JPH11237372A - Method for quantitative determination of ozone concentration in water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make simply and quantitatively determinable ozone of a very low concentration in water by adding a fixed amount of inspection water to a fixed amount of indicator where a divalent iron ion reagent is dissolved, and by judging colorimetrically according to the color changing degree when measuring ozone with an extremely low concentration in water. SOLUTION: A divalent iron ion (Fe<+2> ) is colorless or light in color. On the other hand, a trivalent iron ion (Fe<+3> ) is reddish brown. More specifically, when ozone ranging from extremely low concentration to a concentration of 1-20 ppm in water is measured, a fixed amount of inspection water is added to a fixed amount of indicator where a divalent iron ion reagent is dissolved, and colorimetry is judged by naked eyes or an instrument according to the degree of the discoloration. For the divalent iron ion indicator, in the reaction of Fe<+2> to Fe<+3> , it is preferable that Fe<+3> is not precipitated and is uniform solution, and potassium ferrocyanide k4 [Fe(CN)6 ].3H2 O} ferrous chloride (FeCl2 ) can be selected as the quantitative detection reagent of the ozone concentration in the water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for easily measuring ozone from an extremely low concentration in water.

[0002]

2. Description of the Related Art Ozone is widely used in the fields of washing and removing oil on the surface of electronic components, disinfecting and washing foods and food containers, due to its inherent strong oxidizing power. In particular, in recent years in Japan, some urgent countermeasures have been required for the occurrence of severe colitis patients due to O-157 pathogenic Escherichia coli. One of the earliest attentions is ozone water, as is well known. Ozone water kills pathogenic bacteria in a short time due to its strong oxidizing power, but has the disadvantage that ozone in water is eliminated in a short time due to contact with organic matter. There is no other way to effectively use such ozone water to ensure quality assurance or safety, except to accurately measure the ozone concentration in the water that changes every moment.

[0003] Therefore, in a work site, a method of grasping the ozone concentration in water that changes every moment is indispensable. Conventionally, an underwater ozone concentration meter using an electronic circuit is commercially available and is already used at present, but this equipment is expensive and there is an economic difficulty in installing a large number. In addition, a method of measuring the ozone concentration in water by checking the decolorization of blue indigo (indigosulfonic acid) by the amount of injected water by using the strong oxidizing power of ozone has been attempted, but there is a disadvantage that the accuracy at an extremely low concentration is poor. .

[0004]

In order to solve such a current situation, an urgent development of a detection method which is simple in operation, inexpensive and has a quantitative characteristic even for extremely low concentration of dissolved ozone is required. Is desired. With respect to this problem, the present inventors have examined using any of several reagents whether any of the radical detection methods accumulated so far is applicable.

[0005] The simplest method is to use the discoloration phenomenon of red to blue or blue to red like litmus test paper, but it is difficult to expect quantitativeness in this method. In order to achieve quantitativeness, it is desirable to use a reagent whose color tone does not change but whose color intensity changes linearly with a gradient according to the ozone concentration.

[0006]

The present inventors have found that divalent iron ions (Fe ² +) are colorless or pale, while trivalent iron ions (Fe ³ +) exhibit a reddish brown color. Focusing on, the measurement method of the present invention was established. That is, when measuring ozone from a very low concentration to a concentration of 10 to 20 ppm in water, a certain amount of test water is added to a certain amount of an indicator in which a reagent of divalent iron ion is dissolved, and the discoloration of the discoloration is measured. This is a method for quantifying ozone concentration in water, characterized in that colorimetric determination is made visually or by a meter based on the degree.

[0007] bivalent iron ion indicator, in Fe ² + → Fe ³ + reactions without Fe ³ + is precipitated is preferably a homogeneous solution, in water adapted to such a precondition as quantitative detection reagent ozone concentration, potassium ferrocyanide as a convenience to use _{(k 4 [Fe (CN)} 6] · 3H 2 O) and ferrous chloride (FeCl _2), etc. can be selected.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be specifically described below based on examples. FIG. 1 is an absorption spectrum diagram of a self-recording spectrophotometer, which shows the concentration of ozone in water and the oxidation of divalent iron ions in potassium ferrocyanide.
³ shows the change in absorbance of a multivalent iron ion (Fe ³ +). FIG.
Is a graph showing the relationship between the absorbance at 420 nm and the ozone concentration (ppm) from the absorption spectrum diagram of FIG. FIG. 3 is a graph corresponding to FIG. 2 when ferrous chloride is used.

Example 1 Known ozone generated from an ozone generator (OHZ-04 manufactured by Onit Corporation) is blown into tap water and detected by an ozone concentration meter (PL-320 dissolved ozone monitor manufactured by Ebara Corporation). A concentration of ozone water: 5 ml was mixed with a previously prepared 1% aqueous solution of potassium ferrocyanide: 1 ml, immediately sealed, and vigorously stirred. The absorbance of this mixed solution was measured by changing the ozone concentration using a self-recording spectrophotometer. The results are shown in FIG. It can be seen that there is a maximum absorption wavelength region around 420 nm. In this way, the ozone concentration of the sample of 0 to 10 ppm
When the absorbance at 20 nm was measured and plotted against the ozone concentration, a very good linear relationship was obtained as shown in FIG. However, in FIG. 2, each measured value of the peak height is a value obtained by subtracting the blank test value. Therefore, it can be seen that the reagent: potassium ferrocyanide is excellent as a quantitative reagent in a low concentration region of ozone in water.

Example 2 A 1% aqueous solution of potassium ferrocyanide: 1 ml was freeze-dried in a transparent glass test tube, and 1 ml of water sample was added thereto.
pm) and 0.8 ppm sample could be clearly distinguished. Therefore, when using this reagent in actual use,
A (solid or liquid) potassium ferrocyanide is filled in a transparent sample tube, and a certain amount of water is added thereto and stirred. After a predetermined time (1 to 3 minutes), the absorbance (wavelength: 420 nm), or ozone concentration can be determined by comparing it with a set of liquids having a standard concentration, visually, or comparing it with a color sample made of art paper. Also, a method of impregnating a filter paper with an aqueous potassium ferrocyanide solution, drying the filter paper, and dropping a test sample on the filter paper,
Although ozone in the water is consumed by the filter paper and may cause an error, the accuracy of the ozone concentration is slightly lowered, but the ozone concentration can be determined. If a filter paper that does not consume ozone is used, the accuracy is improved. As such a filter paper, for example, there is a filter paper made of an inorganic material such as a ceramic filter plate or a glass fiber filter cloth.

Example 3 The same measurement as in Example 1 was performed using a 1% aqueous solution of ferrous chloride. As a result, a reddish brown precipitate of Fe ³ + was formed on the high concentration side (8 ppm or more). Therefore, although there is a difficulty in determining a homogeneous solution with an aqueous ferrous chloride solution,
A spot test showing that the ozone concentration in the obtained test water is 8 ppm or more shows sufficient sensitivity. At 8 ppm or less, a linear relationship is established between the ozone concentration and the absorbance peak height in the maximum absorption wavelength region around 420 nm as in the case of potassium ferrocyanide, as shown in FIG. 3, and the ozone concentration in water can be determined.

[0012]

As is apparent from the above description, the reagent that dissolves in water to produce divalent iron ions is quantitatively changed to trivalent iron ions depending on the ozone concentration in the water, and its coloration degree is reduced. Since a proportional relationship is established with the ozone concentration, the dilute ozone concentration in the water can be easily determined with the naked eye or with an absorptiometer. Therefore, it can be used inexpensively instead of the conventional underwater ozone concentration meter using an expensive electronic circuit, and is widely used in application fields of sterilization and oxidation of ozone.

[Brief description of the drawings]

FIG. 1 is a light absorption spectrum diagram showing the relationship between the color development due to oxidation of divalent iron ions in an aqueous potassium ferrocyanide solution and the ozone concentration.

FIG. 2 is a graph showing a relationship between an ozone concentration and a light absorption peak height at a wavelength of 420 nm when potassium ferrocyanide is used.

FIG. 3 Ozone concentration and wavelength 42 when ferrous chloride is used
9 is a graph showing a relationship with a light absorption peak height of 0 nm.

Claims (1)

[Claims] When measuring an extremely low concentration of ozone in water, a fixed amount of test water is added to a fixed amount of an indicator in which a reagent of divalent iron ion is dissolved, and the degree of discoloration is visually determined. A method for quantifying the concentration of ozone in water, characterized in that colorimetric determination is made using a target or an instrument.