JPS62209357A - Method and apparatus for analyzing sulfide ion - Google Patents

Abstract

PURPOSE:To enable easy and stable analysis, by detecting conductivity by converting a sulfide ion to lithium sulfide to analyze the sulfide ion. CONSTITUTION:The sulfide ion in a liquid to be measured is separated chromatographically by a separation column 4 packed with a cation exchange resin and, thereafter, the pH of the eluate of the column 4 is adjusted to convert the sulfide ion to lithium sulfide. This converted lithium sulfide is guided to a conductivity detector to measure conductivity and the sulfide ion is detected by detecting lithium sulfide. By this method, the sulfide ion in the liquid to be measured can be analyzed easily and stable.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for chromatographically separating and analyzing sulfide ions (S''-) in a liquid to be measured, and an analysis apparatus using the method.

<Conventional technology> Sulfide ions (3
When attempting to analyze the two by separating them chromatographically, the dissociation constant (Ka) of hydrogen sulfide a + ZO) is small and the value of pKa = -1og Ka is large (25
pKa = 7.07), so conventionally an electrochemical detector having a silver working electrode that performs a chemical reaction as shown in equation (1) below has been required.

2Ag + S"' -AgzS + 2e-(1)
However, a conductivity detector is generally used as a detector in an apparatus for chromatographically separating and analyzing ions in a liquid to be measured, and its characteristics have been thoroughly studied and stable performance has been obtained.

For this reason, the use of the electrochemical detector, which is different from the conductivity detector, is often inconvenient both in terms of stability of detector characteristics and in terms of parts supply.

In particular, the surface condition of silver, which is the working electrode, changes easily,
In order to stably measure sulfide ions (S2-), maintenance and inspection must always be performed, which is complicated.

<Problems to be Solved by the Invention> The present invention has been made in view of the drawbacks of the conventional examples, and its purpose is to easily analyze sulfide ions in a liquid to be measured using a conductivity detector. The purpose of this research is to provide a method and an analytical device using the method.

Means for Solving the Problems> A feature of the present invention that solves the problems described above is that in a method for analyzing sulfide ions and an analyzer using the same, the eluate of the separation column is adjusted to pH fJ1. The purpose is to convert the sulfide ions in the solution into lithium sulfide and then detect the conduction ffl rate.

<Example> Hereinafter, the present invention will be explained in detail using the drawings. 1st
The figure is an explanatory diagram of the configuration of an embodiment of the present invention. In the figure, 1a is a tank in which an eluate made of, for example, a 2 mN aqueous sulfuric acid solution is stored, and 1b is a tank in which a removal liquid is stored, for example, a lithium hydroxide solution with a 50 mN concentration. tank, Ic.

1d is a waste liquid tank, 2a and 2b are liquid sending pumps, and 3 is a first to sixth connection port 3a to 3f and a measuring tube 3g (for example, internal volume 100μIl), and its internal flow path is connected with a solid line and a broken line. 4 is a separation column filled with, for example, a harsh sulfone cation exchange resin, and 5 is a tube 5a made of, for example, a cation exchange membrane, which divides the inside into an inner chamber 5b and an outer chamber 5c. A suppressor consisting of a divided section, 6 a detector consisting of a conductivity detector, 7
is a constant temperature bath that houses the separation column 4, suppressor 5, and detector 6 and keeps them at a predetermined temperature (for example, 40° C.).

In the embodiment of the present invention having such a configuration, when the pump 2a is driven, the eluent in the tank la is transferred to the pump 2a.
→First and second connection ports 3a and 3b of injector 3
The liquid flows through the flow path of → separation column 4 → inner chamber 5b of suppressor 5 → detector 6 at a flow rate of, for example, 1.5 ml/win, and is discharged to waste liquid tank 1c. Moreover, when the pump 2b is driven,
The removed liquid in tank lb is transferred from pump 2b to outer chamber 5c of suppressor 5 to waste liquid tank! For example, the flow path of d is 1.5 ml/1n,
The conductivity of the eluent flowing in the inner chamber 5b is reduced by performing, for example, cation exchange through the tube 5a in the suppressor 5.

In addition, lithium hydroxide (L
iOII), as described later, lithium hydroxide passes through the tube 5a and reaches the inner chamber 5b, thereby increasing the alkalinity of the liquid flowing inside the inner chamber. In this state, when a sample (for example, a liquid to be measured containing +00 ppm of 52-) is injected from the fourth connection port 3d of the injector 3, the sample flows from the fourth connection port 3d to the third connection port 3.
It flows through the flow path c→metering tube 3g→sixth connection hole 3f→fifth connection port 3c, filling the inside of the metering tube 3g.

Thereafter, the injector 3 is turned on and its internal flow path is switched from the solid line connected state to the broken line connected state. The sample in the measuring tube 3g is carried by the eluent and reaches the separation column 4, where the ions in the sample are separated from other ions. In other words, since sulfide ions (S"-) are weakly ionic, they can be held for a predetermined retention time without being removed by the strong sulfone-type cation exchange resin in the separation column 4. Later, the separation column 4 becomes dissolved.The eluate from the separation column 4 is passed through the suppressor 5.
The above (52-) is converted to Li2S for the reasons (or principles) explained in detail in (a) to (c) below.

(b) Ih5O in the eluent eluted from separation column 4,
is converted to LizS04 by cation exchange as shown in equation (2) below through the tube 5a.

2H” + 5042- + 2Li”→Re5in)
-+2Li" + SOt"-+2"ν esin)
...(2) (b) The concentration of lithium hydroxide (LiO+I) contained in the removal liquid flowing in the outer chamber 5c of the suppressor 5, the pH value of the removal liquid, the pH value of the eluent after passing through the suppressor 5, and The conductivity of the eluent in the detector 6 (ie, the baseline conductivity) is as shown in the table below. As is clear from this table, it can be seen that when the LiOH concentration in the removal solution exceeds 5, the pH value and baseline electrical conductivity of the eluent after passing through the suppressor become particularly large. This is because LiOH in the removal solution
This is because the liquid passes through the tube 5a and reaches the inner chamber 5b.

(c) It is known that hydrogen sulfide (H, S) dissociates as shown in the following formula (3) when the pH value approaches the eye level, producing two sulfide ions (S). In that case, When a large amount of lithium hydroxide (LiOIl) is present, JV is expressed as shown in the following formula (4).

H2S → 2N” + S” (3)2
H"10S" + 2Li" + 20tl-→ Li
zS +21120 (4) When lithium sulfide (LizS) is generated in the suppressor 5 in this way, the effluent of the suppressor is led to the detector 6, and the conductivity of the lithium sulfide is detected. By the way, when the concentration of lithium hydroxide (Li011) in the removal solution is 50 mN, the baseline conductivity 1U rate is 1320 μ as is clear from the above table.
s/cm. Therefore, when the lithium sulfide (LizS) generated by the above equation (4) reaches the detector 6, the conductivity is detected to be lower than the baseline, giving a negative peak. That is, in the above equation (4), when lithium hydroxide decreases by 1 equivalent, lithium sulfide decreases by 0.
5 equivalents are produced, and the degree of dissociation of lithium sulfide is significantly lower than that of lithium hydroxide, resulting in a lower electrical conductivity. As a result, the lithium sulfide that reaches the detector 6 has a one-to-two ratio with the sulfide ions (S'-) in equation (4) above, and its conductivity is lower than the baseline conductivity. be.

2nd Fl! J is a chromatogram drawn by guiding the detection signal detected by the detector 6 as described above to a display unit (recorder, etc.) not shown, in which the horizontal axis represents time (in minutes) and the vertical axis represents time. indicates the conductivity rate (unit: μs/cm).

As is clear from this chromatogram, sulfide ions (S2-) at a low concentration of 1100 pp can be obtained as a good peak, allowing qualitative and quantitative analysis to be easily performed. Note that Water Dip is a peak caused by water contained in the sample, and usually appears as a negative peak.
Since the sulfide ion (S'-) also appears as a negative peak, in the chromatogram shown in FIG. 2, both are represented as positive peaks by signal processing.

It should be noted that the present invention is not limited to the above-described embodiments, and can be modified in various ways, for example, as shown in the following (a) to (c).

(a) As the removal liquid, a sodium hydroxide solution, a potassium hydroxide solution, an ammonium hydroxide solution, or the like may be used instead of the lithium hydroxide solution.

(b) As the eluent, an aqueous hydrochloric acid solution, an aqueous nitric acid solution, an aqueous phosphoric acid solution, an aqueous perchloric acid solution, an aqueous ant liquor solution, or the like may be used instead of an aqueous sulfuric acid solution.

(c) Instead of the tube 5a, a sheet-like cation exchange membrane may be used to divide the inside of the suppressor 5 into an inner chamber 5b and an outer chamber 5c.

<Effects of the Invention> According to the present invention as described in detail above, the conductivity detector is used to analyze sulfide ions in the liquid to be measured. This method has the advantage that sulfide ions in the liquid to be measured can be easily and stably analyzed.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention, and FIG. 2 is a chromatogram prepared using the embodiment of the present invention. 1a to 1d...tank, 2a, 2b...liquid pump, 3
...Sample collection, 4... Separation column, 5... Suppressor, 6... Detector, 7... Constant temperature bath.

Claims (2)

[Claims] (1) In a method of chromatographically separating and analyzing sulfide ions in a liquid to be measured, the sulfide ions are chromatographically separated using a separation column packed with a cation exchange resin, and then the separation column A sulfide ion analysis method in which the sulfide ions are converted to lithium sulfide by adjusting the pH of the eluate and guided to a conductivity detector, and the sulfide ions are analyzed by detecting the lithium sulfide with the detector. . (2) An injector that collects a certain amount of a liquid to be measured, and a separation column that is filled with a cation exchange resin and that chromatographically separates sulfide ions in the liquid to be measured when the liquid to be measured is carried in as an eluent. The interior is divided into an inner chamber and an outer chamber by a cation exchange membrane, and when the eluate from the separation column is introduced into the inner chamber, alkaline solution is supplied from the outer chamber via the ion exchange membrane to adjust the pH. a suppressor in which the sulfide ions are regulated and converted to lithium sulfide;
A sulfide ion analysis device comprising: a conductivity detector for detecting the lithium sulfide; and analyzing the sulfide ions based on an output signal from the detector.