JPH0312703B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a method for measuring ion species that can simultaneously measure the amount of a sample collected in ion chromatography and the ion concentration in this sample amount.

[Prior art]

There are two methods for collecting samples in ion chromatography: one method is to drive an injector with a measuring tube to inject a fixed amount of sample into the mobile phase (eluent), and the other is to use a microsyringe etc. to collect a roughly fixed amount of sample. There is a method of injecting into a mobile phase. In the former, a chromatogram is created using a standard solution (or standard gas) and a sample to be measured, and the sample to be measured is determined from the height ratio (or area ratio) of peaks whose retention times match in the two chromatograms. The so-called absolute calibration curve method is often adopted to determine the ion concentration in the sample. Also, in the latter case,
The so-called internal standard method involves adding a certain amount of internal standard substance to the sample to be measured, then creating a chromatogram, and comparing this chromatogram with the chromatogram of the internal standard substance standard solution substance to determine the ion concentration in the sample. is often adopted. However, when the above-mentioned absolute calibration curve method is employed, there is a drawback that it is generally difficult to adjust the size of the peak of the chromatogram in accordance with the ion concentration in the sample. This is because although the magnitude of the peak is proportional to the volume within the metering tube of the injector, it is generally difficult to increase or decrease the volume within the metering tube. Furthermore, when the internal standard method described above is adopted, there is a drawback that a troublesome operation of accurately adding the internal standard substance to the sample to be measured is required. This is because the internal standard substance must be different from the ion species present in the sample to be measured and must be completely separated from these ion species on the chromatogram.

[Purpose of the invention]

The present invention has been made in view of these drawbacks, and its purpose is to solve the problem in which the amount of a sample to be measured and the ion concentration in the sample cannot be measured simultaneously without accurately weighing the sample to be measured. An object of the present invention is to provide a method for measuring ion species.

[Summary of the invention]

A feature of the present invention is that in a method for measuring ion species in a sample to be measured using ion chromatography, a standard solution containing the same various ion species and water as the ion species to be measured is used to A first graph showing the relationship between the peak area value and the standard solution injection amount and a second graph showing the relationship between the peak area value of the various ion species and the ion amount are created, and then, using the sample to be measured, The injection amount V of the sample to be measured and the ion amount Wi of the ion species to be measured are determined from the respective area values of the moisture peak and each ion peak of the chromatogram obtained by the method and the first and second graphs. The concentration of the ion species to be measured is determined from the quotient (Wi/V).

〔Example〕

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 the figure, 1a is a tank in which an eluent consisting of HNO3 with a concentration of _5mM is stored, and 2 is a plunger type (or diaphragm type or syringe type). etc.), which pumps the eluent under pressure, 3 has, for example, first to sixth connection ports 3a to 3f and a metering tube 3g, and the solid line connection state and the broken line connection state in FIG. 1 are alternately connected. 4 is a damper that prevents pulsation of the eluent; 5 and 6 are a pre-column and a separation column filled with, for example, a cation exchanger with a low ion exchange capacity; and 7 is, for example, a conductivity detector. Detector; 8 is an integrator that receives a detection signal from the detector 7 and processes the signal; 9 is a thermostat that houses the precolumn 5, the separation column 6, and the detector 7 and keeps them at a predetermined temperature (for example, 40°C); 1b is a waste liquid tank that accommodates the liquid discharged from the detector 7. still,
The internal volume of the measuring tube 3g is usually 2 ml (also 2 ml in the embodiment shown in FIG. 1), but is not limited to this, and may be, for example, 10 ml or 20 ml.

The operation of the embodiment of the present invention having the above configuration will be described below. In FIG. 1, when the pump 2 is driven, the eluent in the tank 1a flows from the pump 2 to the damper 4 to the first and second connection ports 3a and 3b of the injector 3 to the precolumn 5 to the separation column 6 to the detector 7. →Flows through the flow path of the waste liquid tank 1b. Also, Li ⁺
0.1ppm, Na ⁺ 0.5ppm, NH ₄ ⁺ 0.5ppm, and K ⁺
200μl of a solution containing 1ppm (hereinafter referred to as standard solution)
accurately measure the amount using a microsyringe, and inject it into the measuring tube 3g from the fourth connection port 3d of the injector 3. When the injector 3 is turned on in this state, the internal flow path of the injector 3 switches from the solid line state in FIG. 1 to the broken line state. Therefore, the eluent that has passed through the damper 4 is transferred to the first injector 3.
Connection port 3a → 6th connection port 3f → Measuring tube 3g → 3rd
It flows through the flow path from the connection port 3c to the second connection port 3b to the precolumn 5. Therefore, the standard solution injected into the measuring tube 3g is transferred to the precolumn 5 by the eluent.
It began to be imported into The ionic species contained in this standard solution undergo predetermined separation in the precolumn 5 and the separation column 6, and then reach the detector 7, where its conductivity is detected. . The detection signal outputted from the detector 7 is guided to an integrator 8 and subjected to predetermined signal processing to provide a chromatogram, an integral value, etc. as shown in FIG. Next, by accurately measuring 1000 μl of the above standard solution using a microsyringe, injecting it into the injector 3, and performing the same operation, a chromatogram and integral values as shown in FIG. 3 are obtained. In Figures 2 and 3,
Each peak in the chromatogram appears in the direction of decreasing conductivity, and the first peak is a peak due to water (so-called water dip). This water dip often becomes saturated as the amount of standard solution injected increases. Additionally, the absolute value of conductivity, which indicates the baseline of the chromatogram, is approximately 2400 μs/cm.
It is. Similarly, 100 μl of the above standard solution,
Obtain chromatograms and integral values for each case of 500 μl and 2000 μl. Based on the integral value etc. obtained in this way, the relationship between the amount of standard solution injected into the injector 3 (μl) and the area value of the water dip (one area count is 0.125μV・sec) is plotted. Figure 4 is obtained. This fourth
From the figure, it can be seen that there is a proportional relationship between the standard solution injection amount and the water dip area value, and if the sample injection amount (standard solution injection amount) is V and the water dip area value is Awd, the following formula (1 ) holds true.

V=4.9×10 ^-6 ×Awd...(1) On the other hand, from the chromatograms obtained as shown in Figures 2 and 3, each of Li ₊ , NH ₄₊ , Na ₊ , and K ₊ When the peak area value is plotted against the ion amount (ng), FIG. 5 is obtained. From FIG. 5, it can be seen that there is a proportional relationship between each of the ion species (ng) and the peak area value (one area count 0.125 μV·sec). Also, Li ₊ ,
The ion amounts of NH ₄₊ , Na ₊ , and K ₊ were determined as W _Li + , respectively.
Let W _NH4 +, W _Na +, and W _K +, Li+,
The peak area values of NH ₄₊ , Na ₊ , and K ₊ are
Assuming A _L1 +, A _NH4 +, A _Na +, and A _K+ , the following equations (2) to (5) can be derived from FIG.

W _Li +=2.44×10 ^-4 ×A _Li + …(2) W _Na +=8.13×10 ^-4 ×A _Na + …(3) W _NH4 +=6.71×10 ^-4 ×A _NH4 + … …(4) W _K+ =1.49×10 ^-3 ×A _K+ …(5) Therefore, if a chromatogram, etc. as shown in Figures 2 and 3 is created for the sample to be measured, the water dip will be The injection amount of the sample to be measured can be determined from the area value and the above equation (1) (ie, FIG. 2). Further, the ion amount of each ion can be determined from the peak area value of each ion in this chromatogram etc. and the above equations (2) to (5) (ie, FIG. 3). Further, the value (quotient) obtained by dividing each of the above equations (2) to (5) by the above equation (1) becomes the ion concentration [ng/μl=ppm] of each ion. Therefore, L ⁺ ,
If the ion concentration values of Na ⁺ , NH ₄ ⁺ , and K ⁺ ions are respectively C _Li +, C _Na +, C _NH4 +, and C _K+ , the following equations (6) to (9) hold, and this The concentration of each ion in the sample to be measured can be easily determined from the formula.

C _Li+ = W _Li + / V = 4.97 × 10 × A _{Li +} / Awd ... (6) C _{Na +} = W _Na + / V = 1.66 × 10 ² × A _{Na +} / Awd ... (7) C _NH4 + = W _NH4 +/V=1.37×10 ² ×A _NH4+ /Awd……(8) C _K+ =W _K+ /V=3.04×10 ² ×A _K+ /Awd……(9) The present invention as explained in detail above According to the embodiment, the injection amount of the sample to be measured is determined from the area value of the water dip, and the ion amount of each ion is determined from the peak area value of each ion, so the sample to be measured can be collected without accurately weighing it. It has the advantage of being able to measure the amount of sample taken and the concentration of ions in this sample. In addition, the conventional so-called concentration column method, which is used to concentrate the ion species to be measured when the ion concentration of the sample to be measured is low, requires the complicated process of precisely injecting a certain amount of sample into the concentration column. However, according to the present invention, it is possible to simplify the operation by injecting the sample to be measured in the approximate amount to be injected into the concentration column. Furthermore, in the conventional concentration column method, some ion species were generated that were not completely captured by the concentration column due to the matrix of ion species to be measured, but according to the present invention, the ion species in the injected sample were Since all of the ion species to be measured are transported to the pre-column or the like, there is also the advantage that measurement errors of the ion species to be measured are significantly reduced.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the configuration of an embodiment of the present invention, Figures 2 and 3 are chromatograms created using a standard solution, and Figure 4 shows the relationship between the amount of the standard solution injected and the area value of the water dip peak. FIG. 5 is a diagram showing the relationship between the amount of each ion contained in the standard solution and the peak area value. 1a, 1b...tank, 2...pump, 3...injector, 4...damper, 5...precolumn,
6... Separation column, 7... Detector, 8... Integrator, 9... Constant temperature bath.

Claims (1)

[Scope of Claims] 1. In a method for measuring ion species in a sample to be measured using ion chromatography, the above-mentioned A first graph showing the relationship between the area value of the peak due to water and the amount of standard solution injected, and a second graph showing the relationship between the peak area value of the various ion species and the amount of ions are created, and then the sample to be measured is Create a chromatogram using From the second graph, the amount of ions Wi of each ion species to be measured contained in the sample to be measured
A method for measuring an ion species, characterized in that the concentration of the ion species to be measured is determined from the quotient (Wi/V). 2. The ion species measuring method according to claim 1, wherein the moisture peak is a water dip. 3 Each of the ion species to be measured is Li ⁺ , Na ⁺ ,
The method for measuring ion species according to claim 1 or 2, which comprises NH ₄ ⁺ and K ⁺ ions.