JPH0772136A - Analysis of dbp, mbp and phosphoric acid in tbp organic solvent - Google Patents

Abstract

PURPOSE:To achieve quick detection of a TBP-decomposed matter contained tributyl phosphate (TBP) at a quantitative lower limit by a method wherein an aqueous solution after extraction passes through a column of an ion chromatography to be atomized by an ultrasonic wave and the concentration of phosphoric acid in the aqueous solution atomized is analyzed by a high frequency induction coupled plasma emission spectral analysis. CONSTITUTION:A 70% n-dodecan solution of dibutyl phosphate (DBP), monobutyl phosphate (MBP) as TBP-decomposed matter and TBP containing phosphoric acid is injected into an automatic sampler 1 and sent to a precolumn 3 and a column 4 by a pump 2 together with an eluent. After components are separated by the columns 3 and 4, the measuring solution is sent to an ultrasonic nebulizer 10 through a Teflon tube 9 to atomize. Then, the solution is introduced to a plasma torch 14 of a plasma emission spectral analyzer 8 through a Tygon tube 13 to measure the concentrations of the DBP, MBP and phosphoric acid respectively at quantitative lower limits 1mg/l, 0.1mg/l and 0.5mg/l from the intensity of emission of phosphor.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to tributyl phosphate (hereinafter abbreviated as TBP) dibutyl phosphate (hereinafter abbreviated as DBP) and monobutyl phosphate (hereinafter referred to as MBP) produced by decomposition of TBP in an organic solvent. And a method for analyzing phosphoric acid.

[0002]

2. Description of the Related Art Conventionally, TBP organic solvents are often used in solvent extraction in the Purex process for reprocessing spent nuclear fuel. In this method, uranium (U) and plutonium (Pu) are extracted from a nitric acid solution of spent nuclear fuel with TBP diluted to 30% with n-dodecane. U and Pu which became TBP complex in the organic phase are back-extracted with dilute nitric acid,
Purified and recovered. The spent nuclear fuel contains fission products having high radioactivity in addition to U and Pu, and a part of the above TBP is decomposed into DBP, MBP and phosphoric acid by this radiation. It is known that these decomposition products cause various problems as described below in the reprocessing process in the Purex method. 1) A loss occurs when extracting and recovering U and Pu. 2) Interfacial clad, emulsion, precipitation, etc. occur. Therefore, the organic phase deteriorated by the decomposition of TBP is washed with an alkaline solution and regenerated. At this time, it is important to know the exact concentrations of DBP, MBP and phosphoric acid present in the organic phase and the aqueous phase after the alkali cleaning in order to pursue the cause of the above defects.

When the organic phase is washed with alkali, DBP, M
Back extract 99% or more of BP and phosphoric acid into the aqueous phase,
That is, it is desirable that the alkali cleaning efficiency is 99% or more. Therefore, DBP contained in the organic phase,
It is necessary to measure the concentrations of MBP and phosphoric acid at about 1/100 of the lower limit of quantification. D contained in the organic phase
The concentration of BP, MBP and phosphoric acid is 100 to 2 respectively.
00 mg / l, 10-25 mg / l and 50-100 m
It is set to about g / l. Therefore, the required DBP, M
The lower limit of quantification for BP and phosphoric acid is 1 mg /
About 1, 0.1 mg / l and 0.5 mg / l are required.

Conventionally, various methods have been studied for measuring TBP degradation products. Although there are methods by high performance liquid chromatography using various columns, each method has a drawback that it takes a long time, and the method by gas chromatography after methylation has a drawback that pretreatment is troublesome. It was

The method by ion chromatography is known to be simple and accurate (see, for example, JP-A-63-55460). But this DB
The target lower limit of quantification of P, MBP, and phosphoric acid, 1.0 mg / l, 0.1 mg / l, and 0.5 mg / l, were not reached.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
D which is a TBP decomposition product contained in a 0% n-dodecane solution
BP, MBP, and phosphoric acid were 1 mg / l, 0.
It is an object of the present invention to provide an analytical method capable of measuring in a short time with only one operation, with a lower limit of quantification of 1 mg / l and 0.5 mg / l.

[0007]

The method of the present invention comprises the steps of quantitatively analyzing dibutyl phosphate, monobutyl phosphate and phosphoric acid in an organic solvent of tributyl phosphate by contacting the solvent with an alkaline aqueous solution to dibutyl phosphate. Phosphate, monobutyl phosphate and phosphoric acid are extracted into the aqueous solution, the aqueous solution after extraction is passed through a column for ion chromatography, the aqueous solution after passing is atomized by ultrasonic waves, and the atomized solution It is characterized in that the phosphorus concentration in the sample is analyzed by high frequency inductively coupled plasma optical emission spectroscopy.

[0008]

In the present invention, the TBP decomposed product is measured by the measuring device shown in FIG. 1 in which the ion chromatography, the ultrasonic nebulizer and the high frequency inductively coupled plasma optical emission spectrometer (hereinafter abbreviated as ICP emission spectrometer) are connected. To do. Generally, in ion chromatography, the elution molecule (X) of the cation (or anion) in the liquid and the cation (or anion; Y) contained as a component of the mobile phase are contained in the column portion. Each ion is separated by a phenomenon of elution while repeating ion exchange with an anion (or cation; R) which is an ionic group of the packing, and the concentration of each separated ion species is detected by detecting the electric conductivity. It is a device for analysis. A suppressor using a cation exchange membrane is provided between the column section and the electric conductivity detecting section so that the Na ion in the eluent does not increase the electric conductivity. In the present invention, the liquid that has passed through the column section is sent to the ultrasonic nebulizer without being sent to the suppressor, and the separated ion species of the separated ion species are detected by the ICP emission spectrophotometer without detecting the electric conductivity. It is to analyze the concentration.

An ultrasonic nebulizer is a device for sending a sample solution to the surface of a piezo transducer by a pump and efficiently converting the sample solution into a fine and high density aerosol (fog) by the action of ultrasonic waves. The aerosol is carried by the carrier gas into a U-tube heated to about 140 ° C and the solvent evaporates. Most of the solvent vapor is then liquefied and removed from the aerosol by passing through a cooling condenser at about 5 ° C. The result is a dry concentrated aerosol. This device has high sample transport efficiency,
Removing the solvent from the aerosol and reducing the solvent load of the plasma improves the detection limit of the detector ICP emission spectrometer. The concentrated aerosol produced here is introduced into an ICP emission spectrometer.

In the ICP emission spectrophotometer, the argon gas is ionized by the energy supplied from the induction coil and turned into plasma. Energy of about several kW is constantly supplied to this plasma. The atomized liquid sample is introduced into this plasma, and the light emission observed in the plasma is dispersed into each element by a spectroscope to measure the concentration of each element. In the present invention, TB is used in the column section.
P-decomposed products, that is, DBP, MBP and phosphoric acid are separated and sent to the ICP emission spectrophotometer over time.
Phosphorus (P) was used as a component in each of these TBP degradation products.
Therefore, the concentration of these TBP decomposition products can be analyzed by analyzing P with an ICP emission spectrophotometer.
That is, any component that can be analyzed by an ICP emission spectrophotometer may be used, and is not limited to phosphorus. Also, DBP,
Since MBP and phosphoric acid are separated and sent to an ICP emission spectrophotometer for analysis with a certain time lapse, the background when analyzing each may be slightly different. It is desirable to perform the simultaneous background correction described in the patent application filed on the same date as this application (reference number: 93-325, title of invention: simultaneous background correction method).

[0011]

【Example】

(Example 1) TBP organic solvent (30% TBP, 70% n)
-Dodecane), to which DBP was added 1.0, 5.
0, 10, 50, 100, 500, and 1000 mg /
1 or MBP 0.5, 1.0, 5.0, 10, 2
0, 50, 100, 200, 500, and 1000 mg
/ L, or phosphoric acid 0.1, 0.5, 1.0, 5.
28 kinds of sample solutions were prepared by adding 0, 10, 20, 50, 100, 200, 500 and 1000 mg / l. 10 ml of each of these sample solutions was dispensed into a 100 ml separating funnel, and 0.005
10 ml of a normal NaOH aqueous solution was added, and the mixture was shaken for 20 minutes with a shaker to perform back extraction. This operation was performed twice each time and only the aqueous phase was collected to obtain a measurement solution.

The apparatus used for the measurement is the apparatus shown in FIG. 1, which is an ion chromatography 6 (IC manufactured by YOKOGAWA).
7000), an ultrasonic nebulizer system 7 (U-5000AT manufactured by Seiko Electronics Co., Ltd.), and an ICP emission spectrum analyzer 8 (SPS4000 manufactured by Seiko Electronics Co., Ltd.). In FIG. 1, the measurement solution 50 described above is used.
μl / dose was injected by the autosampler 1 and the precolumn 3 with the eluent of 2.0 ml / min by the pump 2.
(HPIC-AS4A) and column 4 (DIONEX
It is sent to HPIC-AG4A) and each component is separated. The measurement solution in which each component is separated by the column is connected to the suppressor 5 in front of the ultrasonic nebulizer 1 at the same flow rate by a Teflon tube 9 having an inner diameter of 0.3 mm.
It was sent to 0. Here, the finely atomized measurement solution is introduced into the plasma torch 14 of the ICP emission spectrophotometer 8 through the heater 11 and the cooling tube 12 and the Tygon tube 13 having an inner diameter of 6 mm to measure the phosphorus concentration. I
The measurement conditions of the CP emission spectrophotometer are plasma gas 16 l /
min. , Auxiliary gas 0.5 l / min. , Carrier gas 1.0 l / min. The high frequency output is 1.3 kW and the photometric height is 10.0 mm. The light from the flame in the plasma torch 14 uses two optical processing systems including a collimator mirror 16, a diffraction grating 15, a camera meter mirror 17 and a photomultiplier 18 (only one series is shown in FIG. 1). Then, it was introduced into the data processor 19 as an electric signal and subjected to simultaneous background correction to obtain an analysis value.

As an example obtained with this apparatus, MBP
The chromatogram in the case of the sample solution containing 00 ppm is shown in FIG. A calibration curve for DBP, MBP and phosphoric acid was obtained from the emission intensity of phosphorus and the concentration of DBP, MBP and phosphoric acid measured by an ICP emission spectrophotometer based on each chromatograph. Correlation function r = 0.9992 in the range of 1 to 1000 ppm for DBP, r = 0.9994 and 1 to 1000 ppm for phosphoric acid in the range of 1 to 1000 ppm for MBP
In the range of r = 0.9994 (FIG. 3 shows the case of DBP). It was found that the concentration can be measured in this range.

(Example 2) Next, an experiment was conducted to investigate the lower limit of quantification. For DBP, 0, 1.0, 5.
0 and 10.0 mg / l, 0, 0.
The TBP solvent added so as to be 5, 1.0, and 5.0 mg / l and phosphoric acid at 0, 0.1, 0.5, and 1.0 mg / l was treated in the same manner as in Example 1, 4 each
The measurement was performed once. The concentration at which the (standard deviation / average) value was 10% was the lower limit of quantification. As shown in Table 1, all of them could reach the target lower limit of quantification.

Table 1 DBP MBP H ₃ PO ₄ This Example 0.5 mg / l 0.1 mg / l 0.5 mg / l Comparative Example 1 5.0 mg / l 3.0 mg / l 1.0 mg / l Comparative Example 2 10 mg / l 10 mg / l 10 mg / l

(Example 3) Further, DBP, TBP solvent,
MBP and phosphoric acid were added at 20 mg / l each. This was treated and measured in the same manner as in Example 1. The obtained chromatogram is shown in FIG. In FIG. 4, it is known that the three peaks 21, 22, and 23 are DBP, MBP, and phosphoric acid in order of increasing elution time. From this, it was found that the three components of the TBP degradation product can be measured simultaneously.

(Comparative Example 1) Prior to the present invention, a TBP decomposition product was measured only by ion chromatography. The sample solution obtained in the same manner as in Example 1 and Example 2 above was injected into ion chromatography to investigate the lower limit of quantification. The sample injected into the ion chromatography was 2.0 ml / min. The liquid was sent to the column at a flow rate of. The conductivity of the sample solution separated by the column was detected. The results are shown in Table 1. However, the target lower limit of quantification was not reached.

(Comparative Example 2) A liquid was sent to the ion chromatography column but an electric conductivity detector was not used. Instead of using an ultrasonic nebulizer as in the present invention, a mist blower like a commonly used one was used. Connect an ICP emission spectrophotometer using a gas atomizer as a detector to TB
The P degradation product was measured. The sample solution obtained in the same manner as in the above-mentioned Example 1 and Example 2 is injected into ion chromatography. The sample solution injected into the ion chromatography was 2.0 ml / min. The liquid was sent to the column at a flow rate of. The sample solution separated by the column has an inner diameter of 0.3 connected before the suppressor for ion chromatography.
mm with Teflon tube at the same flow rate
The solution was transferred to a P emission spectrophotometer. Here, the phosphorus concentration of the TBP degradation product was detected, and the lower limit of quantification was investigated. The results are shown in Table 1. Even with this method, the target lower limit of quantification was not reached.

[0019]

According to the present invention, it was possible to measure the concentrations of DBP, MBP, and phosphoric acid added to the TBP organic solvent to the target values of the lower limit of quantification, and to simultaneously measure the above three components in a short time.

[Brief description of drawings]

FIG. 1 is a diagram showing a measuring apparatus for carrying out the method of the present invention.

FIG. 2 shows that MBP was added to TBP organic solvent by the method of the present invention.
It is a figure which shows the chromatograph at the time of analyzing the solution containing only.

FIG. 3 is a diagram showing a DBP calibration curve obtained by the method of the present invention.

FIG. 4 shows that TBP was added to the organic solvent DB by the method of the present invention.
It is a figure which shows the chromatograph at the time of analyzing the solution containing P, MBP, and phosphoric acid.

[Explanation of symbols]

 1 Autosampler 2 Pump 3 Pre-column 4 Column 5 Suppressor 6 Ion chromatography 7 Ultrasonic nebulizer system 8 ICP emission spectrometer 9 Teflon tube 10 Ultrasonic nebulizer 11 Heater 12 Cooling tube 13 Tygon tube 14 Plasma torch 15 Diffraction grating 16 Collimator Mirror 17 Camera meter Mirror 18 Photomar 19 Data processor 21 Peak by DBP 22 Peak by MBP 23 Peak by phosphoric acid

Claims (1)

[Claims] 1. When quantitatively analyzing dibutyl phosphate, monobutyl phosphate and phosphoric acid in an organic solvent of tributyl phosphate, the organic solvent is brought into contact with an alkaline aqueous solution to dibutyl phosphate, monobutyl phosphate and phosphorus. Acid is extracted into the aqueous solution, the aqueous solution after extraction is passed through a column for ion chromatography, and the aqueous solution after passing is atomized by ultrasonic waves,
A method for analyzing DBP, MBP and phosphoric acid in a TBP organic solvent, which comprises analyzing the phosphorus concentration in the atomized aqueous solution by a high frequency inductively coupled plasma emission spectroscopy.