JPH0677008B2 - Continuous reduction vaporizer for high sensitivity analysis - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an element (As, Sb, Bi, Ge, Sn, Pb, Se, which produces a volatile hydride or atomic mercury by a reduction reaction. Te, Hg 9
The present invention relates to a sample introduction device when analyzing an element) by an analyzer such as a plasma emission spectrometer or a plasma mass spectrometer.

[Prior Art] In a conventional continuous reduction vaporizer, hydrogen gas by-produced as a result of a reduction reaction is introduced into plasma at the same time as volatile hydride and atomic mercury.

[Problems to be Solved by the Invention] When the amount of hydrogen gas introduced into plasma increases, the plasma becomes turbulent and analysis noise increases, or even a high energy state is reached in which volatile hydrides and atomic mercury can be analyzed. Since the efficiency of excitation may decrease or the plasma impedance may change and the plasma may disappear, the conventional continuous reduction vaporizer performs the reaction only under mild conditions where the amount of hydrogen gas generated decreases. Was there. Therefore, it is not possible to adjust to the optimum acid concentration or reducing agent concentration for reducing the analysis target element to volatile hydride or atomic mercury, or the flow rate of the reducing agent solution or sample solution fed into the reaction tube. However, there is a problem that the detection limit becomes worse due to the reason that the plasma output cannot be increased or the plasma output has to be raised above the optimum value so that the plasma does not disappear.

The present invention provides a low-power plasma even when the reaction is carried out at the optimum acid concentration or reducing agent concentration for reducing the element to be analyzed, or when the flow rate of the reducing agent solution or the analysis sample solution is increased. The purpose of the present invention is to obtain a high-sensitivity continuous reduction vaporizer for analysis that does not increase analysis noise or reduce or eliminate plasma excitation efficiency even if introduced.

[Means for Solving the Problems] In order to achieve the above object, in the continuous reduction vaporizer of the present invention, a polyimide hollow fiber membrane for selectively permeating and removing hydrogen gas is provided after a gas-liquid separation tube. The module was attached, and a trap consisting of quartz wool and a porous Teflon filter was attached to prevent the droplets containing salts that were scattered from the gas-liquid separation tube from entering the membrane module.

In order to selectively permeate and remove hydrogen gas in the hollow fiber membrane module, an inert gas containing volatile hydride or atomic mercury (carrier gas) sent from the gas-liquid separation tube inside the hollow fiber. Gas), while reducing the pressure on the outside of the hollow fiber, or purging with an inert gas containing no hydrogen gas. As the hollow fiber membrane, a polyimide membrane having excellent hydrogen permeability and acid vapor resistance is effective.

When volatile hydrides and atomic mercury pass through the membrane module, some of them dissolve or are adsorbed on the membrane, but the rate is relatively slow at room temperature (25 ° C), so the signal when analyzed is Volatile hydride or atomic mercury that has gradually become larger and takes a certain amount of time to reach a certain value, or is dissolved or adsorbed in the film when replaced with a blank sample (sample that does not contain any analytical target element) However, there is a problem such as that it melts into the inert gas (memory effect), but this problem was solved by heating the membrane module (60 to 120 ℃). In addition, when heated, the permeability of hydrogen gas also increases, so that the membrane module can be downsized.

[Operation] In the reduction vaporizer configured as described above, a sample solution containing an analysis target element (9 elements of As, Sb, Bi, Ge, Sn, Pb, Se, Te, and Hg) is acid solution (the present invention). Then, when mixed with a hydrochloric acid solution) and a reducing agent solution (sodium borohydride solution in the present invention), each element is reduced to volatile hydride or atomic mercury. In addition, a large amount of hydrogen gas is produced as a by-product with this reduction reaction. These hydrogen gas, volatile hydride,
Alternatively, atomic mercury is separated from the reaction solution into gas by blowing an inert gas through a gas-liquid separation tube. Splashes of the reaction solution generated at this time are removed by quartz wool and a porous Teflon filter attached after the gas-liquid separation tube. Further, hydrogen gas is a hollow fiber membrane module attached after the porous Teflon filter (in the present invention,
Polyimide film) is selectively permeated and removed to a concentration at which plasma excitation efficiency is not reduced or plasma is not extinguished. When a polyimide film is used, water vapor is removed as well as hydrogen gas. On the other hand, volatile hydride or atomic mercury is introduced into the plasma without being removed because the permeation rate of the film is slow.

In the conventional method, when the amount of volatile hydride or atomic mercury introduced into the plasma is increased, the amount of hydrogen gas produced as a by-product also increases, so the excitation efficiency of the plasma decreases, or There were problems such as disappearing,
According to this method, since hydrogen gas can be selectively removed,
A large amount of volatile hydride or atomic mercury can be introduced into the plasma, and more sensitive analysis can be performed.

[Examples] Examples will be described with reference to the drawings.

FIG. 1 is a block diagram of the present invention. 1 in the figure is a sample container, 2
Is an acid solution container, 3 is a reducing agent solution container, 4 is a peristaltic pump, 5 and 6 are three-way connectors, 7 is a reaction tube, 8 is a gas-liquid separation tube, 9 is a quartz wool trap, 10 is a porous Teflon filter, 11 is a hollow fiber hydrogen gas separation membrane module, 12 seems to be at a constant temperature, 13 and 14 are gas regulators, 15 and 16
Is a flow meter with a needle valve, 17 is a carrier gas tube, 18 is a purge gas inflow tube, 19 and 20 are purge gas exhaust tubes, 21 is a tube for introducing carrier gas into plasma, and 22 is a drain tank.

According to the above example, the sample is sucked from the sample container 1 by the peristaltic pump 4, mixed with the hydrochloric acid solution sucked in the same way at the three-way connector 5, and then at the three-way connector 6 with the sodium borohydride solution. It is mixed and sent to the reaction tube 7. In the reaction tube 7, the analysis target elements (9 elements of As, Sb, Bi, Ge, Sn, Pb, Se, Te, and Hg) are volatile hydrides (AsH ₃ , SbH ₃ , BiH ₄ , GeH ₄ , SnH). ₄ , PbH ₄ , H ₂ Se, H ₂ T
e) Or reduced to atomic mercury (Hg). Volatile hydride or atomic mercury is used as a carrier from the reaction solution by blowing an inert carrier gas (Ar or He in the present invention) emitted from the tube 17 into the reaction solution in the gas-liquid separation tube 8. Separate in gas. The reaction solution after being sprayed with the carrier gas is discarded in the drain tank 22. The carrier gas containing volatile hydride or atomic mercury is passed through the quartz wool trap 9 and the porous Teflon filter 10 to remove the droplets of the reaction solution contained in the carrier gas. The carrier gas from which the droplets have been removed is a polyimide hollow fiber hydrogen separation membrane module.
After selectively removing hydrogen gas and water vapor at 11, it is introduced into the plasma through a tube 21. In the hollow fiber hydrogen separation membrane module 11, a carrier gas is passed through the inside of the hollow fiber tube and an inert gas (Ar or N _{2 in the} present invention) for purging is passed through the outside. Alternatively, the outside may be sucked with a vacuum pump to reduce the pressure. Further, the hydrogen separation membrane module 11 is heated to 60 ° C. to 120 ° C. in the thermostat 12 in order to speed up the response of the analysis signal and to reduce the memory effect (the influence of the sample analyzed previously). The purge gas containing the separated hydrogen gas passes through the hydrogen separation membrane module 11 and then is guided to the gas-liquid separation pipe 8 by the tube 19. Hydrogen gas is generated from the reaction solution remaining in the U-shaped tube portion of the gas-liquid separation tube 8 for a while, but the hydrogen gas is discharged from the tube 20 to the duct by passing the barge gas.

Next, a comparison of the results of AsH ₃ analysis using the device shown in FIG. 1 and the results of analysis using a device that does not use a conventional separation membrane module is shown. The plasma power is set as low as 1 kw, and the flow rates of sodium borohydride, the sample solution, and the hydrochloric acid solution (these flow rates are the same in the present invention, and change at the same time).
As shown in Table 1, the plasma was extinguished at a flow rate of about 6.5 ml / min or more as shown in Table 1. Also 6.5
The signal intensity was small even at ml / min or less, and the variation (relative standard deviation after 10 repeated measurements) was 2
It was as high as ~ 3%. On the other hand, in the device shown in FIG. 1, even when the flow rate is 14 ml / min, the plasma does not disappear and the signal intensity increases almost in proportion to the flow rate, and no decrease in excitation efficiency due to hydrogen gas is observed. . Moreover, the variation of the signal is as low as about 0.6%. Thus, the detection limit is greatly improved by increasing the signal intensity and decreasing the variation.

[Effects of the Invention] According to the present invention, as explained above, the excitation efficiency of plasma is reduced by hydrogen gas, or noise is increased or plasma is extinguished due to disturbance of plasma. It is possible to introduce a large amount of volatile hydrides or atomic mercury into the plasma without the result, and as a result, more sensitive analysis can be performed.

[Brief description of drawings]

 FIG. 1 is a block diagram of the present invention. 1 ... Sample container 2 ... Acid solution container 3 ... Reducing agent solution container 4 ... Peristaltic pump 7 ... Reaction tube 8 ... Gas-liquid separation tube 9 ... Quartz wool trap 10 ... Porous Teflon filter 11 ...... Hollow fiber hydrogen gas separation membrane module 12 …… Constant temperature 15 …… Carrier gas flow meter 16 …… Purge gas flow meter 22 …… Drain tank

Claims (1)

[Claims] 1. A reaction tube for mixing and reacting a sample solution with an acid solution and a reducing agent solution to reduce an element to be analyzed to volatile hydride or atomic mercury, and a reaction tube sent from the reaction tube. A gas-liquid separation pipe for separating volatile hydride or atomic mercury from the reaction solution into an inert gas by spraying the reaction solution with an inert gas, and sent from the gas-liquid separation pipe. A continuous reduction vaporizer for high-sensitivity analysis, comprising a hollow fiber membrane module for selectively permeating and removing hydrogen gas from an inert gas containing volatile hydride or atomic mercury.