JPH0310073B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a trace ion species measuring method and apparatus for quantitatively analyzing trace amounts of desired ion species contained in a sample by ion chromatography.

Ion chromatography is extremely effective for quantitatively analyzing ionic species in samples, but when quantitatively analyzing trace amounts of ionic species,
It has been difficult to accurately measure ion species that elute in the vicinity of a negative peak due to water (hereinafter referred to as water dip) in a sample. for example,
When a sample containing ppb levels of F ^- and Cl ^- is measured by ion chromatography using a carbonate-based eluent using an ion exchange membrane tube background removal device, the F ^- and Cl ^- elution positions are The water dips overlapped, creating a major hindrance in measurement.

This water dip is caused by the fact that when the eluent is converted to carbonic acid in a background removal device to reduce the background, the conductivity background of carbonic acid still remains, so the water portion of the sample is eluted. When the carbonic acid is removed, that part contains no carbonic acid and its conductivity becomes even lower.

However, in order to eliminate this water depth, conventional methods have been used in which sodium carbonate or sodium hydrogen carbonate is added to the sample in advance to make it have the same composition as the eluent. This method requires a relatively large amount of sample because it requires the addition of reagents, and also has drawbacks such as the appearance of peaks that are not due to ions present in the sample unless the concentration of carbonic acid is adjusted accurately. It was hot. Furthermore, when the sample is pure water and measurement in the extremely low concentration range is required, the concentration column method is often used; however, when using this concentration column, the aforementioned method of adding carbonate is used. It also had the disadvantage that it could not be used.

The present invention was made in view of these drawbacks, and its purpose is to completely eliminate the water dip described above, and to create a trace amount that can accurately quantitatively analyze even trace amounts of ionic species that elute in close proximity to the water dip. An object of the present invention is to provide a method for measuring ion species and a measuring device therefor.

Hereinafter, the present invention will be explained in detail using figures. FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention, in which 1 to 3 are first to third pumps for feeding water, a first eluent, and a scavenge liquid, respectively; 4 and 5 are Dampers prevent pulsation caused by the first and second pumps 1 and 2, respectively; 6 is a pressure gauge; 7 is an injector for collecting a predetermined amount of sample; A separation column 9 for separation is a background removal device in which an inner chamber 9a and an outer chamber 9b are formed adjacent to each other by an ion exchange membrane 9c, through which the eluate from the separation column 8 and the scavenging liquid flow independently, respectively. , 10 is a detector for detecting the conductivity of the liquid led from the inner chamber 9a, and 11 is a constant temperature bath that accommodates the separation column 8, the background remover 9, and the detector 10 and keeps them at a predetermined temperature. In addition, the first pump 1, the damper 4, the injector 7, the separation column 8, the interior chamber 9a of the background removal device 9, and the detector 10 are connected to the second eluent (the water and the first eluent are connected at the connection part 12). (liquid formed by the merging of the two) flows and constitutes the first flow path.
Furthermore, the first eluent flows via the second pump 2 and damper 5, forming a second flow path.
Note that the conventional device (hereinafter referred to as the conventional device) is configured such that the second flow path is completely removed from the device having such a configuration, and only the first eluent flows into the first flow path. It was configured.

Hereinafter, the operation of the embodiment of the present invention having the above configuration and the results of experiments using the same will be explained. In FIG. 1, a first pump 1 supplies water to the first flow path at a rate of 1 ml/min., and a second pump supplies water to the second flow path at a rate of 8mM Na ₂ CO ₃ /8m.
A first eluent consisting of M.Na ₂ HCO is fed at 1 ml/min. Therefore, the second eluent consisting of 4mM.Na ₂ CO ₃ /4mM.NaHCO ₃ flows at a rate of 2 ml/min. after the connecting portion 12 of the first flow path.
Further, a predetermined scavenge liquid is caused to flow into the outer chamber 9b by the third pump 3. In this state, a signal indicating a reference state (such as a recorder baseline) is obtained from the detector 10. Next, injector 7
For example, 50 ppb F ^- , 100 ppb Cl ^- ,
150ppb ^Cl- , _300ppb ^PO3-4 , 100ppb ^Br- ,
A 100μ standard sample containing 300 ppb NO ₃ ^- and 400 ppb SO ₄ ^2- is taken. The sample is transported by water to the connection 12 and then to the second
The ions are carried by the eluent and reach the separation column 8, where the contained ionic species undergo a predetermined separation. Thereafter, the standard sample is transported by a second eluent to the background removal device 9, where the oppositely charged ionic species (such as Na) contained therein are removed. The conductivity of the eluate led from the inner chamber 9a of the removal device is detected by the detector 10, and the conductivity is detected by a second recorder or the like.
A chromatogram like the one shown in the figure can now be obtained. When ion-free water was measured in the same manner, a chromatogram as shown in FIG. 3 was obtained.

By the way, when using the conventional apparatus described above and measuring the standard sample and water by flowing an eluent consisting of 4mM Na ₂ CO ₃ /4mM NaHCO ₃ into the first channel at 2 ml/min. The chromatograms shown in Figures 4 and 5 were obtained. In FIG. 4, a large negative peak appears near the elution position of F ^- ions, and it can be seen from FIG. 5 that this peak is the water dip caused by water. Therefore, from a comparison between FIG. 3 (or FIG. 2) and FIG. 5 (or FIG. 4), it is clear that according to the embodiment of the present invention as described above, water depth is completely eliminated. .

According to the embodiment of the present invention as described in detail above, the water dip is completely eliminated,
This method has the advantage of being able to accurately and quantitatively analyze trace ion species that elute in the vicinity. Therefore, there is an advantage that it is possible to easily and accurately measure trace amounts of ion species in pure water, etc., which was difficult in the conventional example. Furthermore, the device according to the present invention is second to the conventional device described above.
Since the structure is simple, just adding the second flow path having the pump 2 and the damper 5, it has the great advantage of eliminating water dips, and also has the advantage of being easy and inexpensive to manufacture.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the configuration of the embodiment of the present invention, Figs. 2 and 3 are chromatograms created using the embodiment of the present invention, and Figs. 4 and 5 are chromatograms created using the conventional apparatus. This is a chromatogram. 1-3...Pump, 4,5...Damper, 7...
...Injector, 8...Separation column, 9...Background removal device, 10...Detector, 11...
Constant temperature bath.

Claims (1)

[Scope of Claims] 1. In an ion species measurement method for quantitatively analyzing a desired ion species contained in a sample by ion chromatography, a predetermined connection of a first flow path through which a predetermined amount of the collected sample is conveyed with water. The first eluent from the second flow path is combined in the second flow path, and the eluent and the water are mixed and flowed as a second eluent, thereby eliminating the negative peak caused by the water in the sample. A method for measuring trace ionic species, characterized by: 2. The trace ion species measuring method according to claim 1, wherein the connection part is provided between an injector that collects a predetermined amount of a sample and a separation column that separates ion species in the sample. . 3 an injector that collects a predetermined amount of sample;
a separation column that separates ionic species contained in the sample carried by a predetermined eluent; a background removal device that removes oppositely charged ionic species contained in the eluate from the separation column; In the ion species measuring device comprising a detector for detecting the conductivity of the eluate, a second channel is connected to a predetermined connection part of the first channel through which the sample collected by the injector is transported by water. An ion species measuring device characterized in that the eluent flowing through the second channel is configured to merge with the water. 4. The ion species measuring device according to claim 3, wherein the connection portion is provided between the injector and the separation column.