JPH10318965A - BOD biosensor measuring device and standard solution for the measuring device - Google Patents

Abstract

(57) [Problem] In a BOD biosensor measuring device, a mixture of equal amounts of glucose and L-glutamic acid is used as a standard solution for calibration, but deterioration occurs after a lapse of time after preparation of the standard solution. As the process proceeds, the slope of the calibration curve changes, causing a decrease in measurement accuracy. The present invention solves this problem and provides a highly accurate B
An OD biosensor measuring device is provided. An aqueous solution obtained by adding sodium azide to a mixture of equal amounts of glucose and L-glutamic acid is used as a standard solution. This is because the standard solution is not degraded by suppressing the growth of fungi and fungi in the standard solution.
The measured value of is stable for a long time, and a long-term continuous measurement can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to biochemistry, which is a measure of organic matter contamination in water samples using effluents from sewage treatment plants, factories, business establishments, and environmental water areas such as rivers and lakes. The standard oxygen demand (BOD) relates to the composition of a standard solution used for calibration of an instrument for measurement by a biosensor.

[0002]

2. Description of the Related Art BOD is the amount of dissolved oxygen in water consumed when aerobic microorganisms assimilate organic matter in a test water at 20 ° C. for 5 days, expressed in units of mg / L. It is extremely important as the most representative index of water pollution. The BOD is usually based on Japanese Industrial Standards (JI
SK0102) and by the Japan Sewerage Association Sewage Test Method (1984).

In addition to the BOD measurement method based on manual analysis, there is a BOD measurement method using a biosensor characterized by its simplicity and speed. For example, Japanese Patent Publication No. 61-725.
No. 8, for example. The BOD biosensor measuring device using a microorganism as a biosensor is a very effective BOD measuring method capable of measuring BOD in wastewater in about 20 to 40 minutes. It has been adopted in “JISK3602: Biochemical oxygen demand (BOD _S ) measuring device using a microbial electrode” and has already been commercialized and put into practical use.

[0004]

However, a BOD biosensor measuring device using the above-mentioned microorganism sensor is
There is a problem that the standard solution used for calibration has a large change with time. That is, the calibration standard solution deteriorates with time after preparation, and the concentration of the organic substance measured as BOD decreases. For this reason, the output of the BOD biosensor measuring device in the standard solution left for a long time after preparation is lower than that of the standard solution immediately after the adjustment, and the slope of the calibration curve is reduced. In addition, the measurement accuracy deteriorates. Therefore, when it is necessary to continue measurement for a long period of time, the calibration standard solution must be frequently replaced with a freshly prepared one. This means that it takes time and effort to operate the measuring device, and there is also a problem with the measurement accuracy. Strictly, this measuring device cannot perform continuous measurement for a long period of time.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problem of preventing the deterioration of the BOD standard solution, the present invention provides:
The glucose / glutamic acid standard solution to which sodium azide has been added is used as a standard solution for a BOD biosensor measurement device. By adding this sodium azide to a conventional mixed solution of equal amounts of glucose and L-glutamic acid, it is possible to suppress the propagation of various bacteria in a standard solution and the occurrence of mold. As a result, a decrease in the BOD concentration in the standard solution is suppressed, and accurate BOD measurement can be performed. Furthermore, the frequency of re-preparing the standard solution can be reduced,
It can be applied to long-term continuous measurement.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on an embodiment using a BOD biosensor measuring device. FIG. 1 is a schematic diagram illustrating an example of a main configuration of a BOD biosensor measurement device. This measuring device is a measurement stored in a container,
Five types of solutions for calibration, washing and buffering, solenoid valves for liquid supply control, liquid supply pumps, air pumps, microbial sensors as measurement systems, thermostats, heat exchangers, control units, display units, records It consists of a total.

[0007] In FIG.
Calibration standard solution 1A, standard solution 1B, cleaning solution 2,
The test sample 3 and the buffer solution 4 are filled in each container,
According to the program of the control unit 14, the standard solutions 1A, 1A
The electromagnetic valves 5A to 5D provided in the flow paths of the solution B, the washing solution 2, and the measurement sample 3 are switched so that the selected one type of solution and the buffer solution 4 are transferred to the solution sending pumps 6A and 6B.
And the dissolved oxygen in the solution is saturated by the air from the air pump 7.

The calibration standard solutions 1A and 1B used at this time
Is a BOD standard solution defined by the manual analysis method of JIS K0102 and the sewage test method of the Japan Sewerage Association,
It is a mixture of equal amounts of glucose and L-glutamic acid (hereinafter referred to as a conventional standard solution). This standard solution is used for preparing a calibration curve of the microorganism sensor 10. Further, the washing liquid 2 is used for washing the standard solutions 1A and 1B and the sample 3 remaining in the piping system and for the endogenous respiration of the output of the microorganism sensor 10 (without food).
It is used to return to the state, and every time the measurement is completed by sending another solution, the washing liquid 2 is sent to wash the piping system.

The microorganism sensor 10 includes a microorganism membrane 12 in which microorganisms are immobilized on a porous membrane, a dissolved oxygen electrode 11 and a flow cell 13, and is set together with a heat exchanger 9 for keeping the temperature of the solution at the time of measurement constant. It is incorporated in a thermostat 8 whose temperature is controlled to a temperature. Solutions with saturated dissolved oxygen are:
After passing through the heat exchanger 9 in the thermostat 8 together with the air and being kept at the set temperature, it is sent to the microorganism sensor 10. here,
An electric signal (voltage or current) corresponding to the amount of dissolved oxygen (respiration) consumed when assimilating the organic matter in the solution sent by the microorganism immobilized on the porous membrane and the dissolved oxygen electrode Is output. At this time, the amount of dissolved oxygen consumed is proportional to the amount of organic matter in the measurement solution. Therefore, a calibration curve is prepared by measuring two types of BOD standard solutions having known concentrations in advance, and a measurement sample is prepared. The control unit 14 compares and calculates the electrical output signal obtained when measuring the BOD concentration to calculate the BOD concentration of the measured test water, displays a series of data on the display unit 15, and prints the data on the recording unit 14.

The program of the control unit 14 is as follows. First, in order to set the output of the microorganism sensor 10 to the standard state, the electromagnetic valve 5C is opened so as to send out the cleaning liquid 2. When it is in the standard state or when it is already in the standard state, the solenoid valves 5A, 5C, 5B and 5C are opened in this order,
Send two types of standard solutions 1A and 1B and cleaning solution 2,
Perform measurement and cleaning for calibration. Then, the origin and this 2
A calibration curve is created using the types of calibration values, the data is displayed on the display unit 15 and printed by the recording unit 14.

Next, the sample 3 is sent by opening the solenoid valve 5D.
The BOD concentration of the test water 3 whose concentration is unknown is calculated from the calibration curve, and the data is displayed on the display unit 15 and printed by the recording unit 14. Calibration is started again when the set number of water sample measurements has been completed and the sensor output has reached the standard state. During each of these measurements, the washing liquid 2 is always sent to return the output of the microorganism sensor 10 to the endogenous respiration state. Settings such as the opening / closing time of each valve and the number of times of water measurement can be easily changed by adjusting the program.

[0012] Using the apparatus having the above configuration, the conventional BOD
The result of continuously measuring a standard solution having a value of 33 mg / L is shown by a broken line in FIG. FIG. 2 shows the relationship between the value normalized by the initial sensor output and the number of continuous sensor operation days in order to clarify the difference from the standard solution of the present invention. It can be seen that the sensor output of the conventional standard solution indicated by the broken line starts to decrease due to deterioration from the fourth day, and decreases to 50% or less of the initial sensor output on the ninth day. On the other hand, when the BOD 33 mg / L standard solution to which 1 mM sodium azide of the present invention is added is applied, the sensor output retains 70% or more of the initial value even after 20 days or more as shown by the solid line in FIG. ing.

Probable causes of such deterioration of the standard solution include propagation of various bacteria and generation of molds in the standard solution. Sodium azide, copper complex (Bordeaux solution),
Although there are salicylic acid and calcium polysulfide, the present inventors have determined that sodium azide has no effect on the yeast Trichosporone ctaneum specified in JIS K3602, which is a microorganism used for the microbial membrane of the BOD biosensor. Has been confirmed by experiments. For this reason, it is recognized that sodium azide is effective in suppressing deterioration of the BOD standard solution.

[0014]

According to the present invention, the conventional standard solution used for the BOD biosensor rapidly deteriorates, and requires frequent reagent replacement about every three days for continuous operation, and even when performing intermittent operation. In order to maintain the measurement accuracy, replacement of the standard solution is an important item. However, if the standard solution of the present invention is applied, deterioration of the standard solution is reduced, so that readjustment of the standard solution or the frequency of replacement can be reduced, and stable measurement can be performed continuously for a long time. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a main configuration of a BOD biosensor measurement device.

FIG. 2 is an output comparison diagram of a BOD biosensor measuring device when a standard solution of the present invention and a conventional standard solution are applied.

[Explanation of symbols]

1A: Calibration standard solution A 1B: Calibration standard solution B 2: Cleaning solution 3: Water sample 4: Buffer solution 5A to 5D: Solenoid valve 6A to 6B: Liquid sending pump 7: Air pump 8: Thermostat 9: Heat exchanger 10: Microbial sensor 11: Dissolved oxygen electrode 12: Microbial membrane (trichosporone ctaneum, yeast) 13: Flow cell 14: Control unit 15: Display unit 16: Recorder 17: Drainage

Claims (3)

[Claims] An apparatus for measuring BOD in water using a biosensor, wherein a standard solution used for calibration is obtained by adding sodium azide to a mixed solution of glucose and L-glutamic acid in equal amounts. Biosensor measurement device. 2. The BOD biosensor measuring device according to claim 1, wherein the biosensor is a microbial sensor, and the biosensor comprises a microbial membrane on which the yeast Trichosporone ctaneum is immobilized, a dissolved oxygen electrode, and a flow cell. 3. A BO, wherein sodium azide is added to a mixed solution of equal amounts of glucose and L-glutamic acid.
Standard solution for D biosensor measurement device.