JP2011033576A - Method of determining arsenic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for determining arsenic which enables the concentration of arsenic in wooden building materials to be measured easily and accurately, without having to use expensive equipment. <P>SOLUTION: A sample 2 is placed in an ash-free filter 1. A wooden building material containing CCA etc. after drying is crushed to 100 mesh or smaller and used as the sample 2. The ash-free filter 1 is longitudinally folded in three and laterally folded into three portions. The ash-free filter 1 enveloping the sample 2 is placed in a platinum cage 4 mounted to a stopper part (glass plug) 3 of a combustion flask. A small quantity of absorption liquid 6, for example, 5 ml of a 1 mM solution of hydrochloric acid, is place in a 500 ml conical flask 5 of the combustion flask, and oxygen is filled therein. The ash-free filter 1 is lit, and the platinum cage 4, to which the ash-free filter 1 is fixed, is inserted in the conical flask 5 to burn the sample 2 inside and to make an absorbent 6 absorb arsenic generated by the burning. In this way, arsenic is turned into a solution in this way. Thereafter, the absorbent 6 which has absorbed arsenic is analyzed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for quantifying arsenic suitable for quantifying arsenic contained in wood.

  In recent years, when recycling and disposal of wood containing arsenic wood preservatives such as chromated copper arsenate (CCA), it is required to accurately measure the concentration of arsenic contained in the wood. However, such wood has a large uneven distribution of arsenic concentration, and it is difficult to accurately measure the arsenic concentration. As a conventional method for measuring the arsenic concentration, there are a method using the color of copper in CCA on the surface of wood, a method using reflection of near infrared rays, and the like. However, the quantitativeness of these methods is low. Moreover, although the portable simple fixed_quantity | assay apparatus using a fluorescent X ray is marketed, this apparatus is very expensive. Also, there is a method called microwave irradiation-acid decomposition method, but this method also requires an expensive apparatus. Also, it is difficult to carry this device.

JP 2003-270137 A JP 2005-127932 A

  An object of the present invention is to provide a method for quantifying arsenic that can easily and accurately measure the arsenic concentration in wood without using an expensive apparatus.

  The method for quantifying arsenic according to the present invention comprises a step of obtaining a solution in which arsenic generated from the sample is dissolved by burning a sample containing arsenic by an oxygen flask combustion method, and measuring an arsenic concentration in the solution. And a process.

  According to the present invention, since an oxygen flask combustion method is employed to obtain a solution containing arsenic, an accurate and simple analysis can be performed.

It is a mimetic diagram showing the solution method of arsenic concerning the embodiment of the present invention. 4 is a flowchart showing a method for analyzing arsenic in the absorbent 6.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a schematic view showing a arsenic solution method according to an embodiment of the present invention.

  In this embodiment, first, as shown in FIG. 1, for example, a sample 2 is placed in ashless filter paper 1. As the sample 2, for example, a material obtained by pulverizing dried wood containing an arsenic wood preservative such as CCA to 100 mesh or less is used. The mass of the sample 2 is, for example, 0.01 g.

  After the sample 2 is placed in the ashless filter paper 1, the ashless filter paper 1 is tri-folded in the vertical direction. Then, fold it in the horizontal direction. Subsequently, the ashless filter paper 1 containing the sample 2 is put into a platinum basket 4 attached to the stopper (glass stopper) 3 of the combustion flask. A 500 ml Erlenmeyer flask 5 of the combustion flask is filled with a small amount of absorption liquid 6, for example, 5 ml of 1 mM hydrochloric acid, and further filled with oxygen. Then, the ashless filter paper 1 is ignited, the platinum basket 4 to which the ashless filter paper 1 is fixed is inserted into the Erlenmeyer flask 5, and the sample 2 is burned inside.

  After completion of combustion, the Erlenmeyer flask 5 is tilted and shaken for 2 minutes, and then left to stand for 30 minutes, so that arsenic generated by the combustion is absorbed by the absorbent 6. In this way, arsenic is made into a solution.

  Thereafter, the absorbent 6 that has absorbed arsenic is filtered and then analyzed. In this analysis, for example, hydride generation atomic absorption analysis (HGAAS) is performed.

  In the oxygen flask combustion method, the time required for one combustion operation is about several minutes (about 30 minutes when the standing time is included). For this reason, arsenic solution can be formed in a short time. In addition, processing at each stage is easy, and it is possible to perform an accurate operation without special proficiency. Therefore, according to this embodiment, arsenic in wood can be easily and accurately made into a solution.

  However, an apparatus necessary for hydride generation atomic absorption spectrometry (HGAAS) is difficult to transport, and a simpler analysis method is preferable. Therefore, it is preferable to perform color analysis by the molybdenum blue method. However, since the absorption liquid 6 contains pentavalent arsenic, pentavalent phosphorus, and the like, when the absorption liquid 6 is used as it is, phosphorus exhibits the same color development (absorbance) as arsenic, Accurate quantification is difficult. Therefore, in the present embodiment, the total concentration of arsenic and phosphorus is obtained as follows, the concentration of phosphorus is further obtained, and the concentration of phosphorus is subtracted from the total concentration of arsenic and phosphorus. FIG. 2 is a flowchart showing a method for analyzing arsenic in the absorbent 6.

  In this analysis method, first, the absorbent 6 is filtered and then dissolved in 25 ml, and a reducing agent, for example, 2 ml of a 5 mass% L-cysteine solution is added to a part (for example, 10 ml) (step S11). Subsequently, a hot water bath for 2 minutes is performed (step S12). At this time, the temperature of a bath shall be about 75 degreeC, for example. As a result, the valence of arsenic changes to trivalence while the valence of phosphorus is maintained at pentavalence. Thereafter, an appropriate amount (for example, 1.2 ml) of acidic ammonium molybdate solution (5: 2 mixed solution of 6M nitric acid and 3% by mass ammonium molybdate) is added and left for about 5 minutes (step S13). Then, 1.2 ml of 5 mass% ascorbic acid aqueous solution is added, for example (step S14). And it heats for 3 minutes with a 75 degreeC hot water bath, and is then left to stand for 7 minutes-10 minutes (step S15).

  In addition, for a part of the absorbent 6 after the dissolution (for example, 10 ml), after adding 2 ml of pure water (step S21), an appropriate amount (for example, 1.2 ml) of an acidic ammonium molybdate solution is added, Leave for about 5 minutes (step S23). Then, 5 mass% ascorbic acid aqueous solution is added (step S24). And it heats for 3 minutes with a 75 degreeC hot water bath, and is then left to stand for about 7 minutes-10 minutes (step S25).

  And about the liquid obtained by the process of step S15, and the liquid obtained by the process of step S25, the light absorbency whose wavelength is 830 nm is measured with a spectrophotometer. In the liquid obtained by the process of step S15, since the valence of arsenic is trivalent, arsenic is inactive to the molybdenum blue method, and only the phosphorus concentration is measured. On the other hand, the total concentration of arsenic and phosphorus is measured in the liquid obtained by the process of step S25. Therefore, the concentration of arsenic can be obtained by subtracting the concentration of phosphorus from the total concentration of arsenic and phosphorus.

  The absorbing solution 6 contains various elements such as silicon, chromium, iron, and copper in addition to arsenic and phosphorus, but these do not affect the arsenic and phosphorus concentration results.

  In order to perform such color development analysis, a color development reagent and an absorptiometer are sufficient, and it is easier to transport than a device necessary for hydride generation atomic absorption analysis (HGAAS). For this reason, it becomes easy to perform a quantitative analysis of arsenic in a place where the wood is present, for example, a place where a building is being demolished or a place where wood is being disposed of. That is, it is not necessary to take a sample from the wood to be analyzed and transport it to an analysis facility or the like.

  Next, the results of experiments actually performed by the present inventors will be described.

  In this experiment, first, arsenic solution using the above-mentioned oxygen flask combustion method was performed on five kinds of wood (samples No. 1 to No. 5) containing CCA. Next, the absorption liquid obtained from each sample was quantified for arsenic concentration by hydride generation atomic absorption spectrometry. The absorption liquid obtained from each sample was also quantified for the arsenic concentration by the color development analysis described above. Furthermore, the arsenic concentration was also determined by microwave irradiation-acid decomposition method. These results are shown in Table 1.

  As shown in Table 1, in the case of performing hydride generation atomic absorption analysis and in the case of performing color development analysis, a result equivalent to the measurement result by microwave irradiation-acid decomposition method could be obtained.

Claims (4)

Burning a sample containing arsenic by an oxygen flask combustion method to obtain a solution in which arsenic generated from the sample is dissolved;
Measuring the arsenic concentration in the solution;
Arsenic quantification method characterized by having.   The method for quantifying arsenic according to claim 1, wherein wood containing a preservative is used as the sample.   The method for quantifying arsenic according to claim 1 or 2, wherein the arsenic concentration is measured by a molybdenum blue method. The step of measuring the arsenic concentration comprises
Removing the first solution and the second solution from the solution;
Measuring the total concentration of arsenic and phosphorus in the first solution by a molybdenum blue method;
Changing the valence of arsenic from pentavalent to trivalent while maintaining the valence of phosphorus in the second solution at pentavalence by reducing the second solution;
Measuring the concentration of phosphorus in the second solution after the reduction treatment by a molybdenum blue method;
Subtracting the concentration of phosphorus measured from the second solution from the total concentration of arsenic and phosphorus measured from the first solution;
The method for quantifying arsenic according to claim 3, wherein:

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