JPH056137B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention reacts a sample containing the analyte element with a reagent to generate gaseous atoms or gaseous compounds of the analyte element, and sends these to a detection section to detect the analyte element. Regarding the flow injection analysis method for detection and quantification, more specifically, it prevents uneven mixing and reaction of the sample and reagent due to pump pulsation, and improves detection sensitivity and analysis accuracy by rapidly promoting a uniform reaction. This invention relates to an improved flow injection analysis method that aims to improve the efficiency of the analysis and speed up the analysis. [Prior Art] In recent years, flow injection analysis has attracted attention as a high-speed, high-precision analysis method. Unlike the conventional continuous flow analysis method, the flow injection analysis method does not have an air segment for the sample, but instead consists of a continuous flow of liquid from sample injection to reaction and measurement. I'm waddling along. By the way, a continuous flow analysis method has been proposed in which gaseous atoms or gaseous compounds of the analyte are generated by reacting with the analyte in the sample as a reagent, and these are sent together with a carrier gas to the detection section to detect and quantify the analyte. (Spectroscopy Research vol.32, No.5
pp334-338, Analytical Chemistry vol.30, pp368-374,
Analyst vol.101, pp966-973 and same vol.106,
pp921-930). When the present inventors conducted a follow-up study on the techniques described in these prior documents, they found that although elements such as arsenic, antimony, tellurium, and lead can be detected and quantified, a large amount of sample is required. It was found to be inappropriate for detection and quantification. Furthermore, it has been found that the analysis accuracy and detection sensitivity are still insufficient, and the time required for measurement, that is, the speed, is also insufficient. Therefore, the present inventors attempted to solve the above problem by applying the aforementioned flow injection analysis method, which is completely different from the current continuous flow analysis method. [Object of the Invention] However, even if the flow injection analysis method is simply applied, there are contradictions as shown below in order to satisfy all of the improvement in detection sensitivity, analysis accuracy, and speed, and it cannot be solved overnight. It turned out that I couldn't do it. That is, in order to speed up the detection, it is necessary to quickly send the generated gaseous atoms or gaseous compounds to the detection section, and for this purpose, the amount of carrier gas supplied may be increased. However, when the amount of carrier gas supplied is increased, the gaseous atoms or gaseous compounds of the test element are diluted, resulting in a decrease in detection sensitivity.
Furthermore, in order to achieve high accuracy and improve detection sensitivity, it is necessary to eliminate pressure fluctuations within the system, and for this purpose, a large-capacity buffer device such as a buffer tank is required to alleviate pressure fluctuations. However, the presence of such a buffer device increases the residence time of the sample etc. in the system and reduces the speed. In view of the above problems, the present inventors conducted further research and found that the above-mentioned contradiction could be resolved by mixing the sample and reagent under special conditions. That is, an object of the present invention is to provide a flow injection analysis method that simultaneously enables improvement in detection sensitivity, improvement in analysis accuracy, and improvement in speed, which are contradictory to each other. [Structure and Summary of the Invention] That is, the present invention involves contact-mixing a continuously supplied carrier liquid including an intermittently injected sample zone and a reagent in a jet jet state at a flow rate of 0.1 to 5 m/sec. This is a flow injection analysis method characterized by supplying quantitatively generated gaseous atoms or gaseous compounds of the analyte element to the detection section together with a carrier gas, and detecting and quantifying the analyte element. Flow Injection Analysis Method FIG. 1 shows a flowchart showing an overview of the flow injection analysis method of the present invention. A sample containing a test element is injected intermittently into a continuously flowing carrier liquid using a rotary bubble or the like. The injected sample is present in a carrier liquid as a zone and is subsequently mixed with continuously or intermittently supplied reagents to generate gaseous atoms or gaseous compounds of the analyte element in the reaction zone. . The generated gaseous atoms or gaseous compounds of the analyte element are separated into gas and liquid, and are supplied together with a carrier gas to a detection section where they are detected and quantified. The flow injection analysis method of the present invention will be explained in more detail below. First, a sample liquid is intermittently injected into a carrier liquid that is continuously supplied by a pump. The sample may be injected by a conventional method, ie, a method using a rotary bubble. Regarding the present invention, it is important to contact and mix the carrier liquid containing the sample and the reagent solution in a jet jet state at a flow rate of 0.1 to 5 m/sec. In other words, by jetting both continuously from a thin tube or pore and making both jets collide with each other, pulsation of the reagent solution supply pump and the carrier liquid supply pump can be prevented, and the internal pressure caused by the pulsation can be reduced. There is no need for a pressure damper as fluctuations are eliminated. Since catalytic mixing is ideally carried out, the reaction is quantitatively completed within a short time. Since the reaction is completed quantitatively in a short time, the space required for the reaction section can be reduced. As a result, the following advantages can be obtained. Noise generation due to pressure fluctuations within the system is eliminated, and analysis accuracy and detection sensitivity are improved. Since the reaction progresses quickly and is completed by contact mixing, the detection sensitivity is further improved. Since a pressure buffer device is not required and the spatial volume of the reaction section can be reduced, the residence time in the system is reduced and speed is improved. Since gaseous atoms or gaseous compounds of the test element are separated in a short time, interference by coexisting ions can be significantly suppressed. It is economically advantageous because the amounts of samples and reagents are extremely small, and the amount of waste liquid is also small, which eliminates the problem of waste liquid disposal. In order to contact and mix the carrier liquid containing the sample and the reagent in a jet jet state, the methods shown in FIGS. 2 and 3 can be considered. Figure 2 shows a capillary tube 4 through which the sample carried by the carrier fluid flows continuously.
The liquid flowing out from the tip of the capillary tube 5, through which the reagent solution flows continuously or intermittently, is in a jet jet state, that is, the pump is used with a high back so that the liquid flows out continuously from the tip at a rate of about 0.1 to 5 m/sec. This is a method of applying pressure. On the other hand, FIG. 3 shows a method in which the tips of the tubes 24 and 25 through which the carrier liquid and reagent solution containing the sample flow are constricted to create a jet jet state. In these cases, a tube 4 or 24 for supplying a carrier liquid containing the sample and a tube 5 or 25 are arranged at right angles to each other, and a tube 3 or 23 for supplying carrier gas is provided. The sample solution and the reagent solution are mixed in contact with each other in a jet jet state at a flow rate of 0.1 to 5 m/sec, and the chemical reaction progresses. At the same time, the chemical reaction is completed in the reaction zone, and the gaseous atoms or gaseous compounds of the test element react. Occurs in the department. At this time, since the chemical reaction is completed within a short time, the volume of the reaction section can be small. The generated gaseous atoms or gaseous compounds of the analyte element are separated into gas and liquid by a gas-liquid separator if necessary, and then supplied together with a carrier gas to a detection section where they are detected and quantitatively analyzed. Any known detection method can be applied to the detection section. For example, atomic spectrum analysis methods such as atomic absorption spectrometry, atomic fluorescence method, and inductively coupled high-frequency plasma emission method; electrochemical analysis methods such as diaphragm carbani cell method and constant potential electrolysis method; semiconductor device method; gas thermoelectric conduction device method; An example is optical interference method. Among these, atomic spectrum analysis is particularly preferred. Samples/Carriers and Reagents Samples used in the present invention include arsenic, antimony,
A liquid containing test elements such as bismuth, tellurium, selenium, germanium, tin, lead, or mercury. The carrier liquid or carrier gas is stable and does not react with the sample, reagent, or gaseous atoms or gaseous compounds of the generated test element. For example, the carrier liquid may be pure water, an acidic or alkaline solution, an organic solvent, Examples of carrier gases such as buffer solvents include nitrogen, hydrogen, argon, helium, and the like. Any reagent may be used as long as it reacts selectively with the analyte element and generates gaseous atoms or gaseous compounds of the analyte element. Examples of such reagents include sodium tetrahydroborate. There are acids (mineral acids or organic acids). That is, the sodium tetrahydroborate-acid system acts as a reducing agent and reduces gaseous analyte hydrogen compounds such as AsH ₃ ,
SbH ₃ , SeH ₂ , BiH ₃ , TeH ₂ , SnH ₄ , PbH ₄ ,
Generates vapors such as GeH ₄ or mercury atoms. [Example] As a preferred example of the present invention, a flow-in injection atomic absorption spectrometry method for arsenic will be described below. First, a device as shown in Figure 4 was assembled. A four-channel pellister pump 41 was used to supply pure water as a carrier liquid, various reagent solutions, and nitrogen as a segment gas at a predetermined pressure, and a hexagonal pot 42 was used as a rotary bubble for injecting a sample. The mixing coil 43 has an inner diameter
A 1.5 mm glass tube (2 mm, 20 rolls) was placed in reaction section 4 where the reaction with sodium tetrahydroborate progresses.
For No. 4, a 10 cm Teflon tube with an inner diameter of 2 mm was used. All other connections were made using Teflon tubes with an inner diameter of 0.5 mm. The gas-liquid separator 45 has an inner diameter of 15 mm.
A device with a single-stage plate 12 cm in height was used. Next, the analysis procedure will be described. The arsenic standard solution used for analysis was prepared as follows. Sodium hydrogen arsenate _{( Na2HAsO4} ) 2.28g
to 1 with 1N-hydrochloric acid aqueous solution, and 10ml of it
Take it and make it 1 with 1N hydrochloric acid aqueous solution. Also, take 10 ml from it and make it 1 with 1N aqueous hydrochloric acid solution, then take 10 ml from there and make 100 ml with pure water.
This solution is used as a sample for analysis. The arsenic concentration in this solution is 10 ppb (10 ng/ml). Next, the atomic absorption spectrometer was set in a measurable state, and then water was continuously flowed at a rate of 5 ml/min, and nitrogen as a segment gas was mixed at a rate of 5 ml/min. Subsequently, by switching the hexagonal tip 42, an arsenic-containing sample is intermittently injected into the carrier liquid (pure water) at a rate of 0.5 ml per injection. The injected sample flows continuously in the form of water and nitrogen, that is, water/nitrogen/sample/nitrogen/water. The presence of nitrogen at this time serves to prevent the sample from diffusing into the water, increasing the sample zone width and reducing detection sensitivity. The water containing the sample is subsequently fed with 7 ml/min of 35% v/v hydrochloric acid and 1.5 ml/min of 50% w/v potassium iodide solution. Addition of the potassium iodide solution reduces pentavalent arsenic to trivalent arsenic, improves the generation efficiency of hydrides, which will be described later, and suppresses interference from coexisting ions.
After passing through the mixing coil 43, the carrier liquid containing the sample to which hydrochloric acid and potassium iodide solution have been added is added with 3 w/sodium tetrahydroborate solution.
v% and 1.5 ml/min and nitrogen as a carrier gas at a rate of 300 ml/min. The contact mixing of the sodium tetrahydroborate solution and the water containing the sample (section 46 in the figure) is carried out in a jet jet state using the apparatus shown in FIG. The linear velocity in the jet state is 1.27 m/sec. The carrier liquid containing the sample and the sodium tetrahydroborate solution are contacted and mixed in a jet jet state to cause a reaction, and the reduction reaction is completed in the reaction tube 44 and gaseous hydrogen arsenide (AsH ₃ ) is quantitatively produced. Occur. Subsequently, the gas is sent to a gas-liquid separator 45, where the gas and liquid are separated, and the arsenic hydride and nitrogen are sent to the atomic absorption section. At this time, if the internal volume of the gas-liquid separation separator is made small, the residence time will be shortened, resulting in insufficient gas-liquid separation, and droplets will be introduced into the atomic absorption part along with the gas, which is disadvantageous. Therefore, the gas passes through a hole with a diameter of about 1 mm, collides with the plate, and is recovered to remove impurity liquid. The separated gas is supplied to an atomic absorption section, where arsenic is detected and quantified. This operation was repeated 10 times using 0.5 ml of the arsenic standard sample solution, and the coefficient of variation (CV%) was found to be 1.2%. Also, the sensitivity shows 1% absorption.
The detection limit (S/N=3) was 0.15 ng. Furthermore, this analytical method was able to detect and quantify 120 samples per hour. The amount of waste liquid was 17 ml per specimen, and the amount of specimen sample required was 0.5 ml per measurement. [Comparative Example 1] For comparison, the magazine “Spectroscopy Research” Vol.32 No.5
pp334-335Arsenic was determined using the continuous method shown in Fig1. This continuous method is schematically shown in FIG. As shown in FIG. 5, 15 hydrochloric acid and 6 potassium iodide were added to sample 3 via peristaltic pump 1 to preliminarily reduce As ⁵⁺ in the sample to As ³⁺ . The solution containing the obtained sample is transferred to the mixing coil 7.
After mixing in the chamber, argon gas 8 and sodium tetrahydroborate solution (reagent) 9 are mixed, reacted in a reaction section 10, and sent to a separator 11, where they are separated into a hydride 12 and a waste liquid 13. The compound was sent to a detection section (not shown), and arsenic, which was a test substance, was detected and quantified. The measurement conditions were as follows. HCL aqueous solution (1mo/): 9.2ml/min. NaBH ₄ aqueous solution (3%): 2.3ml/min. KI aqueous solution (35%): 2.3ml/min. Sample flow rate: 7.3ml/min. Arsenic concentration: 200ppb As a result, the detection limit for arsenic (S/N=3) is
Repeated variation coefficient (CV%) of 10ng, 6 measurements
was 2.3%, and it was possible to detect and quantify 30 samples per hour. The amount of waste liquid was 46 ml per specimen, and the amount of specimen sample required was 16 ml per measurement. [Example 2 and Comparative Example 2] In order to compare the measurement time between the flow injection method of the present invention and the continuous method shown in the magazine "Spectroscopy Research" Vol. 32 No. 5 pp. 334-335 Fig. Example 2 and Comparative Example 2 were carried out using the apparatuses used in Example 1 and Comparative Example 1 under the conditions shown in Table 1 below, and the arsenic concentration was detected using an atomic absorption spectrometer AA-630 manufactured by Shimadzu Corporation. are shown in Table 2 and FIG. In addition, the linear velocity in the jet jet state in Example 2 was 1.14 m/sec.

【table】

[Table] [Examples 3 to 5 and Comparative Examples 3 to 5] The mixing speed of the carrier liquid and reagent was 4.3 m/sec.
The width was varied at ~0.05 m/sec, and the other conditions were the same as in Example 1.
The arsenic concentration was detected using a type atomic absorption spectrometer, and the arsenic detection peak height (mm) and noise width (mm) were calculated and shown in Table 3. The change in the mixing rate of the water containing the carrier liquid sample and the reagent (sodium tetrahydroborate solution) was determined in the apparatus shown in FIG.
The experiment was carried out by changing the carrier liquid flow rate and the diameter of the carrier liquid flow path 4. Note that Example 4 is an experiment in which the arsenic detection peak height and noise width were measured under exactly the same conditions as Example 1.

[Table] From the results shown in Table 3, if the mixing speed of the carrier liquid containing the sample and the reagent is 5 to 0.1 m/sec,
Although highly sensitive measurements with a high arsenic detection peak height and a narrow noise width can be obtained, it is clear that sensitivity decreases when outside this range.

[Brief explanation of the drawing]

Figure 1 is a flowchart showing an overview of the flow injection analysis method of the present invention, and Figures 2 to 4.
The figure is an embodiment diagram of the present invention. FIG. 5 is a flow diagram illustrating the continuous method used in the comparative example. 6th
Figures a and 6b are graphs showing the results of Example 2 and Comparative Example 2, respectively. Explanation of symbols, 1... Peristaltic pump, 3... Sample, 6... Potassium iodide, 7... Mixing coil, 8... Argon gas, 9... Sodium tetrahydroborate solution, 10... Reaction section, 11...
... Separator, 12 ... Hydride, 13 ... Waste liquid, 15 ... Hydrochloric acid, 4, 24 ... Carrier liquid flow path, 5, 25 ... Reagent flow path, 2, 22 ... Reaction section, 42 ... Hexagonal Kotuku, 45... Gas-liquid separation separator.

Claims (1)

[Claims] 1. A continuous supply of carrier liquid and reagents containing an intermittent sample zone are
Contact mixing with a jet flow of 0.1 to 5 m/sec,
A flow injection analysis method characterized in that gaseous atoms or gaseous compounds of a test element that are quantitatively generated are supplied to a detection section together with a carrier gas, and the test element is detected and quantified.