by changing the form factor of the conductivity detector, no matter how small the amount of ion components I is in the solution S. Accordingly, impurity ions in ultra pure water (UPW) may be sufficiently detected by the conductivity detector, even though the concentration of impurity ions may be under a degree of ppb or ppt.